environmental impacts of preservative-treated wood conference... · environmental impacts of...

ENVIRONMENTAL IMPACTS OF PRESERVATIVE-TREATED WOOD

February 8 – 11, 2004 Orlando, Florida, USA

Florida Center for Environmental Solutions Gainesville, Florida

(Post - conference proceedings, it supersedes pre-conference proceedings issued earlier).

August 2004

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ENVIRONMENTAL IMPACTS OF PRESERVATIVE – TREATED WOOD Feb 8 – 11, 2004, Orlando, FL, USA

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TABLE OF CONTENTS Forward ..................................................................................................................vii TECHNICAL PAPERS

Variability in Evaluating Environmental Impacts of Treated Wood .......................... 3 Stan Lebow, Paul Cooper and Patricia Lebow

Integrated Studies of the Dynamics of Arsenic Release and Exposure from CCA-Treated Lumber..................................................................................................... 17 Richard Maas, Steven Patch and Jacob Berkowitz

Effects of CCA Wood on Non-Target Aquatic Biota .............................................. 32 Judith Weis and Peddrick Weis

Retention of As, Cu, and Cr leached from CCA-treated wood products in select Florida soils ........................................................................................................... 45 Tait Chirenje, Lena Ma, M Szulczewski, K. Hendry and C. Clark

Environmental Impacts of CCA-Treated Wood Within Florida, USA ..................... 57 Helena Solo-Gabriele, Timothy Townsend and Yong Cai

Scaled-Up Remediation of CCA-Treated Wood .................................................... 71 Carol Clausen and William Kenealy

Modeling of wood preservative leaching in service ............................................... 81 Levi Waldron, Paul Cooper and Tony Ung

Leachate Quality from Simulated Landfills Containing CCA-Treated Wood.......... 98 Jenna Jambeck, Timothy Townsend and Helena Solo-Gabriele

Effect of Coatings on CCA Leaching From Wood in a Soil Environment............. 113 David Stilwell and Craig Musante

Depletion of Copper-Based Preservatives from Pine Decking and Impacts on Soil-Dwelling Invertebrates......................................................................................... 124 Michael Kennedy

Environmental Impact of CCA-Treated Wood in Japan....................................... 146 Toshimitsu Hata, Paul Bronsveld; Tomo Kakitani, Dietrich Meier; and Yuji Imamura

Alternatives to Chromated Copper Arsenate (CCA) for Residential Construction156 Stan Lebow

Assessing Potential Waste Disposal Impact from Preservative Treated Wood Products .............................................................................................................. 169 Timothy Townsend, Brajesh Dubey and Helena Solo-Gabriele


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Health Effects of Preserved Wood: Relationship Between CCA-Treated Wood and Incidence of Cancer in the United States ............................................................ 189 Daniel West

Disposal of Treated Wood................................................................................... 196 Jeffrey Morrell

EU Directives and National Regulations for the Recycling and Disposal of Waste Wood................................................................................................................... 210 Rolf-Dieter Peek

Electrodialytic Remediation of CCA-Treated Wood In Larger Scale.................... 227 Iben Christensen, Anne Pedersen, Lisbeth Ottosen and Alexandra Ribeiro

Recovery and Reuse of The Wood and Chromated Copper Arsenate (CCA) from CCA Treated Wood – A Technical Paper............................................................ 238 Kazem Oskoui

Bioremediation of waste copper/chromium treated wood using wood decay fungi............................................................................................................................ 245 Miha Humar, Pohleven Franc and Amartey O. Sam

Bioremediation and Degradation of CCA-Treated Wood Waste.......................... 259 Barbara Illman and Vina Yang

Compression Tests on Wood-Cement Particle Composites Made of CCA-Treated Wood Removed From Service ............................................................................ 270 An Gong, Donatien Kamdem and Ronald Harichandran

Review of Thermochemical Conversion Processes as Disposal Technologies for Chromated Copper Arsenate (CCA) Treated Wood Waste................................. 277 Lieve Helsen and Eric Bulck

Characterization of Residues from Thermal Treatment of CCA Impregnated Wood. Chemical and Electrochemical Extraction ........................................................... 294 Lisbeth Ottosen, Anne Pedersen and Iben Christensen

TECHNICAL PAPERS SUPPLEMENTING POSTER PRESENTATION

A Complete Industrial Process To Recycle CCA-Treated Wood......................... 310 Jean-Sebastian Hery

Impacts of Wood Preservatives (CCA, CCB, CDDC, ACZA, ACQ and ACC) on the Settlement and Growth of Fouling Organisms............................................... 320 B. Tarakanadha, Jeffrey Morrell and K. Satyanarayana Rao

Leachable and Dislodgeable Arsenic and Chromium from In-Service CCA-Treated Wood................................................................................................................... 336 Tomoyuki Shibata, Helena M. Solo-Gabriele, Lora Fleming, Stuart Shalat, Yong Cai, and Timothy Townsend


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POSTER ABSTRACT

Arsenic speciation in soils and CCA-treated wood leachate ............................... 353 Myron Georgiadis, Yong Cai and Helena Solo-Gabriele

Managing Wood Pallets and Industrial Wood Wastes : Sumter County Wood Reuse & Exchange Center .................................................................................. 354 Miriam Zimms and Shane Barrett

Characterizing Properties and Products of Spent CCA from Residential Decks . 358 Robert Smith, Dave Bailey, and Phil Araman

COST Action E31: Management of Recovered Wood......................................... 359 Gerfried Jungmeier, Bengt Hillring

Copper Fixation Using A Pyrolytic Resin............................................................. 361 Daniel Mourant, X Lu, D.Q. Yang, B. Riedl and C Roy

Deportment and Management of Metals Produced During Combustion of CCA-treated Timbers ................................................................................................... 362 Mary Stewart, Joe Rogers, Ashley Breed, Brian Haynes and Jim Petrie

Energy Recovery from Shredded Waste Railroad Ties ....................................... 363 Karl Lorber

Extent of CCA-Treated Wood in Consumer Mulches .......................................... 364 Gary Jacobi, Helena Solo-Gabriele , Timothy Townsend, Brajesh Dubey and Laura Lugo

Forecast of future uses for CCA outside USA ..................................................... 365 Ian Stalker

Human and Ecological Risk Assessment of Borate-based Wood Preservatives. 366 Christian E. Schlekat, Susan A. Hubbard, Mark E. Stelljes

Impact of restrictions on the use of CCA-treated wood in Sweden...................... 367 Jöran Jermer

Influence of weathering conditions on leaching of CCA, ACQ and Cu-azole components and their reaction with soil .............................................................. 369 Silvija Stefanovic, and Paul Cooper

Leaching of copper containing preservatives according to OECD guideline XXX and YYY .............................................................................................................. 370 Ali Temiz, Fred G. Evans

Leaching of Copper, Chromium and Arsenic from CCA Treated Wood in Sanitary Landfill Leachate ................................................................................................. 371 Brajesh Dubey, Tim Townsend and Helena Solo-Gabriele

Life Cycle Management of Treated Wood - The Canadian Approach ................. 372 Curtis Englot


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Quantification and Speciation of Arsenic Leaching From an In-Service CCA-Treated Wood Deck and Disposed CCA-Treated Wood to Lysimeters Simulating Different Landfill Conditions................................................................................. 373 Bernine Khan, Helena Solo-Gabriele, Timothy Townsend, and Yong Cai

Recycling of CCA Treated Timber....................................................................... 375 Leo Lindroos

Unregulated Use of Toxic Wood Preserving Chemicals in Kenya: Health and Environmental Issues .......................................................................................... 376 Ramakrishna Venkatasamy

Water-Borne Copper Naphthenate: An Arsenic and Chromium Free Preservative for Wood.............................................................................................................. 377 Mike Freeman, Pascal Kamdem and Jim Brient

Wood Preservative 101: Frequently Asked Question (FAQ) ............................... 378 Yuki Sotome, Alysia Muniz, Tomoyuki Shibata and Helena M. Solo-Gabriele

RESEARCH PRIORITIES WORKSHOP DOCUMENT………………………………..388


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Forward

The Florida Center for Environmental Solutions is pleased to present the proceedings of the Environmental Impacts of Preservative-Treated Wood Conference. The proceedings consist of manuscripts submitted by the speakers and abstracts from the poster presenters. We are very appreciative of the participation of our esteemed speakers and presenters. The Center would like to recognize the following for their assistance in planning this conference: Conference Organizing Committee

• Helena Solo-Gabriele, PhD, PE - Conference Chair • Timothy Townsend, PhD, PE, Conference Co-Chair • Marcia Marwede • Larry Robinson, PhD • Rhonda Rogers • John Schert, Director

Conference Technical Committee Kevin Archer, PhD., Chemical Specialities William Baldwin, Arch Wood Protection, Inc. Van den Bulck, Katholieke Universiteit Paul Cooper, PhD, University of Toronto, Session Moderator Carol Clausen, Forest Products Laboratory, Session Moderator Lieve Helsen, PhD, Katholieke Universiteit, Session Moderator William Hinkley, Florida Department of Environmental Protection, Session Moderator John Horton, Osmose, Inc. Barbara Illman, PhD, Forest Products Laboratory, Session Moderator Pascal Kamdem, PhD, Michigan State University, Session Moderator Jeffrey Morrell, PhD, Oregon State University, Session Moderator Lisbeth Ottosen, PhD, University of Denmark, Session Moderator Helena Solo-Gabriele, PhD, PE, University of Miami, Conference Chair, Session Moderator David Stilwell, PhD, The Connecticut Agricultural Experiment Station, Session Moderator Timothy Townsend, PhD, PE, University of Florida, Conference Co-Chair, Session Moderator Judith Weis, PhD, Rutgers University, Session Moderator The Center takes great pride in recognizing the National Science Foundation - Partnerships for Innovation and the Directorate for Engineering for their funding support. Without this


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support, the conference would not have happened. The entities listed below provided additional sponsorship for the conference. We are indeed grateful for their support as well. GOLD PATRONS Janssen Pharmaceutical Southern Waste Systems SILVER PATRONS GeoSyntec Consultants Solid Waste Authority of Palm Beach County Southern Waste Information Exchange (SWIX) Center for Environmental and Human Toxicology, University of Florida BRONZE PATRONS Akzo Nobel Jones, Edmunds and Associates, Inc. Powell Center for Construction and Environment, University of Florida Waste Pro, Inc. Last but by no means least, we wish to thank the conference attendees. We exceeded our expectations to bring together the experts in treated wood from across the world. Thank you for taking the time to attend this conference and participate in the discussions. Your participation is appreciated.


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Technical Papers


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Variability in Evaluating Environmental Impacts of Treated Wood

Stan Lebow, Paul Cooper, Patricia Lebow

Prepared for Proceedings of the Environmental Impacts of Preservative-Treated Wood Conference

Orlando, Florida

February 8–10, 2004

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright.

ABSTRACT

Preservative treated wood contains components that may be toxic to non-target organisms if released into the environment in sufficient quantities. Numerous studies have been conducted to determine the rate of preservative release from treated wood and/or the extent of their subsequent accumulation in the environment. These studies have produced a wide range of results with a corresponding range of interpretations and recommendations. This paper reviews research on wood preservative leaching and environmental accumulation and discusses sources of the variability in research findings. Factors such as wood properties, pressure treatment techniques, construction practices, exposure conditions, and site conditions are discussed. Keywords: Wood preservatives, treated wood, leaching, variability, environmental accumulation INTRODUCTION

Concerns about the safety and environmental impact of preservatives used to protect wood from biodegradation have increased in recent years, as has research to quantify preservative leaching and environmental accumulation. Early studies of preservative leaching tended to focus on the ability of a preservative to provide long-term protection. Preservative permanence in the wood is critical to efficacy, and leaching studies remain an integral part of research to evaluate potential new preservative systems. These types of leaching trials emphasize comparative evaluations of preservative formulations, and they typically use methods that accelerate leaching. More recently, emphasis has shifted to conducting studies that evaluate the environmental impact of wood preservatives. These later studies place greater emphasis on quantifying in-service leaching rates and measurement of environmental concentrations of leached preservative. Researchers who are relatively unfamiliar with preservative formulations, treatment practices, and wood properties often Stan Lebow, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin, USA Paul Cooper, Faculty of Forestry, University of Toronto, Toronto, Canada Patricia Lebow, USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin, USA


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conduct these environmental impact evaluations. Not surprisingly, studies conducted by researchers with varying fields of expertise and a range of research objectives have produced results that are often conflicting and may be difficult to compare and interpret. This paper discusses some approaches used to evaluate preservative leaching and/or environmental accumulation, and the influence of various aspects of these methods on research results. Evaluations of preservative leaching and environmental accumulation can be grouped into two general types: those in which study conditions are controlled and those that are more observational in nature. Controlled studies are often laboratory studies and observational studies typically utilize existing in-service structures, although there is overlap between these groups. CONSIDERATIONS IN LABORATORY STUDIES

In controlled studies, researchers must consider methods involving selection of test specimens and treatment with preservative, exposure of samples to a source of leaching, and determination of preservative loss. Selection of Test Specimens

The size and dimensions of test specimens have a great effect on the percentage of preservative leached from the wood. Smaller specimens have a larger portion of their surface area exposed for leaching and allow more rapid water penetration. The effect of grain orientation is also exaggerated in smaller samples. The rate of movement of liquids along the grain of the wood is several orders of magnitude greater than that across the grain, and samples with a high proportion of exposed end-grain will exhibit exaggerated rates of preservative leaching [1,2]. The standard leaching method used by the American Wood Preservers’ Association (AWPA) purposefully employs small blocks with a high proportion of exposed end-grain to accelerate leaching (AWPA Standard E11 [3]). Although a valuable comparative method, this method and others using small specimens should not be used to predict the amount of leaching that will occur from product-sized material in service. It may not be practical, however, to conduct a laboratory leaching study using full-length lumber, poles, or piles. To avoid the problem of end-grain effect, specimens may be cut from product-size material and end-sealed with a waterproof sealer prior to leaching.

Wood species can also greatly affect the rate of preservative loss from treated specimens. Permeability varies greatly among wood species, and those species that are more permeable tend to leach at a higher rate because of more rapid movement of water through the wood [4,5]. One study of the leaching characteristics of small specimens cut from the surfaces of

commercially treated poles found

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Figure 1 Relative leaching of CCA components from different species (AWPA E11 leaching test) [8].


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that rates of preservative leaching from red pine were approximately double those from lodgepole pine, Douglas-fir, and western redcedar [6]. A subsequent study found that hardwoods such as maple, red oak, and beech have a greater percentage of extractable arsenic than does red pine [7,8] (Fig. 1). Other studies also indicate that preservative components may be more leachable from hardwoods than from softwoods [9–11]. Wood species may also affect the distribution of preservative within the wood and, as discussed below, the chemical reactions that occur to fix water-based preservatives within the wood. Because of these species effects, it is important to use a species that is typical for the application under evaluation or to at least identify and report the wood species.

Leaching of preservatives may also be affected by the presence and amount of heartwood in a sample. In most wood species, the inner heartwood portion of a tree is much less permeable than the outer sapwood portion. Accordingly, heartwood portions of test specimens may contain much less preservative than does the sapwood and may also be more resistant to penetration of the leaching medium. These effects might be expected to result in lower leaching rates from heartwood, but this generalization may be confounded by differences in preservative fixation in heartwood or by the presence of a higher concentration of preservative at the heartwood surface. Because the presence of heartwood in specimens complicates interpretation of leaching results, heartwood should either be avoided or quantified and reported. Heartwood represents a major proportion of the wood produced from some wood species, such as Douglas-fir, but a much smaller proportion of wood produced from Southern Pine species.

In some studies, a researcher may have the objective of characterizing rates of leaching from a particular species/preservative combination. In the design of such studies, the researcher must be aware that even within the sapwood or heartwood of a single tree species there can be variability in wood properties, including rate of preservative leaching. Not surprisingly, wood properties typically vary much more between trees and boards than within a single board. Consequently, it is desirable to obtain specimens from as many different boards as possible. For example, if 10 replicates are to be used in a leaching evaluation, it is usually more appropriate to cut a single specimen from each of 10 boards than to cut 10 replicate specimens from a single board. Obtaining boards from a range of geographic locations can achieve an even greater sense of variability, as well as broaden the inference space. As mentioned previously, specimens cut from longer boards may be end-sealed to prevent exaggerated leaching rates attributable to exposed end-grain. Preservative Treatment and Fixation of Test Specimens

Obtaining preservative treated specimens is a problematic step for many researchers. Many laboratories do not have ready access to stock solutions of commercial wood preservatives or the equipment needed to conduct pressure treatments. In these cases researchers typically purchase commercially treated products for leaching trials. A disadvantage of this approach is that the researcher has no knowledge of the treatment process, treating solution concentration, and fixation conditions. Ideally, the treated products will be purchased from several retailers over a period of time to make the sample more representative. In some cases, researchers have purchased commercially produced lumber and then cut specimens to smaller width or thickness than that of the original board. Because penetration of a preservative is often not uniform throughout the thickness of a board, specimens cut in this manner may have one or more faces that have a different (usually lower) preservative concentration than that of the original board face.

When the researcher treats specimens, care should be taken to prepare or obtain a preservative solution that is nearly identical to the commercial formulation. Leaching of active ingredients can be sensitive to proportions and types of solvents used. For example, leaching of copper from copper amine preservatives can be increased if an excess of amine is used in preparation of the treatment


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solution. In addition, some types of preservatives may be or may have been produced in multiple formulations. Before chromated copper arsenate Type C (CCA-C) became the industry standard, wood was also treated with CCA-A and CCA-B. Past studies indicate that arsenic release from wood treated with CCA-B was greater than that from wood treated with CCA-A or CCA-C [12]. The treatment process used should ensure adequate penetration of the specimens without development of

surface deposits. With some preservative systems, extended soaking periods that allow evaporation of solvents may produce a precipitate surface residue on the wood.

The fixation conditions that specimens are exposed to after treatment can also affect the outcome of a leaching study. In general terms, fixation refers to the series of chemical reactions that render water-based preservatives difficult to leach during service. Although the fixation reactions of preservatives differ, they all depend on solution concentration, time, temperature, and rate of drying. Complete fixation of CCA depends on the wood species; it requires 10 to 20 days at room temperature for pine species [7]. Test specimens exposed to leaching within a few days after treatment may exhibit abnormally high leaching rates of chromium, copper, and arsenic. The fixation reactions also require moisture [7,13], and rapidly drying specimens after treatment may lead to inadequate fixation even after a lengthy fixation period (Fig. 2). This is particularly a concern for small specimens such as the 19-mm cubes specified by the AWPA leaching standard [3]. For CCA, the rate of fixation and subsequent leaching of CCA components are dependent on wood species. In general, species in which fixation occurs very rapidly also tend to have a higher rate of arsenic leaching [7,8]. Differences in the chemical composition of the wood, and especially the amount and type of lignin, can affect the rate of fixation and subsequent preservative leachability [14]. Again, it is important to identify wood species when reporting leaching results. The solution strength or retention of preservative in the wood can also affect the rate of fixation. For CCA, arsenic fixation is more rapid at higher solution concentrations, while fixation of chromium and copper is slowed. Higher retentions have also been reported to slow fixation of copper in amine copper based preservative systems [15]. Controlled Leaching Exposures

Most controlled leaching trials of preservative treated wood expose samples to leaching via immersion. Immersion is perhaps the simplest type of leaching mechanism to control and replicate, and it provides a severe leaching environment. However, the immersion conditions can affect the results obtained. In some situations, the leached preservative in the water may reach concentrations that inhibit further leaching [16]. This problem can be addressed by either frequently changing the leaching water, as specified in AWPA Standard E11 [3], or by constructing a flow-through leaching

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Figure 2 Effect of wood moisture content on chromium fixation


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apparatus that circulates fresh leaching water [16]. In the latter case, care must be taken to accurately control or measure the flow rate so that the dilution factor can be calculated.

The characteristics of the leaching water can also influence leaching of preservatives. Standardized methods, such as AWPA Standard E11, generally specify the use of deionized or distilled water to minimize these effects. The presence of some types of inorganic ions in water has been reported to increase leaching from CCA treated wood [17–20], while they have been reported to decrease leaching with at least one type of preservative [21]. Water pH can also affect leaching of preservatives. Leaching of CCA is greatly increased when the pH of the leaching water is lowered to below 3, and the wood itself also begins to degrade [1,6,22]. Water pH ranges more typical of those found in the natural world are less likely to have a great effect on leaching [23], although the presence of organic acids may influence leaching at more moderate pH levels. Warner and Solomon [24] reported that adding citric acid to leaching water greatly increased leaching in laboratory tests. Although it is doubtful that high levels of citric acid will be a problem in service, surface waters containing high levels of humic or fulvic acid from peaty organic soils can have the potential for increasing CCA leaching [6,9]. Cooper and Ung [25] compared CCA-C losses from jack pine blocks exposed in garden soil and organic-rich compost and found that leaching was more than doubled by compost exposure.

Water temperature has also been reported to significantly affect leaching from wood treated with a CCA formulation [26]. In that study, copper, chromium, and arsenic leaching were approximately 1.4, 1.6, and 1.5 times greater, respectively, from wood leached at 20°C than from wood leached at 8°C. Brooks [16] also concluded that leaching of copper from CCA treated wood could be substantially increased as water temperatures increased from 8°C to 20°C. A similar temperature effect was noted in a study of release of creosote components from treated wood [27].

The rate of water movement around the test specimens can also influence leaching, although this effect has not been well quantified. Xiao et al. [27] reported that release of creosote was greatest at the highest flow rate tested and that turbulent flow may have greatly increased leaching. Van Eetvelde et al. [26] also reported that leaching of CCA was greater when using stirred leaching water than with static leaching trials. The AWPA standard leaching test specifies the use of a slow stirring speed (e.g., a tip speed of 25 to 50 cm/sec) [3]. However, care must be taken that the method of stirring or agitation used does not mechanically abrade the surface of the wood.

Although an immersion leaching exposure may be relatively simple to simulate, most treated wood in-service is not placed directly in water. Terrestrial applications are more common, and in such cases the treated structure is above ground or water or in soil contact. Because studies have illustrated that soil composition may affect both leaching and subsequent mobility of CCA components [28,29], efforts have been made within the AWPA to develop a standard method of evaluating preservative loss in soil exposures [29]. One challenge in this type of exposure is choosing a representative soil type; the authors recommend using at least three different soil types as well as characterizing and reporting soil properties.

Both immersion and soil contact leaching tests are likely to greatly overestimate the amount of leaching that will occur from treated wood exposed above ground. However, laboratory evaluations of aboveground leaching are rare, in part because it is difficult to simulate natural rainfall. It appears that rate of rainfall, not just volume, can affect the amount of leaching from wood exposed above ground. Studies in outdoor exposures have indicated this effect [4,30], and recent laboratory evaluations [31] have attempted to quantify the effect of rate of rainfall on leaching (Fig. 3). Laboratory evaluations also indicate that exposure to UV light may increase leaching from CCA treated wood exposed above ground [32].

The orientation of the wood product (vertical versus horizontal) can also affect the amount of water that enters the wood to facilitate leaching [1]. Although complex, further research is needed


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to determine principal factors affecting leaching from wood exposed above ground and to develop laboratory methods to predict leaching in service. Determining Preservative Leaching in Laboratory Exposures

Regardless of the leaching exposure, one must somehow quantify the amount of preservative that has been lost from the wood. This is usually accomplished by either assaying the wood before

and after leaching, or by analyzing the leaching water and calculating the rate of leaching and cumulative amount leached. Although analysis of the treated wood before and after leaching is a convenient way to assess leaching, this approach may not provide meaningful data unless substantial leaching has occurred. With well-fixed preservative systems, only a small percentage of preservative is typically lost during a laboratory leaching trial, and error in measurement of preservative

content in the wood can easily obscure or over- or underestimate leaching. Lower levels of leaching can be detected by analysis of leaching water, although care must be taken in calculating the dilution factor, and complex error structures may arise if repeated measurements are made over time. Analysis of leaching water also allows a researcher to evaluate changes in the rate of leaching over the course of the exposure period.

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Figure 4 Change in rate of arsenic release from CCA treated 2 by 4 specimens immersed in seawater.

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Figure 3 Effect of rate of rainfall on leaching of chromium, copper, and arsenic from CCA treated decking.


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FIELD STUDIES OF IN-SERVICE STRUCTURES

There has been a recent increase in evaluations of preservative release from in-service structures. These are generally observational (not controlled) studies. Evaluations of in-service structures provide valuable information on leaching and environmental accumulation in actual applications. The disadvantage of these types of studies is that they are specific to the conditions at that specific site and are difficult to relate to other exposures. The original treatment may be unknown, and there may be little historical data to indicate whether the site was previously exposed to contamination from construction debris or other non-leaching sources. In-service leaching results are affected by a range of site-specific conditions in addition to the treatment, fixation, and species effects discussed in the previous text. These include the age of the structure, type of exposure, climate, and construction and maintenance practices. Age of Structure

In general, the greatest rate of leaching from treated wood occurs upon initial exposure to the leaching medium. An initial wave of readily available and unfixed or poorly fixed components moves out of the wood; it is followed by a rapid decline to a more stable leaching rate [1,18,28,30,33,35] (Fig. 4). This time-dependent leaching pattern is a function of the size of the treated product, the amount and type of surface area exposed, and the extent to which the preservative components are fixed. It also appears to depend on the severity of leaching exposure, with a steeper gradient occurring under more severe leaching condition such as water immersion, and a flatter gradient occurring for wood exposed above ground. However, regardless of specific conditions, it is likely that rate of leaching occurring during the first year of exposure will be greater than that during subsequent years. Extrapolating early rates of leaching to longer time periods may overestimate long-term leaching.

Type of Exposure

The type of exposure or application also greatly influences in-service leaching. Regardless of whether the treated wood is exposed to precipitation, freshwater, seawater, sediments, or soil, the movement and composition of water is the key to the leaching of preservative components from the wood. Structures that are only intermittently exposed to precipitation will have much lower leaching rates than those continually immersed in water, especially in water containing solubilizing organic or inorganic components. Cooper [1] proposed a hierarchy of leaching exposures based on application and site conditions (Table 1). Within each of these types of exposures is a range of conditions that may potentially affect leaching. These include temperature and composition of soil and water. Because most treated wood is exposed above ground, climate plays an important role in leaching. Amount and rate of rainfall affect leaching [35], and it is likely that temperature and the presence or absence of freezing temperatures do as well. Although these conditions cannot be controlled, they should be noted and factored into the interpretation of leaching results.

Construction and Maintenance Practices

Construction and maintenance practices for a structure can also affect the rate of preservative leaching or the amount of preservative detected in the environment. If treated wood sawdust or shavings generated during construction are allowed to enter soil or water below a treated structure, they make a disproportionately large contribution to environmental contamination. As shown in Figure 5, leaching of CCA from construction debris immersed in water is vastly greater than that from solid wood. Environmental samples removed from areas where construction debris was deposited are likely to have much higher elevations of preservative components than might be


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expected from leaching alone. This effect may be responsible for some of the higher soil arsenic levels reported in recent studies of soil adjacent to CCA-treated decks [36,37], while other studies reported much lower concentrations [35,38]. Although associated with the treated structure, environmental contamination caused by construction debris is attributable to construction practices and is not an inherent characteristic of the treated

wood [39]. Cleaning and maintenance practices such as aggressive scrubbing, power-washing, or sanding can also remove particles of treated wood and deposit them in soil or water beneath a treated structure. In addition, some ingredients used in deck cleaners have been shown to react with and potentially increase the solubility of preservative components [40].

Application of Finishes

While construction debris and cleaning activities may increase environmental releases from a treated structure, application of finishes appears to have the opposite effect. One report indicated that a clear water-repellent finish greatly decreased CCA release from fencing [41]. Even after 2 years, arsenic concentration in rainwater collected off the finished specimens was approximately five times lower than that from the unfinished specimens. An observational study of the concentrations of arsenic, copper, and chromium in soil under residential decks noted that levels appeared to be lower under a deck that had been painted, although the design of that study did not allow a controlled comparison [36]. A laboratory study has also indicated that latex paint, oil-based paint, and semi-transparent penetrating stains are all effective in decreasing leaching from horizontal surfaces [42]. Again, although construction and maintenance activities generally cannot be controlled in an in-service leaching evaluation, they should be considered in the interpretation of leaching results.

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Figure 5 Comparison of amount of preservative released from solid wood or construction debris.


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Quantifying Leaching for In-service Exposures For in-service evaluations, leaching is generally evaluated by either assaying the treated wood

or by collecting and analyzing environmental samples adjacent to the treated wood. Determining preservative loss by assaying wood after exposure requires knowledge of original preservative retention in the wood. Often original retention is assumed based on the specified target or standard retention for treated wood used in that application. This assumption can be problematic, as preservative retention in a treated product can be substantially higher or lower than the target retention. This is particularly true for some oil-type treatments where retention is controlled by adjusting the treatment process, and not by adjusting the treatment solution concentration. Even with water-based preservatives, retention can vary greatly between material in a single charge and even more greatly between treating plants. Figure 6 shows the distribution of CCA retention in CCA treated 2 by 6 Southern Pine lumber purchased from several retailers over the course of 1 year. All the boards were treated to a target retention of 6.4 kg/m3. It is evident that retention varies greatly between boards, and that leaching would be either overestimated or underestimated for most

boards based on an assumed original retention of 6.4 kg/m3. Variability in retention can be even greater in more difficult to treat wood species.

Another technique used to quantify leaching in-service is comparison of the aboveground or above-water retention to the below-ground or below-water retention, with the assumption that leaching is minimal for samples exposed above ground [10,44,45]. This method can provide an indication of significant losses in the lower portions of treated wood. However, it is vulnerable to underestimation of leaching because some leaching does occur from above ground and the preservative may redistribute within the wood during service [45–47].

Table 1 Hierarchy of Severity of Leaching Exposures in Order of Increasing Severity [1] Exposure condition Typical or example application

Partially protected from rainfall Covered patios, gazebos, siding, substructure of decks and bridges

Occasional or partial exposure to rainfall

Fence boards

Complete exposure to rainfall Shakes and shingles, decking, railings, stairs, steps

Exposure to soil Fence posts, poles, land piles, retaining walls, treated wood foundations

Exposure to fresh surface water Cribs, lock gates, fresh water piles Exposure to seawater, acidified water, or warm water

Marine piles, piers, cribs, cooling towers, acid lakes

Exposure to metal complexing compounds

Silos, bog water (hypothesized), wood stave pipes and tanks, citric acid


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Because of challenges associated with assaying the treated wood to quantify leaching from in-service structures, researchers may instead collect environmental samples adjacent to a treated structure. This approach has the advantage of providing information on environmental accumulation of leached preservatives, but it gives limited information on the amount of preservative released from the wood. Environmental sampling also introduces a range of sources of variability into a leaching study. In addition to leaching rate, environmental concentrations of preservative components will be a function of background concentrations, sampling location, and soil or water characteristics.

Determining background or pre-construction environmental concentrations of preservative components is a key, but sometimes difficult, step in evaluating environmental accumulation. Many wood preservative components, including copper, chromium, and arsenic, have been widely used for other applications in the past, and soil and sediments may contain unpredictable concentrations of these components. This problem has generally been addressed by removing environmental samples at varying distances from the treated structure [36–38] and considering those at an extended distance from the structure as representing the background concentration. While generally a valid approach, there is the concern that human activities probably are, or have been, greater in close proximity to the treated structure, and thus the risk of other sources of contamination is greater in that area than may be in a nearby but less used area. Surface Area

The surface area of a structure contributing to soil levels in a particular area is an important consideration in environmental sampling. In complicated structures such as decks it may be difficult to determine the surface area of the structure that is contributing to soil accumulations in any specific sampling location. Other structures, such as utility poles, have a large aboveground surface that drains into a small volume of soil at the base of the pole, and it is not surprising that relatively high levels of preservative components have been detected in soil adjacent to poles [48]. Number and Location of Samples

For a field study, the specific parameters and/or hypotheses of interest relevant to the inference population(s), such as a 95% confidence interval for the median amount of copper within 152 mm of a structure, need to be identified before the study starts. Then, the best sampling strategy and analysis methodologies to address these information needs can be selected. Selection and number of sampling locations for removal of environmental samples can also influence levels of preservative

components detected. Common preservative components such as copper, chromium, and arsenic are reactive with soil constituents [12] and are not freely mobile in soil. Thus, environmental concentrations tend to be concentrated in areas immediately adjacent to treated wood or where water drips off treated wood into soil. Even when soil samples are removed from directly under the drip line of a deck, environmental concentrations of leached preservative components can vary greatly [35]. Because of

0 1 2 3 4 5 6 7 8 9 10 11 120

2

4

6

8

10

CCA Retention (kg/m3)

Num

ber o

f Boa

rds

Figure 6 Range of CCA retentions measured in 2 by 6 Southern Pine lumber treated to target retention of 6.4 kg/m3.


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this wide variation, a statistically designed sampling plan is needed to characterize preservative concentration in the environment adjacent to treated wood. Practical general advice on environmental studies can be found in van Belle [49], while more specific statistical methodology is given in Gilbert [50], Gibbons and Coleman [51], and Manly [52].

Environmental sampling typically yields many samples with relatively low levels of preservative components and a few samples with much higher levels [35–37]. Because of this skewness, traditional normality-based statistical methods directly applied to samples from an underlying skewed distribution may be overly sensitive to the “outlying” observations and lack power in comparing parts of the distribution where there is less information. Lognormal distributions are commonly assumed in environmental sampling; Ott [53] discusses in detail the physical and stochastic reasons why lognormal populations naturally arise in environmental settings. Gibbons and Coleman [51] provide statistical methods for testing distributional assumptions as well as for testing for outliers. If the lognormal distribution can be assumed, the normality-based methods can be applied to log transformed data, and the results reverse transformed to the original scale, to estimate various population parameters as well as confidence limits. For example, the sample geometric mean provides a simple estimate of the median, which can be a better estimator than the sample median of the median preservative concentration within that area. However, for small sample sizes with high skewness, this estimator has higher levels of associated positive bias [50]. Parametric approaches can offer more sophisticated modeling approaches than do nonparametric procedures, but depending on the particular questions that are to be answered in a particular study, nonparametric methods may also be appropriate [49]. Besides potential sampling, temporal, and spatial variability, analytical uncertainty is another consideration, as discussed by Gibbons and Coleman [51]. Care needs to be taken that analytical uncertainty is not used to characterize other types of variability. Also common to field studies are values that are censored below the quantitation limit(s) of a measurement device, necessitating appropriate statistical analysis methods to accommodate the censored data. Although there is agreement about using an appropriate statistical procedure, the particular choice depends on several things, including the objectives, degree of censoring, and ease of use [51]. Site Characteristics

Independent of leaching rates, site characteristics strongly influence environmental accumulation of leached preservative components. Leached preservative components are reactive with naturally occurring ligands in soil, sediments, and water, which limits their mobility. Movement in soil is generally limited but is greater in soils with high permeability and low organic content [23,54–60]. Mass flow with a water front is probably most responsible for moving metals appreciable distances in soil, especially in permeable, porous soils [60]. It is apparent that preservatives leached into water have the potential for greater migration compared with that of preservatives leached into soil, with much of the mobility occurring in the form of suspended sediment [35,61]. These environmental factors interact with leaching rates to create a pattern of environmental accumulation specific to a particular site. SUMMARY

Evaluation of the leaching and environmental accumulation of preservatives from treated wood is a complex process, and many factors can influence the results of such studies. In laboratory studies, the effects of specimen dimensions, wood species, treatment practices, fixation, and leaching exposure must be considered. Evaluation of in-service structures introduces additional variability, with factors such as age of the structure, type of exposure, construction and maintenance


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practices, and site characteristics. There is no perfect study design to account for all of these factors, and in many cases they are out of the control of the researcher. However, the researcher should be aware of these factors and the relative importance of these sources of variability to a particular study should be considered when interpreting and reporting the study results. REFERENCES 1. Cooper P.A. 1991. Leaching of wood preservatives from treated wood in-service. Report prepared for

Public Works Canada. 79 p. 2. Haloui, A; J. M. Vergnaud. 1997. Study of the release in water of chemicals used for wood preservation.

Effect of wood dimensions. Wood Science and Technology 31:51–62. 3. AWPA. 2002. Standard E11. Standard method of determining the leachability of wood preservatives.

Book of Standards. Granbury, TX: American Wood Preservers’ Association. 4. Cockroft, R.; R.A. Laidlaw. 1978. Factors affecting leaching of preservatives in practice. IRG/WP/3113.

Stockholm, Sweden: International Research Group. 5. Wilson, A. 1971. The effects of temperature, solution strength, and timber species on the rate of fixation

of a copper-chrome-arsenate wood preservative. Institute of Wood Science 5(6): 36–40. 6. Cooper, P.A. 1991. Leaching of CCA from treated wood: pH effects. Forest Products Journal 41(1): 30–

32. 7. Cooper, P.A. 2002. Minimizing preservative emissions by post treatment conditioning and fixation. In:

Proc., Enhancing the durability of lumber and engineered wood products, February 11–13, Kissimmee, FL, pp. 197–201. Forest Products Society, Madison, WI.

8. Stevanovic-Janesic, T., P.A. Cooper; aY.T. Ung. 2000. Chromated copper arsenate treatment of North American Hardwoods. Part I. CCA fixation performance. Holzforschung 54(6): 577–584.

9. Cooper, P.A. 1990. Leaching of CCA from treated wood. In: Proc., Canadian Wood Preservers Association 11: 144–169.

10. Nicholson, J.; M.P. Levi. 1971 The fixation of CCA preservatives in spotted gum. Record Annual Convention British Wood Preservers’ Association, pp. 77–90.

11. Yamamoto, K.; M. Rokova. 1991. Differences and their causes of CCA and CCB efficacy among softwoods and hardwoods. IRG/WP/3656. Stockholm, Sweden: International Research Group.

12. Lebow, S.T. 1996. Leaching of wood preservative components and their mobility in the environment. Summary of pertinent literature. Gen. Tech. Rep. FPL–GTR–93. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 36 p.

13. Kaldas, M.L.; P.A. Cooper. 1996. Effect of wood moisture content on rate of fixation and leachability of CCA treated red pine. Forest Products Journal 46(10):67–61.

14. Kartal, S. N.; S.T. Lebow. 2001. Effect of compression wood on leaching and fixation of CCA-C treated red pine. Wood and Fiber Science 33(2):182–192.

15. Pasek, E. Minimizing preservative losses: Fixation. A report of the P4 Migration / Depletion / Fixation Task Force. Proceedings, American Wood Preservers Association Annual Meeting, Boston, MA. In press. http//www.awpa.com/papers/Eugene_Pasek.pdf.

16. Brooks, K.M. 2002. Characterizing the environmental response to pressure-treated wood. In Proc., Enhancing the durability of lumber and engineered wood products, February 11–13, Kissimmee, FL, pp. 59–71. Forest Products Society, Madison, WI.

17. Irvine, J.; R.A Eaton; E.B.G Jones. 1972. The effect of water of different composition on the leaching of a water-borne preservative from timber placed in cooling towers and in the sea. Material und Organismen 7:45–71.

18. Lebow, S.T., D.O. Foster; Lebow P.K. 1999. Release of copper, chromium and arsenic from treated southern pine exposed in seawater and freshwater. Forest Products Journal 49(7/8):80–89.

19. Plackett, D.V. 1984. Leaching tests on CCA treated wood using inorganic salt solutions. IRG/WP/3310. Stockholm, Sweden: International Research Group.

20. Ruddick, J.N.R. 1993. Bacterial depletion of copper from CCA-treated wood. Material und Organismen 27(2):135–144.


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21. Kartal, S. N; B.F. Dorau; S.T. Lebow; Green, F. III. The effects divalent cations on the leachability of wood preserving N, N-hydroxynaphthalamide (NHA). Forest Products Journal. In press.

22. Kim, J.J.; G.H. Kim. 1993. Leaching of CCA components from treated wood under acidic conditions. IRG/WP/93-50004. Stockholm, Sweden: International Research Group.

23. Murphy, R.J.; D.J. Dickinson. 1990. The effect of acid rain on CCA treated timber. IRG/WP/3579. Stockholm, Sweden: International Research Group.

24. Warner, J.E.; K.R. Solomon. 1990. Acidity as a factor in leaching of copper, chromium and arsenic from CCA treated dimension lumber. Environmental Toxicology and Chemistry 9:1331–1337.

25. Cooper, P.A.; Y.T. Ung. 1992. Leaching of CCA-C from jack pine sapwood in compost. Forest Products Journal 42(9):57–59.

26. Van Eetvelde, G.; J.W. Homan; H. Militz; M. Stevens. 1995. Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Pt. 2. Semi-industrial investigation. In: Proc., 3d International Wood Preservation Symposium. Cannes–Mandelieu, France. IRG/WP 95-50040. Stockholm, Sweden: International Research Group: 195–208.

27. Xiao, Y.; J. Simonsen; J.J. Morrell. 2002. Effects of water flow rate and temperature on leaching from creosote-treated wood. Res. Note FPL–RN-–0286. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 6 p.

28. Bergholm, J. 1992. Leakage of arsenic, copper and chromium from preserved wooden chips deposited in soil. An eleven year old field experiment. Rep. 166. Stockholm, Sweden: Swedish Wood Preservation Institute.

29. Crawford, D; R. Fox; P. Kamden; S. Lebow; D. Nicholas; T. Pettry; L. Schultz; R. Sites, Ziobro. 2002. Laboratory studies of CCA-leaching: Influence of wood and soil properties on extent of arsenic and copper depletion. In: Proc., International Research Group on Wood Preservation, 33rd Annual Meeting, Cardiff, United Kingdom, IRG/WP 02-50186.

30. Evans, F.G. 1987. Leaching from CCA-impregnated wood to food, drinking water and silage. IRG/WP/3433. Stockholm, Sweden: International Research Group.

31. Lebow, S.T.; R.S. Williams; P.K. Lebow.2003. Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood. Environmental Science Technology 37:4077–4082.

32. Lebow, S.T.; D.O. Foster; P.K. Lebow. Rate of CCA leaching from commercially treated decking. Forest Products Journal. In press.

33. Fahlstrom, G.B.; P.E. Gunning; J.A. Carlson,.. 1967. Copper-chrome-arsenate wood preservatives: a study of the influence of composition on leachability. Forest Products Journal 17(7):17–22.

34. Fowlie, D.A.; A.F. Prestron; A.R. Zahora. 1990. Additives: an example of their influence on the performance and properties of CCA-treated Southern Pine lumber. In: Proc., American Wood Preservers’ Association. 86:11–21.

35. Lebow, S.T.; P.K. Lebow; D.O. Foster. 2000. Environmental impact of preservative treated wood in a wetland boardwalk. Part I. Leaching and environmental accumulation of preservative elements. Res. Pap. FPL–RP–582. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 126 p.

36. Stilwell, D.E.; K.D. Gorny. 1997. Contamination of soil with copper, chromium and arsenic under decks built from pressure treated wood. Bulletin Environmental Contamination and Toxicology 58:22-–29.

37. Townsend, T.; K. Stook; T. Tolaymat; J.K. Song; H. Solo–Gabriele; N. Hosein; B. Kahn. 2001. New lines of CCA-treated wood research: In-service and disposal Issues. Technical Report 00–12. Florida Center for Hazardous Waste Management.

38. Chirenje, T; L.Q. Ma; Clark C. M. Reeves. 2003. Cu, Cr and As distribution in soils adjacent to pressure-treated decks, fences and poles. Environmental Pollution 124:407–417.

39. Lebow, S.T.; M. Tippie. 2001. Guide for minimizing the effect of preservative treated wood on sensitive environments. Gen. Tech. Rep. FPL–GTR–122. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 18 p.

40. Taylor, A., P.A. Cooper; Y.T. Ung. 2001. Effect of deck washes and brighteners on the leaching of CCA components. Forest Products Journal 51(2):69–72.

41. Cooper, P.A ; Y.T. Ung. 1997. Effect of water repellents on leaching of CCA from treated fence and deck units. An update. Int. Res. Group on Wood Preserv. Doc. IRG/WP 97-50086.


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42. Lebow, S.T.; K.M. Brooks; J. Simonsen. 2002. Environmental impact of treated wood in service. In: Proc., Enhancing the durability of lumber and engineered wood products, February 11–13, Kissimmee, FL. p. 205–215. Forest Products Society, Madison, WI.

43. Arsenault, R.D. 1975. CCA-treated wood foundations: A study of permanence, effectiveness, durability and environmental considerations. In: Proc., American Wood Preservers’ Association 71:126–146.

44. Freeman, M.H.; D.K. Stokes; T.L. Woods; R.D. Arsenault. 1994. An update on the wood preservative copper dimethyldithiocarbamate. In: Proc.s, American Wood Preservers’ Association 90:67–87.

45. Gjovik, L.R. 1977. Pretreatment molding of Southern Pine: Its effect on the permanence and performance of preservatives exposed in sea water. In: Proc., American Wood Preservers’ Association 73:142–-153.

46. Hegarty, B.M.; P.M.T. Curran. 1986. Biodeterioration and microdistribution of copper-chrome-arsenic (CCA) in wood submerged in Irish coastal waters. Institute of Wood Science 10(76):245–253.

47. Shelver, G.D.; C.D. McQuaid; A.A.W. Baecker. 1991. Leaching of CCA from Pinus patula during marine trials in the southern hemisphere. IRG/WP/4167. Stockholm, Sweden: International Research Group.

48. Cooper, P.A.; Y.T. Ung. 1997. The environmental impact of CCA poles in service. IRG/WP/97-50087. Stockholm, Sweden: International Research Group.

49. Van Belle, G. 2002. Statistical rules of thumb. New York: John Wiley & Sons. 221 p. 50. Gilbert, R. O. 1987. Statistical methods for environmental pollution monitoring. New York: Van

Nostrand Reinhold. 320 p. 51. Gibbons, R. D.; D.E. Coleman, D. E. Statistical methods for detection and quantification of

environmental contamination. New York: John Wiley & Sons, Inc. 384 p. 52. Manly, B. F. J. 2000. Statistics for environmental science and management. CRC Press. 336 p. 53. Ott, W.R. 1995. Environmental statistics and data analysis. Bocan Raton, Fl: Lewis Publishers. 54. Bergholm, J. 1990. Studies on the mobility of arsenic, copper, and chromium in CCA contaminated soils.

IRG/WP/3571. Stockholm, Sweden: International Research Group. 55. Bergholm, J.; K. Dryler. 1989. Studies on the fixation of arsenic in soil and on the mobility of arsenic,

copper and chromium in CCA-contaminated soil. Rep. 161. Stockholm, Sweden: Swedish Wood Preservation Institute.

56. Bergman, G. 1983. Contamination of soil and ground water at wood preserving plants. Rep. 146. Stockholm, Sweden: Swedish Wood Preservation Institute.

57. De Groot, R.C.; T.W. Popham; L.R. Gjovik; T. Forehand. 1979. Distribution gradients of arsenic, copper, and chromium around preservative treated wooden stakes. Journal of Environmental Quality 8:39–41.

58. Holland, G.E.; R.J. Orsler. 1995. Methods for assessment of wood preservative movement in soil. In: Proc., 3d international wood preservation symposium; Cannes–Mandelieu, France. IRG/WP 95-50040. Stockholm, Sweden: International Research Group: 118–145.

59. Lund, U.; A. Fobian. 1991. Pollution of two soils by arsenic, chromium, and copper. Denmark: Geoderma. 49: 83–103.

60. Dowdy, R.H.; V.V. Volk. 1983. Movement of heavy metals in soils. In: Nelson, D.W. et al., eds. Chemical mobility and reactivity in soil systems. Madison, WI: Soil Science Society of America. 220–240.

61. Neary D.; P.B. Bush; R.A. LaFayette; M.A. Callaham; J.W. Taylor. 1989. Copper, chromium, arsenic and pentachlorophenol contamination of a Southern Appalachian Forest System. In: Weigman, D.A., ed. Pesticides in terrestrial and aquatic environments. Blacksburg, VA: Virginia Water Resources Research Center Publication Service. 220–236.


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Integrated Studies of the Dynamics of Arsenic Release and Exposure from CCA-Treated Lumber

Richard P. Maas*, Steven C. Patch and Jacob F. Berkowitz (*presenter)

UNC-Asheville Environmental Quality Institute

Abstract Public health concern has increased greatly in the past few years regarding arsenic (As) exposure from direct and indirect contact with CCA lumber due to the realization that As is a far more potent human carcinogen than previously extrapolated from laboratory animal studies. Various national field survey and laboratory studies currently in progress at the Environmental Quality Institute (EQI) do not find a statistically significant relationship between CCA lumber service age and As dislodgement after the first few months of use. Various treatments reduce As dislodgement; however, the effectiveness of water sealants or water-proofing materials appear to last for only about six months, while stains and paints exhibit As-reduction properties through about two years of outdoor exposure. Clearly, there is a need for CCA lumber treatments which will contain As within the wood for much longer time periods. Several candidate materials are currently under investigation at the EQI using an outdoor accelerated aging set-up involving mirror-intensified sunlight and heat, frequent simulated rainfall and intensive foot traffic. Based on preliminary experimental results and extensive direct observation, we believe that the most effective treatments must include both a penetrant/water repellent material as well as a surface crack sealant. Keywords: arsenic exposure, CCA lumber, arsenic dislodgement I. BACKGROUND AND INTRODUCTION A. Why The Sudden Concern About Arsenic? For about the past 30 years most lumber sold for outdoor use in North America has been treated with chromated copper arsenate (CCA) to resist insect and fungal decay. Although it has long been recognized that some amount of direct or indirect human arsenic (As) exposure would be associated with the widespread use of CCA lumber, the public health concern has escalated in recent years with the discovery that As is a far more potent skin, bladder, lung and kidney carcinogen than previously believed [1,2]. It is now recognized that inorganic As is one of the relatively rare carcinogens whose cancer potency is much less for laboratory test animals than for humans [3]. In fact, recent epidemiological studies in Bangladesh, Taiwan and Chile, where in individual villages there exists a high and variable range of inorganic As levels in drinking water, have established that inorganic As is approximately 100-200 times greater lung, bladder and kidney cancer risk than extrapolated from laboratory animal studies [1-4]. Also of concern are recently emerging medical studies such as Moore, et al [5] which indicate that inorganic As is not only a potent human carcinogen itself, but also that even very small As exposures cause existing human cancer tumors to grow more rapidly and aggressively. These


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researchers are finding increased tumor growth rate and significantly lower survival rates for cancer patients with higher As exposure from their environment. B. Current Cancer Risk Estimates From Contact With CCA Lumber In 2003 the Environmental Risk Management Authority of New Zealand conducted an extensive independent review of CCA-related cancer risk estimate studies [6] which included five major studies conducted subsequent to the updated As human cancer potency factor developed by the National Academy of Science’s Natural Research Council in 2001 [2]. The lifetime cancer risk estimates of these five studies can be briefly summarized as follows: Roberts and Ochoa [7] estimate 502 per million population for skin cancer only; the Gradient Corporation [8] estimates about one per million for skin cancer only; Sharp et al [9]: about 2000 per million population for lung and bladder cancer only; Maas et al [10]: about 1000 per million population for lung and bladder cancer only; and the US Consumer Products Safety Commission [1]: 51 lung and bladder cancers per million population. The variation of estimated lifetime cancer risks between these studies is considerable and can probably be attributed to: 1) inclusion/exclusion of different types of cancers; 2) degree to which the newest NRC human cancer potency estimates have been incorporated into the estimate or model; 3) different assumptions regarding the amount and timing of contact with CCA lumber; 4) different assumptions of the amount of As transferred per unit contact; and 5) differences in direct and indirect hand-to-mouth ingestion ratios. All of the afore-mentioned recent studies of As exposure from CCA lumber, including our own at the EQI, have been limited by factors such as: 1) the CCA lumber used was either new or from a very limited number of geographically proximate sites; 2) they have not included reliable estimates of the effectiveness of various stains and sealants over time; and 3) with the partial exception of the recent CPSC study [1], measurements of dislodgeable As have been based on various wipe/swipe methods as opposed to more realistic actual skin contact. Thus, there has been very little data from which to compare As exposures calculated from wipe data with actual hand/skin contact exposure. Our current research in progress is designed to address these previous experimental limitations by a) testing As dislodgement from over 800 different residential sites representing a wide range of lumber service ages, climate conditions, structure types, and sealant/stain histories, b) specifically comparing standard wipe results with actual handling transfer on adjacent sections of the same CCA boards, and c) determining through controlled outdoor test site experiments the effectiveness over time of various commercially-available and experimental water sealants and stains in reducing As dislodgement. II. METHODS As noted above, the research reported herein encompasses three types of experiments intended to increase the current understanding of As exposure from CCA lumber. These include: a) an ongoing nationwide study of As dislodgement from various in-service CCA structures using samples collected by volunteer participants with a standard wipe-sample kit with sampling templates and detailed instructions; b) controlled experiments comparing arsenic dislodgement on standard wipes versus actual handling transfer; and c) natural and accelerated weathering experiments to determine the As-retainment effectiveness of various commercially-available and experimental CCA wood sealants. A. National Field Survey Study


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Through a wide range of local, regional and national news articles and public service announcements, interested individuals have been alerted to the opportunity to test the As dislodgement from their own CCA structures for a nominal fee as part of this research project. The CCA surface research test kit consists of a thin plastic template which, when taped to the desired CCA lumber surface, delineates an exact 100 cm2 area (5 cm x 20 cm) for wiping with a standard laboratory Ghost-WipeTM . The research test kit also includes a pair of disposable laboratory gloves worn during the sample collection, a 50 mL laboratory hot-block digestion vial for storing and returning the test wipe, appropriate sample labeling materials, detailed and illustrated sampling instructions (see Figure 1), and a research questionnaire asking for the type of information listed in Table 1. Volunteer study participants are instructed to wipe the standard 100 cm2 surface area by the US EPA/HUD method for dust-wipe lead abatement clearance testing. This procedure specifies wiping across the lumber test surface with a horizontal and vertical “S” pattern followed by a spot wipe of each corner of the exposed rectangle, folding in the wipe after each of the three wipe passes. The folded Ghost-WipeTM is then placed directly into the labeled hot-block digestion vial, so that no further handling or sample transfer will be required for subsequent digestion and As analysis. All samples and research questionnaires are then returned directly to the EQI laboratory for hot-block HNO3 – H2O2 digestion and arsenic quantification by graphite furnace atomic absorption spectrophotometry using NIOSH Modified Method 7082 [11]. Although the results are not included in this report, volunteer research participants were also given the option of taking soil samples for As analysis under and/or adjacent to the CCA structure as well as from a background control location at least 10 feet away and not down-gradient from the structure.


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Figure 1 Brochure Wood Wipe Instructions Table 1 Information requested on CCA lumber research questionnaire

• Lumber surface orientation (i.e. horizontal, vertical, inclined) • Exposure to sun (% of the day) • Exposure to rain (yes/no) • Location on structure (i.e. handrail, decking, seat, etc.) • Type of structure (i.e. picnic table, play set, deck, etc.) • Age of structure (years, months) • Purchase location (store and city) • Brand of CCA lumber (i.e. Osmose, TP, etc.) • Lumber moisture condition at sampling time (dry, moist, wet, very wet) • Last sealant/stain treatment ( i.e. none, water sealant, stain, paint, unknown) • Time since last treatment (months or years) • Estimated average child use (minutes or hours per week) • Estimated average adult use (minutes or hours per week)


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Statistical analysis of the field survey data consisted of applying a general linear model to the log-transformed arsenic values to examine which of the factors mentioned above are statistically significant in the presence of all the other factors. Confidence intervals for the median arsenic amounts for each level of each factor were calculated by reverse-transforming results from the linear model back to the original units. Statistical significance for a given factor is declared when the individual p-value from the linear model is less than 0.05. B. Wipe Handling Contact and Arsenic Dislodgement Relationships The purpose of these experiments is to correlate arsenic dislodgement to wipes with arsenic transferred to hands from typical lumber surface contact and to examine the relationships between surface area contacted and As dislodged. CCA boards were marked off in randomized section pairs. These template-marked sections were then wiped by either the EPA/HUD or CPSC method, while the immediately adjacent section was wiped with a single pass of the bare hand. The dislodged As was then immediately removed from the bare hands by wiping them thoroughly with a clean laboratory wipe followed by a rinsing with 5% acetic acid and combining the rinsate with the wipe as a single sample for subsequent digestion. Repeated post-testing documented that this procedure removed virtually all As from the hands. Coordinated experiments simultaneously examined the relationship between total board surface area contacted and mass of As dislodged. C. Natural Accelerated Sealant Effectiveness Study These recently initiated experiments involve treating new and aged CCA lumber with various commercially-available or experimental/proprietary materials. The lumber surfaces are then weathered outside under either natural or accelerated conditions. The weathering acceleration is accomplished by the combination of a) mirrors to reflect and intensify day time sunlight and heat onto the exposed lumber surface; b) a simulated rainfall cycle to increase the number of precipitation/evaporation cycles experienced by the test lumber; and c) almost daily controlled foot-traffic abrasion which we believe will have a major influence on the As-reduction longevity of typical sealants and stains. III. CURRENT RESULTS AND DISCUSSION A. National Field Survey Study The database is constantly being expanded by the inclusion of additional voluntary participant sites. The results shown here were presented in New Zealand in June 2003 [12]. Slightly over 800 sites are included in the analysis and, as shown in Table 2, each of the four major geographic quadrants of the United States are represented with approximate weight of its relative population. The mean As dislodgement mass (AsDM) across all CCA surface types, service ages, geographic areas, and treatment types is just under 64 µg/100 cm2 with a median AsDM of 12.2 µg/100 cm2. Table 2 shows the percent of samples which fall into designated AsDM categories for various CCA lumber types and conditions. From Table 2 it can be seen that typically between about 15% and 30% of samples had AsDM values in excess of 50µg/100 cm2 with the exception of CCA lumber which had been water-sealed, stained or painted within the previous six months.


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Figures 2 and 3 [12] show estimated medians and 95% confidence limits for various lumber conditions. From Figure 2 it can be seen that the As released from decks, play sets and picnic tables was similar while the “other” category which included miscellaneous structures such as handrails, columns, garden borders, gazebos, etc. tended to release higher amounts of As (median ≈ 17.0 µg/100cm2). The amount of sun exposure appears to have some effect on the AsDM, with low sun exposure associated with lower As dislodgement measurements. One striking result shown in Figure 2 is that CCA surfaces sampled in the Northwest US are releasing significantly more As (median ≈ 18.5 µg/100 cm2) than samples from the other regions (median ≈ 9.7 µg/100 cm2).

1 - PS=Playsets, PT=Picnic Tables

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10

20

30

(255) (182) (176) (175)(150) (236) (353)(289) (338) (39 ) (135)

NE NW SE SWLow Med HighDeck PS PT OtherItem1 Sun Exposure Region

OverallMedian

Figure 2 Estimated median As per 100 cm2 and 95% individual confidence limits for significant effects with sample size in parenthesis. Figure 3 illustrates results pertaining to the effectiveness of water sealants, stains and paints over time. Unfortunately, at this point in the study it is necessary for us to combine stains, paints, polyurethane and combinations into one treatment category in order to increase the sample size sufficiently to achieve a reasonable 95% confidence limit. As our national field survey sample size increases, it should become possible to break out various stains, paints and urethane treatments to statistically determine their individual As encapsulation effectiveness over time. A large part of the current information limitation stems from the fact that 66% of the study participants have never applied any type of sealant or coating to their CCA structure. As shown by Figure 3, the waterproofing type materials were associated with reductions in As dislodgement for the first 0.5 years after application (reduction in median AsDM of about 74%);


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23

however, the effect disappears in the 0.5 – 2.0 year age-since-application category. After 2.0 years the median As release is actually higher than for CCA lumber that has never been treated. These results are consistent with those of Stillwell and Gorney [13], who found no statistical difference between As dislodged from CCA lumber treated with water repellents and CCA lumber with no treatment when samples were taken one year after the water repellent application. In the case of the combined stain, paint, polyurethane treatment, As release appears to be reduced for about two years on average with a mean reduction in median AsDM of approximately 69% during the period. The 31% decrease compared to the overall study median for treatment intervals greater than two years is not statistically significant based on the currently relatively small sample [12], but may be found to be statistically significant as the survey study population continues to grow. Clearly more research and product development is needed to address the critical issue of whether As can be contained for extended periods by some type of treatment of existing CCA lumber structures.

1-Waterproofing=Waterseal,Waterproofing; 2-Other=Stains,Paints,Polyurethane,Combination

Med

ian

ugA

s/10

0cm

sq

0

10

20

30

40

N=493 N=28 N=81 N=48 N=20 N=50 N=260-.5 .5-2 2+ 0-.5 .5-2 2+

---Waterproofing ----Time(Yrs.)Treatment None 1 --------Other -------2

OverallMedian

Figure3 Estimated median As per 100 cm2 and 95% individual confidence limits for different treatments and time since treatment applied.


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24

Table 2 Arsenic amounts on wipes by types of sample for field study

% of Samples with As Amount

n

0-10

µg/100 cm2

10-50

µg/100 cm2

> 50

µg/100 cm2

0-1 years

130

50.0

31.5

18.5

1-5 years

311

45.0

27.7

27.3

Age

> 5 years 316

44.6

34.1

21.1

None

493

39.8

32.3

28.0

WS 0-0.5

28

78.6

17.9

3.6

WS 0.5-2

81

44.4

30.9

24.7

WS 2+

48

29.2

45.8

25.0

Other 0-0.5

20

85.0

5.0

10.0

Other 0.5-2

50

76.0

20.0

4.0

Treatment and Years Since Treatment (WS= Waterseal) (Other = Paint, Stain, PolyUr., etc.)

Other 2+

26

42.3

42.3

15.4

Deck

289

48.4

29.8

21.8

Play Set

338

47.3

32.3

20.4

Picnic Table

39

56.4

23.1

20.5

Item

Other

135

37.0

28.2

34.8

0-33%

150

49.3

30.7

20.0

33-66%

236

47.9

30.1

22.0

Sun Exposure

67-100%

353

43.1

30.9

26.1

Northeast

255

54.9

28.6

16.5

Northwest

182

31.9

35.2

33.0

Southeast

176

50.6

31.3

18.2

Region

Southwest

175

45.7

25.7

28.6


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25

Overall, there is no significant association between the service age of the CCA structure and the amount of As dislodged in these experiments (p-value = 0.36) from our survey study [12]. Also, as seen from Table 2, the percentage of samples in the low (< 10 µg/100 cm2), medium (10 – 50 µg/100 cm2) and high (>50 µg/100 cm2) categories is approximately equal for the < 0.5 year, 0.5 – 2.0 year and >2.0 year service age categories, respectively. This field survey observation agrees with our various published and yet-to-be-completed laboratory studies which show the AsDM to decrease by 40 – 70% over the first three to 26 weeks of outdoor exposure, with no observable further reduction thereafter [10]. B. Hand-Wipe-Contact Area Relationships Over the past 18 months we have initiated various experiments to try to determine the relationships between As dislodgement from actual handling compared to using wet laboratory wipes, considering the potential intervening factors of amount of surface area wiped and the moisture condition of the hand and/or board surface. These relationships are proving to be more complex than anticipated, as there appear to be interactions between the variables of hand moisture content, board surface moisture condition and amount of board surface contacted.

Table 3 shows the AsDM values observed for once-over dry hand and standard laboratory wipe contact with dry new CCA lumber as a function of the surface area contacted. These results indicate that the amount of As dislodged to either dry bare hands or to wipes increases approximately linearly over the range of 465 cm2 to 7432 cm2 (i.e. 0.5 – 9.0 ft2). The CPSC’s recent risk estimates assume that hands reach an approximate saturation point (i.e. one “hand-load”) at 7.6 µg of As [1]. However, as shown in Table 3, our results clearly indicate that far more than 7.6 µg of As can be built up even on dry hands from contact with relatively small areas of CCA lumber surface. Thus, this 2003 CPSC study [1], as well as the original August 2000 CPSC staff assessment [14], may seriously underestimate As exposure for people who make several hand contacts over fresh lumber surfaces. From Table 3 it can also be noted that the once-over dry hand contact transfers only about 12.3% as much As on average as a standard wet laboratory wipe on a dry CCA board surface using the CPSC wipe method. Subsequent experiments have indicated that when the hand and/or the board surface itself is moist, the hand behaves much more like the moist laboratory wipe, and the AsDMs observed are much closer. Our preliminary experiments indicate that the EPA/HUD wipe method illustrated previously in Figure 1 provides a unit area AsDM about twice that of the CPSC method. Thus, we have previously estimated the ratio of the EPA/HUD wipe to actual hand contact As DM to be about 15.6 for dry hands and about 6.9 for damp hands and/or board surfaces [12]. Obviously, over months or years of actual skin contact with CCA lumber, there will be some mix of wet and dry hand and board surface conditions which will depend on precipitation patterns and, especially for infants and young children, on the frequency and extent of hand-to-mouth activity. Establishing more quantitatively this complex interactive relationship between wipe versus hand contact conditions will be important in developing more reliable and accurate estimates of As exposure from CCA lumber.


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26

Table 3 Arsenic dislodgement (µg) as a function of surface area contacted for once-over dry hand and laboratory wipes. Surface Area (ft2)

Dry Hand #1

Dry Hand #2

Dry Hand Mean

Laboratory Wipe #1

Laboratory Wipe #2

Laboratory Wipe Mean

Laboratory Wipe/ Dry Hand Ratio

0.5 7.1 56.0 31.6 104.0 157.1 130.6 4.13 1.0 139.6 101.4 120.5 887.4 364.6 626.0 5.20 2.0 281.5 341.8 311.7 3668.0 1123.0 2396.0 7.69 4.0 239.8 159.9 200.0 1640.0 1652.0 1646.0 8.23 8.0 426.7 818.9 622.8 9270.0 8792.0 9031.0 11.00

C. Natural and Accelerated Sealant Effectiveness Study With the current phase-out of the manufacture and sale of CCA lumber, the important and practical issue related to As exposure from CCA lumber has now become whether the dislodgement of As can be greatly reduced for periods of five years, 10 years, or even longer by the application of specific sealants, water-proofers, stains or paints. As noted above, our nationwide field survey studies indicate a significant reduction from currently available products of only 0.5 years to about two years, with evidence that As dislodgement may rebound to even greater levels if care is not taken to repeatedly reapply treatments at appropriate time intervals. To address this critical issue of whether specific existing or newly-developed treatment materials can successfully reduce As dislodgement for more extended periods, in October 2003 we initiated natural and accelerated outdoor aging experiments using new and old (10 year service age) CCA lumber with existing and experimental/proprietary sealant/water repellent formulations. These experiments are being conducted simultaneously with similar weathering experiments recently initiated jointly by the US EPA and the CPSC (using only commercially available treatment materials) [15]. Hopefully, the information obtained from these two separate studies will be complementary in providing practical solutions to the ongoing issue of As and in-service CCA lumber. In an effort to accelerate the weathering/aging of these experimental treatments, we have set up an accelerated experimental design which includes 1) increasing the amount and intensity of daytime heat and sunlight by optimally-positioned mirrors; 2) greatly increasing the number of lumber surface precipitation/evaporation cycles by applying 0.60 cm of simulated rainfall three times per week in addition to any natural precipitation events; and 3) applying intensive daily (5/week) foot traffic equivalent to about 12 shoe-bottom contact abrasions per unit area per day. A photograph of the accelerated aging experimental set-up is shown below as Figure 4.


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27

Figure 4 Photograph of accelerated aging experimental set-up with reflectors and sprinkler. Table 4 below lists what we believe to be general experimental considerations for accurately and cost-effectively determining the As dislodgement reduction capabilities of current and experimental treatments in a time-efficient manner. Also included in Table 4 are specific experimental details which we believe are critical to obtaining accurate and reliable results.


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28

Table 4 General and Specific Experimental Considerations for Determining the Long-Term As Dislodgement Reduction from CCA Lumber Treatments

I. GENERAL DESIGN CONSIDERATIONS A. Age brand new lumber outside through 2-4 precipitation/evaporation cycles to produce a more realistically pre-conditioned and As-stable “new lumber.” B. Take at least three “pre-treatment” wipe samples from all boards immediately before applying experimental treatment to establish baseline As dislodgement. C. Apply treatments according to manufacturer’s instructions. D. Use both “new” and previously in-service CCA lumber since specific treatments may work differently on the two ages of boards. E. Divide experiments into natural and accelerated aging trials. F. Accelerate aging by increasing heat and sunlight using adjustable mirrors, adding simulated rainfall/evaporation cycles three times per week, and applying foot traffic. G. Test all treatments at least in duplicate with appropriate non-treated controls. H. Take simultaneous wipe samples for As analysis at least monthly, noting moisture condition of board at the time of sampling. I. Determine AsDM reduction by comparing monthly wipe sample results with both pre-treatment and coated AsDMs. J. To determine how much acceleration of aging is actually being accomplished, compare the natural and accelerated AsDM results over time for a material (such as conventional water seal) which will wear off even from the naturally-aged board surfaces within one year.

II. Specific Experimental Details A. Adjust mirrors frequently to maximize light/heat reflection to board surface with season. B. Pre-mark out all 100 cm2 surfaces on each board for subsequent wipe samples. C. Buy long CCA lumber so that many treatment and control sections can be produced from the same board. D. Rotate boards within the accelerated experiments to even out the amount of heat and light reflection. E. Physically separate treated and untreated (control) boards during natural or simulated precipitation events to prevent splattering of As from control to treated board surfaces. F. Use separate designated boots for control and experimental board foot traffic to prevent possible As cross-contamination from daily boot bottoms.

We believe that the natural and accelerated aging experiments described above (Figure 4 and Table 4) will produce reliable measurements of As dislodgement reductions (even for treatments providing observable effectiveness for 4-8 years) within one to two years. Two factors are essential to achieve this goal. First, the experimental conditions must be sufficient to significantly accelerate natural aging of the board treatment. Our hypothesis is that aging of the As-reduction treatment is significantly affected by the following three factors: a) The degree of fluctuation of diurnal board surface heat and sunlight conditions which in turn influences the rate of surface crevice, fissure, and fracture formation thereby allowing water to penetrate more deeply and dissolve out additional CCA salt. b) The total number of precipitation and evaporation/drying cycles. Each time precipitation penetrates into the wood and dissolves more internal CCA, subsequent drying and evaporation


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29

should transport this dissolved CCA to the board surface where it will be left behind as a micro salt crust after complete water evaporation. c) Especially for colored stains, we have visually observed that the stain is physically removed (with corresponding increases in As dislodgement) in areas of a deck with heavier foot traffic. We believe that this will prove to be a very important acceleration factor for stain-type treatments. Second, the experimental design must be able to allow the acceleration factor to be estimated with some accuracy. Specifically, in our experiments we are using a popular conventional water sealant for this purpose. Both our field survey study and our preliminary outdoor experiments indicate that conventional water seal will deteriorate substantially in terms of its arsenic retention properties within six to 10 months. Thus, if its arsenic reducing properties are found to deteriorate by 75% for instance after eight months on the naturally-aged boards, and the same degree of As retention deterioration is observed on the accelerated-aging boards after only two months, it would be a reasonable estimate that the aging rate has been increased by a factor of about four. Lastly, based on extensive direct physical observation and As dislodgement measurements over the past three years, we believe that for a CCA lumber treatment (or treatment system) to be effective in preventing As dislodgement for five to 10 years, it must possess the ability to: 1) penetrate to a substantial depth into the wood (at least 0.3 cm); 2) effectively repel both incoming precipitation water and outgoing internal CCA solution water; and 3) seal surface fractures so that such fractures do not continue to expand more deeply into the lumber, thereby exposing (and allowing water access to) new CCA salt. It is visually apparent that currently available water sealers, water repellents and oil- or water-based stains effectively repel water, at least for a time, but they are not designed to seal larger cracks or fissures, especially when applied to highly weathered CCA lumber. Conventional outdoor deck paints, on the other hand, seal surface cracks and fissures very effectively, but by their more viscous and particulate nature, they do not provide the necessary penetrating water repellent layer once the paint surface begins to crack from weathering or from foot/hand abrasion. While it is theoretically possible to produce a treatment mixture wherein individual chemical components might possess each of these necessary properties, it seems more likely that the desired long-term results would be best achieved by a two-step As containment system. This would probably entail an initial penetrant/water repellent application followed perhaps several hours later by a surface crack-sealing flexible coating. At least two of the experimental products we are currently testing meet this general description, and it will be most interesting to observe experimentally over the next 1-2 years how they perform relative to public health needs and compared to currently-available products. IV. CONCLUSIONS The three studies discussed in this paper are all still in progress, and they should provide a better understanding of the dynamics of arsenic exposure from CCA lumber as they are continued and completed in the near future. However, a considerable body of knowledge related to dislodgement of As from CCA lumber has already become evident from these and other studies. Our national field survey study shows clearly that a high percentage of actual in-service CCA lumber is still releasing high levels of As upon contact. Statistically, the amount of As dislodged does not decrease over time following an initial period of weeks or a few months during which a 40-70% decrease is observed. All types of CCA structures show similar As dislodgement levels, with structures from the Northwest part of the US having the highest levels. Overall, water sealers and water-proofing compounds appear on average to be effective in reducing potential As exposure for


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30

only about six months, while there is preliminary evidence that stains and paints generally show some effectiveness for at least two years. Our experiments show that standard laboratory wipes probably overestimate actual hand contact dislodgement by a factor between about six and 15 depending on the moisture condition of the hand and of the area wiped. The relationship is rather complex and needs further controlled study to better estimate human As exposure from CCA lumber. The amount of As dislodged and transferred by hand contact appears to be approximately linear over a range of 0.5 ft2 to 8.0 ft2 of lumber surface area. Although the manufacture and sale of CCA lumber has now been curtailed in the US, there exists an important public health need to develop sealant materials which can greatly reduce As dislodgement from existing CCA structures for periods of time up to a decade or more. We are currently testing a number of such experimental materials, and from our experience and observations, we believe that the most effective materials will be ones that contain both a penetrating water repellent as well as a surface fracture sealant. V. REFERENCES 1. US Consumer Product Safety Commission, Briefing package: Petition to ban chromated copper arsenate (CCA)-treated wood in playground equipment (Petition HP 10-3), Washington: US Consumer Product Safety Commission, February 2003. 2. National Research Council (NRC), Arsenic in drinking water: 2001 update, subcommittee to update the 1999 arsenic in drinking water report, Committee on Toxicology, Board on Environmental Studies and Toxicology, Washington: National Academy Press, 2001. 3. Chiou, H.Y., et al., Incidence of transitional cell carcinoma and arsenic in drinking water: A follow-up study of 8,102 residents in an arseniasis-endemic area in northeastern Tiawan, Am. J. Epidemic., 2001, 153, 411. 4. Agency for Toxic Substances and Disease Registry (ASTER), Toxicological profile for arsenic, Atlanta: US Department of Health and Human Services, Public Health Service, September 2000. 5. Moore, et al, Arsenic-related chromosomal alterations in bladder cancer, J. Natl. Cancer Inst., 2002, 94, 1688. 6. Read, D., Report on copper chromium and arsenic (CCA) treated timber, Environmental Risk Management Authority of New Zealand, 2003. 7. Roberts, S.M. and Ochoa, H., Letter to Division of Waste Management, Florida Department of Environmental and Human Toxicology, University of Florida, 10 April 2001. 8. Gradient Corporation, Evaluation of human health risks from exposure to arsenic associated with CCA-treated wood, Cambridge, Massachusetts, October 2001. 9. Sharp, R., et al., The Poisonwood rivals, a report on the dangers of touching arsenic treated wood, Washington, DC: Environmental Working Group and Healthy Building Network, November 2001. 10. Maas, R.P., et al., Release of total chromium, chromium (VI) and total arsenic from new and aged pressure treated lumber, University of North Carolina-Asheville, Environmental Quality Institute, Technical Report 02-093, February 2002. 11. NIOSH, Lead by Flame AAS, Modified method 7082, NIOSH Manual of Analytical Methods, 4th Edn., 1998. 12. Maas, R.P.; Patch, S.C. and Berkowitz, J.F., Research update on health effects related to use of CCA treated lumber, Chemistry in New Zealand, 2003, 25-31. 13. Stillwell, D.E. and Gorny, R., Contamination of soil with chromium and arsenic under decks built from pressure-treated wood, Bull. Environ. Contam. Toxicol., 1997, 58. 22.


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14. Tyrell, E.A., Project report: Playground equipment – transmittal of estimate of risk of skin cancer from dislodgeable arsenic on pressure treated wood playground equipment, US Consumer Product Safety Commission, Washington, DC, August 2000. 15. Dang, W. and Chen, J., A probabilistic risk assessment for children who contact CCA-treated playsets and decks, draft preliminary report, November 10, 2003.


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32

Effects of CCA Wood on Non-Target Aquatic Biota

Judith S. Weis, Peddrick Weis

Department of Biological Sciences, Rutgers University, Newark, NJ 07102 Department of Radiology, UMDNJ – New Jersey Medical School, Newark NJ 07103

Abstract; Studies are reviewed that demonstrate the leaching of Cu, Cr, and As from pressure-treated wood in aquatic environments. The metals leached out accumulate in sediments near the wood (particularly bulkheads, which have more surface area for leaching than dock pilings). The metals also accumulate in organisms, including epibiota that live directly on the wood and benthic organisms, which live in sediments near the wood. Those inhabiting sediments closer to the wood accumulate higher levels of the contaminants. Other animals can acquire elevated levels of these metals indirectly as a result of consuming contaminated prey (trophic transfer). Once organisms have accumulated metals, they may exhibit toxic effects. Effects of CCA leachates in aquatic biota have been noted at the cellular level (e.g. micronuclei, indicating DNA damage), tissue level (e.g. pathology), individual organism level (e.g. reduced growth, altered behavior, and mortality), and community level (reduced number of individuals, reduced species richness, and reduced diversity). Effects are more severe in poorly flushed areas and in areas where the wood is relatively new. Residential canals lined with CCA wood are particularly toxic. The severity of effects is reduced after the wood has leached for a few months. Deleterious effects in the aquatic environment appear to be due largely to copper. Thus, alternative formulations that lack Cr and As due to concerns about their toxicity to humans, but contain greater amounts of Cu and leach more Cu will be more deleterious than CCA to the aquatic environment. Keywords: leaching, uptake, accumulation, toxic, pathology


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33

INTRODUCTION:

As shorelines are developed, many wooden structures such as bulkheads and pilings have

been placed in marshes and estuaries. Many of these structures have been made of chromated copper arsenate (CCA) treated wood, which contains high quantities (<2.5 lbs/cubic foot) of the toxic metals Cu, Cr, and As, to prevent rotting and boring by invertebrates. The wood is impregnated under pressure with a mixture of these metal salts, and the components can react with lignocellulose in the wood to form insoluble compounds, a process known as fixation. Even when wood has been properly preserved, some quantities of these toxic metals leach out into the ecosystem, especially when the wood is new. Increased drying time has been found to reduce the leaching of metals from the wood [1](Hingston et al. 2002). Many studies have focused on leaching and factors that can affect the rate of leaching [2](Hingston et al., 2001). Factors of importance during the treatment process were the fixation time and formulation (ratio of preservative components), wood anatomy (softwood species high in lignin perform better than hardwoods), preservative treatment including temperature, and loading (concentration of treatment solution). Factors in the environment into which the wood leaches include salinity (higher salinity causes greater leaching), pH (high leaching at low pH), and temperature (higher leaching at higher temperature. The rate of leaching can be affected by the amount of time the wood has been leaching. Breslin and Adler-Ivanbrook [3] found that after 90 days of leaching, the rate of release decreased between 0.5 and 2 orders of magnitude. Archer and Preston [4] found that CCA-treated pine leached up to 25% of total active ingredients within six months, with total losses of 52% after 85 months.

A series of studies in the 1990s demonstrated that both in the lab and in the natural

environment, the metals leached out from the wood accumulated in nearby sediments and biota. Of the three metals, Cu leaches most [5] (Warner and Solomon, 1990) and is the most toxic to marine and freshwater organisms [6] (Weis et al., 1991). Metals accumulated in nearby sediments and benthos, and adverse effects in the benthic organisms (such as polychaete worms and bivalves) adjacent to treated wood bulkheads have been noted. Accumulation and effects were especially severe in areas that were not well flushed by tidal action [7,8] (Weis and Weis, 1994, Weis et al., 1998).

In this paper we review information about uptake and accumulation of the metals leached

from CCA wood in sediments and organisms, and the toxic effects that have been examined at different levels of biological organization. UPTAKE:

In order to have a biological effect contaminants generally must be taken up into organisms, a process known as bioaccumulation. Once inside an organism, the contaminants may concentrate in particular organs and thus exert their effects. Measurements of bioaccumulation are standard parts of field assessments of environmental contamination. Uptake of Cu, Cr, and As has been studied in sediments and organisms living in the vicinity of CCA treated wood. Sediments: A mass balance in a freshwater lake in Virginia indicated that leaching of CCA-treated lumber was responsible for a large percentage of the overall levels of As in lake sediments [9] (Rice et al.,


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34

2002). Sediments have been studied that are adjacent to and at varying distances from CCA-treated wood bulkheads in estuaries. Metals leached from the wood accumulated in the fine particle fraction of the sediments, and were highest right at the wood and gradually declined further away [10]. Sediments adjacent to bulkheads in the northeast US generally had very low percentages of fine particles (silt and clay) but very high concentrations of the metals on these particles. Bulk sediment analysis would show low contamination because of the small percent of fine particles, however. Sediments further away from the bulkheads, and thus in deeper water, had higher percentages of fine particles but lower concentrations of the contaminants on them. Levels of copper were generally higher than the other two metals. Higher metal concentrations were seen in sediments in poorly flushed areas than in more open water environments. The degree of elevation of metals in the sediments was affected by the amount of water movements, the nature of the sediments (how much was fine particles) and the age of the wood [8]. Sediments in the Gulf Coast remained 99% sand, even 10 m out, so that while bulk sediment analysis would indicate low contamination, the fine particles were highly contaminated, showing the highest levels right by the CCA bulkhead (Figure 1). Similar analyses by dock pilings in moderately flushed environments did not show accumulation of the metals in the immediate vicinity of the pilings, presumably because they have less surface area for leaching.

Sediment contamination was also seen under and adjacent to CCA boardwalks (walkways) over salt marshes, and again the age of the wood was a major factor affecting the degree of contamination [11]. Metal concentrations were highly elevated under the walkways and up to 10 m away. This study is similar to that of Stillwell and Gorny [12] who studied contamination of soil under decks, with the difference that in tidal marshes leaching during rainfall sometimes occurs when the walkway is over water (at high tide), which will cause greater dispersion of the leachates. Dispersal of contaminants near an old walkway was greatest in the low marsh, less in the middle, and least in the high marsh, corresponding to the relative periods of tidal inundation. Accumulation under the walkway was generally greatest in the low marsh. Contamination was much higher in sediments under a new walkway than an old one, but metals had not dispersed as far.


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35

Figure 1: Concentrations of Cr, Cu, and As in Sediments by a CCA Bulkhead Organisms: Epibiota: The organisms that live attached to the wood are the organisms in which the greatest uptake would be expected. These are referred to as epibiota or the “fouling community.” Green algae growing on treated wood in Long Island NY had about four times as much copper, twice as much Cr and five times as much As as algae from nearby rocks [13]. Red algae growing on a bulkhead in open water in the Gulf Coast of Florida had three times as much Cu, and two times as much As as those from nearby rocks, while those living inside a canal lined with CCA wood had much higher concentrations. The same phenomenon was seen with barnacles: those on rocks had about 1 ug g-1 Cu, while those on the open water CCA dock had 3 ug g-1, those in the canal had about 10 ug g-1 and those attached to new wood inside that canal had about 80 ug g-1 [14]. This again indicates greater leaching and accumulation from new wood and in areas with less water movement. Oysters (Crassostrea virginica) inside the canal had highly elevated copper levels (over 150 ug g –1), a 12-fold increase over controls, and were frequently greenish in color. Other metals did not accumulate in oysters to such a degree: arsenic concentration was about 2x that of controls. There was a negative correlation of copper level with oyster weight, indicating the concentrations are diluted as the animals grow [15]. This may have negative implications for predators that preferentially eat smaller more vulnerable oysters, since these are the ones with the highest metal concentrations. Green oysters have been previously noted in Taiwan, where they had accumulated copper from industrial sources [16] and were considered a public health risk because they had acquired copper levels far exceeding international limits for human consumption. The marine isopods Limnoria spp. (gribbles) bore through wood, including CCA treated wood, for protection and as a source of food. This is ironic, since one of the reasons for the use of wood preservatives is to prevent damage by marine borers. They can tolerate the high concentrations of metals by storing copper in granules in their digestive caecae. An increased number of copper-containing granules was seen in isopods from CCA treated wood compared to those from untreated wood. The ability to store copper in granular form which is inert may explain why this organism can bore through and consume CCA wood without suffering toxic effects [17]. Arsenic and chromium were not elevated in these granules or in digestive caecal cells, however. Benthic organisms:

Bioavailability of sediment-associated metals depends on a large number of factors

including metal speciation, the degree of binding to the sediments, the degree of oxidation or reduction of the sediments, and the pH. Metals tightly bound to fine particles in the reduced state are believed to play a minor role in toxicity, while those in pore waters are considered more responsible for uptake and toxic effects. Benthic organisms living in sediments contaminated by CCA wood bulkheads have been found to have elevated levels of metals. Fiddler crabs (Uca pugilator) from intertidal burrows near CCA bulkheads had metal levels about double that of controls [13]. Metals in subtidal benthic worms living adjacent to a bulkhead in the Gulf Coast of Florida were also elevated, and the levels decreased with distance from the bulkhead [7]. The levels in the benthic organisms generally paralleled the levels in the sediments in which they lived [8].


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36

Saltmarsh plants (Spartina alterniflora, S. patens, and Phragmites australis) living under and near CCA walkways in Delaware were analyzed for metals together with the afore-mentioned sediments. Accumulation patterns in plants were similar to those in the marsh sediments, but the elevation of metal concentrations did not disperse as far and was not greater under the new vs the old walkway, despite the great differences in sediment concentrations [11]. In ribbed mussels (Geukensia demissa) collected from these locations, bioaccumulation was seldom statistically significant, due largely to small sample sizes. Additional work is needed to further investigate detritus feeding invertebrates in salt marshes under walkways. Trophic Transfer: Animals need not be directly exposed to the source of contamination (i.e. CCA wood) to accumulate contaminants from it. They may be exposed indirectly, via their food. Trophic transfer is considered the major mechanism for contaminant accumulation in larger organisms higher up in the food web. A number of motile animals such as grass shrimp, amphipods, gobies etc. are frequently found associated with wood in the field, probably feeding on the epibiota. This provides a mechanism for contaminants to pass into the food web. Experiments were done in which algae (Ulva lactuca and Enteromorpha intestinalis) collected from CCA wood or from rocks were fed to mud snails (Ilyanassa obsoleta). The snails took up contaminants (largely Cu) from the algae and suffered harmful effects [13]. Chromium in Enteromorpha was transferred to the herbivorous rabbitfish, Siganus canaliculatus, through feeding [18].

Figure 2. Metal accumulation in snails fed oysters from CCA bulkhead and a reference site, and in snails collected from a CCA bulkhead.


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37

Another lab study fed oysters (Crassostrea virginica) collected from CCA wood to Thais haemastoma, a carnivorous snail. Control snails were fed oysters collected from rocks at a reference site. The experimental snails increased their body burden of copper about four-fold over an eight week experiment (Figure 2), and attained Cu levels comparable to that of snails collected in the field from a CCA bulkhead (>150 ug g-1). Juvenile fish (spot Leiostomus xanthurus and pinfish, Lagodon rhomboides) were collected from inside and outside a CCA-lined canal. Those inside the canal had about 5 times as much Cu and 7 times as much As as reference fish. It is likely that these body burdens were obtained at least partly from their food [19]. A field experiment was performed in which organisms were caged along with CCA and untreated wood with epibiota for three months. The epibiota on treated panels had elevated Cu and As compared to epibiota on untreated wood, and amphipods caged with the treated wood developed elevated Cu. However, caged grass shrimp (Palaemonetes pugio), naked gobies (Gobiosoma bosci) and mummichogs (Fundulus heteroclitus) did not accumulate elevated levels of the metals. Thus, trophic transfer was seen only for the amphipods. Fish may have a more efficient mechanism for regulating metal levels in their tissues [20]. TOXICANT EFFECTS: Toxicant effects can be studied at many levels of biological organization. Initially, toxic chemicals interact with molecules inside cells of organisms. Effects can move from biochemical to cellular to tissue, to organ to individual organism to population to community to ecosystem. Understanding effects at one level of organization may provide insights into effects at higher levels of organization. Research into impacts of leachates from pressure-treated wood in the aquatic environment has examined effects on cellular level, to individuals, populations, and communities. Cell Level: Oysters (Crassostrea virginica) living inside a canal in the Gulf Coast of Florida lined with CCA wood bulkheads were found to have twice as many micronuclei in gill cells as reference oysters [21], indicating that there are DNA-damaging contaminants at the site (Figure 3). When control oysters were transplanted into the canal for three months, the number of micronuclei increased significantly [21]. Both chromium and arsenic are known to be genotoxic [22, 23]. The form of Cr used in wood treatment is Cr (VI), which is highly genotoxic.

Bacteria that normally degrade pentachlorophenol (Flavobacterium sp. strain ATCC 53874) play an important role in degrading and waste removal of this other chemical used as a wood preservative. When these bacteria were exposed to CCA, which often occurs in the same places as pentachlorophenol (i.e., wood treatment facilities) their ability to degrade the PCP was inhibited. Inhibitory effects were seen in this laboratory study at concentrations thousands of times less than those used commercially [24]. Both a commercially available and a laboratory prepared CCA solution inhibited the growth of these environmentally beneficial and important bacteria, even at low concentrations [25].


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Figure 3. Micronucleus in cells of oysters from a CCA lined canal, on left.

Figure 4. Pathology of digestive gland in oysters on CCA wood. On left is normal oyster digestive gland diverticula, and on right severe change in CCA oysters with dilation of lumina and loss of cell height. Tissue Level: The oysters living inside the CCA-lined canal in Florida also had an elevated incidence of a pathological atrophic condition of the digestive diverticula (Fig. 4) [15] P. Weis et al., 1993c). This pathology had previously been noted in oysters exposed to a variety of stressors including copper [26]. The condition did not appear, however, in control oysters transplanted into the canal site for 3 months, during which time they attained about two-thirds of the copper level of the canal oysters. Individual Organisms: Effects on individual organisms have been studied both in laboratory toxicity tests and in organisms in the field. There have been numerous lab tests on effects of each of the three metals individually, but there has been relatively little work on effects of treated wood leachates. In fresh water subject to simulated acid rain, the copper leached was far in excess of the lethal level for Daphnia magna


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[27]. The LC50 for this species is about 0.036 mg Cu l-1 which is only about 2% of the leachate concentration. Leachates from treated wood from different tree species all failed LC50 tests using fish [28].

The toxicity of leachates depends on the volume of water in which they are leaching, and the length of time the wood has been leaching. New wood leaches the fastest and is therefore the most toxic. Wood leachates were toxic to fiddler crabs (Uca pugilator), green algae (Ulva lactuca), fish (Fundulus heteroclitus) embryos, and sea urchin (Arbacia punctulata) sperm and embryos [6, 29]. The toxic effects of wood that had already leached for several weeks were much less severe. Sublethal effects observed included bleaching of the green algae, reduced fertilization and inhibition of larval development in sea urchins, and retardation of regeneration and molting in the fiddler crabs. One of the most sensitive organisms was the mud snail, Ilyanassa obsoleta, which upon exposure to leachate retracted into their shells and became inactive on the bottom of the tank. If they were placed back in clean water, they recovered, but if they remained in water with CCA leachates, they died after several days. Studies using individual metals or combinations of metals indicated that the algae bleaching and the snail mortality was due to copper. This phenomenon of retraction into the shell has been reported for other gastropods after copper exposure [30, 31]. When mud snails were fed green algae, Ulva or Enteromorpha, collected from CCA wood or from rocks, the snails consuming the algae from the treated wood retracted and died over a four week period. This indicates that trophic transfer of the contaminants can be responsible for this potentially lethal response to copper [13].

In the experiment described earlier in which carnivorous snails (Thais haemastoma) were

fed oysters (Crassostrea virginica) from a CCA-lined canal, their consumption rate gradually decreased over an eight-week period compared to snails feeding on control oysters. These snails grew significantly less than the snails feeding on control oysters, and increased their body burden 4-fold over this period of time [19]).

Laboratory bioassays of leachate were performed on larval oysters (Crassostrea gigas) to investigate behavioral responses [32]. Early veliger stage larvae were observed to avoid concentrated leachate, and 3- and 7-day old larvae swam faster in leachate than in clean sea water and moved up and down more in the leachate. This altered behavior may retard settlement of the larvae to metamorphose into adults, and may be involved with reducing the numbers of organisms that settle on the CCA wood (see below). Communities: Epibiotic Community:

Epibiota are species that settle and attach themselves to hard structures in aquatic environments. When boards of CCA and untreated wood were placed into an estuary in Long Island NY and examined for settlement on a monthly basis, treated wood had a reduced number of species, lower diversity index, fewer barnacles and reduced growth of those barnacles that did settle. One species of bryozoan, Bugula turrita, was found to grow at greater density on the treated wood [33]. When the epibiota were removed and the same boards placed back in the estuary, the epibiota settling subsequently on the CCA wood had less of a difference from control community, indicating that the toxicity of the wood was reduced after having soaked for a period of time. The third time there were no statistically significant differences between the community on the CCA


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wood and the control panels [34]. However, differences in the growth of certain species including the green alga Enteromorpha and the bryozoan Conopeum were still observed.

Brown and Eaton [35] assessed the epibiotic community on panels of treated and control

wood after 6, 12 and 18 months. They found similar species richness on the CCA and the control panels, although the number of individuals was higher on CCA wood due to higher numbers of certain dominant species (Elminus modestus, Hydroides ezoensis and Electra pilosa) on the CCA wood, which caused the diversity index to decrease. The relative lack of impact seen in this study compared to the previous ones is probably due to the effects being seen in relatively short one-month exposures coinciding with the higher leaching rates, contrasted with the six-month or longer exposure in this study, by which time leaching had probably decreased. Benthic Community: The benthic community in sediments adjacent to bulkheads was reduced in species richness, total numbers of organisms, and diversity compared to reference sediments with lower metal concentrations. The physical characteristics at the sites studied were very similar as was the water depth. The reduction was greater inside a CCA-lined canal compared with an open water CCA bulkhead, but both were significantly less than the number of species, number of organisms and diversity at the reference site (Figure 5) [7]. Within the canal, only two species were found in sediments by the bulkheads, the polychaete worms Neanthes succinea and Hobsonia florida. A follow-up study was performed to see the spatial extent of the benthic impacts at different distances from the bulkheads. Sediments and organisms were collected at CCA bulkheads and at 1, 3, and 10 m out from them at five different sites in the Atlantic coast from New York to South Carolina. Reference areas were bulkheads made of other materials or unbulkheaded areas nearby. At most sites, effects (reduced community) were seen at 1 m but not at 3 or 10. At two of the sites, however, effects were seen at 3 or 10 m where the metal concentrations in the fine particles were less, but the percent of fine particles was greatly increased [8]. Differences in the spatial extent of impacts were attributed to the age of the bulkheads, the energy of the environment, and the nature of the sediments at the different sites. A number of sites with docks rather than bulkheads were examined, and these did not demonstrate accumulation of metals in sediments adjacent to pilings or any consistent differences in benthic communities. It appears that leachates from pilings in reasonably well-flushed areas do not have negative effects in the immediate vicinity. Wendt et al. [35] studying docks in the very well flushed ACE Basin also did not find effects of CCA dock pilings.


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Figure 5. Species richness, number of individuals, and diversity index in sediments from a CCA-lined canal, open water bulkhead, and reference site. Ecosystem: To our knowledge there have not yet been any studies on ecosystem level impacts in aquatic environments. However, a few studies on terrestrial soil ecosystems have been reported. Microbes in CCA-contaminated soils in the field have been shown to be negatively affected [37]. Microbial biomass carbon and nitrogen were lower in contaminated soils. Bacterial respiration, biomass P, and denitrification all declined with increasing CCA contamination. Soil biological activity including respiration, nitrification and sulphatase was found to be reduced in pasture soils contaminated by CCA timbers [38]. CONCLUSIONS:

The recent attention devoted to CCA wood and the recent restrictions posed by the EPA are because of potential risks to humans from playground equipment and decks. Nevertheless, there have been many documented (rather than potential) deleterious effects seen in many types of aquatic organisms, not just in the laboratory where concentrations may be greater than field situations, but in the field at many sites. The effects are greater in poorly flushed areas and when the wood is new. The environmental impact of CCA wood could be reduced considerably if it could be soaked out for a few months before being put on the market. The water into which it leached could then be recycled by being pressure-treated into new pieces of wood.

Most of the harmful effects of CCA wood in the aquatic environment seem to be due

largely to the copper, rather than the arsenic, which is the main concern in the human health field.


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There will continue to be pressure to reduce the use of Cr and As in treated wood preservative formulations. Substitute formulations of treated wood are being developed that do not contain arsenic, but contain greater amounts of copper than traditional CCA does and leach more copper than CCA wood [39]. Many well-meaning people are likely to want to use these products instead of CCA for structures in or near the water, as well as for decks and playgrounds, on the assumption that they are safer than CCA. While these new formulations are preferable for such terrestrial uses, they will be a much greater environmental risk for aquatic environments than CCA is, and they should come with warnings that they should not be used in or near the water. ACKNOWLEDGEMENTS Research was supported in part by NOAA Estuarine Reserves, USEPA. Research Lab, Gulf Breeze Florida, US Geological Service- Water Resources Research Institute Program, the PADI Foundation and NJ Sea Grant. REFERENCES: [1] Hingston, J.A., J. Moore, A. Bacon, J.N. Lester, R.J. Murphy & C.D. Collins 2002. The importance of the short-term leaching dynamics of wood preservatives. Chemosphere 47: 517-523. [2] Hingston, J.A., C.D. Collins, R.J. Murphy & J.N. Lester 2001. Leaching of chromated copper arsenate wood preservatives: a review. Environ. Pollut. 111: 53-66. [3] Breslin, V.T. & L. Adler-Ivanbrook 1998. Release of copper, chromium and arsenic from CCA-C treated lumber in estuaries. Estuar. Coast. Shelf Sci. 46: 111-125. [4] Archer, K., & A. Preston 1994. Depletion of wood preservatives after four years’ marine exposure in Mt. Maunganui Harbour, NZ (IRG/WP94-50036). The International Research Group on Wood Preservation, Stockholm. [5] Warner, J.E. & K.R. Solomon 1990. Acidity as a factor in leaching of copper, chromium and arsenic from CCA-treated dimension lumber. Environ. Toxicol. Chem. 9: 1331-1337. [6] Weis, P., J.S. Weis & L.M. Coohill (1991). Toxicity to estuarine organisms of leachates from chromated copper arsenate treated wood. Arch. Environ. Contam. Toxicol. 20:118-124. [7] Weis, J.S. & and P. Weis (1994). Effects of contaminants from chromated copper arsenate-treated lumber on benthos. Arch. Environ. Contam. Toxicol. 26:103-109. [8] Weis, J.S., P. Weis & T. Proctor (1998). The extent of benthic impacts of CCA-treated wood structures in Atlantic coast estuaries. Arch. Environ. Contam. Toxicol. 34:313-322. [9] Rice, K., K.M. Conko & G.M. Hornberger 2002. Anthropogenic sources of arsenic and copper to sediments in a suburban lake, Northern Virginia. Environ. Sci. Technol. 36: 4962-4967. [10] Weis, P., J.S. Weis & T. Proctor 1993. Copper, chromium, and arsenic in sediment adjacent to wood treated with chromated-copper-arsenate. Estuar. Coast. Shelf Sci. 36: 71-79. [11] Weis, J.S. & P. Weis 2002. Contamination of saltmarsh sediments and biota by CCA treated wood walkways. Mar. Poll. Bull. 44: 504-510. [12] Stilwell, D.E. & K.D. Gorny 1997. Contamination of soil with copper, chromium and arsenic under decks built from pressure treated wood. Bull. Environ. Contam. Toxicol. 58: 22-29. [13] Weis, J.S. & P. Weis (1992). Transfer of contaminants from CCA-treated lumber to aquatic biota. J. Exp. Mar. Biol. Ecol. 161:189-199. [14] Weis, P., J.S. Weis & E. Lores (1993). Uptake of metals from chromated-copper-arsenate (CCA)-treated lumber by epibiota. Mar. Pollut. Bull. 26:428-430.


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[15] Weis, P., J.S. Weis, & J. Couch (1993). Histopathology and metal uptake in oysters (Crassostrea virginica) living on wood preserved with chromated copper arsenate. Dis. Aquat. Org. 17:41-46. [16] Han, B-C., W.-L. Jeng, T.-C. Hung & M.-S. Jeng 1994. Copper intake and health threat by consuming seafood from copper-contaminated coastal environments in Taiwan. Environ. Toxic. Chem. 13: 775-780. [17] Tupper, C., A.J. Pitman & S.M. Cragg 2000. Copper accumulation in the digestive caecae of Limnoria quadripunctata Holthuis (Isopoda: Crustacea) tunnelling CCA-treated wood in laboratory cultures. Holzforschung 54: 570-576. [18] Chan, S.M., W.-X. Wang & I.-H. Ni 2003. The uptake of Cd, Cr, and Zn my the macroalga Enteromorpha crinita and subsequent transfer to the marine herbivorous rabbitfish, Siganus canaliculatus. Arch. Environ. Contam. Toxicol. 44: 298-306. [19] Weis, J.S. & P. Weis (1993). Trophic transfer of contaminants from organisms living by chromated-copper-arsenate (CCA)-treated wood to their predators. J. Exp. Mar. Biol. Ecol. 168:25-34. [20] Weis, P. & J.S. Weis 1999. Accumulation of metals in consumers associated with chromated copper arsenate-treated wood panels. Mar. Environ. Res. 48: 73-81. [21] Weis, P., J.S. Weis, J. Couch, C. Daniels & T. Chen 1995. Pathological and genotoxicological observations in oysters (Crassostrea virginica) living on chromated copper arsenate (CCA) treated wood. Mar. Environ. Res. 39: 275-278. [22] Nakamuro, K. & Y. Sayato 1981. Comparative studies of chromosomal abberration induced by trivalent and pentavalent arsenic. Mutat. Res. 88: 73-80. [23] Tkeshelashvili, L.K., C.W. Shearman, R.A. Zakour, R.M. Koplitz & L.A. Loeb 1980. Effects of arsenic, selenium and chromium on the fidelity of DNA synthesis. Cancer Res. 40: 2455-2460. [24] Wall, A.J. & G.W. Stratton 1994. Effects of a chromated-copper-arsenate wood preservative on the bacterial degradation of pentachlorophenol. Can. J. Microbiol. 40: 388-392. [25] Wall, A.J. & G.W. Stratton 1995. Effects of a chromated-copper-arsenate wood preservative on the growth of a pentachlorophenol degrading bacterium. Water, Air and Soil Pollut. 82: 723-737. [26] Couch, J. 1984. Atrophy of diverticular epithelium as an indicator of environmental irritants in the oyster Crassostrea virginica. Mar. Environ. Res. 14: 525-526. [27] Buchanan, R.D. & K.R. Solomon 1990. Leaching of CCA-PEG and CuNap wood preservatives from pressure-treated utility poles, and its associated toxicity to the zooplankton Daphnia magna. Forest Prod. J. 40: 130-143. [28] Envirochem Special Projects Inc. 1992. Evaluation of leachate quality from CCA preserved wood products. Environment Canada, Pacific and Yukon Region, North Vancouver British Columbia and British Columbia Ministry of Environment, Surrey, British Columbia, Canada. [29] Weis, P., J.S. Weis, A. Greenberg & T. Nosker 1992. Toxicity of construction materials in the marine environment: A comparison of chromated-copper-arsenate-treated wood and recycled plastic. Arch. Environ. Contam. Toxicol. 22: 99-106. [30] Glude, J.B. 1957. Copper, a possible barrier to oyster drills. Proc. Natl. Shellfish. Assoc. 47: 73-82. [31] Harry, H.W. & D.V. Aldrich 1963. The distress syndrome in Taphius glabratus (Say) as a reaction to toxic concentrations of inorganic ions. Malacologia 1: 283-289. [32] Prael, A., S.M. Cragg & S.M. Henderson 2001. Behavioral responses of veliger larvae of Crassostrea virginica to leachate from wood treated with copper-chrome-arsenic (CCA): a potential bioassay of sublethal environmental effects of contaminants. J. Shellfish Res. 20: 267-273. [33] Weis, J.S. & P. Weis (1992). Construction materials in estuaries: reduction in the epibiotic community on chromated copper arsenate-treated wood. Mar. Ecol. Prog. Ser. 83:45-53.


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[34] Weis, J.S. & P. Weis 1996. Reduction in toxicity of chromated copper arsenate (CCA)-treated wood as assessed by community study. Mar. Environ. Res. 41: 15-25. [35] Brown, C.J. & R. A. Eaton 2001. Toxicity of chromated copper arsenate (CCA)-treated wood to non-target marine fouling communities in Langstone Harbour, Portsmouth, UK. Mar. Pollut. Bull. 42: 310-318. [36] Wendt, P.H., R. F. Van Dolah, M.Y. Bobo, T.D. Mathews & M.V.Levison 1996. Wood preservative leachates from docks in an estuarine environment. Arch. Environ. Contam. Toxicol. 31: 24-37. [37] Bardgett, R.D., T.W. Speir, D.J. Ross, G.W. Yeates & H.A. Kettles 1994. Impact of pasture contamination by copper, chromium, and arsenic timbers preservative on soil microbial properties and nematodes. Biol. Fertil. Soils 18: 71-79. [38] Yeates, G.W., V.A. Orchard, T.W. Speir, J.L. Hunt & M.C. Hermans 1994. Impact of pasturecontamination by copper, chromium, and arsenic timber preservative on soil biological activity. Biol. Fert. Soils 18: 200-208. [39] Townsend, T., K. Stook, M. Ward and H. Solo-Gabriele 2003. Leaching and toxicity of CCA-treated and alternative treated wood products. Final Tech. Rept. #02-4. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL.


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Retention of As, Cu, and Cr leached from CCA-treated wood products in select Florida soils

Tait Chirenje1*, L.Q. Ma2, M. Szulczewski2, K. Hendry2 and C. Clark3

1B108 NAMS, Richard Stockton College of New Jersey, PO Box 195, Pomona, NJ 08240; Phone: 609 652 4588, Fax: 609 748 5515

[email protected] (corresponding author) 2Soil and Water Science Department, University of Florida

Gainesville, FL 32611-0290, Ph: 352 392 1951 ext 215, Fax 352 392 3902 3Civil and Coastal Engineering Department, Gainesville, FL 32611, Ph: 352 392 9537 x 1441

Abstract

Up until recently, the use of chromated copper arsenate (CCA)-treated wood had been growing steadily in the United States. Chromated copper arsenate treatment arrests microbial and fungal decay of wood products. Due to the scale of the wood preserving industry, CCA-treated timber may form a significant source of the trace elements: chromium (Cr), copper (Cu), and arsenic (As), to the environment. The aim of this study was to determine the retention of As, Cu and Cr in common soil types in Florida. Soil samples from six soil groups (Histosols, Entisols, Alfisols, Ultisols, Spodosols and Marls) were collected from across the state. Profile samples were collected, with emphasis on surface and diagnostic subsurface horizons, where applicable. Column sorption and desorption studies conducted to determine the retention of leachates from construction and demolition debris-packed columns showed that fine textured soils had the largest retention capacity for Cu, Cr and As. Horizons in which large quantities of soil organic matter (SOM), fine clay, iron (Fe) and aluminum (Al) compounds accumulate had higher retention capacity of Cu, Cr and As than horizons lacking in these components. There were very little differences between surface horizons of all soil types, with the exception of Histosols, which are organic in nature, and Marls. Although the concentrations of the three elements in CCA-treated wood were not very different from each other, As leached out of the wood the most, with leachate concentrations at least an order of magnitude higher than those of Cr and Cu. These results are helpful for CCA-treated wood product users as a reference to determine the leaching potential CCA components from the most common soil groups of Florida.

Abbreviations:CCA, chromated copper arsenate, OC, organic carbon, SCTL, soil clean-up target level; SOM, soil organic matter; MDL, method detection limit

Keywords: CCA-treated wood, natural, anthropogenic background


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Introduction

Untreated wood products do not last long because they are prone to fungal, bacterial and termite attacks. Consequently, differently treated wood products have found their way into the lumber market. Pressure treated wood products have gained popularity because of their durability, especially in warm humid climates like Florida. The most commonly used water based pressure treatment is chromated copper arsenate (CCA), where the copper (Cu) acts as a fungicide and the arsenate, an insecticide (Dawson et al., 1991). Chromium (Cr) is used to fix the other two elements to the cellulose and other components of the wood. Arsenic is generally used in two anionic forms, arsenite [As(III)] and the more mobile arsenate [As(V)]. Copper exists mostly in the cationic form Cu2+, and although Cr is a cation, it commonly exists in two anionic forms, the more mobile and toxic chromate ions from Cr(VI), and the less mobile and toxic Cr(III).

The use of CCA-treated wood products invariably leads to the release of the

constituent elements, arsenic (As), Cr, and Cu and their compounds into neighboring soils (Carey et al., 1996; Cooper and Ung, 1997; Lebow, 1996; Stilwell and Gorny, 1997; Solo-Gabriele et al., 2000). The mobility and retention of these CCA constituents is governed by the form they are released in. A considerable number of studies have shown significantly elevated metal concentrations near CCA-treated decks compared to background concentrations (Stilwell and Gorny, 1997; Chirenje et al., 2003b). Arsenic, Cr and Cu concentrations as high as 550, 200, and 1,000 mg kg-1, respectively have been reported in the vicinity of utility poles (Cooper and Ung, 1997). Other studies have also looked at the effects of CCA-treated wood in aquatic systems due to the proliferation of both residential and public decks in coastal waterways (Hingston et al., 2001).

While the extent of release of As, Cu and Cr from in-service CCA-treated wood

products and its contribution to environmental quality degradation is still a matter of great debate, it is generally agreed that the release of CCA constituents is governed by many factors. These include (i) the nature and surface area of the wood (Solo-Gabriele et al., 2000), (ii) the type (A, B, or C) and retention factor (0.25 to 2.5 lb ft-3, depending on whether it is aboveground, marine or belowground; Hingstrom et al., 2001) of the CCA, (iii) climatic conditions (temperature, humidity and rainfall; Chirenje et al., 2003b), and (iv) soil factors (texture, pH, organic matter content, cation exchange capacity [CEC], ammonium oxalate extractable iron [Fe] and aluminum [Al]; Cooper and Ung, 1997; Kaminski and Landsberger, 2000). However, relatively little is known about the behavior of leached components in different soils and their long term impact on soil quality and environmental health.

Soil As concentrations range between 0.1 and 40 mg kg-1 worldwide, with an

arithmetic mean (AM) concentration of 5-6 mg kg-1 (Kabata-Pendias and Pendias, 1992). Baseline concentrations of As in relatively unimpacted Florida soils vary from 0.01 to 61.1 mg kg-1, with a geometric mean (GM) of 0.27 mg/kg (Chen et al., 1999; Ma et al., 1997). Recent studies on anthropogenic baseline concentrations of As in urban areas, where there


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is likely to be greater anthropogenic impact as well as increased use of CCA-treated wood, revealed considerably higher As concentrations of about 0.40 mg/kg (GM; Chirenje et al., 2001; 2003a). The other two CCA constituents have not received the same attention as As, and data on their distribution is not as easily accessible.

The specific objective of this study was to determine the retention of As, Cu and Cr

in six common soil types (Histosols, Entisols, Alfisols, Ultisols, Spodosols and Marls) in Florida. Spodosols, Entisols, and Ultisols are the most prevalent soil orders in Florida, covering about 73 % of the state (Fig. 1). Although Marls do not constitute a soil order (they are mostly within the order Entisols), they have unique characteristics that warrant their treatment as a separate group. Attention was paid to both surface soils, which constitute the greatest route of exposure to human beings and other animals, and subsurface horizons, which present the route of exposure of groundwater pollution by these three elements. Results obtained from this study will improve our understanding of the retention of As, Cu and Cr in different types of soils and facilitate the differentiation of the effects of CCA-treated wood from those of naturally occurring baseline concentrations of As, Cu and Cr. Methods

The primary objective of this study was to classify the retention of the three elements that can potentially leach out from CCA-treated wood (Cu, Cr, and As) in different soils of Florida. This was accomplished in three stages:

i. sample collection from around Florida ii. sample analysis (adsorption, desorption, physical & chemical characteristics) iii. classification of sorption and desorption capacities of the different soil types

Soil sample collection Soil samples from six soil orders were collected from various places in Florida (Fig 2):

1. A Histosol sample from Belle Glade, South Central Florida 2. A Marl sample from Homestead, South Florida 3. Seven samples from Austin Cary Memorial Forest near Gainesville, North Central

Florida a. One Spodosol b. Three Entisols c. One Ultisol

Two were not classified (only A horizons were sampled) 4. Two samples from Lakeland and surrounding areas, Central Florida

a. One Entisol b. One Spodosol

5. Six samples from Panama City, Tallahassee and Marrietta, Northwest Florida. a. Five Entisols b. One Alfisol

Soil sample analyses


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Soil concentrations of As, Cu and Cr were determined by digestion using an EMS

hot block digester, modified from the United States Environmental Protection Agency (USEPA) Method 3050 (USEPA, 1995; 1996). Half a gram of soil was weighed into a 50-mL Teflon tube and digested in 9 mL concentrated HNO3. The resulting solution was diluted to 50 mL and filtered through a 0.45 micron membrane filter. Arsenic, Cu and Cr concentrations in the digestates were determined with a SIMAA 6000 graphite furnace atomic absorption spectrophotometer (GFAAS, Perkin Elmer, Norwalk, CT), using USEPA method 7060A (USEPA, 1995). Arsenic, Cu and Cr concentrations in column leachate samples were determined the same way after filtration through a 0.45 micron membrane filter. Standard reference materials (SRM 2709, Montana soil from NIST) were used to check the extraction efficiency of the digestion method used for all soil samples. Approximately 20 % of the samples analyzed were spikes, duplicates and reagent blanks, which were used for quality assurance/quality control. Digestion sets showing a relative standard difference of more than 20 % from the known values (for standards and spikes) were repeated. Determination of the relative Cu, Cr, and As sorption capacity of soils

Determination of adsorption isotherms The soil samples were exposed to a minimum of five predetermined Cu, Cr, and As

concentrations and sorption was determined at each of those concentrations. This was achieved by adding 10 mL of solution of desired Cu, Cr, or As concentration to 10 g of soil in a scintillation vial, mixing and centrifuging and then measuring the Cu, Cr, and As concentration in the soil. Determination of Cu, Cr and As desorption capacity

The soil samples used in adsorption were leached with 5mL portions of a weak salt, 50 mM KCl over a period of 6 weeks. The concentrations of Cu, Cr and As in each aliquot were measured. Other soil chemical properties of relevance e.g. ammonium oxalate extractable iron (Fe) and aluminum (Al), soil organic matter (SOM), pH were determined as needed. Determination of retention indices

Regression analyses was used to establish an empirical relationship between soil retention capacity for Cu, Cr, and As and soil properties including pH, SOM, cation exchange capacity (CEC), ammonium oxalate extractable Fe and Al, and texture. In the end, soils were grouped into the following classes for each element:

Class 1: Soils with the greatest retention and minimal likelihood for leaching, Class 2: Soils with moderate retention with moderate potential for leaching, and Class 3: Soils with the least retention, greatest risk for leaching


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Results and discussion Variation in soil properties Soil properties varied greatly between orders, with surface soil pHs ranging from 4.4 in Ultisols to 7.9 in Marls (Fig. 3). The low pHs in Ultisols and Spodosols were a result of the vegetation in the areas where these samples were collected. Most Spodosols in Florida are associated with pine stands whose needles acidify surface soils when they decompose on the ground. On the other extreme end, the high pH in Marls was a result of the mineral components of the soils, which are mostly composed of calcite. Subsurface pHs did not vary to the same extent as surface pHs. Soil pH is critical because the speciation and subsequent leachability of trace elements is considerably affected by pH. Most elements with high association with OC, e.g. Cu, are leached out more at higher pH due to the dissolution and subsequent mobilization of SOM. Those elements that form strong association with CaCO3, e.g. As, have higher retention at higher pH, but they are more mobile at lower pHs as the calcite is dissolved by acid. However, in the presence of high concentrations of ammonium acetate extractable Fe and Al, As is not very mobile at low pH due to its precipitation with both ammonium acetate extractable Fe and Al. Surface soil textures also varied considerably, with Marls having the highest clay + silt content (> 90 %) and Spodosols having the least (< 10 %; Table 1). Table 1 shows the variation of soil texture with horizon across soil orders. There was very little variation observed between A and E horizons although B horizons in both Ultisols and Spodosols showed lower clay+silt content than expected. Soil texture affects soil surface area, with finer textured soils having more surface area and being more reactive, and therefore becoming more likely to retain higher amounts of trace elements than coarse textured soils (Chen et al., 1999; Berti and Jacobs, 1996). Figure 3 demonstrates the increased As retention in the finer Table 1. Percentages of silt + clay content in study soils (except Histosols†)

n Mean Range

Ahorizon 18 14.3 ± 15.1 0.54 - 63.1 Marls 5 95.0 ± 2.28 91.5 - 97.8

Spodosols-A 2 13.7 ± 10.7 6.14 - 21.3 Ultisols-A 3 7.33 ± 0.97 6.55 - 8.41 Entisols-A 2 3.85 ± 4.69 0.54 - 7.16 Alfisol-A 1 8.8 ± 0.00 8.80 - 8.80

Ehorizon 13 15.1 ± 16.8 2.77 - 48.9 Bt 2 7.97 ± 5.49 4.09 - 11.9 Bh 3 11.4 ± 7.76 5.98 - 20.3

† Textural analysis not done for histosols because they are organic soils


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where: Ahorizon represents all A horizons collected for the study Marls represent the surface layer of this soil type Ehorizon represents all E horizons collected for the study Bh and Bt represent all the spodic and argillic horizons in the study size fraction of the different soil types in the study. The same trend was observed for Cu and Cr (data not shown). The silt+clay fractions varied between soil types and therefore any inferences from comparisons between soils should take this into consideration. Arsenic concentrations were highest in the silt+clay fraction in the Marl, which translated to this soil having the highest concentration of As in all the soils studied. No fractionation was done for the Histosol because it is an organic soil.

Apart from increased surface area for reaction, fine textured soils also have higher CEC, which leads to higher retention for cationic species like Cu (Chen et al., 1999). One is also more likely to find higher concentrations of OM in finer textured soils with high CEC than in sandy soils with low CEC. Oftentimes, high OM leads to high CEC, mostly from pH dependent charge. Conditions in fine textured soils are also more conducive to OM accumulation and retention. Organic matter increases retention of both cationic and anionic species. This is achieved through cationic bridging by Al and Fe, leading to anion retention, and the dissociation of edges of organic complexes in response to changes in pH (leading to retention of both cations and anions, depending on pH [pH dependent charge]). pH dependent charge is the predominant charge in Histosols (USDA, 1996).

The concentrations of ammonium oxalate extractable Fe and Al also varied widely among the soils, with Histosols, Spodosol (A) and Entisol (A and E) having high Fe concentrations (Fig 5). Ammonium oxalate extractable AL was higher in the Bh and Bt horizons, as well as in Entisols (A and E; Fig. 5). Determining total Fe and Al in soil does not give an accurate reflection of their reactivity in the soil because the most reactive parts of Fe and Al are the ammonium acetate extractable fraction (Schwertmann and Taylor, 1989). The high concentrations of reactive Fe and Al in subsurface diagnostic horizons has important implications for both cation and anion retention as shown later. Table 2. Concentrations of As, Cu and Cr in study soils† (mg kg-1) n As Cr Cu Ahorizon 19 0.41 ± 0.37 4.87 ± 0.84 0.46 ± 0.39 Histosols 5 3.58 ± 0.19 12.0 ± 3.10 7.41 ± 1.79 Marls 5 19.4 ± 4.98 57.8 ± 7.49 6.46 ± 1.20 Spodosols-A 3 0.14 ± 0.00 3.30 ± 0.36 0.19 ± 0.00 Ultisol-A 3 0.14 ± 0.00 4.10 ± 0.23 0.19 ± 0.00 Entisol-A 2 0.49 ± 0.02 5.10 ± 0.44 0.49 ± 0.22 Alfisol-A 1 0.14 ± 0.00 3.73 ± 0.79 0.19 ± 0.00 Ehorizon 14 0.63 ± 1.25 5.70 ± 1.02 0.19 ± 0.00 Bh 3 0.14 ± 0.00 3.46 ± 1.30 0.19 ± 0.00 Bt 3 1.46 ± 1.90 7.81 ± 2.43 0.19 ± 0.00 †These values do not necessarily represent background concentrations of As, Cu and Cr.


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They are just an indication of concentrations of As, Cr and Cu before the experiment The method detection limits (MDLs) for As, Cu and Cr were 0.28, 0.38 and 0.52 mg kg-1, therefore values less than these MDLs were replaced by 0.14, 0.19 and 0.26 mg kg-1, for As, Cu and Cr, respectively. Retention of As, Cu and Cr The initial concentrations of As, Cu and Cr are shown in Table 2. These soils generally had very low concentrations of Cu, with the exception of Histosols and Marls. It did not seem like any of the soils were impacted by As, Cr and Cu, hence all of them were used in the retention studies. Sorption and desorption experiments showed wide ranging distribution coefficients (Kd values). The Kd is the ratio of the amount of metal sorbed onto particles to that of the amount still in the solution around the same particles (Anderson and Christensen, 1988). The Kd value is important because, apart from giving an estimate of the partition of an element between the solid and liquid phases, it can be used to calculate the retardation factor using the relationship (the higher the Kd, the higher the retardation factor):

R = 1 + Kd*ρb /φ where: R = retardation Kd = distribution coefficient ρb = soil bulk density φ = soil porosity The Kd values calculated for a leaching solutions with compositions up to 48 mg/L As and less than 5 mg/L Cu and Cr respectively, ranged from 0.6 – 85, 0.4 – 64, and 0.7 – 111 in columns for As, Cu and Cr, respectively (data not shown). The retention capacity for each element depended on the initial concentrations of the solution that was eluted through the columns, the number of leaching events and the soil type. The Kd values for Cu and Cr were possibly exaggerated by the low concentrations used. Increasing the concentrations of Cu and Cr over a range yielded different Kd values, which decreased with increasing concentration. Different sorption maxima were also reached for different initial solution concentrations. Although the concentrations of the three elements in CCA-treated wood are generally not very different from each other, As leaches out the most from the wood products, with leachate concentrations at least an order of magnitude higher than those of Cr and Cu. Therefore, this discussion places more emphasis on the behavior and retention of As than Cu and Cr. Because distribution coefficients varied with the initial concentrations of As, Cu and Cr that were added, it was not possible to calculate a unique Kd value that would represent each soil order over a wide range of pH and soil solution As, Cu and Cr concentrations. Batch sorption and desorption studies corroborated these observations, with batch studies consistently yielding lower Kd values than column studies.


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This was possibly due to the lower solution to solid ratio (greater partitioning) and the higher solution-solid contact time in column studies (more likely to reach equilibrium at higher sorption rates). Figure 6 shows the partitioning of As, Cu and Cr between the solid and liquid phase. Although none of the soils tested reached their sorption maxima at the concentration used, the gradients of the curves showed that the Histosols and Marls had the highest sorption potential. The A horizons of Ultisols, Alfisols and Spodosols showed the least potential. Studies are being done with the same soils with solutions with considerably higher concentrations of As, Cu and Cr to determine sorption curves up to their sorption maxima. Figure 7 showed how desorption curves can be used to determine the mechanisms of adsorption and the retention capacity of soils for different metals. The ease with which desorption of an element is achieved speaks to the type of sorption mechanism involved, non-specific (exchangeable) versus specific (non-exchangeable) sorption (Gomes et al., 1997). This is critical because, although As generally leaches out more easily from CCA-treated wood than Cu and Cr, it is not retained by soils more than Cu and Cr (Chirenje et al., 2003; Chen et al., 2002). Copper, which is retained by soils through both specific and non-specific sorption showed very high retention, while Cr, which is retained through mostly specific sorption, demonstrated even higher retention capacity (Fig. 7; Gomes et al., 2001). Berti and Jacobs (1996) showed that elements with high retention are more likely to displace elements (they have higher selectivity) with low retention capacity in soils. In terms of surface soil behavior, the Marls and Histosols retained As, Cu and Cr the most, followed by Entisols, Alfisols, and Ultisols, and finally by Spodosols, which retained the least of all three elements. Marls and Histosols have been shown to have higher natural trace element concentrations than the other soil types in Florida (Chen et al., 1999; 2002). There are a multitude of factors that may have led to this distribution pattern, apart from the soil characteristics discussed earlier. For example, previous research on phosphorus (P) has shown that coated sand grains have a higher tendency to retain elements than bare quartz grains (Harris et al. 1987a, b) because the common coating components (metal oxides, aluminosilicates, etc) have high affinity for trace elements, including As, Cu and Cr. Some of the great groups (e.g. albic horizons of alaquods [Spodosols]) investigated here been exposed to extreme weathering, which strips the coatings from the sand grains (Harris et al. 1987a, b). Rhue et al. (1994) showed that some horizons within the same great groups retain the coatings and exhibit high retention while those that did not retain coatings exhibited low retention. The concentrations of As, Cu and Cr in the subsurface horizons of soils that wer not impacted by CCA-treated wood were not significantly greater than those in surface horizons (Table 1). Subsurface horizons tend to serve as a sink of trace elements only if there is a source. Therefore, if the surface horizons had not been exposed to considerably high concentrations of trace elements that would have leached to the subsurface, there is no reason to expect to find high concentrations in the subsurface. Using high concentrations of As, Cu and Cr, subsurface diagnostic horizons showed their potential to retain more metals


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than surface horizons (Fig. 7). The slow release of trace metals on desorption with KCl showed that these horizons have high As, Cr and Cu retention potential.

Correlation analyses using sorption and desorption curves for Cu and Cr showed

that CEC, texture, and OC, played a significant role in sorption and retention (data not shown). The effects of texture, ammonium oxalate extractable Fe and Al, and organic carbon on As retention have been well documented (Chen et al., 1999; Jacobs et al., 1970). However, CEC also displayed a major role in As retention. This may not have been a direct effect. Rather, the increase in CEC may have been due to an increase in clay content and OC both of which lead to increased As retention (Chen et al., 2002).

Since none of the parameters responsible for As, Cu and Cr retention had

domineering effects in all soils, our knowledge of specific behaviors of certain soils helps us distinguish the mechanisms involved for each soil type. For example, the Marl used in this study had very low ammonium oxalate extractable Fe but it was high in clay content, calcite and OC which also play a large role in retention of trace elements. The high ammonium oxalate extractable Fe in the Entisol led to increased retention in a soils that would otherwise have low retention. A lot of the E horizons used were obtained from Entisols, which are mostly young soils with little profile development. As discussed earlier, CEC correlated well with the clay fraction in the Marl and with OC in the Histosol. This suggests that the charge associated with the Marl is mostly permanent while that in the Histosol was variable. This mostly impacts elements that are specifically adsorbed, e.g. Cu, which is also highly correlated to the high OC in Histosols. Therefore environmental changes in Histosols are more likely to lead to significant changes in trace element retention than in Marls. Soil classification

In terms of As retention, the soils were classified into three groups: i. Class 1: Soils with the greatest retention and minimal likelihood for leaching, ii. Class 2: Soils with moderate retention with potential for leaching, and iii. Class 3: Soils with the least retention, greatest risk for leaching Using surface soil characteristics, two of the soils (Marls and Histosols) met the

requirements for Class 1. The Entisol, Alfisol and Ultisol met the requirements for Class 2, and the Spodosol met the requirements for Class 3. These results are in line with our expectations. Spodosols, such as the ones that were sampled for this study, tended to be acidic and highly leached due to their location in areas where pines are prevalent. In some areas, the soils appeared white from a distance, hence the name ‘sugar sands’.

However, when subsurface horizons were included, the Marls and Histosols still fit in

Class 1 (there was no profile differentiation in these soils), while the remaining soils met the requirements for Class 2. These results were unexpected because soils with subsurface


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diagnostic horizons (Bt and Bh) generally show higher retention in these layers. The inclusion of the Entisol is this category was the most unexpected.

In fact, when the diagnostic horizons (Bt and Bh) were compared to the E horizons

from the Entisol, the E horizon had significantly lower retention of As than the Bt and Bh. However, when the results were adjusted for the E overlying Bh and Bt horizons, there was no difference between Entisols, Alfisols, Spodosols and Ultisols. Conclusions

Both sorption and desorption experiments showed that the soil order was not a good

indicator of retention of As, Cu and Cr in soils. It was texture, the concentration of ammonium oxalate extractable Fe and Al, and OC that were reliable indicators of soil As retention. Since most surface soils are similar, except in Histosols, Marls and some Spodosols (acidic), the retention of As, Cu and Cr in the surface layers of these soils is not affected significantly by the soil type. However, As, Cu and Cr retention in the subsurface was considerably affected by the soil type because the presence or absence of subsurface diagnostic horizons manifests itself in different amounts of ammonium oxalate extractable Fe and Al, OC and fine colloids. Table 3. Classification of soil orders according to the classes we defined

Soil Class Surface Soil Characteristics Subsurface & Surface Soil Characteristics

Class 1

Marls, Histosols

Marls, Histosols

Class 2 Alfisol, Ultisol, Entisol

Entisol, Alfisol, Utisol, Spodosol

Class 3

Spodosol

-None-

References Anderson, P.R., and T.H. Christensen. 1988. Distribution coefficients of Cd, Co, Ni and Zn in soils. J. Soil Sci. 39:15-22. Berti, W.R., and L. W. Jacobs. 1996. Chemistry and phytotoxicity of soil trace elements from repeated sewage sludge applications. J. Environ. Qual. 25:1025-1032. Carey, P.L., McLaren, R.G., and Adams, J.A., 1996. Sorption of cupric, dichromate, and arsenate ions in some New Zealand soils. Water, Air, and Soil Poll. 87:189-203.


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Chen, M., L.Q. Ma and W. G. Harris. 1999. Baseline concentrations of 15 trace elements in Florida surface soils. J. Environ. Qual. 28:1173-1181. Chen, M., L.Q. Ma and W. G. Harris. 2002. Arsenic concentrations in Florida surface soils: Influence of soil type and properties. Soil Sci. Soc. Am. J. 66:632-640. Chirenje, T., L. Q. Ma, E.Z. Zillioux and S. Latimer. 2001. Protocol development for assessing arsenic background concentrations in urban areas. Environmental Forensics (2):141-153. Chirenje, T., L. Q. Ma, and E.J. Zillioux. 2002. Determining arsenic distribution in urban areas: a comparison with nonurban soils. In Arsenic. A Themed Collection of Papers from the 6th International Conference on the Biogeochemistry of Trace Metals Proceedings. The ScientificWorldJOURNAL 2:1404-1417. Chirenje T., M. Chen and L.Q.Ma. 2003a. Arsenic background concentrations comparison in Florida rural and urban areas. Adv. Environ. Res. 8:137-146. Chirenje T., M. Reeves, M. Sczulczewski, and L.Q.Ma. 2003b. Changes in arsenic, chromium and copper concentrations in soils adjacent to CCA-treated decks, fences and utility poles. Environ Poll. 124:407-417. Cooper, P., and Y.T. Ung. 1997. The Environmental Impact of CCA Poles in Service. Paper # IRG/WP 97-50087. International Research Group, Stockholm, Sweden. Dawson, B.S.W., G.F. Parker, F.J. Cowan and S.O. Hong. 1991. Inter-laboratory determination of copper, chromium, and arsenic in timber treated with wood preservative. Analyst 116:339-346. Gomes, P.C., M.P.F. Fontes, A.G. da Silva and A. R. Netto. 2001. Selectivity sequence and competitive adsorption of heavy metals by Brazilian soils. Soil Sci. Soc. Am. J. 65:1115-1121. Gomes, P.C., M.P.F. Fontes, L.M. da Costa and E. de S. Mendonca. 1997. Fractional extraction of heavy metals from a Red-yellow latosol. Rev. Bras. Ci. Solo. 21:543-551. Harris W. G., V.W. Carlisle and S.L. Chesser. 1987a. Clay mineralogy as related to morphology of Florida soils with sandy epipedons. Soil Sci. Soc. Am. J. 51:1673-1677. Harris W. G., V.W. Carlisle and S.L. Chesser. 1987b. Pedon zonation of hydroxy-interlayered minerals in Ultic Haplaquods. Soil Sci. Soc. Am. J. 51:1367-1371. Hingston, J.A., C.D. Collins, R.J. Murphy and J.N. Lester. 2001. Leaching of chromated copper arsenate wood preservatives: a review. Environ. Poll. 111:53-66.


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Jacobs, L.W., J.K. Syers and D.R. Keeney. 1970. Arsenic sorption by soils. Soil Sci. Soc. Proc. 34:750-754. Kabata-Pendias, A. and H. Pendias 1992. Trace Elements in Soils and Plants. Boca Raton, CRC Press. Kaminski, D.M. and S. Landsberger. 2000. Heavy metals in urban areas of East St Loius, IL, Part 1: Total concentrations of heavy metals in soils. Air & Waste Manage. Assoc. 1667-1679. Lebow, S. 1996. Leaching of Wood Preservative Components and Their Mobility in the Environment, General Technical Report FPL-GTR-93. Forest Products Laboratory, United States Department of Agriculture (USDA) Forest Service. Ma, L. Q., F. Tan and W.G. Harris. 1997. Concentrations and distributions of eleven elements in Florida soils. J. Environ. Qual. 26:769-775. Rhue, R.D., W.G. Harris, G. Kidder, R.B. Brown and R.C. Littell. 1994. A soil based phosphorus retention index for animal waste disposal on sandy soil. Final Project Report. Florida Department of Environmental Protection. EPA grant no. 9004984910. Schwertmann, U. and R.M. Taylor. 1989. In J.B. Dixon and S.B. Weed (eds). Minerals in Soil Environments: Iron Oxides p379 - 438. ASA and SSSA, Madison, WI. Solo-Gabriele, H., Townsend, T.G., Kormienko, M., Gary, K., Stook, K., and Tolaymat, T., 2000. Alternative Chemicals and Improved Disposal-End Management Practices for CCA-treated Wood, Report #00-08. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Stilwell, D.E. and K.D. Gorny. 1997. Contamination of soil with copper, chromium, and arsenic under decks built from pressure treated wood. Bull. Environ. Contam. Toxicol. 58: 22-29. US Department of Agriculture (USDA). 1996. Soil Survey of Dade County Area, Florida. USDA-NRCS, Washington, D.C. U.S. Environmental Protection Agency (USEPA). 1995. Test Methods for Evaluating Solid Waste. Vol IA:Laboratory Manual Physical/Chemical Methods SW846. 3rd Ed. USEPA Office of Solid Waste and Emergency Response, Washington DC. U.S. Environmental Protection Agency (USEPA). 1996. Test Methods for Evaluating Solid Waste. SW846, 3rd Edition. USEPA Office of Solid Waste and Emergency Response, Washington, DC.


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Environmental Impacts of CCA-Treated Wood Within Florida, USA

Helena M. Solo-Gabriele1, Timothy G. Townsend2, and Yong Cai3

1University of Miami, Department of Civil, Architectural, and Environmental Engineering, P.O. Box 248294, Coral Gables, Florida, 33124-0630 USA

2University of Florida, Department of Environmental Engineering Sciences,

333 New Engineering Building, Gainesville, Florida, 32611-6450 USA

3Florida International University, Department of Chemistry & Biochemistry and Southeast Environmental Research Center (SERC),

1120 S. W. 8 St., University Park, Miami, Florida 33199

Abstract Studies in Florida, USA, focusing on the environmental impacts of wood treated with chromated copper arsenate (CCA) were initiated because of elevated levels of arsenic and chromium encountered in ash from wood cogeneration plants within the State. During 1996 it was determined that these elevated levels were due to contamination of wood fuel with discarded CCA-treated wood. Since this time, a research team from the University of Miami and the University of Florida have been evaluating: a) disposal pathways for CCA-treated wood within the State, b) new disposal management strategies for CCA-treated wood, and c) impacts of CCA-treated wood during its in-service use.

In-service leaching was evaluated through two focused efforts. These efforts included a study that characterized metal concentrations in soils below 9 pre-existing decks (8 CCA treated and 1 not CCA treated) and a controlled field-scale experiment where 2 decks (one CCA treated and one untreated) were constructed over a leachate collection system. Immediately below the pre-existing decks the average soil arsenic concentration was 28.5 mg/kg. This was contrasted by a value of 1.5 mg/kg for the background samples. Arsenic concentrations in runoff collected from a CCA-treated deck ranged from 0.1 to 8.4 mg/L with 0.7 mg/L, on average. Arsenic in the runoff was predominately in the +5 valence; however, some As(III) was measured. Detectable amounts of arsenic were also measured in the infiltrated water below the sand supporting the decks. A larger fraction of As(III) was observed in the infiltrated water as compared to the runoff water.

Disposal pathways for CCA-treated wood within Florida include construction and demolition (C&D) debris landfills (which are generally unlined in Florida) and inadvertent mixing with mulch and wood fuel that is produced from recycled C&D wood. Leaching test results demonstrate that CCA-treated wood leaches enough arsenic to cause the wood to be a toxicity characteristic (TC) hazardous waste (if it were not otherwise exempted) and to pose a potential risk for contaminating groundwater at unlined landfills. Samples collected from C&D debris facilities located in Florida indicate that CCA-treated wood represents 6% of the recycled wood on average with values as high as 30%, by weight, for some facilities. Contamination from CCA has been detected within some mulch samples purchased at retail stores within Florida, and these mulches exceed the State’s guidelines for land application of recycled waste. When CCA-treated wood represents 5% or more of a recycled wood mixture, the ash from its combustion will typically be characterized as a TC hazardous waste. Results from chemical speciation analysis indicate that unburned wood leaches arsenic primarily in the +5 valence and chromium in the +3 valence.


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Chemical speciation of the ash however was much more variable with some samples showing significant amounts of As(III) and Cr(VI).

Ways to minimize the impacts of CCA-treated wood during disposal include options for waste minimization and disposal-end management. Waste minimization focuses on the use of alternative wood treatment preservatives that do not contain arsenic. Non-arsenical chemicals evaluated include ACQ, CBA, CC, and CDDC. These alternatives were shown to leach less arsenic but more copper than CCA-treated wood. Options for disposal-end management described in this study include sorting technologies to separate CCA-treated wood from other wood types. Sorting technologies evaluated included the use of a chemical stain and two systems based upon the use of lasers or x-rays. Chemical stains were found to be effective for sorting small quantities of CCA-treated wood. Both the laser and x-ray systems were shown to be very promising technologies for sorting large quantities of wood in a more automated fashion. Keywords: CCA, arsenic, chromium, disposal, in-service use BACKGROUND

The most common U.S. formulation for CCA is the “type C” formulation which is

composed of 47.5% CrO3, 18.5% CuO, and 34% As2O5 (AWPA 2001). The amount of CCA chemical added to wood depends upon the intended use of the treated wood product. Wood used for above ground applications is treated in the U.S. using a minimum of 4 kg of chemical per cubic meter of wood product (kg/m3). Utility poles are treated at 6.4 kg/m3 and wood used for pilings within marine environments is treated at 40 kg/m3. The CCA chemical typically imparts a green color to the wood. At low retention levels (4 kg/m3) the color is a very faint green whereas at high retention levels (40 kg/m3) the color is a strong olive green.

Chromated copper arsenate (CCA) was the most common wood treatment preservative

utilized in the U.S. during the 1980s, 1990s, and early 2000’s. A proposed phase-down for residential uses of CCA is scheduled to take effect at the end of 2003 (U.S. EPA 2002). This phase-down will result in an estimated 60 to 80% decrease in CCA-treated wood production. Due to the predominance of CCA-treated wood until recent times, the ma jority of outdoor wood structures currently in-service in the U.S. are treated with CCA and these structures will ultimately require disposal long into the future. Thus the impacts from CCA-treated wood will likely be experienced during in-service use and during disposal for many years to come.

IN-SERVICE LEACHING

In-service leaching of CCA-treated wood was evaluated by measuring soil metal

concentrations below 9 pre-existing decks (8 CCA treated and 1 not CCA treated) and 2 decks (one CCA treated and one untreated) constructed over a leachate collection system. Only the results for arsenic are discussed below for brevity. Results from Sampling Soils Below 9 Pre-Existing Decks

The soils below eight CCA-treated decks and one non-CCA-treated deck were sampled throughout Florida to evaluate the degree to which the decks impact the surrounding environment (Townsend et al. 2001a; Townsend et al. 2003a). Two sets of samples were collected: one set


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corresponded to core samples (roughly 8 inches deep below the center of each deck) and the second set corresponded to surface samples (upper 1 inch of soil) collected in a grid-like fashion below each deck. Between 8 to 9 surface soil samples were collected from below each deck, and between 8 to 9 control samples were collected at a short distance (3 to 10 meters) from each deck. Samples were analyzed for arsenic, copper, and chromium using standardized laboratory methods.

Results indicate that arsenic was detected in all surface soil samples collected from below the decks (figure 1). The arsenic concentrations for surface soils collected from underneath the CCA-treated decks ranged from 1.2 mg/kg to 217 mg/kg with an average of 28.5 mg/kg. The average arsenic concentration of the control samples was 1.5 mg/kg. The average arsenic concentrations for surface soils collected below all the CCA-treated decks were higher than the corresponding control samples at 95% confidence limits.

Results from the soil cores indicate that the maximum concentrations of arsenic were found within the first two inches of the soil within all cores collected. On average, elevated arsenic concentrations were observed within the cores down to a depth of roughly 8 inches. Results from 2 Decks Constructed Over a Leachate Collection System Two decks, one made of CCA-treated wood and the other made of untreated wood, were constructed over two separate leachate collection systems. The decks were 2 meters by 2 meters in surface area and were housed inside a 2.4 meter by 2.4 meter untreated wooden enclosure containing 0.7 m depth of sand. The leachate collection system for each deck consisted of two parts: the first was a gutter system designed to collect direct runoff from the decks. The second was designed to collect infiltrated water from below 0.7 m depth of sand (figure 2). Samples have been collected from the leachate collection system since September 2002. Results to date indicate that the concentration of arsenic in the runoff from the CCA-treated deck was 0.73 mg/L, on average (0.1 to 8.4 mg/L range, n = 43), whereas for the untreated deck the concentrations consistently measured near 0.002 mg/L. The primary arsenic species observed in the runoff was As(V), although low levels of As(III) were detected in particular during times when total arsenic concentrations were elevated (Figure 3) (Khan 2003). The arsenic concentrations of the infiltrated water collected below the CCA-treated deck generally increased from 2 to 3 ug/L at the beginning of the monitoring period to 18 ug/L after 1 year of monitoring (Figure 5). The initial arsenic concentrations are consistent with the concentrations observed from the untreated deck. For the untreated deck, infiltrated water arsenic concentrations were roughly constant between 2 to 3 ug/L. Both As(V) and As(III) were observed in the infiltrated water collected from below the CCA-treated deck, with As(V) predominating. The proportion of As(III) to As(V) was larger for the infiltrated water relative to the runoff water. Possible reasons for the higher proportion of As(III) in the infiltrated water may be due to preferential infiltration of As(III) or due to the conversion of As(V) to As(III) within the sand. DISPOSAL PATHWAYS (A FLORIDA CASE STUDY)

The primary disposal pathway for CCA-treated wood in Florida is through the construction and demolition waste stream. The wood processed at these facilities is ultimately disposed through one of three methods: within construction and demolition (C&D) landfills, recycled as wood fuel, or recycled as mulch. Testing of recycled wood piles throughout Florida has found that the fraction of


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CCA-treated wood within these piles appears to be increasing in more recent years. In 1996, C&D wood waste was found to have 6% CCA-treated wood, on average, for 12 facilities evaluated (Tolaymat et al. 2000). In 1996, an evaluation of wood waste at three C&D facilities found that the wood waste piles were composed of 9 to 30% CCA-treated wood (Blassino et al. 2002). Of interest, is the fact that 2 of the 3 C&D facilities visited in 1999 practiced visual sorting of treated wood from the remainder of the wood waste stream. Visual sorting was accomplished at these facilities by noting the green hue of the wood. The fact that these two facilities used visual sorting methods indicates that this method although helpful in removing some CCA, is not capable of removing enough of the CCA-treated wood for recycling purposes. Disposal within C&D landfills

In Florida, C&D landfills are generally unlined, and research has shown that CCA-treated wood does exceed Florida Department of Environmental Protection (FDEP) guidelines for leaching (Townsend et al. 2001a). These guidelines are based upon two tests, the Synthetic Precipitation Leaching Procedure (SPLP) and the Toxicity Characteristics Leaching Procedure (TCLP). These tests involve the addition of a waste material to a leaching fluid and contacting the waste with the fluid for a period of 18 hours. The metal concentrations in the leachates are then measured at the end of the test. If the concentration of a given metal exceeds a set level, then the waste fails that particular test. In general, SPLP is used to evaluate whether a waste can be land applied or disposed in an unlined landfill. The TCLP test is used to evaluate whether the waste can be disposed in a lined landfill. Results have shown that CCA-treated wood consistently fails guidelines based on the SPLP test (Figure 5) and will on occasion fail guidelines based on the TCLP results. Failures were more frequent when the samples were ground to finer particle sizes. The primary arsenic species observed in the leachates were inorganic As(V) and As(III). More As(III) was observed in leachates from weathered CCA-treated than from unweathered wood (Khan 2003).

Results from a series of paired lysimeters (each pair containing one lysimeter that contained CCA-treated wood and another that contained only untreated wood), suggest that arsenic concentrations in leachates from a CCA-treated wood monofill would result in arsenic concentrations on the order of 50 mg/L, requiring disposal of that leachate as a hazardous waste (Jambeck et al. 2003). Concentrations from the C&D and Municipal Solid Waste (MSW) lysimeters were on the order of a few mg/L.

Groundwater samples were collected from the vicinity of C&D landfills within Florida. Both inorganic As(III), As(V), and the organic methylated forms of arsenic were observed (Khan 2003). It was not clear whether or not the arsenic concentrations detected in the groundwater samples was due to the waste within the C&D landfills (Solo-Gabriele et al. 2003a). Recycling as Wood Fuel

CCA-treated wood within wood fuel is of concern due to potential air emissions, in particular arsenic, during the incineration process and due to the accumulation of metals within the ash. During 1996, CCA-treated wood was identified as the cause of elevated arsenic and chromium concentrations in the ash from wood cogeneration facilities located in Florida (Solo-Gabriele and Townsend 1999). Subsequent studies to characterize CCA-treated wood ash indicate that all ash samples made entirely from CCA-treated wood failed TCLP regulatory levels and would thus be considered a hazardous waste. It was also found that a mixture of 95% untreated wood with 5% CCA-treated wood (0.25 pcf) would cause the ash to fail on some occasions. Therefore, if the goal


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is to generate an ash that is considered non-hazardous, the proportion of CCA-treated wood within the wood fuel mix should be less than 5% (Solo-Gabriele et al. 2001b).

Metals speciation of the ash from CCA-treated wood showed that chromium in the CCA-treated wood is converted from Cr(III) to the more mobile and toxic Cr(VI) form during the incineration process. This conversion is strongly a function of pH with samples characterized by more alkaline pH values showing a greater conversion of chromium towards the hexavalent form. Such results question whether or not CCA-treated wood should be incinerated during disposal. Recycling as Mulch

Given that the cause of elevated levels of metals within wood ash from cogeneration facilities was caused by the presence of CCA-treated wood, these facilities have, in general since 1996, developed more stringent guidelines for the types of wood waste accepted and have thus limited their use of recycled C&D wood waste. As a consequence there has been a recent increase in the use of C&D wood waste within the mulch industry, primarily for the production of colored mulch. Given the high probability of such wood to be contaminated with CCA, the production of mulch from recycled C&D wood waste serves as a mechanism by which CCA-treated wood is being land applied throughout the State of Florida, thereby increasing the potential for contaminating the environment with arsenic, chromium, and copper. A preliminary study conducted by Townsend et al., 2003b, found that among 3 samples of colored mulch purchased at retail establishments, 2 failed regulatory guidelines for arsenic, whereas the 3 controls made of vegetative wood were all negative for arsenic leaching. A follow-up study that is currently on-going has focused on the analysis of over 90 mulch samples purchased from retail stores. To date, the analysis of 20 samples has been completed. Of the 20 samples, 13 were red colored mulch samples and 7 were not colored (Table 1). Among the non-colored samples, one contained elevated concentrations for arsenic, chromium, and copper. Among the red colored samples, 6 or almost half of the samples contained elevated concentrations of the CCA chemicals.

POSSIBLE SOLUTIONS

Disposal alternatives should be developed and implemented, given that the current disposal methods for CCA-treated wood are undesirable due to their potential for dispersing the CCA chemical into the environment. Alternatives can take the form of waste minimization and/or new disposal-end management strategies. Waste Minimization Through the Use of Wood Treated with Alternative Chemicals

Waste minimization is a process by which the amount of CCA-treated wood ultimately disposed is reduced. One waste minimization strategy is to encourage consumers to buy alternatives to CCA-treated wood. Wood has many positive structural qualities including a high strength to weight ratio and ease of machining. Wood is also a relatively inexpensive building material. However, it does degrade when subject to insect and fungal attack and it is thus necessary to treat the wood when used in the outdoor environment.

Several alternative wood preservatives have been used commercially and standardized by the American Wood Preservers’ Association, the standards writing agency for the wood treatment industry. The preservatives that have been found to be the most promising for residential home use are: alkaline copper quat (ACQ), copper boron azole (CBA), copper citrate (CC), and copper


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diethyldithiocarbamate (CDDC) (Solo-Gabriele et al. 2000). These alternative chemicals have been standardized for above ground and ground contact applications. They are considered to be just as effective as CCA for these applications. These alternatives have the advantage from an environmental perspective in that they do not contain arsenic. As such, these alternatives do not leach arsenic into the environment. Data (Townsend et al. 2001b) indicate that these alternatives do leach more copper than CCA (Figure 6). From a regulatory perspective, alternative-chemical treated wood poses a lower risk than CCA-treated wood within the disposal sector and within terrestrial environments. Slightly higher risks are associated with alternative-chemical treated wood products used in aquatic environments due to the toxicity of copper to aquatic organisms. The use of the alternatives is not recommended within highly sensitive aquatic environments in areas characterized by limited flushing. Alternative Disposal-End Management Options

Given that problems associated with the disposal of CCA-treated wood emerged as an ash contamination problem, early research through our research team focused on evaluating methods to extract chromium, copper, and arsenic from CCA-treated wood ash for remediation purposes. The thought was that as long as air emissions could be controlled, incinerating the wood would serve to greatly reduce the volume of the CCA waste and would concentrate the metals. These metals are considered valuable, and in an ideal scenario it would be beneficial to recycle these metals back into the wood treatment process. A series of solvent extraction experiments were conducted (Solo-Gabriele et al. 2001b), which found that nitric acid was capable of removing between 70 and 100% of the copper, between 20 and 60% of the chromium, and 60 to 100% of the arsenic for samples characterized by low retention levels. It was also found that citric acid was particularly effective at removing arsenic (between 40 to 100%) for ash samples produced from wood containing low CCA retention levels. Recycling the extracted metals into a form that can be used for CCA treatment, however, requires a considerable amount of additional research due to the fact that the metals extracted must be converted to their proper valence before reuse. Such additional processing adds to the cost of recycling which are not considered economically feasible at this time, in particular in comparison with the costs for landfilling the discarded wood.

In the absence of a good ash treatment technology, it would thus be important to assure that wood fuel (and also mulch) is free from CCA if recycling of wood waste is to continue. One option to assure clean wood waste is to develop sorting technologies for CCA-treated wood. Sorting technologies are necessary, in particular for lumber and timbers, given that CCA treatment within these products is difficult to identify through visual examination. Three different sorting technologies were evaluated and included: a chemical stain, a detection system based upon the use of lasers, and a detection system based upon the use of x-rays. The chemical stains are based upon the reaction of PAN indicator solution with the CCA. When sprayed on untreated wood, the PAN indicator produces an orange color on wood. In the presence of CCA, PAN indicator produces a magenta color. Experimentation with these stains in the field (Blassino et al. 2002) has shown that the stains are effective for sorting small quantities of wood (less than a few tons) and are good for spot-checking wood waste quality. However, when much larger quantities of wood are to be sorted, the use of chemical stains was found to not be cost effective due to excessive labor costs. For such situations more automated methods, such as the laser and x-ray detection systems, should be employed. Results of testing the laser and x-ray (XRF, x-ray fluorescence) systems indicate that both technologies can easily detect the presence of CCA within treated wood (Solo-Gabriele et al.


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2003b). Of special note is that the x-ray system evaluated was capable of identifying the presence of CCA, even when the wood was wet or painted (Figure 7). The technologies are considered cost effective for facilities that process more than 8,000 tons of wood per year (Solo-Gabriele et al. 2001a). CONCLUSIONS AND RECOMMENDATIONS

CCA-treated structures leach arsenic into the environment. In Florida, the arsenic

concentration observed in soils located below pre-existing decks was 28.5 mg/kg, which is over an order-of-magnitude greater than background concentrations. The below-deck concentrations are elevated to the point that they exceed Florida’s risk-based soil guidelines (a.k.a. soil cleanup target levels), which suggest that the soils may pose a risk to human health and the environment. Such risks should be evaluated further.

Results from the 2 decks constructed over leachate collection systems indicate that the arsenic

concentrations in direct runoff from CCA-treated wood are on the order of mg/L. These are considered high relative to background concentrations in Florida’s waters (e.g background concentration of arsenic in Florida’s groundwater is approximately 0.002 mg/L, Focazio et al. 1999). The data further indicate that metals do migrate through soil once released by runoff. Much of these metals can be sorbed by the soil matrix but over time it is possible that the sorption capacity of these soils is exceeded so that impacts to groundwater can occur. This is a particular concern due to the shallow depth to groundwater drinking water supplies within some parts of the State. Work should focus on evaluating the sorption capacity of different soil types and possible risks to Florida’s groundwater resources.

The potential use of alternative wood preservatives should be promoted as a potential substitute for CCA, as a means of minimizing the CCA waste. Prior to the adoption of these alternatives, reasonable assurances should be provided that these alternatives are less harmful to humans and the environment than the chemicals found in CCA. Given that the alternatives do not contain arsenic, a highly toxic metal, it appears that these alternatives will likely represent a lower human health threat than CCA. It would be useful to further evaluate the human health risks associated with the organic co-biocides associated with the alternatives.

The effects of waste minimization efforts will be observed in the disposal stream in the long term, after the typical service life of CCA-treated wood products, which varies between 10 to 40 years. Regardless of waste minimization efforts, improved disposal-end management practices will play a key role in minimizing the impacts of CCA-treated wood upon disposal within the short term (10 to 40 years) due to the large inventory of CCA-treated wood that is currently in service in the U.S. Promising new disposal strategies have been identified to automate the process of sorting CCA-treated wood from untreated wood within the disposal stream. Such technologies should be explored further and potentially implemented at full-scale operation to validate and fine-tune the sorting process.

Once CCA-treated wood is sorted out from untreated wood, the untreated wood can then be marketed for wood fuel and mulch, as long as reasonable assurances are provided that the material is free of CCA. The CCA treated portion of the wood waste must ultimately be disposed. Currently,


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the most economical disposal strategy for CCA in the U.S. is disposal within lined landfills. Nevertheless, efforts should focus on finding other means for the ultimate disposal of CCA. One promising alternative identified earlier was the use of CCA-treated wood within wood cement composites (Moslemi 1988, Schmidt et al. 1994, Felton and Degroot 1996). CCA-treated wood has the advantage over untreated wood in that it provides for a stronger bond between the wood and cement due to the presence of chromium, which increases the strength of the wood cement composite. Originally it was believed that the CCA chemical could encapsulate the CCA chemical. However recent work by Cooper et al. (2003) has shown that the alkaline nature of concrete results in the conversion of some of the chromium from the +3 valence to the +6 valence, a more mobile and toxic form. The conversion to hexavalent chromium thereby represents a major disadvantage to recycling CCA-treated wood into wood-cement composite materials.

Other ultimate disposal options for CCA-treated wood include possibly incineration or

disposal within dedicated wood monofill landfills. Disposal through incineration has a major disadvantage due to the conversion of chromium from Cr(III) to Cr(VI) during the incineration process. The production of a more toxic form of chromium, in addition to limited recycling options for extracted metals in the ash, represents a major disadvantage to this form of recycling. The high concentrations of metals anticipated in leachates from wood monofills would result in high costs for CCA-treated wood disposal within dedicated monofills due to the production of a hazardous leachate.

Given the higher costs associated with alternative disposal options (Clausen 2003), the

primary option for the ultimate disposal of CCA-treated wood remains through Municipal Solid Waste (MSW) landfills. The cost for disposal within MSW landfills in Florida is approximately $50/ton. As long as disposal within MSW landfills is allowed, it would be difficult for other innovative disposal and recycling technologies to compete with this relatively low-cost disposal option. Furthermore, the availability of MSW landfills throughout the State make this form of disposal practical from a transportation point-of-view. Concerns have been raised nevertheless about the impacts of CCA-treated wood on leachate quality within MSW landfills. Due to these concerns, some MSW landfills in Florida charge surcharge fees or will not accept loads known to contain CCA-treated wood. These landfills are in the minority in Florida, and it appears that for the current time, the disposal of CCA-treated wood within MSW landfills is the most economical and practical option for the State. However, it is believed that the MSW landfills within the State may not have enough dilution capacity to absorb all of the CCA-treated wood that will be discarded. There may be a time in the future where the quantities disposed will adversely impact leachate quality to the point that this form of disposal may no longer be feasible. As a result, more research is needed to identify disposal pathways for CCA-treated wood within communities throughout Florida and the rest of the U.S., especially since the disposal problems found in Florida are likely occurring in other parts of the country. ACKNOWLEDGMENTS Funding for the research presented in this manuscript was received from several different agencies including the Florida Center for Solid and Hazardous Waste Management, Sarasota County through the Florida Department of Environmental Protection Innovative Recycling Grants Program and through the National Institutes of Environmental Health Sciences (Grant No. S11 ES11181). The authors gratefully acknowledge the contributions of the numerous students from the University of Miami, University of Florida, and Florida International University.


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REFERENCES

American Wood Preservers’ Association, 2001. Standards. American Wood Preservers’ Association, Granbury, TX. Blassino, M., Solo-Gabriele, H., and Townsend, T., 2002. “Pilot Scale Evaluation of Sorting Technologies for CCA-Treated Wood Waste.” Waste Management and Research, 20: 290-301. Clausen, C.A., 2003. Reusing remediated CCA-treated wood. Proceedings of Managing the Treated Wood Resource, II, Special Seminar Sponsored by the American Wood Preservers’ Association and the Utility Solid Waste Activities Group held in Boston, MA. American Wood Preservers’ Association, Granbury, TX. p. 49-56. Cooper, P., Ung. T., Kazi, F., and Qi, D., 2003. Two approaches to recycling of CCA-treated wood: extraction for recycling and wood cement composites. Proceedings of Managing the Treated Wood Resource, II, Special Seminar Sponsored by the American Wood Preservers’ Association and the Utility Solid Waste Activities Group held in Boston, MA. American Wood Preservers’ Association, Granbury, TX. p. 65-76. Felton, C., and De Groot, R.C., 1996. "The recycling potential of preservative treated wood." Forest Products Journal, 46(7/8): 37-46. Focazio, M.J., Welsh, A.H., Watkins, S.A., Helsel, D.R., and Horn, M.A., 1999. A Retrospective Analysis of the Occurrence of Arsenic in Ground Water Resources of the United States and Limitations in Drinking Water Supply Characterization, Water Resources Investigative Report 99-4279. U.S. Geological Survey, Reston, VA. Available on-line at: http://co.water.usgs.gov/trace/pubs/wrir-99-4279/ Jambeck, J., Townsend, T., and Solo-Gabriele, H., 2003. The Disposal of CCA-Treated Wood in Simulated Landfills: Potential Impacts, IRG/WP 03-50198. International Research Group on Wood Preservation, Stockholm, Sweden. Khan, B.I., 2003. Quantification, Speciation, and Impact of Arsenic Leaching from In-Service and Disposed CCA-Treated Wood on the Environment. Ph.D. thesis, University of Miami, Coral Gables, FL. Moslemi, A.A., 1988. "Inorganically bonded wood composites." Chemtech, August: p. 504-510. Schmidt, R., March, R., Balantinecz, and Cooper, P.A., 1994. "Increased wood-cement compatibility of chromated treated wood." Forest Products Journal, 44(7/8): 44-46. Solo-Gabriele, H.M., and Townsend, T., 1999. ”Disposal Practices and Management Alternatives for CCA-Treated Wood Waste. ” Waste Management Research, 17: 378-389. Solo-Gabriele, H., Townsend, T., Calitu, V., Messick, B., and Kormienko, M., 1999. Disposal of CCA-Treated Wood: An Evaluation of Existing and Alternative Management Options. Final


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Technical Report #99-06. Submitted to the Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Available at: www.ccaresearch.org Solo-Gabriele, H., Townsend, T., Kormienko, M., Stook, K., Gary, K., and Tolaymat, T., 2000. Alternative Chemicals and Improved Disposal-End Management Practices for CCA-treated Wood. Final Technical Report #00-03. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Available at: www.ccaresearch.org Solo-Gabriele, H., Townsend, T., Hahn, D., Moskal, T., Hosein, N., Jambeck, J., Jacobi, G., and Iida, K.. 2001a. On-Line Sorting Technologies for CCA-Treated Wood. Florida Department of Environmental Protection, Tallahassee, FL. Available at: www.ccaresearch.org. Solo-Gabriele, H., Townsend, T., Messick, B., and Calitu, V., 2001b. “Characteristics of CCA-Treated Wood Ash.” Journal of Hazardous Materials, 89 (2-3): 213-232. Solo-Gabriele, H., Townsend, T., Khan, B., Song, J-K, Jambeck, J., Dubey, B., Yang, Y-C, 2003a. Arsenic and Chromium Speciation of Leachates from CCA-Treated Wood, Draft Technical Report #03-07. Submitted to the Florida Center for Solid and Hazardous Waste Management, Gainesville, Fl. Available at www.ccaresearch.org. Solo-Gabriele, H.M., Townsend, T.G., Hahn, D.W., Moskal, T.M., Hosein, N., Jambeck, J., and Jacobi, G., 2003b. Evaluation of XRF and LIBS Technologies for On-Line Sorting of CCA-Treated Wood Waste. Waste Management. (In press). Tolaymat, T.M., Townsend, T.G., and Solo-Gabriele, H., 2000. ”Chromated Copper Arsenate Treated Wood in Recovered Wood at Construction and Demolition Waste Recycling Facilities. ” Environmental Engineering Science, 17(1): 19-28. Townsend, T., Stook, K., Tolaymat, T., Song, J.K., Solo-Gabriele, H., Hosein, N., Khan, B., 2001a. New Lines of CCA-Treated Wood Research: In-Service and Disposal Issues. Draft Technical Report #00-12. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Available at: www.ccaresearch.org Townsend, T., Stook, K., Ward, M., and Solo-Gabriele, H., 2001b. Leaching and Toxicity of CCA-Treated and Alternative-Treated Wood Products. Draft Technical Report #02-4. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Available at: www.ccaresearch.org Townsend, T., Solo-Gabriele, H., Tolaymat, T., Stook, K., and Hosein, N., 2003a. “Chromium, Copper, and Arsenic Concentrations in Soil Underneath CCA-Treated Wood Structures.” Soil & Sediment Contamination, 12: 1-20. Townsend, T.G., Solo-Gabriele, H.M., Tolaymat, T., and Stook, K., 2003b. “Impact of Chromated Copper Arsenate (CCA) in Wood Mulch.” The Science of the Total Environment, 309: 173-185. U.S. Environmental Protection Agency, 2002. Federal Register, Notice of Receipt of Requests to Cancel Certain Chromated Copper Arsenate (CCA) Wood Preservative Products and Amend to Terminate Certain Uses of CCA Products ( February 22, 2002), Volume 67, Number 36: 8244-8246.


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Gainesville MiamiTallahassee

Figure 1: Comparison of Mean Arsenic Soil Concentration Below Wooden Decks Versus Background Soil Concentrations. Deck LT was the only deck that was not CCA treated.

Figure 2: Configuration of Decks Designed to Capture Runoff and Infiltrated Water

sandy soil

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Figure 3: Arsenic Concentrations in Runoff Water from the CCA-Treated Deck

Figure 4: Arsenic Concentrations in Infiltrated Water Collected Below 0.7 m Sand from the CCA-Treated Wood Deck

Untreated Deck Runoff Concentrations Roughly Constant at 0.002 mg/L

Untreated Deck Infiltrated Water Concentrations Roughly Constant between 2 to 3 ug/L


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Figure 5: SPLP Extraction Results for As, Cu, and Cr from Sawdust (SPLP Regulatory Guideline for Arsenic is 0.05 mg/L)

Sample

# Color PlywoodCu

(mg/kg) Cr

(mg/kg) As

(mg/kg) 17 None No 1 0 0 18 None No 1 0 0 19 None No 3 0 0 20 None No 3 1 0 26 None No 14 24 19 32 None No 1 1 0 34 None No 1 0 0 1 Red Yes 2 1 0 2 Red No 2 2 0 3 Red No 3 5 0 4 Red Yes 106 129 118 5 Red No 2 3 0 6 Red Yes 71 111 69 7 Red Yes 106 123 68

10 Red Yes 212 458 196 13 Red Yes 144 358 150 14 Red Yes 93 182 112 15 Red No 2 2 0 24 Red No 2 1 0 33 Red No 3 2 0

Table 1: Results to Date for Commercial Mulch Study


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Figure 6: Copper Concentrations found in De-ionized water (DI), TCLP, SPLP and Saltwater (SW) Leaching Fluids

Figure 7: Arsenic Counts using the XRF System for CCA-Treated and Untreated Wood (Wet and Dry Conditions, and wood with various surface coatings)


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Scaled-Up Remediation of CCA-Treated Wood

Carol A. Clausen and William R. Kenealy

ABSTRACT

Bioremediation is a novel approach to recycling waste wood treated with chromated copper arsenate (CCA). Remediating CCA-treated waste wood diverts this fiber source from our landfills and provides tangible secondary products from the cleaned fiber. On a laboratory scale, this method, which utilizes oxalic acid extraction and bioleaching with a metal-tolerant bacterium, removed up to 78% Cu, 100% Cr, and 97% As from 1 kg chipped CCA-treated southern pine. The two-step sequence of oxalic acid extraction and bioleaching removed more metals than did either acid extraction or bioleaching alone. Scale-up parameters on 11 kg of particulate, flaked, or chipped CCA- treated wood were evaluated in a 150-L reactor. This process removed 79% Cu, 70% Cr, and 88% As from particulate wood, 83% Cu, 86% Cr, and 95% As from flaked wood, and 65% Cu, 64% Cr, and 81% As from wood chips. Metals released from CCA-treated wood during bioremediation are potentially recoverable from a liquid medium for reuse or disposal. Remediation methodologies remain cost prohibitive, but they may become economically competitive in the event landfill restrictions are imposed domestically. Keywords: remediation, CCA-treated wood, acid extraction, bioleaching, Bacillus licheniformis

____________

Carol A. Clausen, Research Microbiologist, USDA Forest Products Laboratory, Madison, WI 53726. [email protected] Dr. William R. Kenealy, Research Microbiologist, USDA Forest Products Laboratory, Madison, WI 53726 [email protected]


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INTRODUCTION Chromated copper arsenate (CCA) has been the most commonly used wood preservative in

North America for the past 25 years [1], resulting in large volumes of this material entering our landfills after removal from service. It is estimated that 18 billion cubic feet (5.1 × 108 m3) of CCA-treated wood will be removed from service by the year 2020 [2]. A number of approaches to remediate CCA-treated wood have been developed in an effort to divert treated waste wood from landfills. Alternative disposal methods including, but not limited to, incineration, reconfiguration and reuse, composting with decay fungi, acid extraction, and bioleaching of metals by bacteria were reviewed by Clausen [3]. Alternative disposal strategies could divert CCA-treated material from landfills by reducing the biomass, removing and recycling the metals, or simply extending the useful service life of this material through reuse in a secondary application. No alternative to landfilling has been readily adopted due to the inherent costs and lack of means to handle, transport, sort, and process this waste material. Nevertheless, it is important to continue to investigate and develop new methods to remediate treated wood as well as evaluate scale-up of existing remediation methods so that this technology can be readily transferred into the marketplace in the event domestic landfill restrictions similar to those in Europe are imposed in the future.

A two-step remediation process, involving a combination of oxalic acid extraction and

bacterial culture with the metal-tolerant bacterium, Bacillus licheniformis, substantially reduced the amount of copper (70%–78%), chromium (81%–97%), and arsenic (93%–100%) in CCA-treated wood on a laboratory scale [4,5]. This remediation process, which has been shown to be equally effective in the laboratory on a number of copper-based preservatives [6], allows for recycling of both the wood fiber and metals. The objective of this study was to scale up the two-step remediation method of Clausen [4] to evaluate the effectiveness of the process on larger volumes of particulate, flaked, and chipped CCA-treated southern yellow pine. MATERIALS AND METHODS Treated Wood

CCA-treated southern yellow pine was used for all three trials in this study. In trial I, 11.6 kg of

treated lumber (Brunsell Lumber, Madison, WI), hammer-milled and sorted to an approximate particle size of 3 by 8 mm, was processed. In trial II, flaked southern pine (0.5 mm thick by 11 cm long by varying widths) was treated with CCA-C using a full cell treatment process to a nominal retention of 6.4 kg/m3. In trial II, 11.8 kg of treated flakes was processed. In trial III, 11.3 kg chipped southern pine (3 by 2 by 0.3 cm), treated with CCA-C using a full cell process to a nominal retention of 6.4 kg/m3, was processed.

Remediation Process Processing Equipment

The processing equipment consisted of a 300-L fermentor connected to a 150-L stainless steel recirculating tank (Figure 1). In each of three trials, the wood was confined in a polypropylene bag and placed inside the recirculating tank (Legion Utensils Co., Inc., Long Island City, NY). The bag used for particulate wood was manufactured from woven polypropylene filter fabric (Astrup, Chicago, IL), and the bag used for the flaked and pulp chipped wood was manufactured from nominal 1- by 2-mm polypropylene mesh (McMaster-Carr, Elmhurst, IL). Both bags were


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manufactured by Gallagher Tent and Awning (Madison, WI) and designed to fit the dimensions of the 58.4-cm-high by 58.4-cm-diameter recirculating tank.

Acid Extraction

Oxalic acid, (125 L, 0.8%, pH 1.52) (Sigma, St. Louis, MO) in deionized (DI) water was added and recirculated with a uniform spray over the surface of the immersed bag of wood at 50 L/min and 27oC for 18 h. The optimal ratio (<1:10) kg of treated wood to liters of acid was previously determined [7]. Acid extract and wood were sampled at T0 and T18 h for elemental analysis. Following extraction, the acid was drained for 1 h and the volume recovered was recorded (Table 1).

Bioleaching

Nutrient medium (Difco, Detroit, MI) was prepared according to manufacturers’ directions to give 0.8% concentration and sterilized in a 300-L fermentor (Fermentation Design, Inc., Allentown, PA) at 121oC for 20 min. Medium was cooled to 65 oC–70oC and pumped into the remediation tank. Medium was further cooled to 27oC, adjusted to 125 L volume, and pH was adjusted to 5.5–5.6 with saturated NaOH. Antifoam A (Sigma, St. Louis, MO) was added before the tank was inoculated with 1 L of inoculum prepared as follows. Bacterial inoculum preparation consisted of aseptically inoculating Bacillus licheniformis CC01 into 100 mL of nutrient medium, incubating for 15 h at 27oC, transferring 100 mL of the 15-h culture into 1 L of nutrient medium, incubating for 8 h at 27oC, and transferring 1 L of the 8-h culture into 125 L of nutrient medium in the remediation tank of cooled medium. Inoculum contained 6 × 107 colony forming units per milliliter (CFU/mL).

The inoculated medium was recirculated (50 L/min) with a uniform spray over the surface of

the wood at 27oC for 7 to 9 days. Filtrate samples were taken periodically during the incubation for bacterial counts and elemental analysis. Wood samples were submitted for elemental analysis following bioleaching. Spent nutrient medium was collected for either disposal as hazardous waste or future studies on metal recovery. An uninoculated control was subjected to oxalic acid-extraction, drained, and incubated for 7 days in DI water. Samples of filtrate and wood were taken periodically for elemental analysis.

Microbial Growth Analysis

Samples of nutrient medium were taken periodically during the 7-day incubation and

streaked for purity on nutrient agar (Difco, Detroit, MI). A plate count was also conducted on

Figure 1 Fermentator (left) connected to recirculating remediation tank (right).


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74

nutrient agar plates to determine CFU/mL of inoculum and time of peak growth of the bacterium [8].

Table 1 Processing conditions for three CCA-treated chip types and elemental analyses of filtrates and processed wood samplesa

Total metals in filtrate (g recovered)

Metals in wood samples (mg/g)b Wood

geometry Process Time pH

Wood weight

(kg)

Filtrate volume

(L) Cu Cr As Cu Cr As Particle Acid extraction 0 1.52 11.61 125 1.45

(0.03) 2.67

(0.05)2.55

(0.03)

18 h 1.44 91 3.76 17.70 21.11 1.28 (0.05)

1.30 (0.03)

0.90 (0.15)

Bioleaching 1 d 5.60 125

7 d 6.23 125 20.58 7.08 6.70 0.30 (0.01)

0.79 (0.02)

0.30 (0.01)

Flake Acid extraction 0 1.50 11.79 125 2.66 (0.10)

5.19 (0.26)

4.61 (0.33)

18 h 1.58 109 5.12 24.83 28.27 2.23 (0.11)

1.54 (0.06)

0.81 (0.01)


7 d 6.11 125 12.17 5.36 4.51 0.46 (0.04)

0.72 (0.03)

0.22 (0.02)

Pulp chip Acid extraction 0 1.56 11.34 125 1.88 (0.21)

5.13 (0.09)

4.58 (0.06)

18 h 1.62 110 2.75 21.04 24.58 1.87 (0.16)

3.00 (0.09)

1.94 (0.05)


7 d 6.13 125 12.84 13.16 13.36 0.65 (0.04)

1.87 (0.06)

0.89 (0.02)

an = 3.bStandard error in parentheses.


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Elemental Analysis Oven-dried wood samples, ground to pass a U.S. Standard 20-mesh (850-µm) screen, were

digested and analyzed in triplicate for copper (Cu), chromium (Cr), and arsenic (As) content by inductively coupled plasma (ICP) emission spectrometry according to American Wood Preservers’ Association standard A-21-00 [9]. Filtrate samples were submitted in triplicate for ICP analysis for copper, chromium, and arsenic.

Figure 2 Metals removed by acid extraction of CCA-treated particles, flakes, and chips. Figure 3 Percentage of Cu, Cr, and As removed after 7 days of bioleaching with Bacillus licheniformis.

0

20

40

60

80

100

Particles Flakes Chips

Met

al re

mov

ed (%

)

Cu Cr As

0

20

40

60

80

100

Particles Flakes Chips

Met

al re

mov

ed (%

)

Cu Cr As


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RESULTS

Conditions for remediation of CCA-treated southern yellow pine and elemental analyses of

filtrates and wood samples are summarized in Table 1. Extrapolating total metals recovered in large volumes of filtrate is subject to experimental error. Residual metals in processed wood samples are a better indicator of the success of the remediation process. The extent of metal removal following acid extraction is shown in Figure 2. Copper extraction was the lowest, particularly for pulp-chipped wood. Flaked wood showed the highest extraction of chromium (70%) and arsenic (82%) of the three material geometries tested, presumably because of the increased surface area exposed to the acid.

Figure 3 shows the total percentage of each metal removed from CCA-treated particles, flakes,

and chips following step 2, bioleaching. Greater percentages of each metal were removed from particles, flakes, and chips following bioleaching than following acid extraction. Increases in the removal of copper by B. licheniformis were most dramatic; 65% to 68% more copper was removed during bioleaching than by acid extraction alone. Residual acid in the uninoculated control extracted 12% to 35% additional Cu, Cr, and As during the subsequent 7 days (results not shown). That compares to 22% to 65% additional metal removal by bioleaching in the same time frame.

Trial I

The cumulative percent removal of CCA components—12% Cu, 51% Cr, and 65% As

following acid extraction and 79% Cu, 70% Cr, and 88% As following bioleaching—are similar to results seen in bench-scale studies for this method [3–5]. Bioleaching with B. licheniformis clearly increased the removal of all three CCA components and preferentially copper. The filter fabric bag and small wood particle size moderately hampered exchange of acid and medium from the inside to the outside of the bag during recirculation. The bag also inhibited drainage following the acid extraction, which, in turn, required more sodium hydroxide to adjust the pH for the bioleaching portion of the process. Opening the remediation tank several times for pH adjustment eventually led to microbial contamination. Foaming was minimal and confined to the inside of the bag until day 7 of incubation, when signs of contamination were noted on a plate of nutrient agar streaked for purity and on the bag and sides of the remediation tank above the liquid level (Figure 4). Remediated particles were thoroughly rinsed with DI water and air dried before storage.

Trial II

Following the 18-h oxalic acid extraction, flaked pine samples showed 16% removal of Cu,

70% removal of Cr, and 82% removal of As (Figure 2). Following bioleaching, the cumulative proportion of Cu, Cr, and As removed was 83%, 86%, and 95%, respectively (Figure 3). Flaked CCA was more voluminous than particulate CCA. While the mesh bag allowed for equal and unencumbered exchange of medium between the inside and outside of the bag, the flakes had to be settled into a flat configuration. The spray of medium on flat flakes changed the uniformity of the medium spray and may have increased foaming. Despite adding additional antifoam A, foam filled the remediation vessel (Figure 5). Remediated flakes were thoroughly rinsed with DI water and air dried before storage.

Trial III


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Results showed that pulp-

chipped southern pine had 0.5% removal of Cu, 42% removal of Cr, and 58% removal of As following the 18-h oxalic acid extraction (Figure 2). Growth of the bacterium peaked on day 6 post-inoculation, at 2.5 × 109

CFU/mL. Because no contamination was detected, this trial was continued for two additional days to determine if additional metal removal would occur, but it did not. The proportion of metals removed from pulp-chipped southern pine was 65%, 64% and 81% for copper, chromium, and arsenic, respectively (Figure 3). Remediated chips were thoroughly rinsed with DI water and air-dried before storage.

DISCUSSION

Eleven-kg batches of CCA-treated wood were remediated with a two-step process involving oxalic acid extraction for 18 h followed by bioleaching for 7 days. Special attention to details, such as handling increased quantities of raw materials, maintaining aseptic conditions, adequate inoculum, and ensuring robust microbial growth, is essential when scaling up a microbial process. In an industrial scale-

up of a fungal-based remediation process for CCA-treated wood using the brown-rot fungus Antrodia vaillantii, Leithoff and Peek [10] cited difficulties in regulating humidity and contamination by bacteria that were capable of totally inhibiting growth of this fungus. In our study, acid extraction combined with the presence of soluble metals in the filtrate discouraged, but did not

Figure 4 Remediated particles were rinsed with DI water. Evidence of mold growth, which occurred on day 7 of incubation, were evident on the bag above the liquid line (arrow).

Figure 5 Mesh bag and larger wood configurations changed dynamics of surface spray, resulting in foaming that filled remediation tank.


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entirely eliminate, growth of potential microbial contaminants, e.g., mold fungi. Similarly, overwhelming the system with a bacterial inoculum with a short regeneration time provided an opportunity for the Bacillus to out-compete potential contaminants for nutrients, especially those susceptible to the toxic components of CCA.

We were successful in sanitizing and maintaining aseptic conditions for the 7 day’s duration of

the remediation process. Uninoculated controls, however, could not be tested under these conditions without contamination. Therefore, following acid extraction, controls were incubated in DI water for 7 days to determine if residual acid would continue to extract metals, specifically copper. Residual acid from the saturated wood did continue to extract additional metals, but to a lesser degree than did bioleaching. It was previously shown that neither oxalic acid extraction alone for 18 h nor bioleaching with B. licheniformis for 7 days alone were as efficient at metal removal as was acid extraction followed by bioleaching [5].

The bacterial inoculum (108 CFU/mL) was unable to enter log growth phase as quickly as anticipated, which may have allowed for some contamination on the final day of the remediation process, despite the fact that elevated levels of copper, chromium, and arsenic were present in the nutrient medium. Likewise, adjusting pH, adding antifoam one or more times, and sampling the wood and filtrate were also factors that increased the potential for contamination of the otherwise sanitized but not sterilized system.

The polypropylene filter fabric bag used to contain the particulate wood somewhat hindered the free exchange of liquid (both acid and nutrient medium) between the inside and outside of the bag. It also slowed drainage of the acid following the extraction step; 91 L of acid was recovered from the particulate wood after draining the vessel for 1 h. Conversely, the open-weave mesh polypropylene bag used to contain the flaked and chipped wood allowed for unencumbered liquid exchange and rapid drainage of acid following the extraction process; 109 L and 110 L of acid were recovered from flakes and chips, respectively, following 1 h of drainage.

The configuration of the wood played a role in the fluid dynamics of the remediation process. While the surface area and thickness of flaked wood were clearly advantageous to the removal of metals by both acid extraction and bioleaching, they enhanced foaming and limited uniform coverage of wood by the spray of liquids through the recirculating nozzle. However, once the wood became saturated during the acid extraction and remained submerged for the duration of the process, the surface spray of liquids probably played a minor role compared to mixing of the vessel contents.

From an economic perspective, the two-step process described here remains prohibitively expensive. For example, the cost of manufacturing particleboard from virgin southern pine stock is approximately $0.28/kg. Particleboard made from wood fiber remediated by the two-step process would be over 6 times more, due to the cost of oxalic acid ($0.02 to 0.07/kg) and the nutrient medium (~$1.79/kg). Collection, sorting, and transportation costs for treated wood have not been determined for this remediation process. Savings incurred by recovery and reuse of the metals are not addressed here.

With increased restrictions internationally on landfilling CCA-treated wood, domestic landfilling costs may also become prohibitive. Currently, the landfill tipping fee for CCA-treated wood in the midwestern United States is approximately $33/1,000 kg [11]. In California, the average cost for regulating treated wood waste as hazardous waste has been estimated at $291/1,000 kg, which would represent a 500% increase over the current non-hazardous disposal fee of


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$61/1,000 kg [12]. This would be comparable to disposal of CCA-treated wood in special landfills in Europe, which can cost over $300 USD per 1,000 kg (personal communication).

The process described here was not optimized to provide ideal growth conditions for B. licheniformis. Aeration was only provided by recirculating liquid, pH was not continuously controlled, and sanitary conditions can only delay eventual contamination. A system that merely controls temperature and aerates by recirculating and spraying liquid would be considered one of the simplest process designs for wood remediation. Nevertheless, the robustness of the process indicates acid extraction and B. licheniformis growth can effectively remove metals from CCA-treated wood.

CONCLUSIONS

Sample thickness and surface area of CCA-treated wood samples affected metal removal during both oxalic acid extraction and bioleaching processes. Flaked wood, which was thin and had a large surface area, was most amenable to metal removal, followed by small particulate wood (3 by 8 mm). The lowest metal removal rate, seen in pulp-chipped wood, may be improved by increasing acid extraction time. Circulating oxalic acid helped sanitize both the tank and wood, but it did not totally prevent contamination of the remediation process by day 6, despite elevated levels of copper, chromium, and arsenic in the nutrient medium. Similar to previous bench-scale studies, oxalic acid extraction removed a greater amount of chromium and arsenic, while the bacterium was most effective at removing copper. The two-step processing sequence is more efficient than either acid extraction or bioleaching alone. The results of this study show that scaling-up the bioremediation process to 11–12 kg batches of CCA-treated wood removed metals with an efficiency similar to that seen in 1-kg batches at the optimized 1:10 ratio (w/v) of solid to liquid [13], even for chipped and flaked wood.

ACKNOWLEDGMENTS

The authors would like to thank Dan Foster, Chemist, for elemental analyses, and Brian Schlitt for technical assistance.

REFERENCES

[1] Preston, A.F. 2000. Wood Preservation: Trends of today that will influence the industry tomorrow. Forest Products Journal 50(9): 12–19. [2] Cooper, P.A. 1993. Leaching of CCA: Is it a problem? Disposal of treated wood removed from service: the issues. In: Proceedings, Environmental Consideration in the Manufacture, Use, and Disposal of Preservative Treated Wood, Carolinas–Chesapeake Section of the Forest Products Society. May 13, Richmond, VA. [3] Clausen, C.A. 2003. Reusing remediated CCA-treated wood. In: Proceedings, Managing the Treated Wood Resource II, American Wood Preservers’ Association Utility Solid Waste Activities Group, Boston, MA: 49–56. [4] Clausen, C.A. 2000. CCA removal from treated wood using a dual remediation process. Waste Management & Research 18: 485–488. [5] Clausen, C.A. and Smith, R.L. 1998. Removal of CCA from treated wood by oxalic acid extraction, steam explosion, and bacterial fermentation. Journal of Industrial Microbiology 20: 251–257. [6] Crawford, D. and Clausen, C.A. 1999. Evaluation of wood treated with copper-based wood preservatives for Cu loss during exposure to heat and copper-tolerant Bacillus licheniformis. IRG/WP 99–20155. International Research Group on Wood Preservation, Stockholm, Sweden.


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[7] Clausen, C.A. Improving the two-step remediation process for CCA-treated wood Part I. Evaluating oxalic acid extraction. Waste Management (in press). [8] Messer, J.W., Peeler, J.T. and Gilchrist, J.E. 1978. Aerobic plate count. In: R.B. Read, Jr. (ed.), Food and Drug Administration Bacteriological Analytical Manual. 5th ed. Association of Official Analytical Chemists, Washington, DC. [9] AWPA. 2001. Standard method for the analysis of wood and wood treating solutions by inductively coupled plasma emission spectrometry. A21–00. Book of Standards. American Wood Preservers’ Association, Granbury, TX: 313–317. [10] Leithoff, H. and Peek, R.–D. 1995. Experience with industrial scale-up for the biological purification of CCA-treated wood waste. International Research Group on Wood Preservation, Stockholm, Sweden. IRG/WP 97–50095. 10 p. [11] Ince, P.J. 1998. North American paper recycling situation and pulpwood market interactions. In: Pro-ceedings, Recycling, energy, and market interactions, Workshop of the United Nations Economic Commission for Europe Timber Committee. Nov. 3–6, 1998. Istanbul, Turkey. Ministry of Forestry, Turkey: 61–72. [12] Smith, S.T. 2003. Economic analysis of regulating treated wood waste as hazardous water in California. Prepared for Western Wood Preservers’ Institute, Vancouver, WA. [13] Clausen, C.A. Improving the two-step remediation process of CCA-treated wood Part II. Evaluating bacterial nutrient sources. Waste Management (in press).


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Modeling of wood preservative leaching in service

Levi Waldron, Paul Cooper and Tony Ung

Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, M5S 3B3 Ontario,

Canada Abstract: To evaluate the potential environmental and health implications of leaching of wood preservatives in service under different conditions, there is a need for a predictive model that provides estimates of the rate and extent of leaching over a wide range of exposure conditions. In this paper, we test the hypothesis that preservative component emissions can be modeled on the basis of three easily measured parameters: total leachable component based on intensive leaching of fine ground material; amount of dissolved or dissociated component in water saturated wood; and preservative component diffusion coefficients in the longitudinal and transverse directions. These variables are estimated for ACQ, copper azole, CCA and borate wood preservatives and the leaching rates of lumber samples are compared with the rate predicted by the model. This model approach should permit the estimation of leaching rates under a wide variety of product geometries and exposure conditions. Keywords: Leaching, preservatives, diffusion, dissociation, risk assessment

INTRODUCTION In the risk assessment of new and currently in use wood preservatives, it is important to have representative estimates of the preservative component leaching rates under different exposure scenarios and to understand how these leaching rates change with time and other variables. This information, in combination with data on dilution and fate of substances in the environment, permits the estimation of predicted environmental concentrations (PEC) at any time in service [1]. These PEC values can be compared to predicted no effect concentrations (PNEC) to assess their potential environmental impacts. There are a number of initiatives through the OECD, EU, AWPA and other organizations and associations [2,3,4] to devise appropriate leaching procedures that can predict both expected long term efficacy of the treatment and potential impacts of leachates on human health and the environment. Willeitner and Peek [6] discussed the difficulty of devising a practical test that is cheap, fast and reproducible while giving a realistic indication of short term and long term impacts. Exposure of the environment to wood preservative contaminants and the resulting risk is best characterised by the rate of preservative emission from the treated wood, expressed as amount released per unit surface area per unit time or flux (typically µg/cm2/hour). It has been shown that flux decreases with time in service and that the most acute environmental and health exposure to _______


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Levi Waldron, Paul Cooper and Tony Ung; Faculty of Forestry, University of Toronto, 33 Willcocks St., Toronto, M5S 3B3 Ontario, Canada leached substances occurs in the period soon after installation [7] while long term accumulations in soil and sediments result from the lifetime exposure to ever-declining emissions. Previous studies [7,8,9,2] have modeled this declining flux rate, usually with exponential equations. These models can be applied to risk assessment scenarios to predict releases at any given time; long term accumulations in water columns, soils and sediments can be estimated by determining the area under the curve by integration or by use of a “growth model” as suggested by Homan and van Oosten [1]. Based on our comparisons of laboratory and field leaching studies, we believe that leaching consists of a number of concurrent and consecutive phenomena, each of which is affected by a number of wood product, preservative and exposure conditions: • Wetting of wood and penetration of free water into the wood void space (more relevant for

intermittent rain exposure than continuous water soaking conditions). This factor depends on wood permeability, surface wetting properties, orientation to the weather, type of exposure etc.

• Dissolving/dissociation of precipitated or reacted preservative components and diffusion out of the cell walls into free water in the cell lumens to the limit of their solubility under the test conditions (depends on preservative, temperature, MC, etc.). This creates the concentration gradient that drives the diffusion process.

• Diffusion of preservative components to the wood surface. The diffusion rate will depend on a number of factors such as wood permeability, moisture content, temperature, dimensions, direction of movement in wood, and especially the nature of the diffusing species and the concentration gradient established; an understanding of the effects of solute ion size, charge, solubility and other chemical properties will be helpful in predicting how new preservatives will perform.

• Drying of wood after rain exposure and possibly, wicking of dissolved components to the wood surface – not relevant for continuous water soaking conditions (depends on ambient T, RH, air flow conditions).

To model leaching emissions, we propose that there are advantages to using diffusion theory rather than empirical models. Leaching of wood components from two opposing surfaces can be described by one-dimensional Fickian diffusion.

(1) For leaching of a preservative component from wood, C is the concentration of preservative in wood at any time t that is available for leaching. D = diffusion coefficient (cm2/s); l = sample length in the direction of movement of leached component if leached from only one side, or half the sample length if the two opposing faces are leached; x = diffusion direction. The above equation is solved for boundary conditions: (i) Uniform initial analyte concentration in the wood at the start of leaching, ie, the initial concentration C(x,0) is a constant Co, i.e. all of the available solute is dissolved in the cell lumen water and no additional preservative dissociates. (ii) The component concentration is 0 at the wood surface/water interface i.e., the water is changed frequently; (iii) Continuous leaching in one direction only.


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In this case, the mass of material M leached as a function of time, relative to the ultimate amount available (Minf) is given by Equation 2. For preservative systems with low solubility reaction products, Minf is the amount of preservative that is available for leaching rather than the amount of preservative in the wood.

(2) Equation 2 estimates cumulative loss (M/Minf) at time t (s), as a function of specimen dimension in the diffusion direction (2l cm for diffusion from two opposing surfaces) and diffusion coefficient (D). M/Minf can be related to the % of total leached which is a common expression of cumulative leaching if the amount available for leaching is known and expressed as a % of total of preservative retained in the wood. Estimates can be converted to flux estimates (µg/cm2/time) at any elapsed time (t) by computing M (in µg) at two consecutive time intervals and dividing the change in amount leached over the interval by the exposed sample area and the time interval. Application of an appropriate diffusion model to the loss of preservative from wood by leaching offers the following advantages: 1. Diffusion models are science based and should describe the physical process more consistently than empirical models. Extrapolation of results based on diffusion theory should be more reliable than extrapolation of empirical models; furthermore, they provide a theoretical basis to assist with the design of appropriate test methods.

2. The diffusion model corrects for effects of specimen dimensions. It should be possible to use small scale short term laboratory tests to predict long term emission characteristics.

3. Diffusion coefficients can be determined for variables of interest such as wood direction (longitudinal vs. transverse), temperature, wood species, preservative component and formulation.

4. Diffusion equations can be solved for virtually any product geometry (pole, board, block) and can be solved in three dimensions to describe practical leaching scenarios.

We hypothesise that the leaching process for a given product under continuous moisture exposure conditions can be described adequately by three fairly simple-to-measure factors: 1. Percentage of preservative components available for leaching; 2. Equilibrium dissociation of preservative components in wood; 3. Diffusion coefficients for movement of preservative components out of wood

MATERIALS AND METHODS To evaluate the equilibrium dissociation of preservative components, solid treated wood samples (25 mm cubes) at a moisture content of approximately 10 % were cut from southern yellow pine (Pinus sp.) 38mm X 140 mm boards commercially treated with chromated copper arsenate (CCA-C), amine copper quaternary (ACQ-C), copper azole (CA-B) and disodium octaborate tetrahydrate


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(DOT). For more refractory species such as spruce, jack pine and red pine, thinner wafers (20mm X 50mm X 5mm thick were treated with different concentration ACQ-D preservative solutions. The inorganic preservative component retention of ground samples was determined (kg/m3) by digesting a 1 g sample in H2O2/Nitric Acid (AWPA 1993) and analyzed by inductively coupled plasma (ICP) spectroscopy for copper (CCA, ACQ, CA), chromium (CCA) arsenic (CCA) and borate (ACQ and DOT). After preservative stabilization, the wafers were vacuum/pressure impregnated with water. The mass uptake of water was determined and assumed to represent the amount of water in the wood containing dissolved components. The rates of change in amounts of preservative components in the free water in the cell lumens was determined by squeezing the blocks in a press to express solution from matched samples at different times. The expressed solution was analysed for the above inorganic components by ICP and the mass of dissolved component (Di) expressed as a percentage of total content of the wood:

Di = Water uptake (g) X concentration in expressate (µg/g) X 100 %

(3) Retention in wood (µg/g) X sample mass (g)

The percentage of preservative components readily available for leaching was estimated from the leaching performance of finely ground wood. Cross-section samples of the same wood samples as above were ground to pass a 1 mm screen. Five grams of the ground samples were leached in 50 mL water at 21ºC and the water exchanged regularly over a 12-week period. Cumulative percent leaching was determined by analysing the leachate by ICP. Under ideal leaching conditions, when the wood is sufficiently saturated with water and the preservative components are dissolved in the water to their limit of solubility, the diffusion of the components out of wood can be characterized using the non-steady state diffusion model shown in Equation 2. The maximum amount of preservative available for leaching (Minf) should be the total leachable amount (Le) determined as above but the quantity of dissociated preservative at equilibrium (Di) establishes the concentration gradient that controls the diffusion process. Unless these quantities are identical, use of Le will over-estimate the rate of leaching while use of Di will under-estimate the cumulative amount of leaching at any time. Alternatively, Minf can be estimated from the model fitting exercise. In this study, diffusion values are estimated using the amount of dissociated preservative as the first estimate of Minf. As discussed later this is appropriate for some preservative systems but the model will have to be refined for others. To ensure uniform initial preservative component concentration at the start of leaching, the blocks were vacuum treated with water and stored for six days to allow full dissociation of the component(s) before starting leaching. Continuous leaching in one direction only was achieved by sealing all except one face with silicone sealant. Samples were placed individually in 300 ml water and the water replaced periodically. The leachate samples were analyzed for preservative content by ICP and the % of total preservative leached plotted vs. leaching time. For some preservatives, leach water was held at different temperatures (10°C, 20°C, 30°C) to compare T effect on leaching rate. The leaching curves at 20°C were fit with the diffusion model (Equation 2) to estimate D values. For this paper, calculations were performed using a FORTRAN program to determine best fit diffusion coefficients by minimizing the sum of square of differences between experimental and calculated leachate quantities. Since Equation 2 converges rapidly, the calculation could also be done using a spreadsheet to sum the first 8-10 terms of the equation.


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RESULTS AND DISCUSSION The dissolving or dissociation process required some time to reach equilibrium and there were differences in rate of equilibration and extent of component solution in the cell lumen space depending on the preservative system, preservative retention, and ambient temperature. The equilibrium dissociation of copper is shown for a number of wood species and retentions for ACQ treated wood at room temperature in Table 1. For the species compared here, there does not appear to be a species effect as all species have similar amounts of available copper dissolved in the water in the cell lumens and similar % total preservative dissociated for a given preservative retention. However, the amount of dissolved copper available for diffusion increases with preservative retention, although the proportion of total copper available relative to the total in wood decreases with increasing retention. For most preservative components, there is an increase in the amount of dissolved or dissociated preservative with increasing temperature (Table 2). This is especially evident for CCA components and borates. Solubility of copper in the copper amine systems seems to be less affected by ambient temperature. The rates of dissociation and leaching of fine sawdust properties of typical samples of treated wood are shown in Figure 1 (CCA), Figure 2 (ACQ) and Figure 3 (CA-B). The total amounts available for leaching and the equilibrium dissociation amounts for the preservatives and for different preservative retentions are shown in Table 3.


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Table 1 Effect of species and preservative retention on dissociation of copper from ACQ-D treated wood

Species Concentration

ACQ (%)

Retention CuO

(kg/m3)

% CuO concentrati

on in lumens

% copper

dissociated

% copper available

for leaching

Southern pine - 3.14 0.085 22 - Jack pine 0.4 1.32 0.042 22 26 Jack pine 0.8 2.87 0.062 15 14 Jack pine 1.3 4.63 0.087 13 12 Jack pine 1.7 6.27 0.122 14 8 Trembling

aspen 0.4 1.59 0.053 23 -

Trembling aspen

0.8 2.95 0.083 16 -

Trembling aspen

1.3 5.6 0.101 12 -

Trembling aspen

1.7 7.62 0.129 13 -

Red pine 0.4 1.26 0.039 22 19 Rd pine 0.8 2.64 0.058 15 16 Red pine 1.3 4.13 0.084 14 16 Red pine 1.7 5.81 0.126 16 20 Spruce 0.4 1.36 0.038 22 22 Spruce 0.8 2.92 0.060 16 13 Spruce 1.3 4.78 0.099 16 19 Spruce 1.7 6.55 0.148 17 15


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Table 2 Effect of ambient temperature on preservative component dissociation in southern pine Preservative Retention

(kg/m3) Temperatur

e (°C)

% component dissociated

Cr Cu As B CCA-C 4.3 10 1.5 3.0 3.5 - CCA-C 4.3 20 3.0 6.5 7.5 - CCA-C 4.3 30 4.0 6.0 9.0 -- DOT 2.28 B2O3 10 - - - 75 DOT 2.28 B2O3 20 - - - 100 DOT 2.28 B2O3 30 - - - 100 ACQ 3.15 (CuO) 10 - 20 - - ACQ 3.15 (CuO) 20 - 22 - - ACQ 3.15 (CuO) 30 - 16 - - CA-B 1.94 (CuO) 10 - 8 - - CA-B 1.94 (CuO) 20 - 10 - - CA-B 1.94 (CuO) 30 - 12 - -

For all preservatives, the finely ground treated wood exposed to water lost a proportion of each component rapidly, to an asymptotically approached maximum indicating that the remaining component was highly leach-resistant (DOT was an exception since virtually all borate could be extracted). In practice, it is unlikely that leaching in service will progress beyond this asymptote and its value provides an upper limit to the amount potentially lost by leaching. Even with this finely ground material it was evident that some components such as Cu in ACQ and CA treated wood and borates leached much more quickly than other components.


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0

5

10

15

20

25

30

35

40

0 48 96 144 192 240 288 336 384 432 480 528 576 624 672

Time, h

% D

isso

ciat

ion/

Leac

hed

As Cu CrAs Leached Cu Leached Cr Leached

Figure 1 Comparison of rates and amounts dissociated (solid lines) with amounts leached from sawdust (broken lines) for CCA-C components in southern pine


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Figure 2 Comparison of rates and amounts dissociated (solid lines) with amounts leached from sawdust (broken lines) for Cu and B components of ACQ-C in southern pine

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Figure 3 Comparison of rates and amounts dissociated (solid line) with amounts leached from sawdust (broken line) for Cu component of CA-B in southern pine


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The rates of dissociation were also different for different preservatives. For example, the more soluble copper in ACQ and borate in ACQ and DOT formulations reached equilibrium sooner than the copper in CA and the CCA components. The arsenic component of CCA was especially slow to equilibrate. If the treated wood undergoes wetting and drying processes, this could significantly affect the leaching rate due to the limited time available for leaching. For CCA (Figure 1) it is evident that the amount dissociated was limited by solubility and it represented only a fraction of the preservative component available for leaching. In this case, the concentration gradient for diffusion will be low resulting in a reduced leaching rate, but there will be a “reservoir” of available preservative that will replace leached components. The net effect should be characteristic slow leaching of CCA components over a very long period of time. As confirmed by numerous studies, the chromium was the least soluble component and these results show that the ultimate amount of chromium available for leaching is also relatively low (7.4 % of total at this retention). The copper component reaches a leaching equilibrium rapidly suggesting that at the retention evaluated here, it will initially leach faster than arsenic, but the rate of leaching will decline faster than arsenic. The arsenic component appears to dissolve and leach slowly but for a long time. The availability of arsenic to leaching is highly dependent on retention in wood [10] and species [11] so these properties will depend greatly on these and other variables. For ACQ, at the retention evaluated in Figure 2, both the copper and borate components had amounts available for leaching almost identical to the amounts dissolved in the free void space at equilibrium. This means that most of the readily soluble components in the treated wood can dissolve in free water saturating the wood. This creates a steeper concentration gradient during leaching. This was also more or less confirmed for a range of species and ACQ retentions (Table 1, last two columns). This high copper solubility compared to copper in CCA is likely due to free amine dissolved in the cell lumen water.

Table 3: Summary of leaching, dissociation and diffusion parameters for southern pine treated commercially with a number of wood preservatives Preservativ Retention

(kg/m3) Total leachedfrom sawdust

(%) Total

Dissociated

(%)

DL (10-6cm2/s)

DRad. (10-6 cm2/s)

DTan (10-6 cm2/s

Quality of fit

L R TCCA-As 1.44 As2O5 39.5 5.5 1.52 0.20 0.05 P P PCCA-Cu 0.86 CuO 20.4 4.3 0.34 0.05 - P G - CCA-Cr 2.01 CrO3 7.4 2.1 0.77 0.13 - P G -

ACQ 1.82 CuO 34.9 28.1 1.9 0.15 - M M - CuA 1.21 CuO 26.2 9.3 0.65 0.032 0.002 G G PDOT 2.28 B2O3 ~100 91.0 0.15 0.05 0.03 M G G

M - Moderate; P - Poor; G - Good


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At the CA-B retention evaluated (Figure 3), the copper behaved more like the copper in CCA than the copper in ACQ. A much larger amount was available for leaching than was dissolved in the free void space at equilibrium. This is surprising since it is also a copper amine system. The difference is attributed to the lower copper amine concentration compared to the ACQ system, and in fact when higher CA retentions were evaluated, we observed a higher % dissociated (results not shown). For the DOT treatment virtually all of the borate was available both for leaching and dissolved in the free water in the wood void space. However, the fraction of total B dissolved in the wood cell lumens will be restricted at lower temperatures as seen in Table 2 and at high DOT retentions. This creates a very steep concentration gradient to drive diffusion of boron out of wood during leaching. It appears that the dissociation characteristics have several important implications: • Rate of dissolving may be a significant factor in intermittent water exposure conditions where wood dries between exposures; • In some cases, equilibrium dissociated concentrations in the cell lumens is an indicator of total available preservative component for leaching; • The high concentration in the cell lumens and reduced concentration at the surface during a leaching event provides the concentration gradient driving the diffusion of components to the wood surface where they are leached away. The rate of unidirectional leaching is known to depend on both temperature [12,13] and diffusion direction [14]. Preliminary results shown in Table 4 for 20 mm thick, DOT and CA-B samples sealed on all but one face and leached for specific times confirm this. Leaching is much greater along the grain than transversely and in southern pine radial leaching is much greater than in the tangential direction. Examples of the rate of leaching of 20 mm samples in different directions and the best analytical solution for the diffusion coefficient D assuming Minf is the equilibrium dissociated amount are shown in Figures 4-8. The diffusion model fits leaching data very well for leaching of Cu and Cr from CCA treated wood in the radial direction (Figures 4 and 5). At the end of the leaching test, the amount of component leached is still much lower than the amount dissociated in the wood so the amount dissociated is a good short term estimate of Minf.


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Table 4 Effect of water temperature on leaching of copper from CA-B and borate from DOT – southern pine Preservative Water T

(°C) Leaching time (d)

% Component leached Direction

Long. Rad. Tan. CA-B (Cu) 10 9 6.2 2.5 0.6 CA-B (Cu) 20 9 10.2 4.2 0.8 CA-B (Cu) 30 9 10.5 4.4 1.1 DOT (B) 10 3 22 12 9 DOT (B) 20 3 26 20 13 DOT (B) 30 3 41 28 19

Figure 4 Comparison of leaching values with best fit of diffusion model for copper leaching from CCA treated southern pine – Radial direction

Figure 5 Comparison of leaching values with best fit of diffusion model for chromium leaching from CCA treated southern pine – Radial direction


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However, where more vigorous leaching occurs as for arsenic leaching along the grain in CCA treated samples (Figure 6) the model predicts that the leaching rate will level off soon, but this dos not occur because of the large arsenic reservoir that can dissolve and leach as the initial dissociated arsenic is depleted. It will be important to refine the diffusion model in cases where not all preservative available for leaching is dissolved in the wood during the leaching process. For borate treated samples (Figures 7 and 8) the diffusion model fits experimental values relatively well for both longitudinal and transverse diffusion because the amounts dissociated are approximately equal to the amounts available for leaching (100 % of retention).

Figure 6 Comparison of leaching values with best fit of diffusion model for arsenic leaching from CCA treated southern pine – Longitudinal direction

Figure 7 Comparison of leaching values with best fit of diffusion model for borate leaching from DOT treated southern pine – Radial direction


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Figure 8 Comparison of leaching values with best fit of diffusion model for borate leaching from DOT treated southern pine – Longitudinal direction These results show large differences in the inherent diffusion characteristics of the different preservative components and systems. D values were typically greater parallel to grain than across the grain and higher in the radial direction than the tangential direction (Table 3). For borate samples, D values were in the range observed by Ra et al. [14] for boric acid diffusion into southern pine wood. APPLICATION

Based on the above parameters, it should be possible to estimate the rates and amounts of preservatives that leach from wood under a wide range of conditions. For example, the above parameters were applied to estimate copper and borate leaching from the top surface of southern pine decking (38mm) treated with CCA, ACQ and DOT and continuously exposed to rainfall for a 1 year period (Figure 9). For this comparison, dissociated concentration of copper was used in the estimate. It is assumed that all leaching is from the top face of the board. The model predicts that virtually all of the DOT will be lost after 1 year and that about 2/3 of the dissociated copper will be lost from ACQ and CCA treated boards. While these estimates need to be validated, the copper losses from CCA will likely be underestimated since further dissociation of additional leachable copper above the initial dissociation level is not considered. Future work will focus on including the continuing dissociation of these components as leaching proceeds in the diffusion model. Some Special Implications and Limitations of this Approach: 1. If the above principles are accepted, it is clear that prediction of emissions should be based on time of rain and other water exposure rather than intensity of exposure. This is validated by studies that show that more leaching occurs per unit rainfall by slow steady rainfall than by an intense down-pour [15] and that the amount of leaching occurring over a fixed leaching time is independent of intensity of rainfall [16]. This is unfortunate, since it is more common to record meteorological information as mm rainfall rather than duration of actual precipitation. 2. The models assume that wood is fully saturated with water (dissociation is complete) and the surfaces are in continuous contact with water. Refinements to the model are needed to account for wetting and drying during natural exposure and the effects of moisture content changes on rates of solution of components and wicking of solution to the surface;


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Figure 9: Predicted leaching rate from top surface of 38mm deck board continuously exposed to rainfall

3. The procedure should also be applicable to leaching of organic wood preservatives but it does not predict losses from volatilization or bleeding and these factors would have to be considered in a model for organic substances; 4. No approach, including this one can predict the effects of natural exposure conditions that may affect leaching in an unusual way such as UV exposure [17], exposure to organic and other acids and other aggressive leaching media. 5. At this time, the effect of low solubility of some components such as CCA and CA components relative to their ultimate availability is not taken into account in the simple diffusion models presented here and the long term leaching losses of these components will be under-estimated if the dissociated amount is used in the analysis and the rate of leaching will be over-estimated if the total availability is used. CONCLUSIONS

An approach is shown to estimate leaching impacts from inorganic preservative treated wood based on laboratory estimation of the amount of preservative component available for leaching, the equilibrium dissociation of preservative into free water in wood and diffusion coefficients in different wood directions. Combining this information with a simple diffusion test allows the estimation of potential risk from leaching over a wide range of product dimensions and specified conditions.


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The results predict that ACQ-C will have higher initial leaching rates compared to CCA and CA-B but the latter species will continue to leach copper at a measurable rate for a much longer time. We plan to continue to investigate the applicability of this approach with particular emphasis on: • Investigating the rate of replenishment of leached material by continued dissociation and integrating this into a diffusion model; • evaluating effects of rates of wetting and drying of wood between water exposures and their impacts on leaching; • Developing models for three dimensional diffusion in rectangular and pole shaped samples. REFERENCES

1 Homan, W.J. and A.L. van Oosten. 1999. Statistically stable models for determination of PEC. . Int. Res. Group on Wood Preservation, Doc. IRG/WP 99-50135.

2. Hingston, J.A., C.D. Collins R.J. Murphy and J.N. Lester. 2001 Leaching of chromated copper arsenate wood preservatives: a review. Environmental Pollution 111, 53-66.

4. Lebow, S. 1996. Leaching of wood preservative components and their mobility in the environment. Summary of pertinent literature. General Technical Report. Forest Products Laboratory, USDA Forest Service, Madison Wisconsin. FPL-GTR-93:36.

5. Morsing, N. 2003. Leaching of active components from preservative treated timber. Status after approx. 4 months out-door exposure. Int. Res. Group on Wood Preservation, Doc. IRG/WP 03-20276.

6. Willeitner, H., and R.-D. Peek. 1998. How to determine what is a realistic emission from treated wood. The International Research Group on Wood Preservation. Stockholm, Sweden. Document IRG/WP/98-50105.

7. Brooks, K.M. 2001. Literature review and assessment of the environmental risks associated with the use of ACQ treated wood products in aquatic environments. Report prepared for: WWPI, Vancouver, WA.

8. Van Eetvelde, G., M. Stevens and L. Vander Mijnsbrugge. 1994. Comparative study on leaching of CCA from treated timber: Modeling of emission data. Int. Res. Group Wood Preserv. Doc. IRG/WP 04-50027.

9. Van Eetvelde, G., Stevens, M., Mahieu, F., Wegen, H.-W., Platen, A. 1998. An appraisal of methods for environmental testing of leachates from salt-treated wood; part 1. The International Research Group on Wood Preservation, IRG/WP 98-50115.

10. Jin, L. and A.F. Preston. 1993. Depletion of preservative from treated wood: Results from laboratory, fungus cellar and field tests. Int. Res. Group Wood Preserv. Doc. IRG/WP 93-50001.

11. Stevanovic-Janesic, T., P.A. Cooper and Y.T. Ung. 2001. Chromated copper arsenate treatment of North American hardwoods. Part 2. CCA leaching performance. Holzforschung. 55(1):7-12.

12. Van Eetvelde, G., Orsler, R., Holland, G., Stevens, M. 1995b. Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic applications. Part 1. Laboratory scale investigation. . Int. Res. Group on Wood Preservation. Doc. IRG/WP/95-50046.


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13. Van Eetvelde, G., Homan, W.J., Militz, H., Stevens, M. 1995a. Effect of leaching temperature and water acidity on the loss of metal elements from CCA treated timber in aquatic conditions. Part 2: semi-industrial investigation. . Int. Res. Group on Wood Preservation. Doc. IRG/WP 95-50040.

14. Ra, J.B. H.M. Barnes and T.E. Conners. 2001. Determination of boron diffusion coefficients in wood. Wood and Fiber Science. 33(1), 90-103.

15. Taylor, J. 2001. Natural leaching of CCA from treated lumber. M.Sc.F. Thesis, Faculty of Forestry, University of Toronto.

16. Klipp, H., H. Willeitner, K. Brandt and A. Muller-Grimm. 1991. Migration of active ingredients from treated timber into fresh water. Int. Res. Group on Wood Preservation, Doc. IRG/WP/3669.

17. Lebow, S.T.; Williams, R.S. and P.K. Lebow. Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood. Environ. Sci. and Technol. In press.


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Leachate Quality from Simulated Landfills Containing CCA-Treated Wood

Jenna R. Jambeck1, Timothy Townsend1, Helena Solo-Gabriele2

ABSTRACT Landfills represent the predominant disposal method for discarded CCA-treated wood in the US. The current lack of economically viable recycling options for this material will likely result in continued reliance on landfill disposal for the foreseeable future. Previous research has shown that arsenic, copper and chromium leach from CCA-treated wood when in contact with water. Leaching is expected to occur in a landfill as rainwater infiltrates into the waste. In a landfill, however, the biological, chemical and physical reactions that occur may have a great impact the mobility of the metals from CCA-treated wood. Research was conducted to explore this issue. Experimental landfills were constructed to represent three different disposal scenarios: construction and demolition (C&D) debris landfills, municipal solid waste (MSW) landfills, and wood-only monofills. CCA-treated wood is often managed in C&D debris landfills; in many US locations these facilities are unlined. In other locations, CCA-treated wood is disposed in lined MSW landfills. These two disposal scenarios have different chemical environments and the metals may thus behave differently in each environment. While CCA-treated wood is not currently managed in monofills, this option represents conditions where maximum metals concentrations would likely occur. Six lysimeters (simulated landfill columns), two for each disposal scenario, were constructed and operated; both a control lysimeter (containing no CCA-treated wood) and an experimental lysimeter containing CCA-treated wood were included for each scenario. Natural and simulated rainwater were allowed to infiltrate and percolate through the waste in the lysimeters creating leachate. Leachate generated by the lysimeters was collected and analyzed for arsenic, copper and chromium concentrations, as well as general leachate indicator parameters from the fall of 2001 through the summer of 2003. This paper summarizes the preliminary results of metal concentrations in the leachate over time and explores possible mechanisms for leaching. The potential environmental impacts of disposal in each scenario are discussed. INTRODUCTION CCA-treated wood became popular from 1970 to 1980 and the life spans of the structures made with it are in the range of 10 to 40 years; therefore, disposal amounts are increasing as the wood continues to come out of service. However, an estimated 180 million m3 of CCA-treated wood remains in service in the United States (EBN, 2002). With the unrestricted use of CCA-treated wood, the disposal rate would continue to increase and then level off. However, phaseouts or bans on CCA-treated wood have begun to occur. In the US, the use of CCA-treated wood in decks, picnic tables, landscaping timbers, gazebos, residential fencing, patios, walkways/boardwalks, and

1 Department of Environmental Engineering Sciences, University of Florida, PO Box 116450, Gainesville, FL, 32611-6450 2 Department of Civil, Architectural and Environmental Engineering, University of Miami P.O. Box 248294, Coral Gables, FL 33124-0620


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play-structures will be phased out by the end of 2003 (US EPA, 2002; FR, 2002). With the recent draft report on the increased cancer risks to children from coming into contact with CCA-treated wood decks and playsets (USEPA, 2003a), some municipalities and private citizens may want to remove their CCA-treated wood structure immediately. Quicker removal of the CCA-treated wood may peak disposal rates sooner than previously predicted and the focus turns to disposal. Once CCA-treated wood is removed from service, it needs to be properly managed as a solid waste. Under US Environmental Protection Agency (EPA) standardized tests, CCA-treated wood may show characteristics of a hazardous waste because of the leachability of the toxic metals in the CCA-chemical. However, it is exempt from regulation as a hazardous waste when it is used for its intended purpose and discarded by the user (CFR, 2003). Also, recycling and reuse options are not often feasible. With its high metal concentrations, CCA-treated wood should not be made into mulch. If it is burned, it releases emissions of arsenic as well as concentrating arsenic, copper and chromium in the ash (Solo-Gabriele et al., 1998). Landfills are typically where the waste wood is currently disposed, and they will likely continue to represent the primary management option for CCA-treated wood waste in the future (Solo-Gabriele et al., 1999). In the US, some landfills that accept wood waste are not lined (e.g. construction and demolition debris landfills in Florida are not lined (FAC, 2003)). Studies have found that C&D debris containing CCA-treated wood have leached concentrations of arsenic above groundwater standards (Jang, 2000; Weber et al., 2002). In order to further examine some of the impacts of CCA-treated wood on landfill leachate, a simulated landfill leaching column experiment was conducted. LEACHING COLUMN STUDY The objective of the research reported here was to simulate the production of leachate from the co-disposal of CCA-treated wood in simulated landfills. Six 6.7-meter high columns were constructed at the Alachua County Solid Waste Landfill, located in Archer, Florida, US. These columns were filled with waste to simulate different CCA-treated wood disposal scenarios: a wood monofill, a construction and demolition (C&D) debris landfill, and a municipal solid waste (MSW) landfill. A total of six leaching columns (also referred to as lysimeters) were constructed for this study. The lysimeters were split up into pairs, each representing a different disposal scenario, with a control lysimeter and an experimental lysimeter in each pair. The lysimeters were constructed in the following layers (from the bottom up): 0.152 meters of washed gravel, a stainless steel screen, 0.152 meters of washed gravel, 6.1 meters of simulated waste, a cap with a water distribution system, and a catchment basin for rainwater (Figure 1). Thermocouple wires were placed at three separate depths (6.1 meters, 4.6 meters and 1.5 meters) within the lysimeters to obtain temperature readings. Size Reduction and Filling In order to fit simulated waste materials into the lysimeters, the larger materials were size reduced. A nominal waste size of 5.1-cm by 5.1-cm pieces was used when possible. Lysimeters were filled in lifts, by weighing out appropriate masses of each material, mixing them together and then compacting the load in the lysimeter. Details of the size reduction and filling procedures are given in Jambeck et al. (2003). Figure 2 provides the composition (by mass) of the materials in each lysimeter. Further description of the composition of waste in each disposal scenario is given below.


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Wood Waste Composition The wood monofill represents a worst-case disposal scenario for CCA-treated wood since it contains the highest percentage of treated wood. This scenario will also provide information on the leaching of metals that will occur from wood without the interference of other materials. Since the relative contribution of CCA-treated wood from demolition and construction activities varies, and has not been well-quantified, a 50:50 construction to demolition waste ratio by weight was used. The retention value (as reported on the end tag) of the new CCA-treated wood used in the experiments was 6.4 kg/m3 (0.4 lb/ft3), although when determined by the standard industry method for measuring retention value, X-ray fluorescence (XRF), it was shown to be 3.4 kg/m3 (0.214 lb/ft3). The demolition wood retention value as determined by XRF was 6.2 kg/m3 (0.38 lb/ft3) (Solo-Gabriele et. al, 2003). Lysimeter 1 was the control lysimeter in this disposal scenario and contained new untreated Southern Yellow Pine. The in-place densities of the wood in lysimeters 1 and 2 were 353 kg/m3 and 324 kg/m3, respectively. C&D Waste Composition The C&D waste composition selected was modeled after one used in a previous study (Jang, 2000), and was considered representative of typical C&D debris. The previous study, however, contained only a small fraction of CCA-treated wood (0.5%). The percentage of CCA treated wood currently in the waste stream has been reported to be 6% (Tolaymat et al., 2000). CCA-treated wood percentages found in C&D debris in field studies has ranged from 9% to 30%. The range of 9 and 10% were at facilities that actively sorted out CCA-treated wood if they identified it and the 30% was at a facility that did not practice sorting (Blassino et al. 2002). Projections have estimated that up to 50% of the wood waste stream could be CCA-treated wood (Townsend et al., 2001). For this study, wood was assumed to be 33.7% of the waste stream, with 30% of the wood being CCA-treated and 70% being untreated Southern Yellow Pine. The overall contribution of CCA-treated wood in the C&D debris waste stream was 10.2%. Lysimeter 3 was the control lysimeter in this disposal scenario and contained no CCA-treated wood. The in-place densities of the waste in lysimeters 3 and 4 were 345 kg/m3 and 359 kg/m3, respectively. MSW Waste Composition The MSW in lysimeters 5 and 6 was refuse derived fuel (RDF) collected from the Palm Beach County Solid Waste Authority (SWA) RDF plant. This plant processes 2,000 metric tons of MSW per day into RDF. The facility processes MSW by size-reducing it, during which the waste is homogeneously mixed. Two trips were made to SWA to collect RDF from the storage building. The first trip was in May 2001 and the second in September of 2001. Both times RDF was collected in 160-liter garbage cans directly from the RDF storage building. Because of concerns that the food waste content of the MSW was less than typical, an additional source was added. Dog food was added to the MSW at 9% by mass. The CCA-treated wood content in the MSW lysimeters should be less than the amount in the C&D lysimeters since wood is a smaller component of MSW (6.1%, US EPA, 2000). A CCA-treated wood content of 2% by mass of the total waste stream (32% of the total wood portion of the waste) was selected. This estimation is the same amount as used in a study of pentachlorophenol-treated wood co-disposed with MSW in lysimeters (Pohland et al., 1998). The in-place densities of the waste in lysimeters 5 and 6 were 294 kg/m3 and 293.0 kg/m3, respectively.


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Operation and Monitoring of Lysimeters Monitoring and operation of the lysimeters began after construction was completed in fall 2001 and continued until the conclusion of the experiment in fall 2003. The experiment has recently concluded and the results presented here remain preliminary. The temperature of the lsyimeters was measured weekly at 6.1 meters, 4.6 meters and 1.5 meters from the top of the lysimeter with an Omega thermocouple meter. The temperatures within the lysimeters varied with the seasons and fluctuated following ambient temperatures. The composition of gas in the lysimeters was analyzed with a Landtec GEM-500 that measured methane, carbon dioxide, and oxygen content. Gas composition readings were collected weekly for the C&D debris (3&4) and MSW (5&6) lysimeters. In the warm summer months, when the temperatures were in the range of 25 to 30 degrees C, the methane concentrations in the MSW lysimeters rose to over 60%, with carbon dioxide near 40%. The primary gas in the C&D lysimeters at this same time was carbon dioxide. During the cooler winter months, both methane and carbon dioxide decreased, while oxygen increased in both the C&D and slightly in the MSW lysimeters. The gas fluctuations reflect the fact that microorganisms that produce methane and carbon dioxide are more active in warmer conditions than in cooler conditions. Natural precipitation was allowed to infiltrate into all of the lysimeters. If natural precipitation did not occur, it was supplemented by the addition of deionized water (1 centimeter of precipitation resulted in the addition of 0.73 L of water). The lysimeters were sampled one to two times per month. General water quality parameters, including pH, dissolved oxygen (DO), conductivity, oxidation-reduction potential (ORP), and temperature were measured in the field every time leachate was sampled. DO and temperature were measured with an YSI, Inc. DO Meter Model 55/12 FT. pH and ORP were measured with an Accumet Portable pH/mV Meter Model AP62. The conductivity was measured with a Hanna Instruments Multi-range Conductivity Meter, HI 9033. Leachate was collected in 20-Liter containers to homogenize the sample before splitting it up into proper containers for preservation and analysis. The samples were stored in a walk-in cooler at 4 degrees C. Leachate samples were digested following US EPA method 3010A (US EPA, 2003b) and then analyzed with a Thermo Jarrell Ash, model 61E, inductively coupled argon plasma (ICAP). Leachate samples from lysimeter 1 and 3 were also digested using method 7060A (US EPA, 2003b) and analyzed on a Perkin-Elmer Atomic Absorption (AA) graphite furnace.

RESULTS Wood Lysimeters Lysimeters 1 and 2 represented the disposal of CCA-treated wood in a monofill where no other waste interacted with the wood. The wood lysimeters were completed and began operation on August 28, 2001. Natural precipitation has contributed 207 centimeters of rain to the columns; however both lysimeters were supplemented with deionized water to produce sufficient quantities of leachate for sampling. Lysimeters 1 and 2 had a total of 270 and 230 centimeters of water input, respectively, through the duration of the experiment. Leachate was generated from lysimeter 2 first, and collection began September 28, 2001. Leachate was collected from lysimeter 2 on a total of 29 occasions. Leachate was not generated from lysimeter 1 until August 6, 2002. Leachate has been collected from lysimeter 1 on a total of 22 occasions. Samples from both lysimeters were analyzed


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for general water quality parameters and metals up through the end of the experiment, September 22, 2003. Monitoring general water quality parameters provides and indication of activity occurring within the lysimeters and assists in characterizing the leachate. Overall, the pH of both lysimeters decreased slightly over time, although the pH of lysimeter 2 (average of 5.62) remained below that of lysimeter 1 (average of 5.83). Dissolved oxygen levels began in the range of 2 to 4 mg/L, and then stabilized at approximately 1 mg/L by the end of the experiment. Conductivity was in the range of 500 to 1000 µS/cm, with a decreasing trend throughout the experiment. The ORP results began positive (approximately 100mV) for lysimeter 2, while the ORP of lysimeter 1 began in the negative (-200mV to -400mV). The lysimeter 2 ORP decreased to the range of lysimeter 1, and both remained reducing (negative) until the end of the experiment. In general, temperatures inside the lysimeters and of the leachate fluctuated with ambient temperatures. Figure 3 shows the pH, conductivity, and DO versus cumulative volume. Figure 3 also presents the concentrations of arsenic, copper and chromium in the wood lysimeter leachate versus cumulative volume. Lysimeter 2 leached the greatest concentrations of arsenic, copper, and chromium of all the lysimeters. Arsenic leached over three magnitudes more in lysimeter 2 than in the control (lysimeter 1). Chromium and copper leached two and one order of magnitude more in lysimeter 2 than lysimeter 1, respectively. The high concentrations of metals, as well as the increasing trend, correspond to a low and decreasing pH. The low dissolved oxygen concentrations and negative ORP are indicative of microbial activity in both lysimeters. Certain bacteria have been shown to thrive on CCA-treated wood and extract the metals (Illman and Highley, 1996, Cole and Clausen, 1996). Some fungi produce oxalic and other organic acids causing chromium and arsenic to often remain in water soluble forms, while copper can be precipitated as copper-oxalate, which has low water solubility (Peek, 1999). This may explain why copper concentrations were relatively low compared with arsenic and chromium in the experimental lysimeter. C&D Lysimeters Lysimeters 3 and 4 represent a C&D debris landfill disposal scenario. Lysimeter 3 contained untreated southern yellow pine as the wood component along with the other C&D components. The C&D lysimeters were completed and began operation on August 28, 2001. These lysimeters were exposed to 212 centimeters of natural precipitation and were supplemented with deionized water for a total of 321 centimeters to date. Leachate was generated from both lysimeters at the same time and was collected from lysimeter 3 and 4 on a total of 26 occasions, beginning on June 25, 2002. Samples for both lysimeters have been analyzed for general water quality parameters and metals up through the end of the experiment (October 23, 2003). The temperature of the C&D lysimeters also fluctuated with ambient temperatures. No methane was measured, but higher percentages of carbon dioxide and less oxygen were present during the warmer summer months. The maximum carbon dioxide found was 22% (with oxygen at 1%) in July 2003. In the cooler winter months, the carbon dioxide gas percentage was around 8%, while the oxygen remained around 11%. The pH for lysimeters 3 and 4 remained consistent throughout the experiment at 6.5 to 7. This pH is typical for C&D waste and other experiments (Jang, 2000; Weber et al., 2002). Dissolved oxygen concentrations began around 3 to 5 mg/L, then decreased to almost zero in the first summer. During the cooler months of the winter, DO increased to 2 mg/L, and then


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decreased again to almost zero in the warmer months and for the duration of the experiment. The near zero DO levels indicate microbial activity was consuming the oxygen in the leachate at those times. The conductivity for lysimeter 4 began higher than the conductivity for lysimeter 3 (5.5 mS/cm versus 3.5 mS/cm), and then both decreased over time and cumulative volume. Lysimeters 3 and 4 exhibited reducing conditions throughout the experiment with an ORP in the range of –300mV to –600mV. Figure 4 shows the pH, Conductivity, and DO/Temperature versus cumulative volume. Figure 4 also presents the concentrations of arsenic, copper and chromium in the C&D lysimeter leachate versus cumulative volume. In lysimeter 4, which contains 10.2% CCA-treated wood, arsenic and chromium were found in the leachate at higher concentrations than those found in the control lysimeter (lysimeter 3). The arsenic and chromium concentrations of lysimeter 4 varied slightly remaining in the range of 1 to 4 mg/L for arsenic and 1 to 2 mg/L chromium. Copper had a unique leaching trend in that it was initially detected in lysimeter 4 only and then began to leach at very low concentrations (around 0.05mg/L) in both lysimeter 3 and 4 when the temperature decreased and the DO and ORP increased in the middle of the experiment. The copper concentration then decreased again after the DO and ORP decreased towards the end of the experiment. The more oxidizing environment slightly mobilized the copper; however, concentrations still remained relatively low because copper tends to form complexes with numerous organic and inorganic ligands, especially at a pH of 6.5 and above (Snoeyink and Jenkins, 1980). MSW Lysimeters Lysimeters 5 and 6 represent an MSW landfill scenario. Lysimeter 5, the control lysimeter, contained only MSW, food waste, and untreated southern yellow pine. The MSW lysimeters were completed and began operation on September 27, 2001. These lysimeters have been exposed to 200 centimeters of natural precipitation and 23 centimeters of deionized water from September 27, 2001 through October 23, 2003. Leachate was initially generated from lysimeter 5 and was collected on a total of 25 occasions, beginning on June 27, 2002. Leachate was generated in lysimeter 6 on July 17, and was collected on a total of 24 occasions. Samples for both lysimeters were analyzed for general water quality parameters and metals up through the end of the experiment (October 23, 2003). In the warm summer months, when the temperatures were in the range of 25 to 30 degrees C, the methane concentrations in the MSW lysimeters rose to over 60%, with carbon dioxide near 40%. During the cooler winter months, both methane and carbon dioxide decreased, while oxygen increased slightly. The pH of the lysimeters stabilized over time. The MSW lysimeters began with a low pH (4.5), assumedly in the volatile acid forming stage of the biodegradation process (Pohland et al., 1983). After a few months, methane production was noted and the pH increased and stabilized to approximately 7.5 in both lysimeters. Dissolved oxygen was less dependent on temperature for the MSW lysimeters and DO decreased initially to remain around 0.5 mg/L for the duration of the experiment. Conductivity began higher for the MSW lysimeter with CCA, but both lysimeters followed the same trend for conductivity decreasing from a maximum of 40 mS/cm to below 10mS/cm. The ORP for lysimeters 5 and 6 were primarily in the range of –400mV to –650mV, except for at the beginning and end of the experiment where ORP ranged from –100mV to –200mV. Figure 5 presents the pH, conductivity, and DO/Temperature versus cumulative volume.


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An interesting trend for metals appeared in lysimeter 6, which has 2% CCA-treated wood by mass in it. During the initial time period when the pH of the leachate was lower, higher concentrations of both arsenic and chromium were found in the leachate (as compared to the control). As pH values increased and stabilized, the concentrations of arsenic and chromium decreased to concentrations lower than the other lysimeters with CCA (wood and C&D) and then reached concentrations near those of the control MSW lysimeter. Copper concentrations increased and decreased slightly over the duration of the experiment in lysimeter 6; however, concentrations remained relatively low and were similar to those of lysimeter 5 at the end of the experiment. Figure 5 shows the metal concentrations discussed here, versus cumulative volume.

SUMMARY CCA-Treated wood will be entering the waste stream for years to come. Disposal in the US has not likely peaked yet as much of the wood remains in service. Landfill disposal continues to be the primary form of management in Florida and the US (US EPA, 2000; FDEP, 2002). This research examined three different disposal scenarios to evaluate potential impacts from CCA-treated wood landfill disposal. Leaching columns (lysimeters) were constructed to simulate these three different landfill situations: CCA-treated wood monofill, C&D landfill, and an MSW landfill. The greatest concentrations of metals were found in the CCA-treated wood monofill scenario. This column contained the greatest percentage of CCA-treated wood (100%) and no other waste materials were co-disposed to interact with it. The arsenic, chromium, and copper concentrations increased slightly while the pH decreased. An advantage to disposing of CCA-treated wood individually would be that the leachate could be controlled separately; however, the concentrations of arsenic and chromium in the leachate (both above 5 mg/L) would classify it as a hazardous waste under US regulations for toxicity (CFR, 2003). Disposal of this leachate would be very costly. It is not realistic or likely that anyone would desire to have a CCA-treated wood monofill creating leachate concentrations shown in this experiment. The C&D and MSW landfill scenarios showed a similar range of metal concentrations in the leachate. The arsenic and chromium concentrations were in the range of 1 to 4 mg/L, while copper remained relatively low. This is somewhat surprising since the percentage of CCA-treated wood in the simulated waste streams are different (the C&D lysimeters contain 10.2% CCA-treated wood and the MSW lysimeters contain 2% CCA-treated wood); however, the overall leaching trends of the metals from the C&D and MSW scenarios were very different. The arsenic and chromium concentrations in the C&D lysimeters were initially constant around 1 mg/L. However, over time, arsenic concentrations eventually increased to 4 mg/L and chromium increased to 2 mg/L. The MSW lysimeters behaved very differently. The initial arsenic and chromium concentrations were similar to those found later in the C&D leachate at 3.8 mg/L for arsenic and 4.2 mg/L for chromium. Then, after the pH increased and methane was formed in the MSW lysimeters, the metal concentrations decreased to the lowest of the three landfill scenarios with CCA-treated wood at less than 0.5 mg/L. Neither the C&D nor the MSW leachates are classified as hazardous waste under US regulations; however, when compared to the control lysimeter in each scenario, it is clear that the co-disposal of CCA-treated wood in both of these situations has influenced the arsenic, copper and chromium concentrations in the leachate. Even though the MSW lysimeters leached high concentrations


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initially, it appears that the trend of the metals decreasing to lower concentrations makes the MSW disposal scenario the most desirable at this point. Also, MSW landfills are lined in Florida, unlike C&D landfills. Further evaluation and modeling of the concentrations of metals found in the C&D leachate may determine whether or not CCA-treated wood disposal in unlined C&D landfills may contaminate groundwater.


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REFERENCES Blassino, M., Solo-Gabriele, H., and Townsend, T. (2002). “Pilot Scale Evaluation of Sorting Technologies for CCA-Treated Wood Waste.” Waste Management and Research, 20: 290-301. Code of Federal Regulations (CFR), 2003. Title 40 – Protection of the Environment, Chapter 1 – Environmental Protection Agency, Part 261 – Identification and Listing of Hazardous Waste. Cole and Clausen, (1996). “Bacterial Biodegradation of CCA-Treated Waste Wood,” Forest Products Society Conference Proceedings, September 1996, Madison, Wisconsin. Environmental Building News (EBN), (2002). “CCA Phaseout: Now the Hard Part Begins,” Vol. 11, No. 3, p. 2, A publication of Building Green, Inc., Brattleboro, VT. Federal Register (FR) (US), 2002. Notice of Receipt of Requests to Cancel Certain Chromated Copper Arsenate (CCA) Wood Preservative Products and Amend to Terminate Certain Uses of CCA Products, February 22, Vol. 67, No. 36. Florida Administrative Code (FAC), 2003. Chapter 62-701 – Solid Waste Management Facilities. Florida Department of Environmental Protection (FDEP), 2002. “Solid Waste Management in Florida 2001-2002,” Solid Waste Management Annual Report based upon 1999-2000 data. Illman, B. L., and Highley, T., L., (1996). “Fungal degradation of wood treated with metal-based preservatives: 1. Fungal tolerance,” prepared for the IRG 27th Annual Meeting, Guadaloupe, French West Indies. Jambeck, J. R., Townsend, T. G., Solo-Gabriele, H., (2003). “The Disposal of CCA-Treated Wood in Simulated Landfills: Potential Impacts,” prepared for the IRG 34th Annual Meeting, Brisbane, Australia. Jang, Y.C., (2000). “A Study of Construction and Demolition Waste Leachate from Laboratory Landfill-Simulators,” PhD dissertation, University of Florida, Gainesville, FL. Peek, R-D., (1999). “Recycling of Treated Poles in Germany,” Forest Products Society, Workshop on Utility Poles: Environmental Issues, Gainesville, Florida, 1999. Pohland, F.G., Dertien, J.T., Ghosh, S.B. (1983). Leachate and Gas Quality Changes During Landfill Stabilization of Municipal Refuse, Georgia Institute of Technology, School of Civil Engineering, Atlanta, GA. Pohland, F.G., Karadagli, F., Kim, J.C., Battaglia, F.P., (1998). “Landfill Codisposal of Pentachlorophenol (PCP)-Treated Waste Wood with Municipal Solid Waste,” Water Science Technology, Vol. 38, No. 2, pp. 169-175. Snoeyink and Jenkins, 1980. Water Chemistry, John Wiley and Sons, Inc., New York.


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Solo-Gabriele, H., Townsend, T., Penha, J., Calitu, v., Tolaymat, T., (1998). “Generation, Use, Disposal and Management Options for CCA-Treated Wood,” Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Solo-Gabriele, H., Townsend, T., Calitu, V., Kormienko, M., Messick, B., (1999), “Disposal of CCA-Treated Wood: An Evaluation of Existing and Alternative Management Options,” Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Solo-Gabriele, H., Townsend, T., Cai, Y., Khan, B., Song, J., Jambeck, J., Dubey, B., Jang, Y., (2003), “Arsenic and Chromium Speciation of Leachates from CCA-Treated Wood,” Draft Report, Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Tolaymat, T, Townsend, T, Solo-Gabriele, H. 2000. “Chromated Copper Arsenate-Treated Wood in Recovered Wood,” Environmental Engineering Science, Vol. 7, No. 1, p. 19-28. Townsend, T., Solo-Gabriele, H., Stook, K., Tolaymat, T., Song, J.K. Hosein, N., Khan, B., (2001), “New Lines of CCA-Treated Wood Research: In-Service and Disposal Issues,” Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. United States Environmental Protection Agency (US EPA) (2000). “Municipal Solid Waste Generation, Recycling and Disposal in the United States: Facts and Figures for 1998,” Solid Waste and Emergency Response, EPA530-F-00-024. United States Environmental Protection Agency (US EPA) (2002). “Whitman Announces Transition from Consumer Use of Treated Wood Containing Arsenic,” Headquarters Press Release, February 12, 2002. United States Environmental Protection Agency (US EPA) (2003a). “A Probabilistic Risk Assessment for Children Who Contact CCA-Treated Playsets and Decks,” Draft Preliminary Report, Office of Pesticide Programs, Antimicrobials Division, November 10, 2003. United States Environmental Protection Agency (US EPA) (2003b). “Test Methods for Evaluating Solid Waste, Physical/Chemical Methods,” SW-846, Office of Solid Waste, Third Edition. Weber, W. J., Jang, Y.C., Townsend, T.G., Laux, S., (2002). “Leachate from Land Disposed Residential Construction Waste,” Journal of Environmental Engineering, Vol. 128, No. 3, p. 237-245.


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FRONT LYSIMETER VIEW SIDE LYSIMETER VIEW

CONCRETE BLOCKS

SUPPORT POST

STRAPPING STRAPPING

TREATMENT PLANT RAILING

GROUND LEVEL

30.5cm30.5 cm

6.7m

CONCRETE PAD

6.1m WASTE

6.1m WASTE

CATCHMENT BASINS

DRAINAGE MATERIAL

DRAINAGE MATERIAL

Figure 1. Lysimeter Construction Schematic


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Untreated wood

100%

New CCA50%

Old CCA50%

Percentage by Weight in Lysimeter 1 Percentage by Weight in Lysimeter 2

Drywall12.4%

Concrete29.3%

Untreated Wood33.7%

Aluminum0.6%

Steel Bar0.6%

Steel Sheet0.6%

Copper Wire0.6%

Roofing13.7%

Insulation0.6%

Cardboard8.0%

Old CCA5.1%

New CCA5.1%

Drywall12.4%

Concrete29.3%

Untreated Wood23.5%

Copper Wire0.6%

Steel Sheet0.6%

Aluminum0.6%

Steel Bar0.6%

Roofing13.7%

Insulation0.6%

Cardboard8.0%


MSW89%

Untreated Wood

2%Food9%

Food9%

New CCA1%

Old CCA1%

MSW89%


Figure 2. Composition of Materials in the Lysimeters (by total mass)


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Figure 3. pH, Arsenic, Chromium, Copper, Conductivity and DO in Wood Lysimeters

(Copper results under the reporting level of 0.004mg/L shown at 0.004mg/L)


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Figure 4. pH, Arsenic, Chromium, Copper, Conductivity and Temperature/DO in C&D Lysimeters (Copper results under the reporting level of 0.004mg/L shown at 0.004mg/L)


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Figure 5. pH, Arsenic, Chromium, Copper, Conductivity and Temperature/DO in MSW Lysimeters (Copper results under the reporting level of 0.004mg/L shown at 0.004mg/L)


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Effect of Coatings on CCA Leaching From Wood in a Soil Environment

David E. Stilwell and Craig L. Musante

ABSTRACT We are conducting a study to determine the extent that coating CCA wood with a variety of paints and stains has on preventing leaching of the preservative into soil. A total of 10 boxes (27x28x14 cm) were constructed, six of which were coated. The coatings consisted of oil based, semi-transparent stains (two brands, one with and the other without alkyd resin ingredients), two clear cover coatings (two brands, one with a penetrating alkyd/acrylic formulation), an opaque acrylic deck stain, and an opaque polyurethane enamel. Two of the boxes made from CCA wood were left uncoated, as were the control box and the box made using the ACQ preserved wood. The boxes were filled with a mixture of 90% soil (sandy loam) and 10% compost, by volume, and placed out to weather on April 30, 2002. The soil was sampled using a core sampler from each side of the box, 0-3 cm from the wood, 107and 365 days after weathering. Elevated arsenic and copper levels were detected in soils from the uncoated boxes and in some cases from the coated boxes. Concentrations (mg/kg) of As in soils receiving different treatments were; No Coating (13.5±2.7) > Oil based stain with alkyd resin (13.3±2.0) > Oil based clear cover sealant (10.5±1.9) > Oil based without alkyd resin (8.6± 0.1) > Water based clear with alkyd and acrylics (7.3±1.0) > Acrylic opaque (4.9±1.2) > Polyurethane (3.7±0.3)> Control (3.1±0.2). Key Words – CCA Wood, Arsenic, Leaching, Coating, Soil INTRODUCTION

The potential environmental problems associated with chromated copper arsenate (CCA) wood preservative resulted in a phase out of its use in the US for residential applications effective January 2004 (1). However, wood produced prior to the phase out is expected to remain in-service for many years (2). Moreover, this formulation is still permitted for use outside the residential setting. Arsenic dispersal from the wood can occur by leaching, erosion, weathering, decay and physical dislodgement (3-10). Coating the wood could minimize this arsenic dispersal by forming a barrier between the wood and the environment.

Limited amounts of information have been published on coatings for CCA wood. Some studies have focused only on the on durability of the finish to withstand weathering (11,12), while others have focused on the ability of the finish to reduce surface dislodgeable arsenic (13,14) or leachable arsenic (15-17). In general, opaque polyurethane and acrylic finishes form the most durable coatings (11,13,14), presumably due to their ability to protect the wood surface from ultraviolet radiation and David E. Stilwell and Craig L. Musante, The Connecticut Agricultural Experiment Station PO Box 1106, New Haven CT, USA, 06504, (203-974-8457) [email protected]


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water penetration (11,16). Nonetheless, for some surfaces, particularly horizontal ones subjected to foot traffic, use of a penetrating stain that results in a slow wearing of the coating may be preferable. Opaque coatings applied to horizontal surfaces are prone to peeling and cracking with age. Other types of coatings could form a barrier to arsenic but not maintain its integrity over time. For example, we found that even though spar varnish formed a barrier to arsenic dislodged from the surface (>90% over 1 year), it later underwent severe deterioration after 2 years of weathering (14). Studies have been published comparing the durability of commercially available coatings in residential settings (18). However, these studies did not address the coating’s potential to form a barrier to arsenic migration from the wood.

In this study we are evaluating the effectiveness of coatings to form a barrier to preservative dispersal from CCA wood in a soil environment. Soil contact uses include raised beds used in gardens, posts, and utility poles. The results over the first year of weathering are presented in this report. EXPERIMENTAL

A total of 10 boxes (27x28x14 cm) were constructed, 8 using 3x15 cm CCA boards, one using an alternative preservative containing copper and quaternary ammonia (ACQ), and 1 control using untreated pine. The CCA containing boxes were constructed using 2.5 m x 3 cm x 15 cm pine boards, purchased at a lumber yard, nominally treated with 6.4 kg/m3 of CCA preservative by Universal Forest Products. The boards originated from three sets. The first set, consisting of 3 boards purchased in April 2002, was used to construct the two, 28 cm sides. Set 2, also purchased in April 2002, consisted of 1 board treated with water repellent plus CCA (Thompsonized), and was used to construct one 27 cm side of each box, while Set 3, consisting of 3 boards purchased in 1998, was used to construct the other 27 cm side of each of the 8 boxes.

Each paint or stain was applied in two coats on a particular box. As shown in Table 1, the coatings consisted of oil based, semi-transparent stains (two brands, one with and the other without alkyd resin ingredients), water based coatings (two brands, one with a penetrating alkyd/acrylic formulation), an acrylic solid color deck stain, and a polyurethane enamel. Two of the boxes made from CCA wood were left uncoated, as were the control box and the box made using the ACQ preserved wood.

The boxes were filled with a mixture of 90% soil (sandy loam) and 10% compost, by volume. The soil properties of this mixture are given in Table 2. The boxes were placed out to weather on April 30, 2002 (Figure 1). Natural rainfall supplied most of the water, but in times of drought, the soil in the boxes was watered at a rate of about one inch per week (0.4 inches per application). The soil was sampled using a soil corer (2.2 cm dia.) to take one sample from each of the four sides of the box, 0-3 cm from the wood to box bottom, 4 times over 2 years. The results of first two sets of soil samples, taken after 107 and 365 days of weathering are given here. The results for the 1.5 and 2 year sample sets will be given elsewhere.

The Cu, Cr, and As were determined in the soil samples by nitric acid digestion followed by analysis using Thermo Jarrell Ash ICP-AES Atom Scan 16 atomic spectrometer. In samples containing low arsenic (<0.1 mg/l in solution) the more sensitive technique of graphite furnace atomic absorption (GFAA) was employed using a Perkin Elmer 5100 instrument, as described previously (9). The Cu, Cr, and As in the wood were similarly obtained by analyzing wood composite sawdust samples from each set of boards.


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Table 1 Description of Coatings Coating/Box # Coating* Base Color Cover

1 None 2 Sealant with Alkyd and Acrylics Water Clear Clear 3 Deck and Siding Stain Oil Gray Semi 4 Sealant Oil Clear Clear 5 Deck Stain with Alkyd Resin Oil Gray SEMI 6 Solid Color Acrylic Deck Stain Water White Opaque 7 Polyurethane Floor and Deck Enamel Oil Gray Opaque 8 None

ACQ None

Untreated None

Pine * Brand and Code.. Coating 2, Behr, 300; 3, Behr 1-765; 4, Thompson’s; 5 Olympic, 53178; 6, Olympic, 53097; 7, Sapolin, 40-9309.

Figure 1 Coated and uncoated box assemblies.


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Table 2 Soil Properties Property Measurement pH 6.0 ± 0.3 (n=9) CEC* (cmol/kg) 8.2 ± 0.9 (n=6) P (mg/kg) 1040 ± 80 (n=3) Fe (mg/kg) 9090 ± 1500 (n=3) Sand (g/kg) 712 ± 17 (n=2) Silt (g/kg) 114 ± 55 (n=2) Clay (g/kg) 174 ± 71 (n=2) Organic Matter (g/kg) 52 ± 4 (n=2) *Cation Exchange Capacity RESULTS

Arsenic Leached

The average soil arsenic levels right next to the wood in the boxes over time for different treatments are given in Figures 2-4 (see table 1 for the coatings corresponding to numbers 2-7). The results from the soil samples from the uncoated CCA boxes (Box 1 and 8) were combined (n=8) in computing the averages for each weathering. All other averages were from each side from a particular box (n=4). The percent reduction was calculated by subtracting the amount of arsenic in soil from the control box from that in soil from each coated box, and dividing this by the difference between the arsenic in soils from uncoated boxes and the control boxes, i.e. 100*(Coat Value-Control Value)/(No Coat Value-Control Value). As shown in figures 2 and 3 the arsenic levels in the soil samples from the CCA boxes generally increased with time of weathering. Furthermore, the average arsenic level (13.5±2.7 mg/kg) in soil samples taken from the uncoated boxes, after 365 days of weathering exceeded State of Connecticut limit of 10 mg/kg (8). The opaque acrylic finish (#6) reduced the arsenic level by about 80% while the polyurethane based finish was virtually 100% effective over the one year time frame. Opaque finishes were also found to be the most effective coating to reduce arsenic dislodged from surfaces (13,14). The oil based deck and siding stain (#3), the sealant with alkyd and acrylics (#2) and the oil-based sealant (#4) were somewhat less effective and reduced the arsenic level by only 30-60%. The oil based stain (#5) which had no apparent effect on arsenic leaching in this soil environment, was found earlier, however, to reduce arsenic dislodged from surfaces (14).

The fact that the soil retained as much as 13 mg/kg As next to the uncoated boxes is indicative of this soils ability to trap arsenic. In effect the soil acts to integrate the amount of arsenic that comes out of the wood over time. We attribute this trapping ability to the high clay and iron content in the soil (table 2), which are known to immobilize As (10).


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Figure 2 Comparison of soil arsenic versus time using various coatings

Figure 3 Average soil arsenic after 0, 107, and 365 days of weathering, ranked by coating effectiveness

2468

10121416

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[As]

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kgNo CoatCoat 2Coat 3Coat 4Coat 5Coat 6Coat 7Control

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[As]

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kg

Day=0Day=107Day=365


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Figure 4 Percent reduction in soil arsenic levels with coating Copper Leached

The average copper levels in soils from various treatments are given in Figure 5. The copper in

the soil samples next to uncoated CCA wood exhibited only limited increases compared to the pre weathering values, making comparisons with the samples taken next to coated wood more uncertain. For example, the average increase in the arsenic content in soil samples next to the uncoated wood compared to the unweathered samples increased about 200 and 350 percent after 107 and 365 days of weathering (3.7±0.1, 7.5±1.5 and 13.5±2.7 mg/kg at day 0,107,365 respectively), while the copper increased by 130 and 123 percent over the same time period (23±1, 30±4, 28±3 mg/kg after day 0,107,365 respectively). Note that the copper tends to level off after one year weathering time, which may be due to similar leaching rates out of the wood compared to the migration rate through the soil. A tendency for the copper content to level off with time was also noted by Lebow et al. (4,15) in sediments next to boardwalks constructed with CCA wood. In order to further investigate this point we plan to take soil samples at various distances from the wood are the end of this study (two years total). Nonetheless, there were indications that opaque coatings (#6&7) formed a good barrier to copper as well as to arsenic. The copper in the soil samples next to these coated woods was within 5% of their pre- weather values on both sample dates. In contrast, the soil samples next to the ACQ treated wood increased noticeably compared to the initial value. The percentage increase in these samples was 160 and 200 after weathering 107 and 365 days, based on the copper content of 24±0.5 (day=0), 39±6 (day=107), and 50±14 (day=365). All of the copper levels in the soil samples from all treatments were less than the State of CT limit of 2500 mg/kg (8).

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Chromium Leached

The average chromium levels in the soil for different treatments are given in Figure 6. Like

copper, the chromium in the soil samples next to uncoated CCA wood exhibited only limited increases compared to the pre weathering values. For example the increase in the soil Cr in the uncoated wood treatment increased from an initial value (mg/kg) of 10±2, to 12±2 (day=107), and to 13±1 (day 365). These small increases coupled with the variation in baseline Cr (range 9-11 mg/kg) makes evaluation of the coatings effectiveness for Cr leaching more uncertain compared to the arsenic data. In no case did the Cr level approach the State of CT limit (8) of 100 mg/kg (hexavalent Cr) or 3900 for trivalent Cr (8).

Summary of Copper, Chromium and Arsenic Leached A summary of the amounts of Cu, Cr, and As in the soil samples after one year of weathering is

given in Table 3. The concentration of As in the soil ranged from 3 to 13 mg/kg, depending on the effectiveness of the coating material used. In uncoated wood and in treatment 4 (clear oil based sealant) and 5 (semi-transparent oil based deck stain), the As levels exceeded the 10 mg/kg Connecticut State limit. In contrast to As, the relatively minor increases in Cu, and Cr, reflects one, the relatively low amount of Cu in the wood (next section), and two, the lower leaching rate of Cr (8,10).


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Figure 5 Average soil copper after 0, 107, and 365 days of weathering, ranked by coating effectiveness

Figure 6 Average soil chromium after 0, 107, and 365 days of weathering, ranked by coating effectiveness

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TABLE 3 Effects of Coating on the Cu, Cr, and As (mg/kg) Content in Soil after 1 Year of Weathering

Coating # Concentration* (mg/kg) Cu Cr As

Untreated 23.1 ± 2.0 10.9 ± 0.7 3.1 ± 0.2 7 22.8 ± 1.3 11.1 ± 0.5 3.7 ± 0.3 6 23.6 ± 1.7 11.2 ± 0.5 4.9 ± 1.2 2 24.8 ± 0.8 12.0 ± 0.05 7.3 ± 1.0 3 23.5 ± 0.9 11.6 ± 0.7 8.6 ± 0.1 4 25.4 ± 1.6 12.3 ± 0.8 10.5 ± 1.9 5 27.3 ± 2.5 12.1 ± 1.0 13.3 ± 2.0

Uncoated CCA 28.3 ± 2.6 13.3 ± 0.9 13.5 ± 2.7 ± ±

ACQ 49.6 ± 14 10.9 ± 0.7 3.3 ± 0.2 ± ± Before Weathering** 23.4 ± 1.2 10.2 ± 1.3 4.0 ± 0.3 *(n=4, except for uncoated CCA, n=8) ** Average in soil from all boxes (n=2 per box, n=20 total)

Variation in CCA Leaching Within Treatments

As mentioned earlier, each box was constructed from three sets of CCA boards. The Cu, Cr,

and As content (mg/kg) in the wood composite samples from these board-sets were 1773±16 (Cu), 3156±68 (Cr), and 2746±56 (As) in wood from Set 1, 1263±54 (Cu), 2461±426 (Cr), and 2020±231 (As), in wood from Set 2, and 1050±307 (Cu), 1946±681 (Cr), and 1870±624 (As), in wood from Set 3. The nominal amounts for this treatment level are 1840 (Cu), 3120 (Cr) and 2800 (As). Thus, when compared to the nominal value the treatment levels in Sets 2 and 3 are somewhat low, while the level in Set 1 closely matches the nominal value. The ACQ wood contained 3073±58 (Cu), <20 (Cr), and <20 (As) (mg/kg), while the control wood and the plywood contained <20 mg/kg Cu, Cr, and As.

Note in Table 3 that the copper content in the soil samples next to the ACQ wood increased by 26 mg/kg, compared to a 5-mg/kg increase in soils next to the CCA wood. Thus, there was about 5 fold increase in the soil copper next to the ACQ wood compared to the soil next to the uncoated CCA wood with only a 2.25 fold increase in the copper in ACQ versus CCA wood. These results suggest that copper may leach to a greater extent, on a percentage basis, in the ACQ wood, as also noted by Townsend et al. (19).

The amount of arsenic in soil samples taken after 365 days of weathering is shown in Figure 7 as a function of board-set and coating. Each box was made from two pieces of wood from set 1, one from set 2, and one from set 3, so the results in the figure are the average arsenic in set 1 and a single measurement in set 2 and 3. Though the As levels in the wood from set 1 was about 40% higher, the amounts of arsenic in set 1 soil samples exceeded those in set 2 and 3 in only one


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instance. Similar results were obtained after weathering for 107 days, where the arsenic in soil from set 1 exceeded the others only once. The amounts of copper in the soil samples from set 1 exceeded the others 4 times in the samples after 107 days and one time in samples after 365 days. These findings suggest that the As and Cu content in the soil may not be directly proportional to the amount in the wood. Clearly, the concentration in the wood is not the only factor determining its migration into the soil.

Figure 7 Effects of arsenic in soil next to board-sets after 365 days of weathering. Average As in the wood (mg/kg), 2746±56 (Set 1), 2020±231 (Set 2), 1870±624 (Set 3) CONCLUSIONS

Opaque coatings formulated using acrylics or polyurethane when applied to CCA wood

reduced the migration of arsenic from the wood into the surrounding soil over a one year time period by 80% to virtually 100%. Other coatings, either oil or water based, but with clear or semitransparent coverage, reduced the arsenic migration by only 60% or less. The arsenic next to uncoated CCA wood increased to levels exceeding the State of Connecticut limit of 10 mg/kg within one year of weathering. On the other hand, only minor increases in the copper and chromium content occurred in the soil next to CCA wood over this one-year period. Variation in the soil arsenic levels within a treatment suggest that other factors, as yet unknown, than merely the bulk concentration of As in the wood influence its migration into the surrounding soil. REFERENCES 1) Federal Register. Notice of receipt of requests to cancel certain CCA wood preservative products and amend

to terminate certain uses of CCA products. Fed Regis. 67:8244-8246 (2002). 2) Solo-Gabriele, H.; Townsend, T. Disposal practices and management alternatives for CCA-treated wood

waste. Waste Manage Res. 17:378-389 (1999).

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3) Stilwell D.; Toner M.; Sawhney B. Dislodgeable copper, chromium, and arsenic from CCA-treated wood surfaces. Sci. Total Environ. 312:123-131 (2003).

4) Lebow, S.T.; Lebow, P.K.; Foster, D.O. Part I. Leaching and environmental accumulation of preservative elements. In Environmental impact of preservative treated wood in a wetland environment. Res. Paper FPL-Rp-582; USDA Forest Service, Forest Products Laboratory, Madison, WI (2000).

5) Townsend T.; Stook K.; Tolaymat T.; Song J.K.; Solo-Gabriele H.; Hosein N.; Khan B. Metals concentrations in soils below decks made of CCA-treated wood. Report #00-12 (excerpts). Florida Center for Solid and Hazardous Waste Management, Gainesville, FL (2001).

6) Zagury, G.J.; Samson R.; Deschenes L. Occurrence of metals in soil and ground water near chromated copper arsenate-treated utility poles. J. Environ Qual. 32:507-514 (2003).

7) Weis J.S. and Weis P. Contamination of saltmarsh sediments and biota by CCA treated wood walkways. Marine Pollution Bull. 44:504-510 (2202).

8) Stilwell D.E. and Gorny K.D. Contamination of soil with copper, chromium, and arsenic under decks built from pressure treated wood. Bull. Environ. Contam. Toxicol. 58:22-29 (1997).

9) Stilwell D.E. and T.J. Graetz Copper, chromium and arsenic levels in soil near traffic sound barriers built using CCA pressure –treated wood. Bull. Environ. Contam. Toxicol. 67:303-308 (2001).

10) Lebow S.T. Leaching of wood preservative components and their mobility in the environment. Summary of pertinent literature. Gen. Tech. Report FPL-RP-93; US Department of Agriculture, Forest Service, Forest Products Laboratory, Madison, WI (1996), p36.

11) Feist W.C. and Ross A.S. Performance and durability of finishes on previously coated CCA-treated wood. Forest Products Journal 45:29-36 (1995).

12) Petric M.; Pavlic M.; Kricej B. Humar M.; Pohleven F. Blue Stain Testing of Alkyd and Acrylic Stains. The International Research Group on wood Preservation, Document IRG/WP 03-202373 Stockholm, Sweden (2003).

13 Kizer K.W. Report to the legislature. Evaluation of hazards posed by the use of wood preservatives on playground equipment. Calif. Office of Environmental Health Hazard Assessment, Department of Health Services, Health and Welfare Agency (1987).

14) Stilwell D.E. Arsenic from CCA-Treated Wood Can Reduced By Coating, Front. Plant Sci. 51(1), 6-8 (1998). 15) Lebow S.T.; Brooks K.M.; Simonsen J. Environmental impact of treated wood in service. In Proc. Enhancing

the durability of lumber and engineered wood products, February 11-13, 2002, Kissimmee, FL, pp 205-216, Forest Products Laboratory, Madison, WI (2002).

16) Lebow S.T; Williams S.R.; Lebow P. Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood. Environ. Sci. Technol. 37:4077-4082 (2003).

17) Cooper P.A; Ung Y.T.; MacVicar R. Effect of water repellents on leaching of CCA from treated fence and deck units. An update IRG/WP 97-50086; International Research Group: Stockholm, Sweden (1997).

18) Deck treatments, house paints. Consumer Reports 67#6:47-9 (2002). 19) Townsend T.; Stook K.; Ward M.; Solo-Gabriele H. Leaching and toxicity of CCA-treated and alternative-

treated wood products. Florida Center for Solid and Hazardous Waste Management, Report 02-4, Gainesville, FL (2003).


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Depletion of Copper-Based Preservatives from Pine Decking and Impacts on Soil-Dwelling Invertebrates

Michael J Kennedy

∗Agency for Food and Fibre Sciences, Forestry Research (formerly QFRI), Department of Primary

Industries, Brisbane, Queensland, Australia ABSTRACT

Radiata pine decking was treated with CCA or Copper Azole wood preservative to Australian Standard H3 retention using conventional and modified Bethel schedules, and air-dried. Treated and durable hardwood (kwila) control decking boards were subjected to natural leaching in weather-exposed decks in Brisbane, Queensland. Analysis of collected deck runoff water revealed losses up to 700mg Cu, 175mg Cr, 600mg As, 750mg B, 10 mg tebuconazole or 18000 mg tannin per square meter of deck after 10 months, but flux rates had not yet reached zero for any component.

Deck runoff water was applied to three soils using an OECD soil leaching column procedure. Although boron was more mobile than others, components tended to be retained in the topmost (first contacted) layer. Deck runoff water was also applied to mown lawn soil. Soil samples were collected before and twice after the first application, and three times after the second. Soil arthropods were dominated by mites (84%), which were identified to family level. No differences in total mite densities were detected between the treatments, except for a significant increase associated with the kwila deck runoff water. However, there were detectable differences in mite community structure between all treatments, indicating differential effects of the treatments on the soil arthropod community. Keywords: natural leaching, copper-based preservatives, decks, soil mobility, soil microarthropods INTRODUCTION

Laboratory tests have been developed to estimate depletion of wood preservative components in service, and many ‘standard’ tests exist. These tests have been useful for relative comparisons of preservative formulations, but until recently, little absolute data had been published on natural depletion rates in service [1]. One study [2, 3] compared the loss of boron, copper, chromium and arsenic from timber treated with several wood preservatives, including a CCA and an ACQ preservative during 6 months outdoor exposure to urban rain. Natural depletion rates varied inversely with specimen size, and decreased with end-sealing - results quite predictable from the varying ratio of exposed surface area to volume. But as full-dimensioned material was not exposed, the study did not generate absolute depletion data.

∗ Mailing Address: Agency for Food and Fibre Sciences, Forestry Research, P.O. Box 631, Indooroopilly QLD 4068 AUSTRALIA. Phone: +617 3896 9754. Fax: +617 3896 9628. Email: [email protected]


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This paper reports absolute depletion (flux) rates of two copper-based wood preservatives from above-ground decks exposed to the weather. Results of accelerated laboratory leaching tests on matched material are reported elsewhere [4]. Because of the impracticality of collecting and containing the runoff from a complete deck in such a manner as to avoid loss or enhancement of preservative components, it was necessary to reduce the deck size considerably, but this was done without compromises in realism. Although the deck boards were cut to a short length, most board ends were sealed to leave only one unsealed end per 1.2 m of deck board. This simulated an average deck board length of 2.4 m, for a realistic average number of cut ends per square metre of deck.

To assist in interpreting the environmental significance of leached preservative components in the deck runoff water, we also conducted a series of soil mobility studies using the draft OECD soil leaching column protocol [5]. But while flux rate and water and soil concentration data may be useful, their environmental significance needs to be interpreted. What are the impacts of wood preservative or natural hardwood extractive contaminated deck runoff water on soil biota? For an initial study, we monitored the effect on soil and litter non-target microarthropods, especially mites (Acarina), because they are numerically predominant in soils and are important components of below-ground food webs of soils in temperate forest ecosystems. A detailed justification of this choice may be found elsewhere [6].

MATERIALS AND METHODS Preparation Of Treated Specimens

End-sealed seasoned sapwood radiata pine (Pinus radiata) decking boards 450 x 90 x 22 mm, with mean air-dry density 488 kg/m3, reeded one side, were treated with two preservatives; Tanalith® O (Oxide type C CCA wood preservative: Cu 86g/kg, Cr 147.9 g/kg, As 132.7 g/kg) or Tanalith® E (Copper-Azole wood preservative: Cu 166 g/L, boric acid 64 g/L, tebuconazole 6.4 g/L). The treatments were performed in a laboratory impregnation plant using conventional vacuum-pressure techniques and typical Australian commercial schedules, without accelerated fixation. Two processes were used for each preservative - a full-cell (Bethel) process achieving 600 L/m3 and a modified Bethel process achieving 250 L/m3. Concentrations of preservative in the treatment fluid were adjusted so that both processes achieved the Australian/New Zealand Standard H3 (above ground) retention in the cross-section, ie 0.38% m/m Cu+Cr+As or 0.27% m/m Cu+tebuconazole. The boards from each treatment, still end-sealed, were immediately wrapped in polythene sheeting and stored under mid-summer ambient conditions (mean daily max. 30°C, mean daily min. 21°C) for one week. After unwrapping they were strip-stacked to air dry under similar conditions until reaching equilibrium moisture content (approximately four to six weeks). 75 mm was removed from each end of each board, and from these pieces were cut cross-sections for

chemical analysis. Boards for use in the test decks were selected from the remaining 300 mm lengths closest to the required preservative retention, and end-sealed as required to leave 8.8 unsealed ends per square metre of deck.

Construction of, and Sampling of Water from, Decks

Decks were constructed and designated CF, CR (CCA: Bethel and modified Bethel respectively) EF, ER (Copper Azole: Bethel and modified Bethel respectively), K and X. The K decks were constructed from untreated heartwood of the naturally-durable hardwood kwila (Intsia bijuga) in the same dimensions, as preservative-free controls.


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The X decks were unpopulated by boards, to act as control rainwater collectors. Decks consisted of four 300 mm boards, parallel and 5 mm apart, attached to two stainless steel angle supports running perpendicular to the board direction. Attachment was by a single stainless steel screw through the support into the under (reeded) side of the board at each board-support junction (8 per deck). Each deck was suspended within a stainless steel runoff director device so that there was a gap of 3-5 mm between the deck boards and the inside walls of the device, and the top surface of the deck boards was 15 mm below the upper rim of the director. A large glass storage bottle positioned below the director contained the runoff water until it was collected after each rain event. The ‘X deck’ (runoff director without deck boards) accumulated a corresponding volume of ‘pure’ rainwater. The use of only stainless steel and glass in the deck supports, runoff director and containment system ensured that the runoff water was not contaminated with compounds that could interfere with or erroneously enhance the chemical analysis. Decks were first exposed to the weather three months after the treated deck boards reached equilibrium moisture content. Exposure took place in a clean urban location in Brisbane, Australia (27.50 S, 153.03 E), for 300 days.

After each rain event all runoff water was collected, volume recorded, a sample taken in a glass container for analysis and a further portion (a constant 11% of the total amount collected) frozen in a stainless steel container for later use in soil column studies. After small rain events (< 2 mm) that did not produce sufficient water for analysis the analytical sample was reserved and pooled with the sample from the following event. Analyses were conducted for total Cu, Cr and As (CCA decks), Cu, B and tebuconazole (copper azole decks) and tannin (kwila deck). Analysis for Cu and Cr used atomic absorption spectrophotometry (AAS), As was determined by inductively-coupled plasma atomic emission spectrometry (ICP_AES), B by ICP_AES or colorimetry using azomethine-H reagent, tebuconazole by gas chromatography with nitrogen-phosphorus detector after extraction onto a C18 solid phase extraction (SPE) cartridge, and tannin by UV-visible spectrophotometry using Folin-Denis reagent. No attempt was made to distinguish between valence states of metals.

Soil leaching column studies

The OECD procedure [5] was followed, except that we were evaluating the soil mobility of preservative components already dissolved in deck runoff water, rather than the individual compounds for which the method was written. This necessitated minor changes to the methodology, but the principle of the OECD test was strictly observed. Three soils were selected to give the required spread of properties, which are given in Table 1

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Table 1: Properties of soil used in leaching columns

Soil Soil property Units S1 S2 S3

CEC meq/100g 5 27.1 21.5Organic C % 1.7 4 3.3pH units 5.1 5.1 5.9Clay % 10 20 23Silt % 14 47 32Sand % 76 33 45Sand fractions: Coarse % 38 6 14

Fine % 38 27 31Exchangable cations:

Ca mg/kg 198 104 616Mg mg/kg 75.5 234 470Na mg/kg 22.6 34 137K mg/kg 10 120 90

Cu mg/kg <1 1.7 1.4 Runoff water composites for each deck were prepared by blending a constant proportion of

each of the water samples collected from that deck at the first 14 rain events (during the first 10 weeks of exposure). The total amount of rainfall in these 14 events was 123 mm. Runoff from later events, which generally contained less of each component, was not included in these composites, as the 1300 mL minimum volume required for the soil column experiments had been reached. It was recognised that the amount of deck runoff resulting from a rain event varied from deck to deck, because of variations in the amount of water retained by or deflected from the deck – the ‘hold-up’ factor. A very light shower which produced a measurable sample below the unpopulated deck could be completely absorbed by the boards in another deck, and differences in absorption between timber species and treatments resulted in variations in the amount of runoff. This variation was reflected proportionately in the volumes of runoff water applied to the soil columns.

Soils were packed into 40 mm i.d. glass columns, saturated with deionised water, and allowed

to drain under gravity. Portions of composite were added dropwise to soil columns over a period of 48 hours, using a multi-channel peristaltic pump. For the control columns (to which was added composite from the unpopulated deck), 154 mL of composite was added, corresponding to 123 mm of rainfall on the surface area of the soil. The volume of composite added to other columns was reduced in proportion to the hold-up factor for the relevant deck. An additional equal volume of deionised water was then added to the column at the same rate. Column effluent solution was collected on four occasions – after 50% and 100% of the leachate composite had been added (CE1 and CE2), and after 50% and 100% of the additional deionised water had been added (CE3 and CE4). The soil in the column was removed and sectioned into five equal layers, coded (from topmost to lowest layer) as SL1 to SL5. Each column effluent sample and each soil layer sample was analysed for the preservative components of the relevant deck.

Microarthropod study Site

The experiment was conducted in an area of mown lawn within the Queensland Government Science campus at Indooroopilly (in Brisbane, which has an annual average rainfall of 1158 mm with a summer maximum). There was a sparse cover of Eucalyptus propinqua and other native Australian trees over an even sward of lawn grasses. Soil characteristics are in Table 2. The study


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site was divided into 4 application areas (Figure 1), which corresponded to each deck (C, E, K) and to a wet control zone (U) (rainwater from the unpopulated X deck only). The surface of each area was 61 x 38 cm, exactly twice the surface area of the deck collector, and was marked off with a welded steel frame 6 cm high. Each application area was protected from natural rainfall events by a raised clear polyethylene cover. Application zones were separated from each other by 80 cm, within which we established a dry control (O). Table 2: Soil characteristics of the experimental area (n = 9 samples). Characteristic Mean Range pH 5.2 4.8-5.7 Conductivity (mS/m) 118 81-155 Organic carbon (%) 10.9 9.3-12.7 CEC (meq/100g) 49.8 46-53 Clay (%) 36.7 30-39 Silt (%) 23.9 16-26 Fine sand (%) 23.3 21-25 Coarse sand (%) 16.2 11-32

Figure 1: Layout of treatments. C = CCA; E = Copper Azole; K = kwila; U = rainwater only, from the X (unpopulated) deck; O = unwatered “dry” controls between each area. Leachate application and soil sampling

Two applications of each treatment were made in order to simulate natural rainfall events: the first equivalent to 29.5 mm of rain and the second two weeks later (10 mm rain). At each application, water from duplicate decks was applied to each area using watering cans. Immediately adjacent to each frame, an equivalent amount of standard artificial rain was applied in order to avoid gradients in soil moisture between the treatment areas and the surrounding soil.

Soil samples were taken with a metal cylinder 6 cm in diameter, to a depth of 5 cm. Samples were taken twice (3 days and 12 days) after the first treatment and three times (3 days, 8 days and 12 days) after the second. At each sampling time, 15 soil cores were taken (4 areas x 3 replicates + 3 dry control samples), and the sampling holes were backfilled with sterile sand. The 3 replicate cores from each treatment were <10 cm apart. Cores were placed in plastic bags and transported to the laboratory on the day of collection for immediate extraction of organisms. Soil organisms were extracted using Tullgren funnels (heat extraction process) and collected into 70% ethanol. Samples were randomly arranged in the Tullgren funnels, powered by light globes, and organisms extracted for 4 days. The light intensity was increased each exposure day from 15W to 60W to progressively dry the sample and force animals out. Tullgren funnels were an appropriate extraction technique because they extract only live animals.

Cores were wet-weighed before extraction. After invertebrates were extracted, samples were sieved to separate the material into rock and coarse organic matter (>2 mm) and soil (<2 mm), and weighed. Organism density was expressed as number per 100 g dry sample weight. Organisms extracted from cores were identified [7, 8, 9] to family for mites (except Euoribatida which were

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taken to cohort level) and order level for other groups, and counted. Immature animals that could not be recognized were sorted to order.

Data analyses

Mite community data and the effects of treatments over time were analysed using multivariate techniques within the PRIMER package [10]. Non-metric multidimensional scaling (MDS) based on a Bray-Curtis similarity matrix was used to investigate patterns of community structure. Two-dimensional solutions with lowest stress were used for interpretation. ANOSIM (a multivariate non-parametric equivalent of analysis of variance) with 5000 permutations was used to test for differences between treatment effects and time periods, and similarity percentages (SIMPER) was used to elucidate which taxa were contributing most to similarities between samples within each treatment, and to dissimilarity between treatments. For MDS ordinations and ANOSIM all taxa were included: for SIMPER juveniles and unidentified “others” were omitted, but immature Mesostigmata were retained. All data were square-root transformed before analysis.

RESULTS AND DISCUSSION Depletion from Decks:

During the weather exposure period, total rainfall of 600 mm occurred in 48 rain events as depicted in Figure 2. The central dry period is typical of the Brisbane spring. During the exposure period, mean air temperature minima and maxima during autumn, winter, spring and summer were 15°&25°C; 8°&19°C; 14°&23°C and 19°&28°C respectively. Concentration data of each component in the collected runoff water from each deck type is given in Table 3. Initial retention and 300 day depletion of each component in the deck boards is given in Table 4. Table 3: Deck runoff water concentration (mg/L) data. *Teb = tebuconazole Deck: CF CR EF ER K Component: Cu Cr As Cu Cr As Cu B Teb* Cu B Teb* TanninMinimum 0.013 0.039 0.100 0.013 0.042 0.108 0.136 0.138 0.0006 0.094 0.178 0.0007 2.91Mean 0.453 0.561 1.97 0.554 0.554 1.11 3.29 2.87 0.0263 2.52 2.61 0.0284 78.7Maximum 2.53 2.43 5.69 2.19 2.72 3.77 20.1 13.4 0.137 13.0 10.6 0.113 853Std. Dev. 0.543 0.534 0.992 0.451 0.472 0.705 4.13 2.69 0.0391 2.68 2.28 0.0312 154


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Table 4: Retention and depletion of preservative components from decks. *Teb = tebuconazole Deck: CF CR EF ER

Cu 0.0838 0.120 0.266 0.269Cr or B 0.157 0.147 0.0182 0.0184

As or Teb* 0.137 0.107 0.0124 0.0077

Mean retention (%m/m) in deck boards (before exposure)

TAE 0.378 0.374 0.278 0.277Cu 8.58 11.7 23.3 26.1

Cr or B 16.1 14.4 1.60 1.78Amount of component in deck (g/m2) (before exposure)

As or Teb* 14.0 10.5 1.08 0.747Cu 100 153 708 607

Cr or B 149 171 744 769Amount (mg/m2) depleted in 300 days

As or Teb* 623 414 8.62 10.4Cu 1.17 1.31 3.03 2.33

Cr or B 0.924 1.18 46.5 43.2% of component depleted in 300 days

As or Teb* 4.44 3.95 0.795 1.39


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Rainfall during 300 day exposure period of decks

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Figures 3 to 5 show the chromium depletion data from the CF deck plotted in different ways. Against time, the rate of depletion appears quite erratic, reflecting the erratic rainfall pattern. When the amount of rain is used as the independent variable, the plot becomes more regular and better correlated to a smooth trendline. The goodness of fit is still not perfect, because the rate of depletion depends not only upon the amount of rain but also upon the way in which it falls. It became obvious during the work that short heavy showers did not produce as much depletion as an equivalent number of mm of steady rain, probably because the latter kept the wood wet for longer and also wet deeper into the interior zones, thus mobilising additional leachable species. Data relating to depletion of the other components has therefore been presented as function of rainfall rather than time (Figures 6 - 8).

Chromium depletion during 300 day exposure period of CF deck

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Figure 7: Cu, Cr and As depletion from C decks Figure 8: Cu, B and azole depletion from E decks The model equations (Table 5) gave the best fit to the deck component depletion. These models should be more useful than simple flux rates (Table 6), as they should be applicable to all locations with comparable environmental conditions.

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m2

azol

e le

ache

d

Cu-EF

Cu-ER

B-EF

B-ER

Azole-EF

Azole-ER


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Table 5: Depletion models: y = mg of component lost per m2 of deck per x mm of rainfall since first exposed. Component Bethel process (CF or EF) Modified Bethel (CR or ER) CCA treated radiata pine: Cu y = 3.265x0.5540 R2=0.982 y = 2.152x0.6873 R2=0.990 Cr y = 0.771x0.8316 R2=0.981 y = 0.5846x0.8955 R2=0.986 As y = 1.529x0.9467 R2=0.994 y = 0.326x1.118 R2=0.992 Copper Azole treated radiata pine: Cu y= 151.1ln(x) –265.9 R2=0.988 y = 20.634x0.5507 R2=0.960 B y = 16.84x0.6091 R2=0.949 y = 14.32x0.621 R2=0.959 Tebuconazole y= 1.899ln(x) –2.809 R2=0.956 y= 2.292ln(x) –4.508 R2=0.981 Untreated kwila: Tannin y = 2616x0.3076 R2=0.995

Changing from a full Bethell process (CF) to the low uptake process (CR) appeared to markedly reduce the depletion of As from CCA-treated decks, at the expense of somewhat increased depletion of Cu and Cr, but the lack of replication prevents forming a firm conclusion. In the case of the Copper Azole decks, the lower uptake process (ER) may have produced some decrease in Cu depletion but a similar increase in tebuconazole depletion, with B unaffected.

Table 6: Flux rates (mg m-2 d-1) of components from decks during various periods since first exposed Component Bethel process (CF or EF) Modified Bethel (CR or ER) Days from installation 21 90 300 21 90 300 CCA treated radiata pine: Cu 1.54 0.508 0.341 1.88 0.642 0.521 Cr 1.05 0.411 0.495 1.12 0.433 0.580 As 3.14 1.64 2.10 1.47 0.749 1.402 Copper Azole treated radiata pine: Cu 16.9 3.47 2.39 11.3 5.04 2.05 B 12.5 3.92 2.51 11.0 3.36 2.59 Tebuconazole 0.269 0.074 0.029 0.257 0.077 0.035 Untreated kwila: Tannin 448 129 59.4

Soil leaching studies

Concentration of each preservative component present in the composite runoff water sample applied to the soil columns, as determined by chemical analysis, is given in Table 7.


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Table 7: Concentration of components in 10 week composite runoff water samples of stated volume

Deck Volume As Cr Cu B tebuconazole tannin mL mg/L mg/L mg/L mg/L mg/L mg/L

CF 1360 1.198 0.315 0.393 0.047 CR 1430 0.539 0.267 0.428 0.035 EF 1340 0.030 3.810 3.209 0.033 ER 1390 0.054 2.654 2.759 0.039 K 1450 86.1 X 1700 0.015 0.013 0.011 0.008 <0.001 <1

Detectable concentrations of As in the EF and ER runoff water and of B in the CF and CR

runoff water could be taken to indicate a small but measurable extent of cross-contamination between these decks, which could be due to rain droplet bounce or splashing. But the fact that considerably smaller concentrations of As were detected in the U deck, which was immediately adjacent to the CF deck, than in the more distant E decks tends to suggest that these elements may have been present at low concentrations in the preservative solutions used to treat the boards, and that removal of components from the system by droplet bounce was minimal – probably 1-5%.

After conducting the soil column experiments, chemical analysis of soil layers and column effluent fractions was able to distinguish differences between the unpopulated deck and decks EF and ER only, and then only for the Cu and B components. For all other components except tebuconazole and for all other decks, the amount of component present in the aliquot added to the column was too small when compared with the amounts of that component naturally present in the soil. In the case of tebuconazole, the aliquot contained only about 4 µg, and state-of-the-art instrumentation was unable to detect the resultant concentrations in each fraction. So generally, analytical results of fractions from columns spiked with composites from test decks were not significantly different from those obtained from the corresponding columns spiked with composites from the unpopulated deck. In short, the deck leachates contained insufficient of all components to make a measurable difference to the soil, except for Cu and B from the Copper Azole decks (Tables 8 & 9).


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Table 8: Distribution of copper from EF and ER composites in soil column and column effluent Deck: EF deck ER deck mg Cu added in aliquot: 0.457 0.346 Soil in column: S1 S2 S3 S1 S2 S3 mg Cu found in fractions

SL1 0.530 0.466 0.380 0.330 0.307 0.244 SL2 <0.025 0.04 <0.025 0.026 0.02 <0.025 SL3 <0.025 0.04 <0.025 <0.025 <0.025 <0.025 SL4 <0.025 0.03 <0.025 <0.025 <0.025 <0.025 SL5 <0.025 <0.025 <0.025 <0.025 0.03 <0.025 CE1 <0.01 <0.01 <0.01 <0.01 0.02 <0.01 CE2 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CE3 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CE4 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01

Found as % of added: 116% 126% 83% 103% 109% 71% Table 9: Distribution of boron from EF and ER composites in soil column and column effluent Deck: EF deck ER deck mg B added in aliquot: 0.386 0.328 Soil in column: S1 S2 S3 S1 S2 S3 mg B found in fractions

SL1 0.033 0.016 0.040 0.031 0.019 0.036 SL2 0.067 0.093 0.129 0.051 0.046 0.144 SL3 0.096 0.120 0.181 0.075 0.083 0.118 SL4 0.072 0.059 <0.020 0.060 0.103 <0.020 SL5 0.027 0.023 <0.020 0.032 0.020 <0.020 CE1 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CE2 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CE3 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CE4 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01

Found as % of added: 76% 81% 91% 76% 83% 91% Recoveries of copper were variable, possibly reflecting the variability between the soils in

terms of their absorptivity for cations and their native copper content. Generally the applied copper did not migrate far, with a possible exception in S2, but the high recoveries from this soil indicate considerable native copper content which may have contributed to the apparent movement. Boron recoveries were more reproducible. Boron migrated more readily than copper, in accordance with general perceptions of the mobility of this element. Although boron did not break through the lowermost soil layer, it would probably do so (at least with soils S1 and S2) if given additional leaching water.

In order to generate soil leaching column data for the remaining components (Cu, Cr As from CCA decks and tebuconazole from copper azole decks) spiking the relevant runoff waer composites with these components was undertaken. All components thus enhanced tended to remain in the surface layers; mainly SL1 but sometimes also in SL2. However, we refrain from reporting these


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data as the lack of information about the form in which the components are present in the runoff water makes it impossible to be sure that our component spikes were in the same form (oxidation state, ionic species, etc) and thus behaved the same as equivalent concentrations of naturally-present components. Soil invertebrate studies compositions of the deck runoff composites applied to the field soil at application are given in Table 10. Predictably, the second application contained lower concentrations of most preservative components.


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Table 10: Concentration (mg/L) of components in deck runoff for the two field soil applications. Application: 1 2 Source deck: C E K X C E K XAS 1.05 - - <0.02 1.37 - - <0.02Cr 0.58 <0.05 - <0.05 0.47 <0.05 - <0.05 Cu 0.85 5.68 - 0.025 0.73 2.93 - 0.029 B - 4.24 - 0.05 - 2.16 - 0.07 Tebuconazole - 0.038 - <0.001 - 0.016 - <0.001 Tannin - - 170 3.3 - - 98 4.3

Minimal variability in soil moisture developed during the application period, as shown in

Figure 9, for the last four sampling periods. The changes between the periods are principally the result of applying the treatments. The level of soil moisture was naturally very high in the study area (between 40% and 50%), but there were significant differences between each treatment area: soil moisture for the C area was higher than for the E and K areas. The changes between each treatment zone may partially explain variability in the invertebrate communities. Moisture can have a significant impact on the abundance of soil fauna [11]. The rapid response of the mites to change in soil moisture seems to be the result of vertical movement of the animals.

0

10

20

30

40

50

60

C E K U O

treatments

% m

oist

ure

sample1.2sample2.1sample 2.2sample 2.3

Figure 9: Field soil moisture in latter half of trial- mean (n=3) ± two standard deviations. The second runoff water application occurred before sampling period 2.1.

Invertebrate order, mite families and densities more than 13 000 invertebrates were collected during the study. Overall, samples were dominated by mites (84%) and springtails (8%). The most dominant groups were the oribatid (7815 individuals) and mesostigmatid (2589) mites. Because of the domination of mites in this area, we decided to focus analysis on mite taxa, and identified eighteen families. The Euoribatida (Oribatida) were not identified to family level because of the complexity of this cohort (more than 100 families).

Total mite densities are presented in Figure 10. There are differences in sampling times between the two controls (U and O), with a higher density of mites in the U control after the second


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application, probably due to changes in soil moisture. The O control has The very large standard deviations in the O controls are probably due to their spread over the whole site (width 2.4 m)

. There appeared to be no significant effect of CCA and copper-azole-contaminated runoff

water, whereas the kwila-contaminated runoff had a positive impact on the density of soil-dwelling mites. This increasing density of mites (mainly oribatids) may be due to an increase in microbial activity caused by elevated tannins in the soil and consequent greater food availability for mites (oribatid are known to feed primarily on fungal spores [9]); or through an indirect impact by removal of tannin-sensitive predators or pathogens of the mites.

Mite Community structure The 2-dimensional MDS ordinations of samples at the same

sampling period are presented in Figure 11. Samples that are closer together in the ordination space are more similar than those further apart. There is substantial overlap of communities at the start of the experiment: after application of the preservative treatments, communities in each tend to drift apart in ordination space, suggesting a community-level effect of these chemicals.

0

50

100

150

200

250

300

0 1.1 1.2 2.1 2.2 2.3

sampling period

dens

ity o

f mite

s (p

er 1

00g

dry

wei

ght)

CEKUO

Figure 10. Total densities of mites in each treatment at each sampling period ± two standard deviations. The triangles indicate the timing of the two runoff water applications. n = 3 for all treatments.


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139

C

C

C

E

E

E

K

KK

UU U

O

OO

Sampling period 0stress = 0.11

C

C

C

E

EE

K

K

K

U U

U

O

OO

Sampli ng period 1.1stress = 0.09

C

C

C

EE

E

K K

KU

U

U

O

O

O

Sampling period 1.2stress = 0.15

C C C

E EE K K

KU

U

U

O

O O

Samp ling per iod 2.1stress = 0.09

C

CC

E EE

K

KK

U

UU

O

O

O

Samp ling per iod 2.2stress = 0.11

C

C

C

E

E

E

K

K

KU

U

U

O

O

O

Sampling period 2.3stress = 0.11

Figure 11. MDS ordinations of mite communities at each sampling period. U = watered control; O = unwatered control; C = CCA; E = Copper Azole; K = kwila.

MDS ordinations for each treatment separately are shown in Figure 12. The independent “dry” control (0) shows changes due to natural changes in soil moisture and temperature. The watered U control shows oscillations after an initial shift in composition, again probably due to changes in soil moisture after the first application. The microarthropod communities in the three treatments C, E and K show differing responses to chemical application. The K treatment community appears to be returning towards the initial state after some short-term changes. For the two other treatments (C and E), the points are moving away from the initial state, indicating that the effects of the treatments are on-going.


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C0

C11

C12

C21

C22

C23

Treatment Cstress = 0.03

E0

E11

E12

E21

E22

E23

Treatment Estress = 0.00

K0

K11

K12

K21

K22

K23

Treatment Kstress = 0.02

U0U11

U12

U21

U22

U23

Treatment Ustress = 0.00

O0O11 O12

O21

O22

O23

Treatment Ostress = 0.00

Figure 12. MDS ordinations of mite communities in each treatment. Arrows indicate trajectories of community composition over time.

ANOSIM results are presented in Table 11, and show that there were significant differences in mite community structure between time 0 (before application) and all subsequent sampling periods. However, there was only one significant pairwise difference between post-treatment periods, which suggests that there is no difference between times after runoff water applications. Comparisons between treatments were all significantly different from each other, but none was different from the O control. These differences could reflect the large variation in mite abundance between the treatments, partly explained by differences in soil moisture and natural spatial variation between the widely separated O samples.

The global similarity between the different treatments is quite high, but is decreasing over

time after the first runoff water application. The increase of similarity percentage between time 0 and time 1.1 can be explained by an increase in soil moisture, then the decrease could reflect the differential effect of each treatment on the mite community. This result is compatible with the ordination analyses. Moreover, the dissimilarity between time seems to increase between each period, which confirms the differential effect and the increasing “specialisation” of the mite community.

At each sampling time, only three taxa were necessary to explain 50% of similarity between

samples (Table 12). These three families are the same in each case, and are all oribatid taxa (Euorobatida, Oppiidae and Nanhermanniidae). The same ratio of dissimilarity was explained by about 4 or 5 different taxa each time, which confirms that the community is complex, with none of the taxa dominant. Taxa responsible for discriminating between treatment effects (all post-treatment


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samples combined) are given in Table 13. Eurobatida appear to increase in abundance and Nanhermannidae to decrease in response to all leachate treatments, compared to treatment 0.

Table 11. ANOSIM results for the mite family level data, 5000 permutations. Critical P-value=0.01.

Factor R-statistic Significant statistics P-value Significant at experiment level Sampling periods: 0-1.1 0.356 10 0.002 yes 0-1.2 0.437 6 0.001 yes 0-2.1 0.385 33 0.007 yes 0-2.2 0.481 2 0.001 yes 0-2.3 0.541 2 0.001 yes 1.1-1.2 -0.059 3376 0.675 no 1.1-2.1 0.244 169 0.034 no 1.1-2.2 0.193 192 0.039 no 1.1-2.3 0.215 244 0.049 no 1.2-2.1 0.163 592 0.119 no 1.2-2.2 0.037 1618 0.324 no 1.2-2.3 0.333 48 0.010 yes 2.1-2.2 0.104 869 0.174 no 2.1-2.3 0.089 1248 0.250 no 2.2-2.3 0.022 2080 0.416 no Treatments:

C vs E 0.358 3 0.001 yes C vs K 0.852 0 <0.001 yes C vs U 0.506 0 <0.001 yes C vs O 0.123 562 0.113 no E vs K 0.809 0 <0.001 yes E vs U 0.432 1 <0.001 yes E vs O 0.179 201 0.040 no K vs U 0.784 0 <0.001 yes K vs O 0.253 62 0.013 no U vs O 0.117 551 0.110 no


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Table 12. Degree of similarity of mite communities at each sampling period (from SIMPER).

Sampling period Average similarity (%) Number of taxa to explain 50% of similarity 0 76.50 3

1.1 79.28 31.2 77.35 32.1 75.94 32.2 71.97 32.3 69.17 3

These statistical results suggest that changes occurred in the mite community structure after

runoff (or rain) water application, in each of the four treatments (C, E, K and U). As the dissimilarity between treatments was still increasing at the end of this study, these differential effects are still being manifest, even though the K-contaminated community seems to return to a pre-treatment state.

We identified mites to family level in order to assess the utility of the technique as a

relatively rapid method of identifying community change. It is questionable whether family-level determination is sufficient to give statistically meaningful and ecologically interpretable results. Taking the taxonomic resolution to genus or even species level would enable a more accurate assessment of community response to leachates, and allow analysis of species replacements within families. It would also facilitate comparisons of functional group or trophic level changes (herbivores, carnivores, fungivores, detritivores). Further research is necessary before these trade-offs can be analysed and a robust and reproducible method of biomonitoring the impacts of timber preservatives can be devised. CONCLUSIONS

Rates of depletion from decks during 300 days service varied widely between preservative components, ranging from 0.029 mg m-2 d-1 for tebuconazole to 2.5 mg m-2 d-1 for boron, both from copper azole treated decks. Corresponding rates for CCA elemental components varied from 0.34 to 2.1 mg m-2 d-1, while the naturally-durable hardwood kwila lost 59 mg m-2 d-1 tannin. Models for depletion behaviour based upon loss vs rainfall were more useful than similar models or calculated rates based upon loss vs time of exposure, as they were less dependent on the specifics of the rainfall pattern during the period. Amounts depleted from decks represented from 0.8% (tebuconazole) to 46% (boron) of the amounts initially present in the deck boards. About 1% of the copper and chromium and 4% of the arsenic initially present was depleted from the CCA-treated decks over the 300 day period.

Deck runoff water generally contained low concentrations of preservative components. When

runoff samples from a given area of deck were applied to an equivalent area of soil, concentrations of most components in the soil were not detectably increased over the background. The exceptions to this generalisation were copper and boron from copper azole treated decks, which increased copper concentrations in the surface layer of soil by about 5 mg/kg, and increased boron concentrations deeper into the profile by about 2 mg/kg.


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Table 13. Taxa responsible for dissimilarities between treatments: post-treatment samples combined. Top 2 most influential taxa only. From SIMPER analysis. Treatment comparison (Tmt 1 vs Tmt 2)

Taxon Average abundance

(Tmt 1)

Average abundance

(Tmt 2)

Contribution to overall

dissimilarity % immature Mesostigmata 65.4 25.9 14.0

C vs E Euoribatida 114.3 61.8 12.7Nanhermanniidae 22.2 179.0 22.9

C vs K Euoribatida 114.3 248.6 14.1Nanhermanniidae 22.2 67.4 13.9

C vs U Euoribatida 114.3 77.6 9.9Nanhermanniidae 22.2 58.88 13.4

C vs O immature Mesostigmata 65.4 44.2 10.0Nanhermanniidae 11.9 179.0 22.9

E vs K Euoribatida 61.8 248.6 18.9Nanhermanniidae 11.9 67.4 19.6

E vs U Phthiracaroidea 0.7 7.2 9.3Nanhermanniidae 11.9 58.9 18.4

E vs O Euoribatida 61.8 124.4 14.2Euoribatida 248.6 77.6 20.9

K vs U Nanhermanniidae 179.0 67.4 15.0Nanhermanniidae 179.0 58.9 18.2

K vs O Euoribatida 248.6 124.4 15.8Euoribatida 77.6 124.4 13.9

U vs O Eupodidae 4.5 13.4 10.5

During the short-term field soil impact study, the global density of invertebrates seemed to be

significantly affected only by the kwila-extractive runoff water. While CCA and copper-azole contaminated runoff appear to have had no measurable impact on the density of soil-dwelling mites, the mite community structure seems to have been affected by all treatments. Differential effects of each treatment were recognised but not quantitatively evaluated. A longer-term study is required to determine whether the community structures are permanently altered, or are returning to a natural “equilibrium” state.

The method used, with both independent and dependent controls, was useful for estimating

the magnitude and direction of change. The rapid response of soil invertebrates to an addition of water has several important implications. Firstly, it highlights the necessity of sampling at different times, when soil moisture levels are different to estimate species richness of the soil fauna. Second, it suggests that management impacts on soil fauna should be assessed with different soil moisture contents [12].

Although we chose as uniform an environment as possible, natural spatial variation in soil

microarthropod populations means that full-cycle shifts in community composition (i.e. away from the initial state on disturbance and back again on recovery) are difficult to track, as initial states themselves vary in space and time, and there may be natural changes irrespective of the treatments applied. Examining communities at a more detailed taxonomic level (species) would provide more


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accurate data, but requires considerably more technical expertise. As is often the case with using organisms in their natural environment to indicate disturbance and recovery, a compromise between accuracy and efficiency is necessary.

Finally, such studies must be made on different types of organisms to identify species or

species groups which could be used as bioindicators in field conditions. These studies should also lead to the standardisation of research and testing procedures. Ultimately, a biotic index of soil quality might be developed to objectively quantify pollution. Single taxon studies and tests are a step towards environmental risk evaluation, but progressively more complicated systems should be designed to analyse interactions between environment and ecology.

ACKNOWLEDGMENTS

This work was supported by the Queensland Government, Koppers-Hickson Timber Protection (Australia) Pty Ltd and Hickson Timber Products Ltd, U.K. My colleagues at AFFS-Forestry Research Paul Collins (chemist) and Alan House (ecologist) participated extensively in the research. Heather Proctor (Griffith University) and David Walter (University of Queensland) provided valuable advice on soil arthropods. The timber technology skills of Leanne Stephens, and the patient collection and classifying of mites by Noémie Crumière were central to the success of the project.

REFERENCES 1. Hingston, J.A., C.D. Collins, R.J. Murphy and J.N. Lester (2001) Leaching of chromated copper arsenate wood preservatives: a review, Environmental Pollution, 111, 53-66. 2. Yamamoto, K., S. Motegi and A. Inai (1999) Comparative study on the leaching of wood preservatives between natural exposure and accelerating laboratory conditions, The Inter. Res. Group on Wood Preserv., Stockholm, Doc. No. IRG/WP 99-50134 3. Yamamoto, K., S. Motegi and A. Inai (1999) Leaching amount of wood preservatives from treated wood in different size during outdoor exposure for 6 months, The Inter. Res. Group on Wood Preserv., Stockholm, Doc. No. IRG/WP 00-50160 4. Kennedy, M.J. and P.A. Collins (2001) Leaching of preservative components from pine decking treated with CCA and copper azole, and interactions of leachates with soils, The Inter. Res. Group on Wood Preserv., Stockholm, Doc no. IRG/WP 01-50171. 5. Anon (1999) Leaching in Soil Columns (Draft New Guideline, February 1999), OECD's Guidelines for the Testing of Chemicals, Section 3 - Degradation and Accumulation, OECD Environment Directorate, Paris. (http://www.oecd.org/ehs/test/testlist.htm) Revised Draft Document, December 2000 url: (http://www1.oecd.org/ehs/test/ Leach200011.pdf). 6. Crumière, N., A. House and M.J. Kennedy (2002) Impact of leachates from CCA- and copper azole-treated pine decking on soil-dwelling invertebrates, The Inter. Res. Group on Wood Preserv., Stockholm, Doc no. IRG/WP 02-50183.


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7. Walter, D.E. and Proctor, H.C. 1999. Mites: ecology, evolution and behaviour. University of New South Wales Press, Sydney. 8. Walter, D.E. and Proctor, H.C. 2001. Mites in soil: an interactive key to mites and other soil microarthrpods. CSIRO Publishing, Collingwood. 9. Krantz, G.W. 1978. A Manual of Acarology. Oregon State University, Corvallis. 10. Clarke, K.R. and Gorley, R.N. 2001. PRIMER v5: user manual/tutorial. Primer-E Ltd, Plymouth. 11. Osler, G.H.R., Westhorpe, D. and Oliver, I. 2001. The short-term effects of endosulfan discharges on eucalypt floodplain soil microarthropods. Applied Soil Ecology 16, 263–273. 12. Ruf, A. 1998. A maturity index for predatory soil mites (Mesostigmata: Gamasina) as an indicator of environmental impacts of pollution on forest soils. Applied Soil Ecology 9, 447–452.


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Environmental Impact of CCA-Treated Wood in Japan

Toshimitsu Hata1,*, Paul Bronsveld2; Tomo Kakitani1, Dietrich Meier3; and Yuji Imamura1

1. Wood Research Institute, Kyoto University, 2. Department of Applied Physics, Materials Science Center, University of Groningen, The

Netherlands 3. Institute of Wood Chemistry and Chemical Technology of Wood, Federal Research Centre for

Forestry and Forest Products, Germany ABSTRACT

Recycling of waste wood is important for the effective utilization of natural resources not only in Japan but also in the world at large. In practice, most such wood is put in an incinerator due to lack of an appropriate system to deal with it. However, the incineration of waste wood can be converted into a practical way of producing energy under the condition that emission of arsenic is suppressed. Recently, interest into this type of conversion has been growing although an environmentally benign technology is still to be developed.

It was reported that a strong acid such as sulfuric acid could dissolve and extract CCA compounds which had been fixed in wood. The solvent extraction of CCA chemicals by other type of acids or decomposition by micro-organisms has been tried for the efficient disposal of treated products. Recently, immobilization of the toxic elements only by heat was applied to CCA-treated wood, which is an effective and environmental friendly technique without using any reagent. In this paper, the situation of CCA-treated wood in Japan and the potential technologies to fix or extract CCA elements in the wood are explained.

Keywords: chromium-copper-arsenate, preservative, waste wood, fast pyrolysis, recycling

technology, bio-oil, charcoal

INTRODUCTION Recycling of waste wood is important for the effective utilization of natural resources not only

in Japan but also in the world at large. In practice, most such wood is put in an incinerator due to lack of an appropriate system to deal with it. However, the incineration of waste wood can be converted into a practical way of producing energy under the condition that emission of arsenic is suppressed. Recently, interest into this type of conversion has been growing although an environmentally benign technology is still to be developed.

Pyrolyzing CCA-treated wood is a possible solution to this problem and the topic of this paper. Pyrolysis results in three products, wood charcoal, oil and gas [1]. Since the first reports on the volatilization of arsenic during the combustion of arsenic-treated wood in the 1950’s, many studies have been carried out on the burning of contaminated wood [2]. The relative distribution of volatilized arsenic increases with temperature and oxygen partial pressure [3]. At combustion temperatures of 1000 °C the arsenic volatilization approaches zero under limited airflow.

*Corresponding Author. Mailing Address: Kyoto University, Wood Research Institute, Div. of Wood Material Science, Uji Kyoto 611-0011, Japan. Phone: +81 774 38 3667. Fax: +81 774 38 3678. Email: [email protected]


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Pyrolyzing CCA-treated wood at lower temperature without any oxidizing agent is a promising path to disposal [4]. The amount of Cu and Cr were thought to be low enough not to be an environmental problem.

The purpose of this pilot project is to capture as much as possible the arsenic containing fraction in the charcoal while at the same time minimizing the mass reduction with the ultimate goal of exploiting the bio-oil from CCA-treated wood. Laboratory-scale pyrolysis was conducted in order to determine mass balances of the yield and the relative distribution of arsenic over the total system. An experimental facility was built to examine the influence of process parameters such as pyrolysis temperature and pyrolysis time. The particle distribution and microstructure of CCA-treated wood in the pyrolysis residue is studied in order to find the most effective way of capturing arsenic during pyrolysis.

In this paper, the situation of CCA-treated wood in Japan and the potential technologies to fix or extract CCA elements from wood are dealt with. Preservative Treatment of Wood

CCA used to be a popular water-borne wood preservative, and has been used all over the world. CCA was standardized as a wood preservatives for pressure processes (pressure-type preservative) treatment in Japan, and accepted as a Japanese Industrial Standard in 1963. After that, the production of CCA- treated wood increased noticeably.

Table 1 shows the production volume of pressure-type preservative wood and Fig. 1 shows the change in production of pressure-type preservative treated wood in Japan from 1996 to 2002. Non-CCA type chemicals have replaced the CCA preservative recently. The production of CCA-treated wood has decreased to below 2 % of the total amount in 2002. On the other hand, the amount of CCA-treated wood discharged as waste from demolished houses is increasing with the rebuilding of large numbers of old houses, running parallel to the construction boom in Japan. It is predicted that the amount of CCA-treated waste wood from residential houses will increase to over 200,000 m3 in 2003 (assuming the lifetime of a house to be 25 years). Non-treated Japanese cypress (Chamaecyparis obtusa), as well as CCA-treated Western hemlock (Tsuga heterophylla) have been used for sills. The calculation assumes the basic unit of scrap wood chips to be 0.15m3/m2 based on the floor area and the production of CCA sills in one year. CCA used in the sills of houses built since 1965 has gradually increased. However, the ratio of sills is about 2%.

In the incineration of waste CCA-treated wood, the behavior of the preservative chemicals under thermal conversion should be examined with consideration to the environment. It is said that arsenic compounds change to volatile arsenic or arsenious acids and cause air pollution after burning. On the other hand, chromium and copper compounds are considered to remain in the solid fraction as water-insoluble solids on the heating of CCA-treated wood. It was reported that a strong acid such as sulfuric acid could solve and extract CCA chemicals which had been fixed in wood [5]. The solvent extraction of CCA chemicals by other types of acid or decomposition by micro-organisms has also been tried for the efficient disposal of treated products [6, 7, 8]. Recently, even carbon dioxide in super-critical condition was applied to recover CCA chemicals by exploiting its excellent extraction and penetration [9]. However, these methods are yet to be practically established. CCA and Non-CCA Preservative-Treated Wood

Pressure-type preservation factories are widely distributed over Japan. The Wood Preservatives Industry Association of Japan was composed of 39 companies with 55 factories as of March 2003 and the number of non-member factories of small scale is presumed to be even higher, about 70.


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Table 1 Production Volume of Pressure-Type Preservative Treated Wood (in Units of m3 , for the Year 2002)

Note: 1) ACQ, Copper boron azole 2) AAC 3) Fatty acid metal soap The data are based on statistics from Wood Preservatives Industry Association of Japan.

Some of those companies have satellite preservation facilities at the sawmill or at the precutting facilities.

The volume of preservative-treated wood produced in 2002 is presumed to be 273,000 m3 (332,000 m3, 1999) in the associated factories. In Japan, the discharge of industrial liquid waste is legally restricted and the market strongly requests a clean environment. The replacement of CCA by non-CCA preservatives is going on only recently. The CCA preservative, which used to be the main wood preservative chemical for conventional pressure processes, decreased from 7.2% in 1998 to only 2.0% in 2002 (Table 1). Expected Volume of Preservative-Treated Waste Wood

Table 2 shows a prediction of the volume of preservative-treated wood to be disposed in Japan. It is understood from the table that a lot of wooden sleepers were produced. Kempas (Koompassia malacensis) treated with creosote as preservative has mainly been used for these sleepers. The service life of the treated wooden sleeper, which is of course affected by site and conditions and by species and penetration of the preservative, is 20-30 years.

The service life of utility poles was assumed to be 15 years, and the amount of the disposed wood volume was calculated on the basis of production data. About half of all utility poles have been treated with CCA. The production of utility poles treated with preservative decreased from 300,000 m3 to 200,000 m3 from 1975 to 1985 and continued to decrease since then.

In Japan, the use of CCA-treated wood that was standardized by the JIS in 1963, spread rapidly when the price of Japanese cypress suddenly rose in 1965. From that time 300,000 m3 of CCA-treated wood was produced each year. At the moment, those wooden houses that were constructed

Sleeper Utility pole Sill

Other construction

materials Exterior

wood Others Total

Creosote 25,117 253 0 25 3,834 4,132 33,361CCA 0 0 0 5,416 0 0 5,416Copper type water-soluble chemicals 1)

117 815 94,427 44,981 11,031 7,664 159,035

Non-copper type water-soluble chemicals 2)

0 0 35,440 16,276 9,644 1,855 63,215

Oil-soluble and emulsifier 3) 6 0 6,071 4,090 1,389 430 11,986

Other chemicals 0 0 0 0 0 0 0

Total 25,240 1,068 135,938 70,788 25,898 14,081 273,013


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Table 2 Prediction of the Disposal Volume of Preservative-Treated Wood in Japan (in Units of 103 m3).

Note: The service life for sleepers､utility poles, sills, and exterior and others is 25､15, 25, and 15 years, respectively (mainly for outdoor use). The data are based on statistics from Wood Preservatives Industry Association of Japan.

Figure 1 Change in production of pressure-type preservative-treated wood in Japan (1996 - 2002). The data are based on statistics of The Wood Preservatives Industry Association of Japan .

during the second housing construction boom after the Second-World War are being replaced. Even more preservative-treated wood is generated from foundation sills. The prediction of the volume of such wood used in sills was calculated assuming a service life of 25 years. It is predicted that the amount of CCA-treated waste wood from residential houses will increase

─────────────────────────────────────────────────────────── Year Sleepers Utility Sills Exterior and other poles construction materials ─────────────────────────────────────────────────────────── 2003 142 15 200 104 2004 145 14 230 107 2005 147 12 208 106 ───────────────────────────────────────────────────────────


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to over 200,000 m3 in 2003 (assuming the lifetime of a house to be 25 years). Non-treated Japanese cypress (Chamaecyparis obtusa), as well as CCA-treated Western hemlock (Tsuga heterophylla) have been used for sills. The calculation assumes the basic unit of scrap wood chips to be 0.15m3/m2 based on the floor area and the production of CCA sills in one year. CCA used in the sills of houses built since 1965 has gradually increased. However, the ratio of sills is about 2%.

Exterior wood is used for outdoor facilities. In the fifth column of Table 2, wood for decks or for other outdoor facilities occupies a considerable proportion of the total production volume. Exterior wood has been used in boardwalks and piers in the redevelopment of waterfronts, in benches and playgrounds in parks, in harbors, in wooden bridges, in promenades, and in decks and walls used in houses in natural parks and resorts, etc.

CCA-treated wood accounts for the majority of these exterior wooden applications. The prediction of the volume to be disposed was calculated assuming a service life of 15 years.

On the whole, the volume of sleepers and utility poles tends to decrease, however, the amount of waste CCA-treated wood used for exterior purposes is gradually increasing. PYROLYSIS OF CCA-TREATED WOOD Materials and Methods Description of the System

An experimental facility has been built for the pyrolysis of CCA-treated wood. A schematic

diagram of the glass reactor is shown in Fig.2. The sample is situated in the heated section. An N2

Sample Thermo couples

N2

Heater Cooler

Washing bottle (TBAH-solution)

Gas

Figure 2 Schematic diagram of the experimental glass-reactor system for CCA-treated wood.


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gas cylinder is connected to the inlet and at the gas outlet a wire screen is inserted to filter dust particles while the volatile product is captured in a cold trap and glass washing-bottle through a cotton filter.

Inside the cold trap is a liquid N2/acetone solution. The washing bottle contains 30 ml of acetone based tetra-butyl-ammonium hydroxide (TBAH) with the volume ratio being 2 to 1, which collects the arsenic (III) oxide [3]. The reaction temperature was monitored with a thermocouple connected to a controller that regulates the heating system. A complete yield balance was determined with this set up, in particular the one for arsenic. Preparation of the Samples

The feedstock used in the experiment was western hemlock (Tsuga heterophylla, 100 x 100 mm cross section) treated with type III CCA salt supplied by Koshii & Co Ltd. Type III CCA is a formation containing 47±3 parts by weight of hexavalent chromium Cr(VI)O3, 19±2 parts of divalent copper Cu(II)O, and 34±4 parts of pentavalent arsenic As(V)2O5. The concentration was measured to be 7.73, 6.42 and 7.18 kg/m3, respectively. The CCA-treated planks were broken down into chips and passed through a hammer mill. The resulting particles were filtered through a 2 mm sieve before being used in the pyrolysis experiment. The Actual Pyrolysis

Each time one gram of the CCA-treated wood was heated in a N2 atmosphere. Wood powder was put in the reactor before each test. A constant flow rate (12.5ml/s) of N2 was maintained throughout the pyrolysis reaction. N2 passed through the accumulated wood charcoal residue and swept away the volatiles to the outlet. The gas stream was passed through a cotton filter to separate the solid from the liquid and gaseous fraction.

Smoke can be characterized as a combination of oil vapor, micron-sized droplets and polar molecules bonded to water vapor. The gas went through a condenser with an acetone-base liquid N2 solution. The pyrolysis condensate is collected and the remaining gases went through the washing bottle with an acetone-base TBAH solution. Important Parameters and Analysis

Important variables in the pyrolysis of the CCA-treated wood samples were temperature, rate of increase in temperature and duration of pyrolysis. The reactor temperature was varied from 400 to 500°C, the rate of increase was 3 °C/sec and the duration of the pyrolysis was 0 and 180 s. The pyrolysis time of 0 sec means no retention time after reaching the pyrolysis temperature. After the process, the entire glass reactor and cotton filter were washed with 10 ml of distilled acetone. The yield of charcoal, oil and gas were calculated from the weight difference of the glassware before and after pyrolysis. The washed solution was analyzed for arsenic content by using an inductively coupled plasma analyzer (ICP) .

Important variables in the pyrolysis of wood are temperature, rate of rising temperature and duration of pyrolysis. The reactor temperature was varied from 400 to 500°C, and the duration of pyrolysis was 0 and 180 s. After the process, the entire glassware and cotton filter were washed with 10 ml of distilled acetone. Yields of charcoal, oil and gas were calculated from the weight difference of the glassware before and after pyrolysis. The washed solution was analyzed for arsenic by using inductively coupled plasma (ICP).

Changes in arsenic content were defined as the percentage ratio of the arsenic content in the pyrolysis residue based on the arsenic content in the original CCA treated wood. Composition and structure of the metal compounds in the pyrolysis residue were examined by transmission electron microscopy (JEOL 2010F with GATAN Imaging Filter and EDS).


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Results and Discussion Mass Balance and Yield of Pyrolysis Products

Fig. 3 shows the yield of pyrolysis products as a function of target temperature. The gas stream was determined by the difference. The yield of charcoal was extremely reduced whereas a reverse trend was observed for pyrolysis oil obtained by 180 s pyrolysis of CCA-treated wood. The increase in yield of pyrolysis oil and the reduction of wood charcoal is related to the heat transfer in wood particles.

Pyrolysis at 500°C resulted in more oil and less charcoal. Pyrolysis of 180 s resulted in more oil and more charcoal. There was little difference in the yield between 400 and 500°C. Microstructural change was caused by the thermal degradation process leading to such a result. This is due to the

Pyrolysis oil

Wood charcoal

Gas

Figure 3 Yield of pyrolysis products as a function of target temperature and pyrolysis time. The pyrolysis time of 0 sec means no retention time after reaching the pyrolysis temperature.


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limited heat transfer in the wood particles. The yield of gas varied little by changing the target temperature and pyrolysis time. Mass Balance and Relative Distribution of Arsenic in Pyrolysis Products

Fig. 4 shows the relative arsenic distribution in the pyrolysis products as a function of target temperature [10]. The percentage was calculated from the initial amount of arsenic in each specimen. The relative distribution of arsenic was increased in pyrolysis oil with the increase of temperature from 400 to 500°C.

The relative distribution of arsenic in pyrolysis oil increased with temperature from 400 to 500°C, then reached about 1.5 %. A shorter pyrolysis time gave a lower percentage (at 400°C, around 0.5 %). The relative distribution of arsenic in wood charcoal was over 40 %, and independent of temperature from 400 to 500°C. The pyrolysis time had little effect on the relative arsenic distribution in the wood charcoal. It is believed that arsenic is strongly bound to cellulose

and lignin [1]. Before the temperature reached 400°C, the decomposition of both chemical components occurred.

Pyrolysis oil

Wood charcoal

Figure 4 Arsenic concentration (%) in pyrolysis products as a function of target temperature and pyrolysis time. The pyrolysis time of 0 sec means no retention time after reaching the pyrolysis temperature.


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Electron Microscopy

In order to evaluate the effect of pyrolysis we started out by preparing CCA treated wood samples before and after the extra heat treatment at 450 °C for 10 min. After the pyrolysis a dense collection of nanoparticles was found in the residue as shown in the double image of Fig.5 [10]. The smaller particles were mostly spherical and 10 to 50 nm in size. A few of them were clearly faceted. Composition determination with EDS was not conclusive. Not with standing the fact that the beam of the 2010F microscope can easily be squeezed to below 1 nm, the background spectrum contained almost always Cr, Cu and As. For example, the EDS spectra indicated a strong Cu peak even when the spot was put in a Ni grid background. Subsequently, the GIF was used to map these particles with the specific EELS signal for As, Cr and Cu. It was possible to map a larger lump of sample material, indicating a strong C, O and Cr signal, but only a minor contribution in As and Cu. Reproducing these rather noisy graphs is not well feasible [10].

For that reason, we concentrated more on taking selected area electron diffraction patterns combined with bright- and dark-field images in conventional TEM. In Fig. 6, we have reproduced an image with its corresponding diffraction pattern as insert. The particle turned out to be Cr2As24O12. The spots closest to the central beam are the most specific. In this case they are interpretable as due to the (001) planes with a lattice spacing of d001 = 0.760nm. CONCLUSION

One can conclude that over 50 % of the original arsenic content is already lost at pyrolysis temperature below 400 °C, which is close to the optimal temperature for fast pyrolysis. This may be caused by the volatilization of the unreacted arsenic pentoxide. The reacted chromium arsenate captured in the pyrolysis residue decreases linearly with increasing pyrolysis temperature.

The types of particles observed are the original arsenic pentoxide, arsenic trioxide and the reacted chromium arsenate. EDS scans could distinguish the two arsenic oxides from the reacted arsenate simply by checking the presence of a Cr peak. Structure determination could be better done by making use of selected area electron diffraction patterns in conventional transmission electron microscopy.

Figure 5 Micro and nanoparticles in CCA-treated wood after a heat treatment at 450 °C for 10 min [10].


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ACKNOWLEDGEMENT The authors are grateful to Vinicius Castro for the critical reading of the manuscript. Thanks are

also due to Mr. Osone for his help with the analysis of the data from Wood Preservatives Industry Association of Japan. REFERENCES [1] Broek K.V.D. et. al.: Analyst 122, 695-700 (1997) [2] Dobbs A.J., Phil D., Grant C.: Holzforschung 32, 32-35(1978) [3] Helsen L., Bulck E.V.D.: in A.V.Bridgewater, D.G.B.Boocock (eds.) “Developments of

Thermochemical Biomass Conversion”, Volume1, Blackie Academic & Professional, 220-228 (1997)

[4] Helsen L., Bulck E.V.D.: Holzforschung 52, 607-614 (1998) [5] Honda A et al: IRG Document, IRG/WP/3651 (1991) [6] Kanjo Y., Kimoto A., Honda A.: Journal of Japanese Society of Waste Management Experts

5(5) 185-192 (1994) [7] Kartal N.S., Imamura Y.: Wood Research 90, 111-115 (2003) [8] Peek R-D., Stephan I. and Leithoff H.: IRG Document, IRG/WP/93-5001, 313-325 (1993) [9] Takeshita Y.: Abstract of the 15th Japan Wood Preservation Association, 37-42 (1999) [10] Hata T., Bronsveld P., Vystavel T., Kooi B., DeHosson J., Kakitani T., Otono A., Imamura

Y.: Journal of Analytical and Applied Pyrolysis 68-69, 635-643 (2003). [11] Kercher A.K. and Nagle D.C.: Wood Science & Technology 85, 325-341 (2001)

Figure 6 Cr(VI)2As(III)4O12 particle in CCA-treated wood (450°C/10min), which could be identified by its strong diffraction spots of (001) planes with a lattice spacing of d001 = 0.760 nm as indicated in the inset [10].


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Alternatives to Chromated Copper Arsenate (CCA) for Residential

Construction

Stan Lebow

USDA Forest Service, Forest Products Laboratory Madison, Wisconsin

Prepared for Proceedings of the Environmental Impacts of Preservative-Treated Wood Conference

Orlando, Florida

February 8–10, 2004

The Forest Products Laboratory is maintained in cooperation with the University of Wisconsin. This article was written and prepared by U.S. Government employees on official time, and it is therefore in the public domain and not subject to copyright. ABSTRACT

For decades chromated copper arsenate (CCA) was the primary preservative for treated wood used in residential construction. However, recent label changes submitted by CCA registrants will withdraw CCA from most residential applications. This action has increased interest in arsenic-free preservative systems that have been standardized by the American Wood Preservers’ Association. These include acid copper chromate (ACC), alkaline copper quat (ACQ), copper azole (CBA-A and CA-B), copper citrate (CC), copper dimethyldithiocarbamate (CDDC), and copper HDO (CX-A). All of these CCA alternatives rely on copper as their primary biocide, although some have co-biocides to help prevent attack by copper-tolerant fungi. They have appearance and handling properties similar to CCA and are likely to be readily accepted by consumers. Prior studies indicate that these CCA alternatives release preservative components into the environment at a rate greater than or equal to that of CCA, but because these components have lower mammalian toxicity they are less likely to cause concern in residential applications. As the treated wood industry evolves it is probable that a wider range of types and retentions of wood preservatives will become available, with the treatment more closely tailored to a specific type of construction application.

Stan Lebow, U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, One Gifford Pinchot Drive, Madison, Wisconsin 53726–2398


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Keywords: Chromated copper arsenate (CCA), alternative preservatives, leaching, environmental concerns INTRODUCTION

Because it is biodegradable, wood used in applications where it may be attacked by decay fungi or insects should be protected by pressure treatment with wood preservatives. Wood preservatives are broadly classified as either water- or oil-based, depending on the chemical composition of the preservative and the carrier used during the treating process. The oil-type preservatives creosote, pentachlorophenol, and copper naphthenate are commonly used for applications such as posts, poles, piles, and glue-laminated beams. They are not usually used for applications that involve frequent contact with human skin or inside dwellings because they may be visually oily, oily to touch, or have a strong odor. Water-based preservatives have become more widely used in recent years because the treated wood has a dry, paintable surface and no odor. The most common of these preservatives has been chromated copper arsenate (CCA). Wood treated with CCA, commonly called “green treated” wood, dominated the residential market for several decades and was sold at lumberyards under a variety of trade names. However, as a result of voluntary label changes submitted to the Environmental Protection Agency (EPA) by the CCA registrants, the EPA labeling of CCA will limit the use of the product primarily to industrial applications. The label change is effective December 31, 2003, although suppliers will be allowed to sell existing stocks of CCA-treated wood after that date. It is important to note that the recent action does not affect end-uses of wood treated before December 31, 2003, or any existing structures. APPLICATIONS AFFECTED BY CCA LABEL CHANGES

The label changes cite specific commodity standards listed in the 2001 edition of the American Wood Preservers’ Association (AWPA) standards [1]. The changes were made as part of the ongoing CCA re-registration process and in light of current and anticipated market demand for alternative preservatives for non-industrial uses. Most applications of sawn lumber and timbers are affected, although CCA will still be allowed for treatment of roundstock (poles, building posts, and piles). However, there are exceptions that allow use of CCA for some sawn products. Examples of sawn products that still may be treated with CCA include the following: • Lumber in permanent wood foundations (Fig. 1) • Sawn structural piles used to support residential and commercial structures • Sawn building poles and posts used in agricultural construction • Wood used in highway construction, including lumber and timbers • Utility pole crossarms • Wood of all dimensions used in salt water and subject to marine borer attack

Treatment of engineered wood products, such as glued-laminated beams and timbers, structural composite lumber, and plywood will also be allowed in most applications. Overall, the label changes are expected to result in a 70% to 80% reduction in the volume of CCA-treated wood. This raises the question, What preservatives will be

Figure 1 CCA is still registered for some residential applications, such as permanent wood foundations.


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used to replace CCA and what are the characteristics of these alternatives? CHALLENGES IN DEVELOPING NEW WOOD PRESERVATIVES

In today’s society we have become accustomed to rapidly developing and changing products in most residential commodities. Consumers and regulators sometimes seem frustrated that the wood preservation community does not rapidly produce a wide selection of

effective replacements for CCA. Unfortunately, it currently takes many years to bring a new wood preservative to market. A formulation must meet several important criteria to be an effective wood preservative. The first challenge is identification of a combination of active ingredients that will provide long-term protection against a wide range of organisms that damage wood. In addition to decay fungi, the preservative must protect against attack by termites, carpenter ants, beetles, and other insects. Even within decay fungi there is a range of species and strains that differ in chemical tolerance. The preservative must also resist detoxification by non-wood-attacking fungi and bacteria. These requirements preclude the use of compounds that have a very narrow or specific toxicity to only one type of organism. A wood preservative needs some degree of broad spectrum efficacy, which is in direct conflict with the goal of identifying environmentally friendly compounds.

Because a wood preservative must protect against a range of organisms while simultaneously resisting environmental degradation, it has proven difficult to develop reliable methods of accelerating evaluation of preservatives. Typically, at least 3 to 5 years of test stake exposure in multiple locations is needed to demonstrate the potential for long-term efficacy in ground-contact applications (Fig. 2). In addition, a battery of tests, including laboratory fungal and leaching evaluations, corrosion tests, and mechanical property evaluations, are needed to obtain a listing of a preservative formulation within the AWPA Book of Standards. AWPA members, who represent government agencies, universities, and chemical suppliers, review the results of these tests. The data must then be supplemented with commercial treatment trials to demonstrate that the formulation can be effectively and practically applied to wood products.

This efficacy testing and evaluation is independent of that needed to obtain EPA registration of a new pesticide product. Registration of a new biocidal active component may require several years and millions of dollars to complete. Because of the high cost of EPA registration of new compounds, there is a strong tendency to use compounds that have already been registered for other applications.

As a result of all these factors, it is difficult to develop new preservatives and bring them quickly to market. The wood treatment industry cannot immediately respond to changing regulatory or societal expectations, but instead must attempt to anticipate and plan for future changes. ALTERNATIVES TO CCA PRESERVATIVE TREATMENT

Preservative manufactures have been working for years to develop arsenic-free alternatives. The AWPA has standardized several arsenic-free preservative formulations, although not all are available commercially. All of these alternatives rely on copper as their primary active ingredient

Figure 2 Wood preservative formulations undergo rigorous testing, including lengthy field trials.


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because copper is an excellent fungicide, is relatively inexpensive, and has relatively low mammalian toxicity. These preservatives are discussed in alphabetical order in the following text. Acid Copper Chromate

Acid copper chromate (ACC) has been used sporadically as a wood preservative in Europe and the United States since the 1920s. In the last few decades, it has been primarily used for the treatment of wood used in cooling towers. ACC contains 31.8% copper oxide and 68.2% chromium trioxide (Table 1). The treated wood has a light greenish-brown color and little noticeable odor. Tests on stakes and posts exposed to decay and termite attack indicate that ACC provides acceptable average service life, but that wood used in ground contact may suffer occasional early failure from attack by copper-tolerant fungi [2]. ACC is listed in AWPA standards for treatment of a wide range of softwood and hardwood species used above ground or in ground contact. However, in critical structural applications such as highway construction, its AWPA listings are limited to sign posts, handrails and guardrails, and glue-laminated beams used above ground. It may be difficult to obtain adequate penetration of ACC in some of the more refractory wood species such as white oak or Douglas-fir. This is because ACC must be used at relatively low treating temperatures (38ºC to 66ºC, 100ºF to 150ºF), and because rapid reactions of chromium in the wood can hinder further penetration during the longer pressure periods needed for refractory species. The high chromium content of ACC, however, has the benefit of preventing much of the corrosion that might otherwise occur with an acidic copper

preservative. As of the writing of this report, ACC does not have an EPA label and its future availability is unclear. . Alkaline Copper Quat Alkaline copper quat (ACQ) is one of several wood preservatives that has been developed in recent years as an alternative to CCA. It has been commercially available in some parts of the United States for several years (Fig. 3). The active ingredients in ACQ are copper oxide (67%) and a quaternary ammonium compound (quat). Multiple variations of ACQ have been standardized or

are in the process of standardization. ACQ type B (ACQ-B) is an ammoniacal copper formulation, ACQ type D (ACQ-D) an amine copper formulation, and ACQ type C (ACQ-C) a combined ammoniacal–amine formulation with a slightly different quat compound. ACQ-B treated wood has a dark greenish-brown color that fades to a lighter brown and may have a slight ammonia odor until the wood dries. Wood treated with ACQ-D has a lighter brown color and little

Figure 3 ACQ-treated wood has been available commercially for several years in some areas of the United States.

Table 1 Preservative Formulations Standardized for Applications Typical of Residential Construction

Retention kg/m3 (lb/ft3)

Preservative formulation as listed in AWPA standards

Proportion of preservative component Above ground

Ground contact

Acid copper chromate (ACC) 32% CuO 68% CrO3 4.0 (0.25) 6.4 (0.40) Alkaline copper quat (ACQ-B, D) 67% CuO 33% DDACa 4.0 (0.25) 6.4 (0.40) Alkaline copper quat (ACQ-C) 67% CuO 33% BACb 4.0 (0.25) 6.4 (0.40) Copper azole (CA-B) 96% Cu 4% Azolec 1.7 (0.10) 3.3 (0.21) Copper azole (CBA-A) 49% Cu 2% Azolec 49% H3BO3 3.3 (0.20) 6.5 (0.41) Copper citrate (CC) 62% CuO 38% citric acid 4.0 (0.25) 6.4 (0.40) Copper bis dimethyldithiocarbamate (CDDC) 17%–29% CuO 71%–83% SDDCd 1.6 (0.10) 3.2 (0.20)

Copper HDO (CX-A) (pending EPA registration) 61.5% CuO 14% CuHDOe

24.5% H3BO3 2.4 (0.15) NAf a Didecyldimethylammoniumchloride; b Alkylbenzyldimethylammoniumchloride; c Tebuconazole d Sodium dimethyldithiocarbamate; e Bis-(N-cyclohexylddiazeniumdioxy)copper; f Not in standards as yet.


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noticeable odor, while the appearance of wood treated with ACQ-C varies between that of wood treated with ACQ-B or ACQ-D, depending on the formulation. The ACQ formulations are listed in AWPA standards for a range of applications and many softwood species, although the listings for ACQ-C are limited because it is the most recently standardized formulation. Minimum retentions of ACQ formulations are specified for wood used above ground and in ground contact (Table 1). The multiple formulations of ACQ allow some flexibility in achieving compatibility with a specific wood species and application. When ammonia is used as the carrier, ACQ has improved ability to penetrate into difficult-to-treat wood species. However, in wood species that can be readily treated, such as Southern Pine, an amine carrier can be used to provide a more uniform surface appearance.

Ammoniacal Copper Citrate Ammoniacal copper citrate (CC) is a recently developed wood preservative that utilizes copper oxide as the fungicide and insecticide and citric acid to aid in the distribution of copper within the wood structure. The color of the treated wood varies from light green to dark brown (Fig. 4). The wood may have a slight ammonia odor until it is thoroughly dried after treatment. Exposure tests with stakes and posts placed in ground contact indicate

that the treated wood resists attack by both fungi and insects. However, it appears that the lack of a co-biocide may render wood used in ground contact vulnerable to attack by certain species of copper-tolerant fungi [3]. CC is listed in AWPA standards for treatment of a range of softwood species and wood products for wood used above ground or in ground contact. CC is not listed in AWPA standards for use in highway construction or other structurally critical applications. As with other preservatives containing ammonia, CC has an increased ability to penetrate into difficult-to-treat wood species such as Douglas-fir. At the time of publication of this report, CC had only limited commercial availability. Copper Azole

Copper azole is another recently developed preservative formulation that relies primarily on amine copper, but with co-biocides, to protect wood from decay and insect attack. The first copper azole formulation developed was copper azole Type A (CBA-A), which contains 49% copper, 49% boric acid, and 2% Tebuconazole (Fig. 5). More recently, the copper azole Type B (CA-B) formulation was standardized. CA-B does not contain boric acid and is comprised of 96% copper and 4% Tebuconazole. Wood treated with either copper azole formulation has a greenish-brown color and little or no odor. The formulations are listed in AWPA standards for treatment of a range of softwood species used above ground or in ground contact. Although listed as an amine

Figure 4 Lumber treated with copper citrate (CC).


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formulation, copper azole may also be formulated with an amine–ammonia solvent. The ammonia may be included when the copper azole formulations are used to treat refractory species, and the ability of such a formulation to adequately treat Douglas-fir has been demonstrated. The inclusion of ammonia, however, is likely to have slight effects on the surface appearance and initial odor of the treated wood.

Copper Dimethyldithio-Carbamate

Copper dimethyldithio-carbamate (CDDC) is a reaction product formed within the wood after treatment with two different treating solutions. It contains copper and sulfur compounds. CDDC is standardized for treatment of Southern Pine and some other pine species at copper retentions of 1.6 kg/m3 (0.1 lb/ft3) or 3.2 kg/m3 (0.2 lb/ft3) for wood used above ground or in ground contact, respectively. CDDC-treated wood has a light brown color and little or no odor. At the time of this publication, CDDC treated wood was not commercially available.


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Copper HDO (CX-A)

Copper HDO is an amine copper based preservative that has been used in Europe and recently standardized by the AWPA. The active ingredients are copper oxide, boric acid, and copper-HDO (Bis-(N-cyclohexyl-diazeniumdioxy copper). The appearance and handling characteristics of wood treated with CX-A are similar to those of other copper-based treatments. CX-A formulations have been evaluated in a range of exposures, but at this

time have only been standardized for uses above ground. The minimum retention of copper HDO for above-ground use is 2.4 kg/m3 (0.15 lb/ft3). At the time of this publication, EPA registration of CX-A was pending. Borates

Borate-treated wood should be used only in applications where the wood is kept free from rainwater, standing water, and ground contact. Borate preservatives are sodium salts such as sodium octaborate, sodium tetraborate, and sodium pentaborate that are dissolved in water. These formulations have received increased attention in recent years because they are inexpensive and have low mammalian toxicity. Borate-treated wood is also odorless and colorless, and it may be painted or stained. Borates are effective preservatives against decay fungi and insects. Borate preservatives are diffusible, and, with appropriate treating practices, they can achieve excellent penetration in species that are difficult to treat with other preservatives. However, the borate in the wood remains water soluble and readily leaches out in soil or rainwater. Borate preservatives are standardized by the AWPA, but only for applications that are not exposed to liquid water. An example of such a use is in the construction of wooden buildings in areas of high termite hazard. Practical Differences Between CCA Alternatives

From a practical, end-use basis, the consumer will notice little difference between CCA and the recently developed alternatives. Most residential consumers of treated wood will probably not even be aware that CCA has been replaced because all types of treated wood are referred to as “green-treated” wood. The appearance, strength properties, and handling characteristics are very similar to those of CCA. CCA alternatives are slightly more expensive, however, with the treated wood costing from 10% to 30% more than CCA-treated wood. With the possible exception of ACC, the alternatives also tend to be somewhat more corrosive to metal fasteners than is CCA. Hot-dipped galvanized or stainless steel fasteners should be used when building with wood treated with CCA alternatives. ENVIRONMENTAL CONCERNS WITH CCA ALTERNATIVES

Environmental and health concerns have been raised over the use of CCA-treated wood. It is likely that CCA alternatives will circumvent some of these concerns simply because they do not

Figure 5 CCA-treated supports and CBA-A treated decking.


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contain arsenic. Because they have been developed relatively recently and/or have been used infrequently, only limited research has been conducted on their potential leaching and environmental impact. Much available data have been obtained using small samples that accelerate leaching and allow more rapid comparisons between preservative formulations. Although useful as a comparative tool, leaching rates derived from small samples should not be directly extrapolated to commodity size material. The release and environmental impact of copper from ACQ-B treated

wood was recently evaluated in a wetland boardwalk study (Fig. 6) [4]. Elevated levels of copper were detected in rainwater, soil, and sediments collected adjacent to the treated wood. The rainwater collection indicated that release of copper peaked by 6 months after construction, reaching average release rates of 35 ug per cm2/inch of rain. Much lower average release rates (approximately 5 ug/cm2/inch of rain) were observed by 11.5 months after construction. The relatively high release of copper during the first 6 months of the study was reflected in the concentrations of copper detected in the soil; geometric mean soil concentrations were elevated by approximately 373 ppm directly under the edge of the boardwalk. However, the copper accumulations were localized in soil very close to the boardwalk; the geometric mean concentration was elevated by only 16 ppm 60 cm (24 inches) away from the boardwalk. Sediment copper concentrations also appeared to peak at about 6 months, when the geometric mean of samples removed from directly under the edge of the boardwalk reached 113 ppm, an elevation of approximately 92 ppm over background levels. Copper mobility was greater in the sediment than in the soil, causing slight elevations in three samples removed 300 cm (10 ft) away from the boardwalk 11.5 months after construction. This study can truly be considered a “worst case” scenario, since the boardwalk decking was over-treated and inadequately conditioned [4]; smaller releases might be expected from material treated to a retention more appropriate for this application. Despite the accumulations of copper detected in the environment, no significant impact was detected on the quantity or diversity of aquatic insects at the site [4].

Other studies of leaching from ACQ-treated wood have been conducted with small specimens intended to exaggerate leaching and accelerate comparisons. Copper leaching from ACQ-B and CCA was compared in a soil-bed test with 19- by 8- by 200-mm (0.75- by 0.30- by 7.9-inch) stakes [5]. After 9 months, copper loss from stakes treated to 9.6 kg/m3 (0.6 lb/ft3) averaged 19% from ACQ-B and 18% from CCA. The ACQ-treated stakes also lost 30% of their DDAC, while the CCA-treated stakes lost 11% chromium trioxide and 16% arsenic pentoxide during the test. In a subsequent soil-bed test, leaching of ACQ-B and ACQ-D was compared in Southern Pine stakes (6 by 19 by 203 mm, 0.25 by 0.75 by 8 inches) that had been treated to 6.4 kg/m3 (0.4 lb/ft3) retention [6]. After 3 months, the ACQ-D stakes had lost 15.4% CuO and 12.9% DDAC, and ACQ-B stakes had lost 17.4% CuO and 32.7% DDAC [6]. ACQ-B and CCA leaching data were also collected from 44-month ground-contact depletion tests conducted in Hilo, Hawaii, using 19- by 19- by 1,000-mm (0.75- by 0.75- by 39-inch) stakes treated to 6.4 kg/m3 (0.4 lb/ft3) retention [5]. Averaging losses from the top, bottom, and middle of the stakes revealed that 21% copper oxide, 9% chromium trioxide, and 22% arsenic pentoxide were lost from CCA-treated stakes and 19%

Figure 6 Evaluation of ACQ-B treated wetland boardwalk for leaching and environmental impact.


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copper oxide and 42% DDAC were lost from the ACQ-B treated stakes. A subsequent study with similar size CCA-C treated stakes reported only 5% loss of arsenic pentoxide after 5 years of exposure in Florida [7]. It is evident that these tests presented severe leaching conditions because of the small stake size and the extreme conditions, and the leaching rates should not be extrapolated to commodity size material.

Above-ground depletion tests were conducted in Hawaii on 51- by 19- by 356-mm (2.0- by 0.75- by 14.0-inch) CCA- and ACQ-B-treated Southern Pine samples [5]. After 12 months, copper oxide losses from stakes treated to 4 kg/m3 (0.25 lb/ft3) were 14% from ACQ-B and 8% from CCA. Twenty-seven percent of the DDAC was lost from the ACQ-treated stakes, and 14% chromium trioxide and 19% arsenic pentoxide were lost from the CCA-treated stakes. A similar test was conducted with samples treated with ACQ-D and CCA-C. After 6 months, the ACQ-D samples treated to 4 kg/m3 (0.25 lb/ft3) had lost approximately 10% copper oxide and 32% DDAC, and the CCA-C treated samples had lost 9% copper oxide [6].

In a study that provides insight into leaching rates of treated wood exposed above ground under in-service conditions, depletion tests were conducted on decks built with 38- by 140-mm (1.5- by 5.5-inch) lumber that had been treated with CCA-C, ACQ-B, or copper boron (Cu:BAE = 25:25) with formulation characteristics similar to those of CBA-A [8]. The boards were treated with either full cell or empty cell processes to a retention of 4 kg/m3 (0.25 lb/ft3) copper for the copper boron or to 6.4 kg/m3 (0.4 lb/ft3) (total retention) with either ACQ-B or CCA-C. During 20 months in Conley, Georgia, the decks were exposed to more than 2 m (80 inches) of rainfall, which was periodically collected and analyzed for copper and boron. The copper–boron decks leached 8% to 12% copper and 55% to 65% boric acid, the ACQ-B decks lost 8% to 10% copper, and the CCA-treated decks lost 5% copper. This loss corresponded to leaching rates of approximately 1,722 and 1,184 µg/cm2

(0.0035 and 0.0024 lb/ft2) for copper from the copper–boron treated material, 1,292 and 969 µg/cm2

(0.0026 and 0.0020 lb/ft2) for the ACQ-B treated material, and 215 and 161 g/m2 (0.0004 and 0.0003 lb/ft2) for the CCA-treated material for modified full-cell and full-cell treatments, respectively. With both types of treating schedules, copper loss from the copper–boron treated wood was greatest during the first 508 mm (20 inches) of rainfall and minimal during the last 254 mm (10 inches) of rainfall.

A 5-year study of copper loss from 178- to 229-mm- (7- to 9-inch-) diameter Southern Pine pole stubs that had been treated with copper citrate to a target retention of 9.6 kg/m3 (0.6 lb/ft3) was conducted in Gainesville, Florida [9]. The researchers removed increment cores from 152 mm (6 inches) below ground, at groundline, and 610 mm (24 inches) above ground before exposure and 12, 24, 36, 48, and 60 months after exposure. Leaching data were variable between sampling periods, but copper losses of approximately 50%, 10%, and 39% were noted for the 0 to 13, 13 to 25, and 25 to 52 mm (0 to 0.5, 0.5 to 1, and 1 to 2 inch) assay zones, respectively, in the below-ground zone after 5 years. The authors estimate a total copper loss of approximately 28% from the below-ground zone during the first year, with minimal losses in subsequent years.

Also pertinent to the leaching of boron and copper from ammoniacal formulations is a study evaluating leaching from 38- by 89-mm (1.5- by 3.5-inch) stakes treated with ammoniacal copper borate and exposed for 11 years at a test site in Mississippi [10]. The original copper oxide retention in the stakes varied from 0.29% to 1.98%, and the boric acid content varied from 0.10% to 0.71%. During exposure, 95% to more than 99% of the boron leached from the groundline portion of the stakes and 78% to 93% of the boron was lost from the aboveground portion of the stakes. Copper losses varied from 3% to 33% in the groundline portion of the stakes and 0 to 28% in the aboveground portion. With both copper and boron, the greatest percentage of loss occurred at the lower retention levels. Because of the relatively large dimensions of the stakes used in this study,


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the leaching rates noted for ammoniacal copper may be more representative of losses in service than are stake test data reported previously for other ammoniacal formulations.

The release and environmental accumulation of copper from CDDC-treated wood was recently evaluated in a wetland boardwalk study [4] (Fig. 7). During the first three post-construction inspections, copper concentrations immediately adjacent to the boardwalk slowly increased; 5.5 months after construction, the average copper level in the top 15 cm (5.9 inches) of soil was only 28 ppm higher than the average pre-construction level. This trend changed at

the 11-month inspection, when the combination of sand applied to the walkway and heavy rainfall increased geometric mean soil copper levels immediately adjacent to the boardwalk to a level approximately 135 ppm higher than pre-construction levels. It is likely that much of the increase in soil copper levels during this period was due to removal of wood particles by abrasion, and that levels would have been lower if sand had not been applied to the boardwalk. However, one can conclude that sand should not be applied to CDDC-treated wood (or probably other types of treated wood) when it is used in areas where release of copper into the environment is a concern. It is notable that soil movement of the copper was apparently quite limited; during the course of the study, only a few of the samples removed 15 cm (6 inches) away from the boardwalk contained elevated levels of copper, and the maximum copper concentration detected at greater distances from the wood was 37 ppm. Copper movement downward in the soil was also quite limited; the vast majority of copper leached was confined within the top 15 cm (6 inches) of soil. Thus, it appears that any environmental contamination is restricted to immediately adjacent to the wood when CDDC-treated wood is used in or over soil. Long-term (23 years) leaching data were reported for CDDC for 19- by 19- by 457-mm (0.75- by 0.75- by 18-inch) Southern Pine stakes exposed in Bainbridge, Georgia [11]. The stakes were treated to either 9.6 kg/m3 (0.6 lb/ft3) with CCA or to 3.5 kg/m3 (0.22 lb/ft3) (as copper) with a CDDC formulation in which copper sulfate was the copper source. Copper retention levels in the above- and below-ground portions of the stakes were compared to estimate preservative leaching. The CDDC-treated stakes had 77% less copper below than above ground, and the CCA-C treated stakes had 72% less copper below than above ground. Actual copper losses may have been greater because some leaching did occur above ground. These leaching rates may sound extreme, but it is important to remember the length of the test and that small-sized stakes lose a much greater percentage of their preservative than does product-sized material.

Little information is available on the rate of leaching from ACC-treated wood. One study compared the depletion of ACC and an older formulation of CCA (CCA-A) from several softwood species of cooling tower slats [12]. After 10 years, the average depletion from the ACC-treated slats was approximately 35%, while that from the CCA-A treated slats was 25%. The unusual dimensions of the slats (10-mm by 32-mm by 182-cm, 0.375- by 1.25- by 71.5 inches) and the unique exposure environment make it difficult to compare the leaching results to other applications. However, the results do suggest that the rate of depletion from ACC-treated wood is comparable to

Figure 7 This CDDC-treated boardwalk is being evaluated for leaching and environmental accumulation of copper.


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or slightly greater than that from CCA-A treated wood. The ACC treatment solution does utilize hexavalent chromium, but the chromium is converted to the more benign trivalent state during treatment and subsequent storage of the wood. ACC treatment solutions contain a higher proportion of hexavalent chromium than do CCA solutions, and recent research indicates that a longer reaction period is needed for ACC [13]. The literature indicates that all the CCA alternatives will release copper into the environment at a rate greater than or equal to that of CCA. This is not surprising because all of the recently standardized CCA alternatives contain several times as much copper (proportionally) as does CCA. Fortunately, copper is associated with fewer mammalian health concerns than is arsenic. Environmental release of co-biocides such as boron or quaternary ammonium compounds is also to be expected, but these co-biocides also have relatively low mammalian toxicity. The CCA alternatives may not offer significant advantages over CCA in aquatic applications or other applications where copper release might be a concern. From this perspective, the recent label changes on allowable uses of CCA are logical. CCA will still be allowed for most aquatic uses, while the arsenic-free alternatives will be used where human exposure is greatest.

Leaching from wood treated with water-based preservatives is also dependent on completion of fixation reactions. The active ingredients of various waterborne wood preservatives (copper, chromium, arsenic, and/or zinc) are initially water-soluble in the treating solution but become resistant to leaching when placed into the wood. This leaching resistance is a result of the chemical “fixation” reactions that occur to render the toxic ingredients insoluble in water. The mechanism and requirements for these fixation reactions differ depending on the type of wood preservative. For each type of preservative, some reactions occur very rapidly during pressure treatment, while others may take days or even weeks to reach completion, depending on post-treatment storage and processing conditions. If the treated wood is placed in service before these reactions are completed, the initial release of preservative into the environment may be many times greater than that for wood that has been adequately conditioned. Concerns about inadequate fixation have led Canada and European countries to develop standards or guidelines for “fixing” treating wood. The AWPA has recently formed several task forces to consider the development of fixation or “leaching minimization” standards for CCA-C and other wood preservatives, but there are not yet nationally recognized standards for fixation of waterborne preservatives in the United States. In addition, an on-going effort is underway to develop Best Management Practice (BMP) type standards to ensure that treated wood is produced in a way that will minimize environmental and handling concerns. The Western Wood Preservers Institute (WWPI) has developed guidelines for treated wood used in aquatic environments [14], and the AWPA has active task forces working to develop guidelines for waterborne preservatives. As BMP-type standards are developed, it will be important to include them in specifications of treated wood products.


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As researchers continue to respond to environmental concerns, further progress will be made in reducing environmental impacts from preservative treated wood. Current preservatives are used in a broad range of applications, ranging from mild to very severe deterioration hazards. Because of this, the amount or type of chemical used is stronger than necessary for many applications. Future preservative treatments may be more closely aligned with certain types of applications, allowing use of less toxic chemicals in many applications. In addition, greater emphasis will be placed on using

the minimum amount of preservative needed to protect the wood. This stratification has already begun, as some manufacturers are offering decking treated to a lower retention than are the stringers, which may be treated to a lower retention than are support posts (Fig. 8). This evolution will require changes in the way that treated wood is currently marketed and specified. To guide selection of the types of preservatives and loadings appropriate to a specific end-use, the AWPA recently developed Use Category System (UCS) standards [1]. The UCS standards simplify the process of finding appropriate preservatives and preservative retentions for specific end-uses. The UCS standards categorize all treated wood applications by the severity of the deterioration hazard. For example, the lowest category, Use Category 1 (UC1) is for wood that is used in interior construction, completely protected from the weather. At the other end of the spectrum is UC5, which encompasses applications that place treated wood in contact with seawater and marine borers. To use the UCS standards, one only needs to know the intended end-use of the treated wood.

Figure 8 Stacks of ACQ-C and CA-B treated lumber await sale at a lumberyard. Multiple retentions are available for different end-uses.


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SUMMARY The treated wood industry is undergoing a major transition as CCA is replaced in most residential applications. CCA alternatives have been developed and are becoming more widely available. The alternatives rely heavily on copper as the primary biocide, with a range of co-biocides to help protect against copper-tolerant organisms. Studies indicate that the CCA alternatives do release measurable quantities of copper and co-biocide into the environment. However, these components have lower mammalian toxicity than does arsenic, and they are less likely to raise concerns about environmental impacts. As the treated wood industry evolves, it is likely that a wider range of types and retentions of wood preservatives will become available, with the treatment more closely tailored to a specific type of construction application. REFERENCES 1. AWPA. 2001. Book of Standards. Granbury, TX: American Wood Preservers Association. 2. Lebow, S.T.; Hatfield, C.A.; Crawford, D.M.; and Woodward, B. 2003. Long-term stake evaluations of

waterborne copper systems. In: Proceedings, 2003 American Wood Preservers Association Annual Meeting, Boston, MA. In press. http://awpa.com/papers/Lebow_2003.pdf

3. Clausen, C.A.; Green, F. III. 2003. Copper tolerance of brown-rot fungi: time course of oxalic acid production. International Biodeterioration and Biodegradation. 51(2003):145–149.

4. Forest Products Laboratory. 2000. Environmental impact of preservative-treated wood in a wetland boardwalk: Res. Pap. FPL-RP-582. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 126 p.

5. Jin, L.; Archer, K.; Preston, A.F. 1992. Depletion and biodeterioration studies with developmental wood preservative formulations. In: Proceedings, American Wood Preservers’ Association; 108–125.

6. Anon. 1994. ACQ Type D. Proposal to the AWPA technical committees to include ACQ type D in Standards P5, C1, C2, C15, C9, and M6. Charlotte, NC: Chemical Specialties, Inc.

7. Anderson, T.C.; Ziobro, R.J. 2001. Residual levels of CCA-C in ¾” x ¾” x 18” Southern Pine Stakes Exposed to One, Three and Five Years in Gainsville, FL. Technical Forum Presentation, American Wood Preservers Association Annual Meeting, Minneapolis, MN.

8. Fox, R.F.; Pasek, E.A.; Deshan, P.N. [and others]. 1994. Copper azole wood preservatives. Proposal to the American Wood Preservers’ Association Committees to include copper azole type A in AWPA Standard P-5. July 12, 1994. Conley, GA: Hickson Corporation.

9. Anderson, T.C.; Inwards, R.D.; Leach, R.M.; McNamara, W.S. [and others]. 1993. A proposal for the standardization of ammoniacal copper citrate. Submitted to American Wood Preservers’ Association Committee P-4 and the General Preservatives Committee. Buffalo, NY: Osmose Wood Preserving, Inc.

10. Johnson, B.R.; Foster, D.O. 1991. Preservative loss from stakes treated with ammoniacal copper borate. Forest Products Journal. 41(9): 59–63.

11. Freeman, M.H.; Stokes, D.K.; Woods, T.L; Arsenault, R.D. 1994. An update on the wood preservative copper dimethyldithiocarbamate. In: Proceedings, American Wood Preservers’ Association; 90: 67–87.

12. Gjovik, L.R; Bendtsen, B.A.; Roth, H.G. 1972. Condition of preservative-treated cooling tower slats after 10 years of service. Forest Products Journal. 22(4): 35–40.

13. Pasek, E. 2003. Minimizing preservative losses: Fixation. A report of the P4 Migration/Depletion/ Fixation Task Force. Proceedings, 2003 American Wood Preservers Association Annual Meeting, Boston, MA. In press. http//www.awpa.com/papers/Eugene_Pasek.pdf

14. Western Wood Preservers Institute. 1996. Best management practices for the use of treated wood in aquatic environments. Vancouver, WA: Western Wood Preservers Institute. 35 p.


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Assessing Potential Waste Disposal Impact from Preservative Treated Wood Products

Timothy G Townsend1, Brajesh Dubey1 and Helena Solo-Gabriele2

1Department of Environmental Engineering Sciences, University of Florida,

PO Box 116450 Gainesville, FL 32611, USA

2Department of Civil, Architectural and Environmental Engineering,

University of Miami, Coral Gables, FL 33124, USA

ABSTRACT The management of discarded treated wood products upon disposal is one of the many factors that should be considered when evaluating a new wood preservative or when comparing wood preservatives as part of a life cycle assessment. Future environmental ramifications of disposal, as well as regulatory requirements and costs, must be assessed and weighed. This paper presents an overview of the factors that must be evaluated when assessing the disposal issues associated with discarded treated wood products. The discussion is based on current US regulations and policy, but the general approach toward evaluating disposal issues will be valid for most countries. A primary consideration is whether a wood preservative has the potential to cause a treated wood product to be a hazardous waste. Only a limited number of compounds can cause a solid waste to be a regulatory hazardous waste, and since the costs of hazardous waste management are high, this should be examined critically. Discarded treated wood products that are not hazardous may still pose environmental and regulatory concerns. Impact on landfill disposal, combustion systems, and wood recycling operations should be addressed. The concepts described in the paper are illustrated by examining four treated wood types: chromated copper arsenate, alkaline copper quaternary, a commercially available borate-treated product and a hypothetical treated wood product containing a silver-based biocide.

Keywords: treated wood, disposal, landfills, combustion

INTRODUCTION Many factors must be considered when selecting chemical wood preservatives for full-scale commercial application (Milton, 1995). The wood preservative must meet the requirements for preventing biological deterioration of treated wood products in aggressive environments. A method must be available to introduce the preservative chemical(s) efficiently into the wood product, and the preservatives should demonstrate an ability to remain in the wood for an extended period of time. Other factors that must be considered include appearance and odor of the preserved wood, the impact of the preservative on wood product mechanical properties, and the cost of the preservative treatment. Favorable ratings with respect to each of these characteristics resulted in chromated copper arsenate (CCA) being the primary wood preservative used in North America in recent decades. The recent switch from CCA to other wood preservatives for many treated wood products (US EPA, 2002) resulted from another factor – concern over potential impact on human health and


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the environment. In the past decade, questions were raised with respect to human exposure to CCA-treated wood products during manufacture and use, contamination of soils underneath or adjacent to treated structures, and possible impact on water supplies and aquatic organisms (Cooper, 1991; Weis et al., 1993; Merkle et al., 1993; Breslin, 1996; Stilwell and Gorny, 1997; Adler-Ivanbrook, 1998; Lebow et al., 1999; Solo-Gabriele et al., 2002; Solo-Gabriele et al., 2003; Lebow et al., 2003; Townsend et al., 2003a; Townsend et al., 2003b). The management of discarded CCA-treated wood at the end of its useful life has also been raised as an issue of possible concern (McQueen and Stevens, 1998; Solo-Gabriele and Townsend, 1999). Common management practices for discarded CCA-treated wood include disposal in landfills and combustion in waste-to-energy (WTE) systems. Potential adverse effects posed by these practices include elevated metal concentrations in landfill leachate and groundwater (Jang and Townsend, 2001; Townsend et al., 2001; Weber et al., 2002; Jang and Townsend, 2003a; and Jambeck et al., 2003) and WTE combustion ash (Solo-Gabriele et al. 2001). An unexpected concern that surfaced in Florida is the inclusion of CCA-treated wood in landscape mulched produced from processed C&D debris (Tolaymat et al., 2000; Townsend et al., 2003c). The registration or standardization of a new chemical wood preservative with regulatory agencies such as the US EPA or with an industry organization such as the American Wood Preservers’ Association (AWPI) requires demonstration of preservative efficacy and must address environmental and human safety during normal use. Issues pertaining to ultimate disposal are not, however, always considered. In light of the lessons learned with CCA, it would be prudent for developers and manufacturers of new preservative chemicals to evaluate possible disposal issues (as one part of the overall preservative evaluation). Assessing possible impact on disposal can be a confusing process. This paper was written to provide an overview of current US regulations and policies that would apply to a treated wood product upon disposal and to outline steps that could be helpful in assessing future disposal impacts. The information could be used to evaluate a proposed preservative formulation or it could be used by those comparing different treated wood products, for example, as part of a life-cycle assessment.

SOLID WASTE REGULATIONS PERTAINING TO TREATED WOOD In the US, a solid waste is any discarded or abandoned material that is not otherwise exempted from the regulations. The primary statute governing solid waste in the US is the Resource Conservation and Recovery Act (RCRA). The regulations developed under the authority of RCRA provide a framework for the management of wastes that pose an unacceptable risk to human health and the environment when improperly managed. RCRA defines a subset of solid wastes as hazardous wastes. Any solid waste, unless otherwise exempted, may potentially be a hazardous waste by either being included on a list of defined hazardous wastes (listed hazardous wastes) or by meeting a certain physical or chemical characteristic (characteristic wastes). The RCRA regulations provide specific and rigorous requirements for managing hazardous wastes and it is the generator’s responsibility to determine whether their solid waste is hazardous. The costs associated with hazardous waste management are greater than those for non-hazardous solid wastes. The US EPA has published several documents that provide an overview of the requirements of RCRA (US EPA, 2000).

The regulatory requirements for solid wastes that do not meet the definition of a hazardous waste are less well defined. Non-hazardous solid wastes are typically grouped into a number of different categories, including municipal solid waste (MSW), construction and demolition (C&D) debris and industrial wastes. While federal location and design requirements have been


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promulgated for MSW landfills, industrial waste and C&D debris disposal are regulated at the state level; the regulatory requirements vary dramatically among states. In Florida, for example, C&D debris can be disposed in unlined landfills, while in New Jersey, C&D debris can only be disposed of in a lined facility. Non-hazardous solid wastes are often disposed in manners other then landfilling. The beneficial use of waste materials is becoming commonplace, and again, regulations governing such activities are governed at the state level.

The regulatory requirements that must be addressed when disposing of treated wood products depend on how the materials are managed (e.g., are they disposed in a lined or unlined landfill). The following sections address hazardous waste determination, disposal in lined landfills, disposal in unlined landfills, effects on WTE systems, and impacts on beneficial use applications.

DETERMINATION OF HAZARDOUS WASTE STATUS As described above, a solid waste may be a hazardous waste either through listing or by

meeting a characteristic. Discarded treated wood products are not listed hazardous wastes. The characteristic that would most likely result in discarded treated wood being hazardous is the toxicity characteristic (TC). The TC is determined by performing a leaching method known as the toxicity characteristic leaching procedure (TCLP, US EPA, 1996)). The TCLP utilizes a buffered organic acid solution as an extraction fluid, and was designed to simulate contaminant leaching under acid-forming conditions in a MSW landfill environment (Francis et al., 1984; Francis et al., 1986). The acid used is acetic acid, an organic acid formed during the anaerobic decomposition of MSW organic matter (e.g., food waste, paper products). The test involves leaching one hundred grams of the waste with two liters of the extraction solution. The waste sample must first be size reduced to less than 0.95 cm. After mixing for 18 hours on a rotary extractor, the resulting leachate is filtered and analyzed for pollutants of concern.

When evaluating the impact of a treated wood product on disposal, TCLP results may prove useful on several fronts. They may provide an indication of the treated wood’s propensity to leach preservative chemicals in an MSW landfill. The TCLP’s applicability for this objective will be discussed in the next section. TCLP results can also be used to determine whether the discarded treated wood product might be a TC hazardous waste. To do so, the TCLP leachate concentrations are compared to the TC threshold concentrations in Table 1. If the concentration in the TCLP leachate (mg/L) exceeds the threshold concentration, the waste is characterized as hazardous by the TC. It should be noted that the list only contains a limited number of elements or compounds. To assist in a quick evaluation for determining whether a treated wood product even has the possibility of being a TC hazardous waste, the total concentrations (mg/kg) above which sufficient chemical exists to be a hazardous waste are included in Table 1 as well. These concentrations were determined by assuming that 100% of the element or compound leaches during the TCLP. Total concentrations above those listed in Table 1 do not mean that the waste will be hazardous, just that it has the potential to be hazardous. For example, creosote and pentachlorophenol (PCP) treated wood products may contain total concentrations of cresol or PCP greater than listed, but the TCLP leachable concentrations have been reported to be less than the TC threshold concentrations (EPRI, 1991).

Arsenic and chromium are the two metals in CCA encountered on the list, each having a TC threshold concentration of 5 mg/L. Copper is not a TC compound, and thus discarded treated wood can not be a TC hazardous waste for copper under federal rules. New CCA-treated wood samples have been found to exceed the TC limits for arsenic on many occasions (Townsend et al., 2003a). CCA-treated wood is, however, excluded from the definition of a hazardous waste under


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RCRA (U.S. EPA, 2001, 40 C.F.R., 261.4(b)(9)). No other treated wood products are excluded from the definition of hazardous waste. It is also important to note the exclusion is not necessarily adopted by every state, and that CCA-treated wood remains a solid waste under RCRA and must meet all other applicable requirements (as will be discussed in subsequent sections).

The manufacturer of a new preservative containing one of the elements or compounds on the TC list should compare the total concentration (based on preservative concentration and retention level in the wood) to the concentrations in Table 1 to determine whether it has the potential to be a TC hazardous waste. If such a potential exists, the manufacturer should perform testing to determine whether concentrations leached using the TCLP are exceeded. Results produced from experiments on test samples of treated wood products would most closely represent conditions where the wood product was disposed as scrap construction lumber. Treated wood exposed to environmental weathering does lose some preservative through leaching and abrasion, raising the possibility that weathered samples (which represent the majority of material disposed) will leach less. Research on weathered CCA-treated wood, however, demonstrated that weathered samples exhibit a similar propensity to leach arsenic in comparison to new samples (Solo-Gabriele et al., 2003). .

In the US, states have the option to develop more stringent regulations than that required under federal rules. A notable example that affects the possible characterization of treated wood products as a hazardous waste in the US is California and its rules related to hazardous waste characterization. In addition to using the TCLP to determine hazardous waste status, California employs a method known as the Waste Extraction Test (WET). It contains a solvent that tends to leach more metals than the TCLP (WET uses citric acid), and the number of elements that must be evaluated is greater (CCR, 1998). Table 2 presents California’s Soluble Threshold Concentration Limit (STCL). Table 2a presents the California limits for inorganic elements or compounds, while Table 2b presents the limits of the organic compounds. If the WET leachate concentration of any chemical in Table 2 exceeds the STCL, the solid waste is a hazardous waste unless otherwise exempted. In a similar fashion as Table 1, Table 2 presents the total concentrations above which a waste has the potential to leach enough chemical to exceed the STCL. Finally, wastes in California that exceed the Total Threshold Limit (TTL) concentration, regardless of how much leaches, are hazardous wastes unless exempted.

EVALUATING IMPACT ON LINED LANDFILLS Discarded treated wood that does not meet the definition of hazardous waste under RCRA, or

treated wood that fails TCLP but is produced by an exempt generator category (such as a household, or a non-household generator of less than 100 kg per month), may legally be disposed in a lined Subtitle D landfill (under federal rules). Subtitle D refers to a section of RCRA dealing with non-hazardous solid wastes. MSW must be disposed in a Subtitle D landfill (design requirements found in 40 CFR 258), but many of these landfills also accept C&D debris, WTE ash and industrial waste. Subtitle D landfills are lined to protect the groundwater, and the leachate that is produced is collected and treated. In many cases, states have adopted liner requirements more stringent than Subtitle D; several states also require liners for C&D debris landfills.

It is important to note that while it is legal under federal solid waste rules to dispose of treated wood in a lined landfill, landfill operators are not required to accept the material. Reasons why landfill operators might be reluctant to accept discarded treated wood products include problems with handling and compaction (which are not a function of the preservative type) and


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potential impacts on leachate quality. A majority of landfills haul their leachate to off-site treatment facilities, and in many cases pretreatment standards are imposed. Elevated concentrations of pollutants can result in excessive strength charges for the landfill operator, or possibly in the treatment facility declining to accept the leachate. Some wastewater treatment facilities may also regulate metal concentrations because of concerns over impact on biosolids quality.

The TCLP provides one method that may be used to assess the impact of treated wood disposal on lined landfill leachate quality. As previously described, the TCLP was designed to simulate conditions occurring in a MSW landfill when acids are produced from decomposing organic waste. Most landfills do not, however, contains acids at concentrations equivalent to the TCLP. If such concentrations were to occur, they would only be for a relatively short time. Based on this observation, one would expect that the TCLP would overestimate pollutant release compared to actual landfill environments. This has been observed in the case of lead (Jang and Townsend, 2003b), but others have found elements such as arsenic and chromium (metalloids that exist as oxy-anions) often leach more in landfill leachates compared to the TCLP. Jambeck et al. (2004) reported the largest arsenic and chromium concentrations to occur early in a simulated MSW landfill’s life when the acid concentrations were highest (and pH was lowest). A whole host of other chemical, biological, and physical factors impact the migration of a chemical from the landfilled waste to the leachate collected from the liner system, and these can not all be accounted for using one single test such as the TCLP.

EVALUATING IMPACT ON UNLINED LANDFILLS Many states do not require liners for C&D debris landfills. Notable examples include

Florida, Texas and California. The legality of disposing of treated wood in an unlined C&D debris landfill depends on the state. Some states prohibit the disposal of certain treated wood products in C&D debris landfills, while others allow it. When evaluating disposal of waste components not specifically discussed in a regulation, state regulators often have policies that prohibit the disposal of wastes that have a potential to leach and cause an impact on groundwater. Leaching tests can be used to evaluate the risk presented by a waste co-disposed in an unlined landfill to contaminate groundwater. The TCLP may be used if the landfill is contains putrescible organic matter that would result in the production of organic acids. If a landfill contains only inert debris, another test often recommended is the Synthetic Precipitation Leaching Procedure (SPLP). The SPLP is similar to the TCLP, but a simulated rainwater is used instead (pH = 4.2). The SPLP tends to be less aggressive towards metal leaching compared to the TCLP and WET (the TCLP and WET contain buffered weak acids, while SPLP is unbuffered and contains only small amount of nitric and sulfuric acids). When the EPA evaluated SPLP and TCLP results for lead based paint debris, they assumed that TCLP would be representative of MSW landfills while the SPLP was more representative of C&D debris landfills (FR, 1998).

A common approach used by the states to assess whether a waste poses a potential risk to groundwater when disposed of in unlined landfill is to run the SPLP on the waste and compare the results, not to TC limits, but directly to groundwater criteria. Table 4 presents examples of water quality criteria for many compounds. It is important to note that there may be many compounds with numerical standards or limits. The drinking water standards are usually included, as well as other compounds that have health based limits established. Table 4 illustrates that concentrations are much lower than the TC and STCL thresholds presented earlier. When evaluating a new preservative for potential impact on groundwater, water quality criteria such as the drinking water standards or other health based standards (such as presented in the Table 4) should be consulted. If leaching data are available, the results can be compared to assess whether groundwater


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contamination might be an issue. When comparing and contrasting different treated wood products, the ratio of leachate concentration to water quality limits for chemicals of interest may provide a sense of the relative risk posed by each product. When leaching data are lacking, the treated wood products can be assumed to leach the same fraction of preservative chemicals, and these concentrations can be compared to their respective groundwater limits.

ASSESSING IMPACT ON COMBUSTION OPERATIONS A common form of managing waste wood is through combustion. This occurs both as

combustion of bulk loads of wood (e.g. utility poles, railroad ties) and loads of mixed C&D wood. From an environmental standpoint, the combustion of treated wood poses potential problems with respect to air emissions and ash generation. Facilities that combust wood will in nearly all cases have some form of air pollution control equipment (APC). The type of APC needed depends on the type of emission hazards presented by the preservatives in the wood and the regulatory requirements. Proper combustion techniques can be used to destroy organic preservative compounds used in wood. Several facilities in the US routinely combust pentachlorophenol and creosote treated wood; issues with dioxin and furan emissions are controlled by maintaining proper temperature and gas mixtures. The control of metals, however, requires additional pollutant removal systems such as bag houses, chemical scrubbing and carbon injection. Some metals will be more prone to air emission problems. Arsenic, for example, volatizes and is thus an issue when CCA-treated wood is combusted (Hirata et al. 1993; McMahon et al. 1986, Pasek and McIntyre 1993). Thermodynamic chemical modeling techniques (Iida et al., 2004) or basic data on the volatility of chemical species from a chemical reference book can be used to assess the potential of inorganic compounds to present an air emission problem.

The presence of preservative treated wood can also have a major impact on the management requirements for the resulting ash. Organic preservatives should not prove to be a large problem as they will likely be destroyed in well-operated combustion systems, but inorganic preservative compounds will magnify in concentration. When examining the possible impacts of a preservative treated wood on combustion ash, the first step should be to determine whether the preservative can cause the ash to be a hazardous waste. This is the same procedure discussed for the wood itself. A mass balance may be performed to estimate the final ash concentration of the element of , and this could be compared to the values presented in Table 1 to assess whether or not the ash has the potential to be a hazardous waste. But because of the large concentrations of preservatives used in treated wood and the degree of magnification that occurs in the combustion process, most treated wood samples that contain a TC element will have the potential to cause the ash to be hazardous. Research on the impact of CCA-treated wood on ash properties (Solo-Gabriele et al. 2002) found all samples of CCA-treated wood ash to exceed the TC limit for arsenic. It was estimated that at levels of approximately 5% CCA-treated wood in a mixture of wood, the ash would fail the TCLP. A basic knowledge of how certain element tend to leach from combustion ash might give the preservative developer some idea whether leaching is likely, but the amount of leaching that actually occurs can be very waste specific.

Even if the ash is not a hazardous waste, elevated metals concentrations might limit reuse options from the ash or dissuade subtitle D landfill operators from accepting the ash. The same considerations discussed above for lined landfill operators would be evaluated. Many states have guidelines for determining when solid wastes such as WTE ash can be beneficially used in the environment. These steps are discussed in the next section.


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LAND APPLICATION ISSUES Another potential disposal route for discarded treated wood products is land application.

Treated wood might impact land application of waste through two primary pathways: landscape mulch and combustion ash. Many C&D debris landfills and recycling facilities recycle recovered C&D wood for use as landscape mulch, and this may contain treated wood (Tolaymat et al., 2000). A second route is the land application of ash as discussed above. When evaluating land disposal of wastes, it is customary to compare the results from leaching tests such as the SPLP directly to water quality standards in the same manner as described above for unlined landfill disposal (Saranko et al. 1999, WDNR 2003 ). SPLP results from mulch or ash would be compared directly to quality criteria such as those in Table 3, and if the measured concentrations were above the levels in the table, a potential risk of leaching when land applied is indicated.

Leaching risk is not, however, the only concern for land applied wastes. Direct human exposure must also be evaluated. Table 4 presents generic soil screening levels that are used to determine whether a land applied material (that is similar to soil in nature) poses a risk under a given set of exposure scenarios. The values in Table 4 represent risk-based soil screening levels in Florida (referred to as the soil cleanup target levels, SCTLs), and most states have similar lists. The risk of a land applied waste on direct exposure is examined by comparing the measured concentration of chemicals of concern to the screening levels; exceedances indicate a possible risk. It should be noted that unlike water quality criteria, the clean soil criteria in some cases vary dramatically among states. Arsenic is one example, with acceptable concentrations for soil in residential areas in some states to be less than 1 mg/kg, while in other states the value is greater than 50 mg/kg. Differences from state to state result from differences in natural background concentrations and the toxicity and exposure assumptions used to develop the criteria.

Both land application scenarios (landscape mulch and combustion ash) require assumptions regarding the amount of treated wood present in the wood mix. The potential of different treated wood products to pose a land application risk can be performed by assuming the fraction of a treated wood product to occur in a C&D debris wood mix, calculating the concentration of preservative chemical in the mix, and comparing these results to values such as those presented in Table 4. In the case of the wood ash scenario, the fraction of ash remaining after combustion would require estimation. In a similar manner as indicated for the unlined landfill discussion above, the ratios of the predicted concentrations to the risk-based criteria could be compared to assess the relative impact among different treated wood products.

CASE STUDY: EVALUATION OF FOUR TREATED WOOD PRODUCTS To illustrate the principles discussed above, four different preserved wood types were

evaluated and compared with respect to their potential environmental and regulatory impact upon disposal. The preservatives include CCA, alkaline copper quatenary (ACQ), a boron-containing preservative (Envirosafe™), and a hypothetical silver-based preservative.

Description f Wood Types Evaluated Table 5 summarizes the wood preservative types examined, their major components and the

concentrations of the major preservative components. The CCA-treated wood product evaluated was treated with Type C CCA to a retention level of 0.25 pcf . The ACQ-treated wood product was treated with ACQ type D to a retention level of 0.25 pcf. The retention level for both the CCA- and ACQ-treated wood products is that required for above-ground contact, and thus represents the minimum retention level standardized by the AWPA. The third wood product evaluated was a boron-based formulation currently marketed under the trade name of Envirosafe Plus™. Its primary


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component is disodium octaborate tetrahydrate (DOT). Typical boron concentrations measured in preliminary tests by the authors is on the order of 1,000 mg/kg. The fourth wood product evaluated is not based on any existing product, but assumes that treatment solution contains silver. Silver has recently been suggested as a possible promising wood treatment chemical (Silver Institute, 2003) and it is reportedly being researched. The concentration of silver in the wood was assumed to be 1,000 mg/kg. This value was not selected based on any proposed formulation, but rather because it falls in the magnitude of the major components in the other wood preservatives. It simply provides a conentration with which the waste disposal assessment can be conducted. The results of the waste disposal assessment are presented in the following sections, and are summarized in Table 6.

Hazardous Waste Determination Of the components of the four wood preservatives evaluated, arsenic, chromium and silver

are the only ones found in Table 1 (the RCRA TC limits), and thus only CCA-treated wood and the silver-based biocide treated wood have the potential to be a TC hazardous wastes under US federal rules. The information presented in Table 1 and Table 5 shows that CCA-treated wood does contain enough arsenic and chromium to potentially be a TC hazardous (when total concentrations are compared). Leaching tests do, in fact, show that the TC level for arsenic is typically exceeded (Townsend et al., 2001). However, as described earlier, the RCRA regulations exclude CCA-treated wood from the definition of hazardous waste. That data in Tables 1 and 5 also indicate that the silver-based treated wood product contains enough silver to potentially be a hazardous waste, but it would depend on how much leached. Since no such data are available, and product developers would be recommended to conduct such tests.

When the California hazardous waste rules are applied, the ACQ treated wood product also becomes characterized as a hazardous waste. Not only does it contain enough copper to potentially exceed the STCL using the WET, but the total concentration itself exceeds the TTLC. The silver-based wood product would also exceed the TTLC under the preservative concentrations assumed. To the authors’ best knowledge, no treated wood product other than CCA-treated wood is excluded from the definition of hazardous waste in California.

Impact on Lined Landfill Leachates Both CCA-treated wood and ACQ-treated wood have been shown to leach quantities of

arsenic, copper and chromium that might present a concern with respect to elevating leachate concentrations from lined landfills (Townsend et al., 2001; Townsend et al., 2003a). Previous work comparing metal mobility in the TCLP versus leaching with actual landfill leachates shows that arsenic and chromium tend to leach more (Hooper et al., 1998) in actual landfill leachates relative to TCLP. This observation was not made for copper. Arsenic and chromium have also been found to occur at greater concentrations than copper in leachates from simulated landfills (Weber et al., 2002; Jang and Townsend, 2002; Jambeck et al., 2004). These observations were believed to be a result of copper’s propensity to precipitate (e.g., with sulfides) and the fact that arsenic and chromium may exist as anions in solution under typical leachate pH conditions. It could be argued from these observations that CCA-treated wood presents a greater problem for lined landfill disposal than ACQ-treated wood. TCLP or other leaching data on the particular borate treated wood examined were not available, though previous studies have shown borate-treated wood to often be readily leachable. No data were found regarding leaching from other silver-containing wastes where TCLP leachate concentrations were compared to those concentrations produced using actual landfill leachates as an extraction solution. TCLP testing on the borate-treated wood and the silver-treated wood would be a valuable first step in assessing potential impacts on lined landfills,


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but based on observations with copper from CCA-treated wood, it is likely that additional testing would be needed to assess the true likelihood of elevated boron and silver leachate concentrations.

Impact on Unlined Landfill Leachates The potential impact of discarded treated wood products on groundwater at unlined landfills

can be evaluated by comparing leaching test results to groundwater criteria. As described previously, the TCLP can be used, but the SPLP is a more common approach for unlined C&D debris landfills. SPLP leaching results are available for both CCA- and ACQ-treated wood. In a side-by-side comparison, CCA-treated wood leached 8.9, 2.5, 4.1 mg/L of As, Cr, and Cu respectively, while ACQ treated wood leached 29 mg/L of Cu (Townsend et al., 2003a). The respective drinking water standards for As, Cr and Cu are 0.05, 0.1, and 1.0 mg/L, though the As standard is being lowered to 0.01 mg/L in the near future. In absence of data on all four products, a comparison was made assuming that 5% of the preservative chemicals leach from each treated wood product during a SPLP analysis. The resulting leachate concentrations were then divided by the relevant water quality criteria presented in Table 3. The results are presented in Table 6. The treated wood products with the greatest ratio (i.e., the leachate concentration exceeding the water quality criteria by the greatest amount) was CCA (due to arsenic), followed by the silver-based preservative, then ACQ, and finally the borate-treated wood. This analysis provides an initial indication of the relative risk posed by each of the wood products in unlined landfills. Many other factors would confound the true impact on groundwater (e.g., the fraction leaching over time, the mobility of the chemical in environment), and additional work could be performed to refine this analysis (e.g., conducting leaching tests, performing groundwater modeling).

Impact on Waste to Energy Systems When evaluating impact on combustion systems, both air emissions and ash quality should

be considered. Of the metals in CCA, arsenic is likely to volatilize to the greatest extent (Iida et al., 2004). This would indicate that in a side by side comparison with between CCA- and ACQ-treated wood, the CCA-treated wood product would pose a greater concern with respect to combustion. Data would need to be gathered on the potential air emission issues associated with boron and silver.

Based on the previous discussion concerning the potential for the treated wood products to be a hazardous waste, ash from the combustion of wood containing CCA-treated wood and wood treated with the silver-based biocide could be hazardous wastes. The exclusion from the definition of hazardous waste that CCA-treated wood has for the wood itself does not apply to ash. Assuming that a wood mix containing 10% treated wood was burned, and that 5% of the wood fuel remained as ash, the fraction of As and Cr that would have to leach from ash from the combustion a CCA contaminated fuel mix would be 2.9 % and 2.6 %, respectively (as presented in Table 6).. The fraction of silver that would have to leach would be 5 %.

Land Application Issues Two methods were used to evaluate the potential impact of the four treated wood products

on land application. In one analysis, the treated wood products were assumed to comprise 10% of the weight of a landscape mulch mix, the resulting concentrations of the preservative elements were calculated. These concentrations were then divided by the risk-based soil criteria in Table 4. The results are presented in Table 6. CCA-treated wood was found to exceed the soil criteria by the greatest amount (by 213 times; a result of arsenic), followed by ACQ (3.5 times). The ratio calculated for both the boron-based and the silver-based treated wood products was less than one indicating that at a contribution of 10%, the inclusion of the wood products did not result in an


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exceedance of the soil criteria. The wood mix could contain 100% of the borate-treated wood and not exceed the soil criteria for boron, and 39% of the silver-treated wood and not exceed the soil criteria for silver. The reader is reminded that the soil criteria used for this example were taken from those currently used in Florida, US, and may not be representative of criteria in other locations.

In a second analysis, the concentrations of the preservative elements in the ash described in the previous section (10% treated wood in wood fuel, 5% ash residue after combustion) were compared to the risk-based soil criteria in a similar fashion as done for the land applied mulch. The results are presented in Table 6. Ash from the combustion of wood mixture containing CCA-treated wood was found to exceed the soil criteria by the greatest amount (by 4,275 times; a result of arsenic), followed by the ACQ mixture (by 69 times), and finally the silver-based preservative mixture (by 5.1 times). The ratio calculated for ash from the boron-based treated wood product was less than one indicating that at a contribution of 10%, its inclusion did not result in an exceedance of the soil criteria. The ash could contain 35% of the borate-treated wood and not exceed the soil criteria for boron.

SUMMARY AND CONCLUSIONS The management of discarded treated wood products upon disposal should be considered

when evaluating a new wood preservative or when comparing wood preservatives as part of a life cycle assessment. This paper presented an overview of the factors that must be evaluated when assessing the disposal issues associated with discarded treated wood products. Factors that should be evaluated include whether the discarded wood products have the potential to be a hazardous waste, and what the impacts on lined landfill leachate quality, unlined landfill groundwater quality, combustion systems, and landscape mulch might be. The assessment strategy was illustrated by considering four treated wood products, three existing products (CCA, ACQ, and a borate treatment) and one wood product treated with a hypothetical silver-based treating solution. The results provided an indication of the relative impact of the treated wood products on waste disposal. The approach provides a tool that can be used to evaluate possible waste disposal issues, but its utility depends on the quality of the data available for the assessment. Clearly, especially for the newer treated wood products, additional data would be necessary for a complete evaluation. Where the assessment approach may be most useful with respect to new products where the data are lacking is in the comparison of different treated wood products, as part of, for example, a life cycle assessment.

ACKNOWLEDGMENTS The authors acknowledge the Florida Center for Solid and Hazardous Waste Management for their continued support of research on treated wood.

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Breslin, V. and Adler-Ivanbrook, L. (1996) Release of Copper, Chromium and Arsenic from CCA-C Treated Lumber in Estuaries. Estuarine, Coastal and Shelf Science 46, 111-125. CCR, C. C. O. R. California Code of Regulations, Title 22 Chapter 11, Article 5, Appendix II. 1998. Cooper P. (1991). Leaching of CCA from Treated Wood: pH effects. Forest Products Journal, 41(1): 30-32. EPRI (1991). Pentachlorophenol-treated wood poles and cross arms: Toxicity characteristic leaching procedure results. Report summary EN7062S Electric Power Research Institute, Palo Alto, CA. FR, Federal Register 63 (1998) 70190 Francis C., and Maskarinec, M (1986) Field and Laboratory Studies in Support of a Hazardous Waste Extraction Test, DE86 007068, U.S. Environmental Protection Agency, Oak Ridge, TN.,1986. Francis, C., Maskarinec, M., and Goyert, J. (1984). Mobility of Toxic Compounds from Hazardous Wastes, OENL-6044, U.S. DOE., Oak Ridge, Tennessee. Hageman, P., Briggs, P.,Desborough, G., Lamothe, P.,and Theodorakos, P (2000) Synthetic Precipitation Leaching Procedure (SPLP) Leachate Chemistry Data for Solid Mine-Waste Composite Samples from Southwestern New Mexico, and Leadville, Colorado Denver CO, Department of Interior USGS. Hirata, T., Inoue, M., and Fukui, Y. (1993). "Pyrolysis and Combustion Toxcicity of Wood treated with CCA." Wood Science and Technology, 27, 35-47. Iida, K., Pierman, J., Tolaymat, T. Townsend, T. and Wu, C, Y.,(2004) "Control of Heavy Metal Emissions and Leaching from Incineration of CCA-Treated Woods Using Mineral Sorbents", Journal of. Env. Eng., 130(2), 184-192 Jambeck, J., Townsend, T and Solo-Gabriele, H (2003). The Disposal of CCA-Treated Wood in Simulated Landfills: Potential Impacts: The 34th Annual Meeting of the International Research Group on Wood Preservation, Brisbane, Australia, pp. 17. Jambeck, J., Townsend, T and Solo-Gabriele, H (2004). Leachate Quality from Simulated Landfills Containing CCA-Treated Wood: Environmental Impacts of Preservative-Treated Wood Conference Feb 8-11, Orlando, FL. Jang, Y and Townsend, T (2001) Occurance of Organic Pollutants in Recovered Soil Fines from Construction and Demolition Waste.. Waste Management 21 703-715 2001 Jang, Y and Townsend, T (2003a) Effect of Waste Depth on Leachate Quality from Laboratory Construction and Demolition Debris Landfills. Environmental Engineering Science 20 (3) 183-196 Jang, Y.., and Townsend. T. (2003b) Leaching of Lead from Computer Printed Wire Boards and Cathode Ray Tubes by Municipal Solid Waste Landfill Leachate. Environ. Sci. Technol. 37, 4718-4784. Lebow, S., Foster, D., and Lebow, P. (1999) Release of Copper, Chromium, and Arsenic From Treated Southern Pine Exposed in Seawater and Freshwater. Forest Products Journal, V49, N. 7/8. Lebow, S., Williams, R., and Lebow, P. (2003) Effect of Simulated Rainfall and Weathering on Release of Preservative Elements from CCA Treated Wood. Environmental Science & Technology 37: 4077-4082. McMahon, C., Bush, P., and Woolson, E. (1986). "How Much Arsenic is Released When CCA-Treated Wood is Burned." Forest Products Journal, 36(1912), 45-50. McQueen J and Stevens J. (1998) Disposal of CCA treated wood. Forest Products Society Journal 48(11/12): 86-90.


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Merkle, P., Gallagher, D. and Solberg, T. (1993) Leaching Rates, Metals Distribution, and Chemistry of CCA Treated Lumber: Implications for Water Quality Modeling. Paper presented at a meeting on Enviromental Considerations in the Use of Pressure-Treated Wood Products sponsored by the Carolinas-Chesapeake Section of the Forest Products Society and Virginia Tech, May 13, 1993 in Richmond VA. Milton, F. (1995) The Preservation of Wood: A Self Study Guide for Wood Treaters. Minnesota Extension Service. University of Minnesota, College of Natural Resources. Pasek, E., and McIntyre, C.(1993) "Treatment and Recycle of CCA Hazardous Waste." 24th Annual Meeting of the International Research Group on Wood Prservation, Stockholm, Sweden. Silver Instititute (2003). “Legislation Introduced to Study the Effectiveness of Silver-Based Biocides for Wood Preservation.” Press Release, Washington DC, February 21. Solo-Gabriele, H., Townsend, T., Khan, B., Song, J-K, Jambeck, J., Dubey, B., Jang, Y. (2003). Arsenic and Chromium Speciation of Leachates from CCA-Treated Wood, Florida Center for Solid and Hazardous Waste Management, Gainesville, FL, Report #03-07. Solo-Gabriele, H., Townsend, T., Messick, B., and Calitu, V., (2001) Characteristics of CCA- Treated Wood Ash. Journal of Hazardous Materials, 89 (2-3): 213-232. Solo-Gabriele, H.M., and Townsend, T., (1999). Disposal Practices and Management Alternatives for CCA-Treated Wood Waste. Waste Management Research, 17: 378-389. Stillwell, D., and Gorny, K.(1997) Contamination of Soil with Copper, Chromium and Arsenic Under Decks Built from Pressure Treated Wood. Bulletin of Environmental Contaminant Toxicology. 58:22-29. Tolaymat, T., Townsend, T., and Solo-Gabriele, H. (2000) Chromated Copper Arsenate-Treated Wood in Recovered Construction and Demolition Debris. Environmental Engineering Science. 17 (1): 19-28. Townsend, T., Solo-Gabriele, H., Stook, K., Tolaymat, T., Song, J., Hosein, N., Khan, B. (2001) New Lines of CCA-Treated Wood Research: In-Service and Disposal Issues. Florida Center for Solid and Hazardous Waste Management. Gainesville, FL, Report #01-X. Townsend T, Solo-Gabriele H, Stook K, Ward M (2003a) Leaching and toxicity of CCA-treated wood and alternative-treated wood products. Florida Center for Solid and Hazardous Waste Management. Gainesville, FL, Report # 02-4 Townsend, T., Solo-Gabriele, H., Tolaymat, T., and Stook, K., (2003c). “Impact of Chromated Copper Arsenate (CCA) in Wood Mulch.” The Science of the Total Environment, 309: 173-185 Townsend, T., Solo-Gabriele, H., Tolaymat, T., Stook, K., and Hosein, N., (2003b). “Chromium, Copper, and Arsenic Concentrations in Soil Underneath CCA-Treated Wood Structures.” Journal of Soil and Sediment Contamination, 12 : 779-798. US EPA (1996). Test Methods for Evaluating Solid Waste, SW846, 3, Office of Solid Waste and Emergency Response, Washington D.C. US EPA (2000). RCRA Orientation Manual EPA 530R-00-006 Office of Solid Waste and Emergency Response, Washington D.C. US EPA (2002). Notice of Receipt of Requests to Cancel Certain Chromated Copper Arsenate (CCA) Wood Preservative Products and Amend to Terminate Certain Uses of CCA Products. Office of Pesticides Washington D.C.,.


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WDNR. (2003). "Guidance on the Use of Leaching Test for Unsaturated Contaminated Soils to Determine Groundwater Contamination Potential." PUBL RR-423-03, Wisconsin Department Of Natural Resources, Madison. Weber, J., Jang, Y., Townsend, T. and Laux, S. (2002) “Leachate from Land Disposed Residential Construction Waste.” Journal of Environmental Engineering, 128(3):237-245. Weis, P., Weis J.S. and Proctor T. (1993). “Copper, Chromium and Arsenic in Estuarine Sediments Adjacent to Wood Treated with Chromated-Copper Arsenate (CCA)”. Estuarine, Coastal and Shelf Science 36, 71-79.


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Table 1. Threshold Concentration of Contaminants for the Toxicity Characteristic under RCRA (40 CFR Section 261.31)

EPA Hazardous Waste No. Contaminant Regulatory

Level (mg/L) Total Concentration above which a solid waste may fail TCLP (mg/kg)

D004 Arsenic 5.0 100 D005 Barium 100.0 2000 D018 Benzene 0.5 10 D006 Cadmium 1.0 20 D019 Carbon tetrachloride 1.0 20 D020 Chlordane 0.03 0.6 D021 Chlorobenzene 100.0 2000 D022 Chloroform 6.0 120 D007 Chromium 5.0 100 D023 o-cresol 2200.0 4000 D024 m-cresol 2200.0 4000 D025 p-cresol 2200.0 4000 D026 Cresol 2200.0 4000 D016 2,4 D 10.0 200 D027 1,4-Dichlorobenzene 7.5 150 D028 1,2-Dichloroethane 0.5 10 D029 1,1-Dichloroethylene 0.7 14 D030 2,4 Dinitrotoluene 10.13 2.6 D012 Endrin 0.02 0.4

D031 Heptachlor (and its epoxide) 0.008 0.16

D032 Hexachlorobenzene 10.13 2.6 D033 Hexachlorobutadine 0.5 10 D034 Hexachloroethane 3.0 60 D008 Lead 5.0 100 D013 Lindane 0.4 8 D009 Mercury 0.2 4 D014 Methoxychlor 10.0 200 D035 Methyl Ethyl Ketone 200.0 4000 D036 Nitrobenzene 2.0 40 D037 Pentachlorophenol 100.0 2000 D038 Pyridine 5.0 100 D010 Selenium 1.0 20 D011 Silver 5.0 100 D039 Tetrachloroethylene 0.7 14 D015 Toxaphene 0.5 10 D040 Trichloroethylene 0.5 10 D041 2,4,5-Trichlorophenol 400.0 8000 D042 2,4,6-Trichlorophenol 2.0 40 D017 2,4,5-TP (Silvex) 1.0 20 D043 Vinyl chloride 0.2 4

1 Quantitation limit is greater than calculated regulatory level. The quantitation limits therefore becomes the regulatory level.

2 If o-, m-, and p-Cresol concentrations can not be differentiated the total cresol (D026) concentration is used. The regulatory level of total cresol is 200 mg/L.


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Table 2A Summary of WET Limits (Inorganic Persistent and Bioaccumulative Toxic Substances)

a STLC and TTLC values are calculated on the concentration of the elements, not the compounds. b In the case of asbestos and elemental metals, the specified concentration limits apply only if the substance

are in friable, powdered or finely divided state. Asbestos includes chrysotile, amosite, crocidolite, tremolite, anthophyllite, and actinolite.

c Excluding barium sulfate. d If the soluble chromium, as determined by determined by the TCLP is less than 5 mg/L, and the soluble

chromium as determined by WET procedures equal or exceeds 560 mg/L and the waste is not otherwise identified as a RCRA hazardous waste, then the waste is non-RCRA hazardous waste.

e Excluding molybdenum disulfide.

Contaminantsa b

Soluble Threshold Limit Concentration

(mg/L)

Total Threshold Limit Concentration wet-

weight (mg/kg)

Total Concentration above which a solid waste may exceed STLC (mg/kg)

Antimony and /or antimony compounds

15 500 300

Arsenic and /or arsenic compounds

5 500 100

Asbestos - 1.0 (as percent) - Barium and /or barium

compounds (excluding barite) 100 10,000c 2000

Beryllium and /or beryllium compounds

0.75 75 15

Cadmium and /or cadmium compounds

1 100 20

Chromium (VI) compounds 5 500 100 Chromium and / or

chromium(III) compounds 5d 2,500 100

Cobalt and/or cobalt compounds

80 8,000 1600

Copper and /or copper compounds

25 2,500 500

Fluoride salts 180 18,000 3,600 Lead and /or lead compounds 5 1,000 100

Mercury and/or mercury compounds

0.2 20 4

Molybdenum and/or molybdenum compounds

350 3,500e 7,000

Nickel and/or nickel compounds

20 2,000 400

Selenium and/or selenium compounds

1 100 20

Silver and /or silver compounds

5 500 100

Thallium and /or thallium compounds

7 700 140

Vanadium and /or vanadium compounds

24 2,400 480

Zinc and /or zinc compounds 250 5,000 5,000


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Table 2B Summary of WET Limits (List of Organic Persistent and Bioaccumulative toxic substances)

Contaminants

Soluble Threshold Limit

Concentration (mg/L)

Total Threshold Limit Concentration wet-weight (mg/kg)

Total Concentration above which a solid waste may exceed

STLC (mg/kg) Aldrin 0.14 1.4 2.8

Chlordane 0.25 2.5 5 DDT, DDE, DDD 0.1 1.0 2

2,4-Dichlorophenoxyacetic acid 10 100 200

Dieldrin 0.8 8.0 16 Dioxin (2,3,7,8-TCDD) 0.001 0.01 0.02

Endrin 0.02 0.2 0.4 Heptachlor 0.47 4.7 9.4

Kepone 2.1 21 4.2 Lead Compounds, organic - 13 -

Lindane 0.4 4.0 8 Methoxychlor 10 100 200

Mirex 2.1 21 42 Pentachlorophenol 1.7 17 34

Polychlorinated biphenyls (PCBs) 5.0 50 100

Toxaphene 0.5 5 10 Trichloroethylene 204 2,040 4,080

2,4,5-Trichlorophenoxypropionic

acid 1.0 10 20


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Table 3 Summary of Typical Water Quality Criteria for Groundwater (selected from Florida’s Groundwater Cleanup Target Levels, Florida Administrative Code 62-777)

Contaminant Criteria (mg/L)

Total concentration above which

waste potentially

exceeds criteria (mg/kg)

Contaminant Criteria (mg/L)*

Total concentration above which

waste potentially

exceeds criteria (mg/kg)

Antimony 0.006 0.12 Total Nitrate and Nitrite 10 (as N) 200 (as N)

Arsenic 0.05 (0.01) 1 (0.2) Selenium 0.05 1

Asbestos 7 MFL - Sodium 160 3200 Barium 2.0 40 Thallium 0.002 0.04

Beryllium 0.004 0.08 Benzene 0.001 0.02 Boron 0.63 12.6 Ammonia 2.3 46

Cadmium 0.005 0.1 Vinyl chloride 0.001 0.02 Chromium 0.1 2 2,3,7,8-TCDD (Dioxin) 3×10-8 6×10-7 Cyanide 0.2 4 Diquat 0.02 0.4 Fluoride 4.0 80 Pentachlorophenol 0.001 0.02

Lead 0.015 0.3 Chloride 250 5,000 Mercury 0.002 0.04 Copper 1.0 20 Nickel 0.1 2 Iron 0.3 6

Nitrate 10 (as N) 200 Silver 0.1 2

Nitrite 1.0 (as N) 20 pH 6.5-8.5 -

Total Dissolved Solids 500 10,000 Odor

3 (threshold

odor number)

-

Carbon tetrachloride 0.003 0.06 Chlordane 0.002 0.04

Chlorobenzene 0.07 1.4 Paraquat 0.032 0.64 Chloroform 0.0057 0.11 1,2 Dichloroethane 0.003 0.06

1,4 Dichlorobenzene 0.075 1.5 Toluene 1.0 20

Endrin 0.002 0.44 Heptachlor 0.0004 0.008 Hexachlorobenzene 0.001 0.02 Hexacholorocyclopentadine 0.05 1

Lindane 0.0002 0.004 Methoxychlor 0.04 0.8 Trichloroethylene 0.003 0.06 Toxaphane 0.003 0.06

MCL = maximum contaminant level MFL = million fibers per liter greater than 10 micrometers mg/L = milligrams per liter *except odor and pH


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Table 4 Summary of Typical Clean Soil Criteria for Land Application (selected from Florida’s Soil Cleanup Target Levels,

Florida Administrative Code 62-777) Direct Exposure (mg/kg) Contaminant

Residential Commercial/Industrial Arsenic 0.8 3.7

Ammonia 550 3,700 Boron 7,000 160,000

Carbazole 53 190 Chromium (VI) 210 420

Copper 110 76,000 Dioxin (2,3,7,8-TCDD) 0.000007 0.00003

Iron 23,000 480,000 Lead 400 920

Paraquat 310 4,000 Pentachlorophenol 7.7 23

Selenium 390 10,000 Silver 390 9,100

Barium 110 87,000 Benzene 1.1 1.6

Cadmium 75 1300 Carbon tetrachloride 0.4 0.6

Chlordane 3.1 12 Chlorobenzene 30 200

Chloroform 0.4 0.5 1,4 Dichlorobenzene 6 9 1,2 Dichloroethane 0.5 0.7 2,4 Dinitrotoluene 1.3 3.7

Endrin 21 340 Heptachlor epoxide 0.1 0.4

Hexacholorobenzene 0.5 1.1 Hexacholoro-1,3

butadine 6.3 12

Hexacholoroethane 34 78 Lindane 0.7 2.2 Mercury 3.4 26

Methoxychlor 370 7,500 Nitrobenzene 14 120

Pyridine 13 95 Toxaphane 1 3.7

2,4,5 Trichlorophenol 6000 82,000 2,4,6 Trichlorophenol 72 180

Vinyl Chloride 0.03 0.04


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Table 5. Summary of Preservative Types Evaluated

Wood Preservative Preservative Components Typical Concentrations of Components

CCA1 Chromium, Copper and Arsenic Chromium = 1,900 mg/kg

Copper = 1,100 mg/kg Arsenic = 1,710 mg/kg

ACQ1 Copper, Boron; Didecyl ammonium chloride (DDAC)

Copper = 3,800 mg/kg Boron = 480 mg/kg

DDAC = 2,900 mg/kg= Borate Preservative

(Envirosafe™)2 TWP-27 (a patented formulation) with

0.84% Boron and 2.4% Silicon Boron = 1,000 mg/kg Silicon = 2,800 mg/kg

Silver Based Preservative3 Silver based biocide Silver = 1,000 mg/kg

1 The concentrations for CCA and ACQ correspond to 0.25 pcf retention level 2 Typical concentration measured in authors’ laboratories 3 Hypothetical scenario, not based on any proposed formulation


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Table 6. Results of Waste Disposal Assessment

Evaluation Criteria CCA

(0.25 pcf) ACQ

(0.25 pcf) Borate

(0.28 pcf as DOT)

Silver-Based

PreservativePotential to be a Federal TC hazardous waste?

Yes No No Yes

Potential to be a California TC hazardous waste?

Yes Yes No Yes

Ratio of Leachate Concentration to Water Quality Criteria (5% chemical leaching)

As =86 Cr =48 Cu =2.8

Cu =9.5 B = 2

B = 4.2 Ag = 25

Ratio of Mulch Concentration to Soil Screening Level (10% treated wood in mulch)

As = 213 Cr = 0.9

Cu = 1

Cu = 3.5 B = 0.007

B = 0.014 Ag = 0.26

Ratio of Ash Concentration to Soil Screening Level (10% treated wood in wood fuel, 5% wood remains as ash)

As = 4275 Cr = 18 Cu = 20

Cu = 69 B = 0.14

B = 0.28 Ag = 5.1

Percentage of element that would have to leach from the ash to be a federal TC hazardous waste (10% treated wood in wood fuel, 5% wood remains as ash)

As = 2.9% Cr = 2.6%

Not applicable

Not applicable

Ag = 5%


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Health Effects of Preserved Wood: Relationship Between CCA-Treated Wood and Incidence of Cancer in the United States

Daniel C. West, MD

Associate Professor of Pediatrics, University of California, Davis

Introduction

There is growing concern about the health effects of exposure to preserved wood due to arsenate, a form of arsenic found in the chemical CCA (Copper Chromium Arsenate), which until recently was used to preserve the wood. It has been shown that CCA in preserved wood can rub off onto hands when wood structures are touched and leach from the wood into surrounding soil after exposure to rain and water.1-3 Humans could potentially ingest CCA by transferring it from their hands to their mouth or by consuming contaminated soil. Children are particularly at risk because they frequently play on structures made from CCA-preserved wood. In addition, children demonstrate behaviors, such as increased hand to mouth activities that might increase the likelihood of ingestion.4

Although arsenic exposure has been linked to a variety of adverse health effects, the greatest

concern is the risk of developing specific types of cancer later in life. For instance, there is epidemiological evidence that chronic ingestion of water contaminated with arsenic significantly increases the risk of developing lung and urinary bladder cancer about 15-20 years after exposure.5-9 In the case of CCA-preserved wood, there are no epidemiological studies to indicate whether routine exposure to CCA in the wood is associated with similar risk. In the absence of such evidence, a number of investigators have attempted to estimate the risk by extrapolating information known about arsenic in drinking water. Risk calculations from these studies vary widely from as high as 1 case of cancer per 500 children chronically exposed for 5 years to CCA-preserved wood to as low as 1 case per 1,000,000 exposed children.10, 11

Given these disparate cancer risk calculations and the lack of direct epidemiological

evidence, we sought to determine whether exposure to CCA-preserved wood is associated with an increased risk of developing cancer. As a first step towards answering this question, we reasoned that millions of children have played on structures made of CCA-preserved wood since this product was first introduced to the U.S. market 30-35 years ago. We

Correspondence to: Daniel C. West, MD, Department of Pediatrics, UC Davis Medical Center 2516 Stockton Blvd., Sacramento, CA 95817 Email: [email protected], Phone: 916-734-2428, Fax: 916-734-0342


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hypothesized that if exposure to CCA-preserved wood increased the risk of cancer, then the rate of arsenic-related cancers should be significantly higher in young adults today, who were potentially exposed to CCA-preserved wood structures as a child, than it was in young adults 30 years ago, prior to the widespread use of CCA-preserved wood. METHODS

We used cancer incidence data from the Surveillance Epidemiology and End Results 9 (SEER 9) registry maintained by the National Cancer Institute. At the time of this study the registry contained complete data on cancer incidence from 1975-1999 from 9 geographic regions of the United States. The 9 geographic regions included Atlanta, Connecticut, Detroit, Hawaii, Iowa, New Mexico, San Francisco-Oakland, Seattle-Puget Sound, and Utah. These areas were chosen to be included in the SEER registry because of their ability to operate and maintain a high quality population-based cancer registry and their epidemiologically significant population sub-groups. Quality control measures were in place to ensure the accuracy of data collected by the SEER registry. The SEER program is considered the standard for quality among cancer registries throughout the world.

Because CCA-preserved wood came into widespread use in the United States in the 1970s and there is a known 15-20 year latency period between exposure to arsenic and the development of arsenic-related cancer, we reasoned that 20-29 and 30-39 year old individuals between 1995-1999 were potentially exposed to CCA-preserved wood as a child. The same age individuals during the period 1975-1979 could not have been exposed. Therefore, to test our hypothesis we compared the incidence of arsenic-related cancer in the 20-29 and 30-39 year old population in 1975-1979 (i.e. unexposed group) with the same age groups in 1995-1999 (i.e. exposed group).

We determined the incidence of all types of lung and bronchus cancer and urinary bladder cancer during the time period and in age groups described above. In addition, we separately identified the incidence of the two most common sub-types of lung cancer, Squamous Cell Carcinoma and Adenocarcinoma. We also determined the change in incidence of all lung and bronchus cancers, Squamous Cell Carcinoma and Adenocarcinoma subtypes, and all urinary bladder cancers each year from 1975-1999, the period of potential exposure to CCA-preserved wood.

We analyzed these data using SEER Stat 4.0 provided by the National Cancer Institute. We used linear regression to analyze the change in annual incidence over time. A P value < 0.05 was considered significant. RESULTS Lung Cancer

We found that the incidence of all types of lung and bronchus cancer among 20-29 year old population between 1995-99 was unchanged compared with that during 1975-1979 (0.4 cases/105 persons)(Table 1). In the 30-39 year old population the incidence of lung cancer decreased (3.3 cases/105 persons [1995-1999] vs. 4.7 [1975-1979])(Table 1). We analyzed the incidence of specific sub-types of lung and bronchus cancer and demonstrated similar findings (Table 2). The incidence of both Squamous Cell Carcinoma and


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191

Adenocarcinoma of the Lung and Bronchus were not different in the 20-29 year old age group in 1995-1999 compared with 1975-1979. In the 30-39 year old population the incidence of Squamous Cell Carcinoma in 1995-1999 was less than that in 1975-1979 (0.2 cases/105 persons [1995-1999] vs. 0.9 [1975-1979]). Likewise, the incidence of Adenocarcinoma in the 30-39 year old group in 1995-1999 was less than that reported in 1975-1979 (1.4 cases/105 persons [1995-1999] vs. 1.9 [1975-1979]). Urinary Bladder Cancer We also compared the incidence of all types of urinary bladder cancer (Table 1). We found that the incidence of urinary bladder cancer was less in 1995-1999 in both age groups (20-29 year olds, 0.5 cases/105 persons [1995-1999] vs. 0.6 [1975-1979]; 30-39 year olds, 1.4 cases/105 persons [1995-1999] vs. 1.7 [1975-1979]). No data was available to compare the relative incidence of sub-types of urinary bladder cancer. Annual Percentage Change Over Time We also compared the annual percentage change in the incidence of all types of lung and bronchus cancer and urinary bladder cancer and sub-types of lung and bronchus cancer in both at risk age groups from 1973 to 1999 (Table 3). In the 20-29 year old age group there was no significant change in incidence for lung and bronchus cancer and reported sub-types. Urinary bladder cancer demonstrated a statistically significant decrease of 1.2 percent each year. In the 30-39 year old age group all lung and bronchus cancer and subtypes showed statistically significantly decreases each year (range 1.4 to 6.2 annual percent). We found a similar decreased incidence of urinary bladder cancer each year in the 30-39 year old group (1.4 annual percent). DISCUSSION About 30 years ago CCA-preserved wood was introduced to the U.S. market and since that time potentially millions of children have been exposed to CCA by playing on wood structures made from this product. With this fact in mind, we hypothesized that if exposure to CCA-preserved wood as a child increased the risk of cancer later in life, then the incidence of arsenic-related cancers in the U.S. should be greater now than it was prior to the use of CCA-preserved wood. On the contrary, we found that the incidence of arsenic-related cancers in adults who could have been exposed to CCA-preserved wood as children was the same or less than it was prior to the widespread use of CCA-preserved wood. Furthermore, we found that the incidence of arsenic-related cancers in potentially exposed individuals has not changed or has decreased each year since the introduction of CCA-preserved wood to the US market. These findings do not support our hypothesis and provide preliminary evidence suggesting that routine exposure to CCA-preserved wood does not increase the risk of developing arsenic-related cancer. Although to our knowledge there are no other epidemiological studies that attempt to directly measure the association between CCA-exposure and the development of cancer, several groups of investigators have investigated the risk of developing cancer after long-


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term ingestion of arsenic in drinking water.5-9 In contrast to our findings, high levels of arsenic in drinking water have been associated with the development of lung and urinary bladder cancers. Perhaps more concerning is that long-term exposure to even relatively low levels of arsenic in drinking water appears to substantially increase the risk of developing urinary bladder cancer. The contrast between these findings and those in our study can be explained, at least in part, by differences in the bioavailability of CCA in preserved wood compared with arsenic in drinking water. For instance, CCA from preserved wood is much less soluble than arsenic in drinking water, and therefore one would expect CCA to be absorbed less efficiently from the gastrointestinal track. Several groups of investigators have performed risk calculations in an effort to estimate cancer risk of children who play on structures made from CCA-preserved wood.10-

12 Results vary widely from as high as 1 cancer case per 500 exposed children to as low as 1 case in 1,000,000 exposed children, well within the range considered safe by the US Environmental Protection Agency. The reasons for this variability are primarily due to differences in critical assumptions that are required to perform the calculations. For example, calculated risk varies depending on assumptions made by the investigator regarding the extent and duration of exposure to the wood, the efficiency with which CCA rubs off onto children’s hands and is transferred into the mouth and then ingested, and the extent to which ingested CCA is absorbed from the gastrointestinal track. Our findings provide preliminary epidemiological evidence supporting risk assessments suggesting that routine play on wood structures made from CCA-preserved wood does not increase cancer risk. Our study was designed to be preliminary, and therefore, has several limitations that must be considered. We used only data collected from the 9 geographic areas included in the 1975-1999 SEER database. Therefore, it is possible that the population represented in the SEER registry is not representative of other regions of the United States. However, this seems unlikely since the population covered by the SEER registry is comparable to the population of the entire United States with regard to education, socio-economic status, and ethnicity. In addition our study did not directly measure the population’s exposure to CCA-preserved wood or other potential confounding variables, such as smoking rates. Therefore, we cannot exclude the possibility that some unmeasured confounding variable unique to the SEER registry population is responsible for our observations. More research that directly measures exposure and controls for potential confounding factors is needed to confirm our findings.

We conclude that the incidence of cancer known to be associated with arsenic exposure is either unchanged or decreased in age groups that would have been exposed to CCA-preserved wood structures during childhood. The rate of arsenic-related cancers has been the same or decreasing over the time in which CCA preserved wood has been sold in the United States. Thus, these data provide preliminary evidence suggesting that there has not been an increase in arsenic-associated cancers during the period of extensive use of CCA-preserved wood in the United States.


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Table 1. Incidence of Cancer in Individuals Who Could Have Been Exposed

To CCA-Treated Wood At Least 15-20 Years Ago. CANCER TYPE

AGE RANGE

1975-1979*

1995-1999*

20-29 year old

0.4

0.4

Lung and Bronchus

30-39 year old

4.7

3.3

20-29 year old

0.6

0.5

Urinary Bladder

30-39 year old

1.7

1.4

From the SEER Cancer Incidence Public-Use Database 1973-1999 *Expressed as incidence per 100,000 persons. Table 2. Incidence of Specific Types of Lung Cancer In At Risk Population CANCER TYPE

AGE RANGE

1975-1979*

1995-1999*

20-29 year old

0.0

0.0

Squamous Cell Carcinoma of Lung and Bronchus

30-39 year old

0.9

0.2

20-29 year old

0.1

0.1

Adenocarcinoma of Lung and Bronchus

30-39 year old

1.9

1.4

From the SEER Cancer Incidence Public-Use Database 1973-1999 *Expressed as incidence per 100,000 persons.


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Table 3. Estimated Annual Percentage Change In Cancer Incidence In The At Risk Population Over Time CANCER TYPE

20-29 YEAR OLD*

30-39 YEAR OLD*

All Lung and Bronchus

0.6

-1.7**

Squamous Cell Carcinoma of Lung and Bronchus

0.0

-6.2**

Adenocarcinoma of Lung and Bronchus

0.0

-1.4**

Urinary Bladder

-1.2**

-1.4**

From the SEER Cancer Incidence Public-Use Database 1973-1999 *Estimated annual percentage change over time. **Change is significantly different from zero (P<0.05)


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References 1. Solomon KR, Warner JE. Persistence, leaching, and bioavailability of CCA and pentachlorophenol

wood preservatives. Interim report to the Ontario Ministry of the Environment 1989. 2. Maine Department of Health Services. Evaluation of children's health hazards from arsenic exposure

associated with the use of CCA-treated wood in residential structures and municipal playgrounds. 1998.

3. California Department of Health Services. Report to the Legislature: Evaluation of hazards posed by the use of wood preservatives on playground equipment. 1987.

4. Calabrese EJ, Barnes R, Stanek EJ, 3rd, et al. How much soil do young children ingest: an epidemiologic study. Regul Toxicol Pharmacol. Oct 1989;10(2):123-137.

5. Smith AH, Goycolea M, Haque R, Biggs ML. Marked increase in bladder and lung cancer mortality in a region of Northern Chile due to arsenic in drinking water. Am J Epidemiol. Apr 1 1998;147(7):660-669.

6. Hopenhayn-Rich C, Biggs ML, Fuchs A, et al. Bladder cancer mortality associated with arsenic in drinking water in Argentina. Epidemiology. Mar 1996;7(2):117-124.

7. Hopenhayn-Rich C, Biggs ML, Smith AH. Lung and kidney cancer mortality associated with arsenic in drinking water in Cordoba, Argentina. Int J Epidemiol. Aug 1998;27(4):561-569.

8. Tsuda T, Babazono A, Yamamoto E, et al. Ingested arsenic and internal cancer: a historical cohort study followed for 33 years. Am J Epidemiol. Feb 1 1995;141(3):198-209.

9. Chen CJ, Chuang YC, You SL, Lin TM, Wu HY. A retrospective study on malignant neoplasms of bladder, lung and liver in blackfoot disease endemic area in Taiwan. Br J Cancer. Mar 1986;53(3):399-405.

10. Environmental Working Group. Poisoned playgrounds: Arsenic in pressure-treated wood 2001. 11. Gradient Corporation. Evaluation of human health risks from exposure to arsenic associated with

CCA-treated wood 2001. 12. Roberts SM, Ochoa H. Concentrations of dislodgeable arsenic on CCA-treated wood: Letter to

Florida Deparment of Environmental Protection. 2001.


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Disposal of Treated Wood

Jeffrey J. Morrell

Oregon State University, Corvallis, Oregon 97331 ABSTRACT Preservative treatment has markedly extended the useful lives of a variety of wood products, but eventually these materials must be disposed. There is a continuing dilemma about how to manage materials that, while treated with toxic chemicals, have largely had little or no impact while in use. This presentation reviews the disposal options currently available and their limitations using utility poles as the primary examples. Introduction Preservative treatment has many beneficial aspects, but one of its most important is that it prolongs the useful life of wood products exposed in extreme environments, markedly reducing the need to harvest our forests while improving the reliability and safety of a variety of structures. While preservative treatments can extend the useful life of a wood product by 20 to 40 times that of untreated wood, eventually, even this durable material must be removed from service. The same chemicals that protect wood against degradation can have negative impacts at the end of the product’s useful life. Disposal of treated wood was once of minimal concern to users and society as a whole, but changing public perceptions concerning the risk of chemical usage and, ultimately, the disposal of products in which they are contained have resulted in a re-evaluation of disposal practices. The dilemma facing users of treated wood is how to convey the message that products that have served benignly in a variety of environments for decades do not instantly become hazardous when they are removed. Challenging this perception will require a combination of education and development of technical information on the various methods of disposal and the relative risks they pose. Compounding the problem is the fact that nearly all preservatives are inherently toxic at some level to a variety of non-target organisms. As a result, developing solutions for dealing with treated wood wastes will require a combination of approaches that recognize and perhaps even take advantage of these attributes.


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Figure 1. Production of treated wood between 1950 and 1990 (AWPA, 19 ). In addition to changing perceptions about chemicals, a number of other factors will influence treated wood disposal. The production of treated wood increased steadily beginning in the 1970s and although growth has slowed somewhat, demand continues to increase (Figure 1). In the 1950s, most treated wood was used for industrial purposes such as poles, railroad ties and piling. These materials were largely handled by personnel who were familiar with their properties, albeit with an environmental ethic consistent with the times. Treated products were most often discarded because they experienced either decay or mechanical wear and the primary chemical used at that time (creosote) was eventually biodegradable. The growth in treated wood production has primarily occurred on the dimension lumber side where chromated copper arsenate (CCA) treated decks have become a common housing feature. The users of these products generally have a poor understanding of the properties. In addition, these products are often removed from service while they are still biologically sound because of unsightly weathering of the wood surface. The chemicals in these products do not biodegrade and large quantities remain in the wood that is disposed. Finally, the user has little knowledge of what constitutes proper disposal. One major concern with this material is the knowledge that the growth in treated wood production seen in the 1970s will be followed by a similar growth in disposal as these materials reach the end of their useful lives. There is some debate about when this will occur. Recent studies of consumer deck perceptions (Smith, XXXX) suggesting average service lives between 10 and 15 years would mean that this disposal phenomena is already underway. A second factor confounding this issue is the overall disposal process. For decades landfilling was the most common method for disposing of bulky materials such as wood. The process, however, was crude, with a high potential for surface and groundwater contamination. Federal regulatory changes led to the installation of landfill facilities with liners and leachate collection systems. These changes also sharply reduced the number of available landfills in some regions and encouraged the development of alternative disposal options, including cogeneration, construction/demolition facilities and stronger recycling programs to extend landfill life. These efforts varied widely among the states. Many western states continued to rely on traditional land-

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disposal. Some states, such as Florida saw sharp reductions in available landfill space and aggressively develop alternative strategies. It is some of these alternative strategies that have caused the greatest concern. Paramount among these has been burning of treated wood collected from C and D facilities to produce electricity. This practice initiated the series of events that led to the planned withdrawal of CCA for treatment of wood used in nonresidential applications. While this process will have been completed by the end of 2003, billions of board feet of wood treated with this and other chemicals remain in service. The question is can we devise a national strategy for dealing with this resource that takes into account public concerns. While ensuring a reasonable ability to safely dispose of these materials. In this report, we will review the options available for dealing with treated wood in the disposal stream. One challenge facing those seeking to find options for disposal is the dispersed and diverse nature of the treated wood resource. Treated wood comprises a variety of commodities including poles, piles, ties, timbers. lumber, and plywood. These materials are treated with any number of chemicals that include organic and metallic systems. While some of these materials are easily distinguished, weathering can make if almost impossible to visually sort some treatments. Finally, treated wood is produced in relatively few locations (<600), but it is used across the landscape. This dispersed resource is costly to collect, sort and ship to sites where it can be effectively recycled. We will examine disposal strategies using three commodities, railroad ties, utility poles, and CCA treated decking. RAILROAD TIES Railroad ties formed the backbone of the original treating industry in North America. Railroads used enormous quantities of wood to support the rails with up to 3500 ties per mile of track. The expansion of the railroads in the late 1800s placed enormous pressure on forest resources and fears about depletion of domestic timber supplies for ties was one of the underlying reasons for the establishment of our national forest system. The development of the preservative treatment industry markedly improved wood service life and effectively ended the concerns about running out of wood. Most ties are treated with creosote or creosote/petroleum mixtures, although some are treated with pentachlorophenol in oil. A well-treated tie is usually removed because it has failed mechanically either through an inability to hold spikes or through excessive wear beneath the plate. In many cases, a majority of the tie remains serviceable and the relatively sound wood has found a ready secondary market for use in retaining walls or as parking bumpers. Concerns have been raised about the potential for migration from these secondary uses, however there is little data showing any significant potential effects. Given their prior usage, it is likely that any large chemical losses occurred in track, markedly reducing the risk of further substantial migration. In addition, creosote components are largely biodegradable in soil. Creosote-treated ties that are no longer serviceable for walls have found ready outlets for cogeneration facilities since the materials have excellent fuel value. As a result, disposal of treated ties is relatively simple process.


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UTILITY POLES Wood utility poles remain the mainstay of the North American distribution and lower voltage transmission systems. The combination of low initial cost, ease of handling, high reliability, and exceptional service life have combined to make wood an obvious choice for a variety of applications. Although treated wood poles will provide exceptional service, eventually, the pole condition declines to the point where it must be replaced. For decades, utilities disposed of used poles in a variety of simple ways including give-aways to adjacent landowners, donations to civic groups and when all else failed, leaving the cutup pole by the side of the road where it mysteriously disappeared. Increasing public sensitivity concerning the use of chemically treated products has heightened awareness of pole disposal among both utility engineers, their environmental specialists and the general public. Many utilities are re-evaluating their disposal options, but there is little information on many possible disposal technologies, nor do all strategies appear to be suited for all treatments used across the U.S. Magnitude of the Issue There are over 160 million utility poles in service in North American with a majority of these poles being in the range of 30 to 40 feet long. Creosote poles represent perhaps 20% of the population, penta 50% and inorganic arsenicals the remainder. While utilities estimate pole service life at 30 to 40 years, poles appear to last far longer in most areas, ranging from 60 to 80 years. Combinations of better inspection, aggressive remedial treatments and reinforcing could further extend these figures. In total, it would appear that approximately 1 million poles are purchased each year, but this figure includes new construction. If we assume that 20% of this production is new construction, then utilities must deal with disposal of 800,000 poles per year. A 1998 survey in the western U.S. suggested that a majority of utilities still gave away nearly all their poles and had little problem taking the remainder to Municipal Solid Waste (MSW) facilities (Table 1). These utilities reported that disposal was a concern, but noted that they spent relatively little on disposal (<$50,000/year). This suggests that the reality of pole disposal is different from its perception. Utilities in more urban settings that lack agricultural outlets for poles face the greatest challenge, but there are also a variety of possible outlets for these materials. Factors Affecting Disposal Pole Condition: While we typically think of disposed poles as badly damaged, many poles are removed for reasons other than degradation including road widening and line upgrades. These poles are probably reusable, but would require reinspection. Many utilities hesitate to reuse poles, although there is tremendous evidence that it can save money without compromising the system. The remainder of removal poles have some type of defect. For example, decay at ground in, shelling or a weathered top. Even these poles are not completely unusable, although some processing would be required to recover the reusable portion of the pole and the creation of some waste that required disposal would be inevitable. Although some poles, such as those impacted by automobiles, may be largely destroyed, it is important to consider that a majority of poles retain considerable usable material when removed from service. In addition, the material requirements for poles such as knot limitations, grain patterns and the near absence of spiral grain make this wood a potentially valuable resource for other applications (ANSI, 1992).


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Table 1. Summary of responses to pole disposal practices surveys administered in 1988, 1997, 1999 (Hess, 1988; Morrell and James, 1997, Morrell, 1999; Love et al., 2000).a Topic 1988 1997 1999 2000 # of poles - 8.2 million 9.2 million 1.9 million # poles disposed - 44,480 44,180 15,500 Treatment Chemicals Penta 92 % 95 % 92 % 64 % Creosote 13 % 23 % 33 % 33 % Arsenicals 6 % 5 % 22 % <1 % Cu-Naphthenate 12% 32 % 18 % 1 % Disposal Method Give away 85 % 77 % 88 % 90 % MSW Facility 40 % 45 % 55 % 60 % Hazardous 5 % 13 % 14 % 20 % Incinerate - 5 % 4 % - Sell - 19 % 10 % - Resaw - 3 % 2 % - Disposal Costs Per Year < $50,000 - 83 % 96 % - $50,000-100,000 - 2 % 4 % - $100,000 to 250,000 - 11 % - - >$250,000 - 4 % - - Sample size 65 62 51 10 a Values in some columns add to more than 100 % because of rounding.

Wood Species and Initial Treatment Chemicals: Wood species can influence potential reuse as a result of initial treatment characteristics. For example, western redcedar has a naturally durable heartwood that resists preservative treatment. Most of the wood in the pole is free of chemicals, although the outer sapwood is often weathered and has lower strength. Douglas-fir also has a high percentage of difficult to treat heartwood; but this wood is only moderately durable. There may also be a substantial internal decay near the original ground in as well as near any field drilled holes. These defects will reduce recovery and increase the amount of waste generated. Southern pine has a high percentage of easily treated sapwood, but some treatments are prone to surface decay. Surface decay may make the below ground portion of the pole unusable. In addition, a majority of the wood will have preservative treatment. The presence of treatment largely relegates this material to exterior applications where there is a risk of decay; however, some retreatment will be necessary since the preservative distribution will likely differ from that of freshly treated lumber. Treatment chemicals and the degree to which they penetrate the wood can also influence disposal. This problem is minor with cedar, but could be a major concern with southern pine. These concerns may limit applications to exterior locations where odors and residual chemicals are of less concern. The presence of some preservatives in this material may also preclude some disposal options such


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as combustion for cogeneration. For example, metal preservatives should not be burned nor should large quantities of pentachlorophenol treated wood be used for cogeneration. Distance from Disposal Site: Wood is a bulky material with relatively low value. As a result, transportation costs for moving poles from the line to a disposal site can be significant, particularly given the low value of a now unusable pole. For example, Love and Morrell (2001) examined trucking costs for poles in the Pacific Northwest and found that transportation of cedar poles for resawing into lumber was practical within a range of 200 miles, although the benefit was greatest with increasing pole size (where recovery would presumably be greater)(Table 2). Transportation costs for other disposal options with less potential for value recovery, such as cogeneration for energy recovery, would be further constrained. Lumber and Timber Dimension lumber treated with chromated copper arsenate comprises one of the two largest contributors to the treated wood disposal issue. Unlikely other treated wood products which are mostly used for industrial applications, CCA treated lumber tends to be widely dispersed in residential applications. The users of these products despite marginal industrial education efforts, are largely ignorant of the properties of these materials. As a result, most users inherently know that treated wood is more durable and that it contains chemicals, but they know little about its properties or routes for proper disposal. In addition, much of this material is used in decks and other horizontal exposures where it is highly prone to Ultraviolet (UV) light degradation, cupping, warping, and twisting that change the appearance. The poor physical performance of CCA-treated decking is a major contributor to the rise in levels of these materials entering the waste stream and clearly illustrates why changes in practices to produce more UV and water resistant decking wood should be a major goal of the treating industry. Table 2. Number of poles per truckload and costs to transport Douglas-fir and western redcedar poles 70 or 200 miles

Number of poles/truckload Transport Cost/Pole Douglas-fir W. redcedar

Pole Class/Length Douglas-fir

W. redcedar 70 mi 200 mi 70 mi 200 mi

4- 40 feet 40 59 $6.50 $13.33 $4.41 $9.03 1-70 feet 10 14 $26.00 $53.30 $18.57 38.07

Table 3. Relative costs to dispose of distribution and transmission poles in municipal solid waste facilities charging two tipping fees.

Disposal Costs/Pole ($) Wood Species Class/Height Lowest Cost Highest Cost 4/40 feet $5.41 $20.00 Douglas-fir 1/70 feet $19.60 $65.38

Western redcedar 4/40 feet $4.70 $15.68 1/70 feet $17.73 $59.09


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At present, however, users of CCA-treated wood are faced with a dilemma about how to dispose of this material at the end of its useful life, when it may be physically weakened, but free of biological attack and retain nearly all of the original preservative. While the EPA would recommend reuse of these materials, there are several challenges to this approach. First, the material is disposed in many locations among numerous users. The wood has often been cut to varying lengths and may still contain nails or screws. Surface appearance is a major limit to reuse in similar applications and resawing of dimension lumber to remove the weathered surfaces would markedly reduce the dimensions, producing boards with dubious structural value. Finally, while the wood is treated, current standards allow retentions for soil and above ground applications and it is impossible to determine which treatment level is present without chemical analysis. As a result, traditional reuse and remanufacturing such as that observed with poles and ties is largely not feasible for these materials. The looming volumes of CCA treated wood that will enter the waste stream over the next 30 years, place added urgency on the need to identify suitable methods for dealing with these materials in an environmentally responsible fashion. Landfilling, while simple, would consume large volumes of precious capacity while wasting a potential reusable resource. The challenge over the next decade will be to identify economical alternatives and implement strategies for using this resource. Disposal Options Give-Aways: Utilities have given away poles for decades, but there is increasing concern about the potential for misuse by the recipients of these materials. Many utilities now require that recipients of used poles sign a release form acknowledging that they have read an information sheet about the chemicals in the wood. Some utilities file these in the event issues arise, but it appears that most utilities do not track these records. Giving away treated lumber is inherently problematic. The wood is often damaged and, given the small dimension, easy to cut up and burn. Give aways have the advantage of low cost and simplicity, but they also mean that the utility has little control over the ultimate disposal of the treated wood. While most uses have minimal risk, the primary concerns would be that the recipient would either burn the wood, use large numbers near surface waters, or in the cases of oilborne chemicals, use the wood in an enclosed, inhabited space without some form of surface sealing. Educating potential users probably represents the best approach for limiting risk on this issue, but requires continuous vigilance to be certain that the education continues as clients change. Land Filling: Most landfills that are lined and have leachate management systems will accept treated wood wastes, although the costs can vary. Some communities have also established wood waste recycling programs to divert this material from landfilling, but care must be taken to ensure that treated materials do not enter the recycling stream where the wood is normally either composted or combusted (Alderman and Smith, 2000; Morrell and Lopath, 2000; Solo-Gabriel et al., 2000). Landfilling can be a relatively low cost option in some regions. Pole disposal in the Pacific Northwest costs as little as $5.41 for a class 4-40 foot long Douglas-fir pole (Love and Morrell. 2001) (Table 3). As a result, landfilling should be the last alternative for disposal. The ability to


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dispose of treated wood in a landfill is driven by the ability of the material to pass a Toxicity Characteristic Leaching Profile (TCLP) test. TCLP involves grinding and extracting the wood, then analyzing the extracts. At present, all treated wood is disposable in municipal solid waste facilities, although these facilities retain the discretion to reject these materials. Virtually all creosote or pentachlorophenol treated wood will pass TCLP, although landfill operators may ask for specific tests from individual users (Goodrich-Mahoney, 1992; Malecki, 1992; Murarka et al., 1996; Vassou et al., 1998). Chromated copper arsenate and ammoniacal copper zinc arsenate are exempt from TCLP. Landfilling all wood removed from service would produce tremendous volumes of material that would quickly overwhelm our existing landfill capacity. Some utilities take landfilling concerns as a great responsibility and dispose of their poles in secure hazardous waste facilities. There is no evidence to suggest that this approach is necessary and it adds obvious costs to the disposal process. Combustion for Cogeneration: One disadvantage of both give aways and landfilling is that the wood remains largely intact and a potential liability for the former owner. Combustion offers the potential for completely eliminating the wood, while simultaneously offering the ability to create electricity and steam. Combustion has long been used for ?????????????? of creosoted railroad ties, poles and timbers (Conlon, 1992; Kempton, 1992; Webb, 1992). Combustion of creosote at high temperatures is relatively simple and there are a number of facilities licensed for this purpose across the U.S. Combustion of pentachlorophenol (penta) or the inorganic arsenicals poses a much greater challenge. Combustion of penta treated wood can produce dioxins and furans, and most facilities that burn wood try to avoid exceeding emission limits usually by limiting the overall percentage of penta treated wood that is burned (Karakash and Lipinski, 1998; Smith, 1992). Table 4. Estimated disposal costs for the treated component of Douglas-fir and western redcedar distribution and transmission poles. Wood Species Pole

Class/Length Treated Zone (in)

Treated Wood Weight (lbs.)a

Disposal Costs ($/Pole)b

1.0 241 lbs $ 2.17 4-40 feet 2.0 419 lbs $ 3.77

1.0 622 lbs $ 5.60

Douglas-fir

1-70 feet 2.0 1,139 lbs $10.25 0.5 106 lbs $ 0.95

4-40 feet 1.0 199 lbs $ 1.79 0.5 274 lbs $ 2.47

Western redcedar

1-70 feet 1.0 526 lbs $ 4.73 a Assumes that treated densities for Douglas-fir and western redcedar are 36 and 28 pounds per cubic foot, respectively. b Assumes a disposal cost of $18.00 per ton in a municipal solid waste facility


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Table 5. Relative volumes of treated wood in poles containing various amounts of preservative treated shell

Total Treated Wood Volume (ft3) Wood Species Pole Class/Length

Estimated Total Volume (ft3) 0.5 in. 1.0 in. 2.0 in.

4/40 feet 16.69 - 6.70 11.64 Douglas-fir 1/70 feet 60.54 - 17.28 31.65 4/40 feet 18.67 3.78 7.11 - W.redcedar 1/70 feet 70.34 9.77 18.78 -

Combustion of CCA and ACZA creates two risks. First, arsine gas can be produced, although this material can be trapped and removed from the stack gases. The resulting ash however will contain high metal levels that necessitate more expensive disposal options. The current furor over CCA was driven, in part, because of the discovery that substantial quantities of CCA treated wood entering Florida construction and demolition facilities was being burned to produce electricity. Tests of the resulting ash initiated a more detailed investigation of disposal practices (Solo-Gabriele et al., 1999). At present, combustion of inorganic arsenically treated wood is neither recommended nor practical on a large scale. Since creosoted wood represents only 15 to 20% of the treated wood in service, it would appear that combustion is only a limited disposal option for treated wood. Reuse: While some utilities will recycle poles that have been in service for only a short time, most see this practice as risky since it is sometimes difficult to accurately assess internal condition. In most cases, there is little risk of decay in the first few years, so reusing poles that have been in service for less than 5 to 10 years probably poses little risk. Where deterioration is a concern, the application of an external preservative paste or bandage or internal fumigant can limit the potential for decay and allow reuse. The potential for reusing older poles remains unknown. While typical internal inspection methods are relatively crude, it may be possible to combine some of these methods with emerging non-destructive evaluation (NDE) technologies to detect large internal defects and estimate residual strength. This would allow utilities to identify truly weak poles and only reuse those poles that still conform to their original design values. Reuse of solid-sawn, treated wood would pose some different challenges primarily related to the fact that this wood often has been fabricated on site. As a result, the reuse must taken into account the present of bolt holes, notches and other features that may affect material properties. In addition, the wood is often weathered, checked and warped, making construction more challenging. Finally, the appearance of the wood will likely lead to concerns about material properties. Although surface defects are unlikely to markedly reduce strength, perceptions based upon appearance may make it difficult to find markets for these materials. The development of consistent methods for assessing wood condition would allow utilities to reuse a higher percentage of poles, reducing both procurement and disposal costs. At present, however, total recycling of treated wood is probably not feasible. Resawing: Pole stock could also be highly desirable for saw logs, provided there was some way to handle the treated wood component (Table 4, 5). For example, field trials with older cedar poles by


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the Bonneville Power Administration and USDA Forest Service indicated that recoveries from poles did not differ markedly from that found with sawlogs (Cahill and Parry, 2002). Poles are straight, have minimal taper and knots, and tend to be cut from slower growing trees. These attributes should produce a higher grade of lumber and there are several smaller commercial operations processing used cedar poles. Similar outcomes would be expected for large treated timbers. Douglas-fir poses a slightly greater recovery challenge because of the slightly higher proportion of treatment and the tendency for the pole to contain some internal deterioration. Despite the slightly lower recoveries, preliminary tests indicate that resawing Douglas-fir poles is both feasible and economical. Resawing southern pine poles and timbers is also relatively simple, but finding markets for the resulting products will be more difficult because a majority of the wood will be chemically treated (Roliadi et al., 2000b; King and Lewis, 2000). While it might be possible to sell this wood as treated, resawing will produce boards with varying degrees of preservative retention. At least one study has looked at recovery rates from southern pine poles, but their theoretical rates imply that much of the recovered wood was treated. This wood could be retreated, but it is unclear whether this material would have suitable markets since retreatment is likely to produce excessively high retentions and there would be questions about compatibility between oilborne treatments in some disposed wood and the waterborne preservatives that are currently used. Two other problems with resawing poles are transportation to the saw and disposal of the treated wood. To date, resawing operations have often not paid for the wood they receive, although they may pay to transport it to the mill. Disposal of treated byproducts does not appear to be a problem in locations where these operations exist, but it does add a cost to the process. Metal fasteners (nails, bolts and other hardware) can also pose a problem, but these can be removed prior to sawing. At present, resawing operations using treated wood appear to be localized entrepreneurial activities that primary process poles. They can play a role for some utilities that have adequate supplies of rejected poles in relatively contiguous areas, but it is unlikely that they are feasible for all utilities nor is it likely that there is an economic justification for construction of larger resaw facilities that could consolidate disposed poles from a number of utilities. At present, resawing or otherwise reprocessing treated lumber remains problematic. Resawing of CCA-treated lumber is probably not feasible because nearly all of this material is already in dimensional configuration (2 to 3 inches thick). While it might be possible to plane the wood to remove the weathered wood, this process reduces the cross section and generates treated wood waste. Reconstituted Wood Products: Engineered wood products composed of veneers, flakes, strands or other wood components represent an increasingly important segment of the wood products industry and it is relatively easy to see how treated wood might be reconstituted into such products (Cooper, 1993; Anonymous, 1990; Felton and DeGroot, 1996; Geimer, 1982; Huang and Cooper, 23000; Munson and Kamden, 1998; Roliadi et al., 2000a; Vick et sal., 1996). Wood breakdown would entail some of the same issues faced by resawing operations including metal contamination, decay, and preservative presence. The presence of some preservatives can have dramatic effects on the ability to bond individual wood components (Vick et al., 1996). In addition, particles and flakes are


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typically cut from relatively low density woods with less value. It is difficult to see how the species used for treated wood products in the U.S. could compete in this market without some type of subsidy. For example, many municipal recycling facilities charge a fee to take waste wood and then sell this material on the open market. Even with free wood and a user fee, most facilities require subsidies to operate. A further issue would be the willingness of composite manufacturers to incorporate preservative treated wood at their facilities. Many manufacturers have a strong aversion to the use of preservatives, although some are now incorporating biocides such as boron in their furnish to produce durable panels for special markets. Given the dispersed nature of the disposed treated wood, it may be difficult to economically assemble sufficient quantities of material to support an individual facility. Extraction/Detoxification: A number of efforts have been made to remove preservative from wood, either by chemical extraction or bioremediation. These efforts have primarily occurred in Europe where differing regulations regarding chemicals have encouraged the development of these processes. Extraction using organic solvents is clearly possible for penta and creosote treated wood, but the costs of these procedures are extremely high and it is sometimes difficult to completely recover all solvent. Supercritical carbon dioxide extraction has been used experimentally for removing pentachlorophenol (Levien et al., 1994; Ruddick and Cui, 1995), but the equipment is costly and the process incomplete. Bioremediation using bacteria or fungi has also shown promise for organic preservatives, but it is slow and incomplete (Lamar, 1995; Lamar and Dietrich, 1992; Messner and Bohmer, 1998; Portier and Kressbach, 1992). Bioremediation of metal treated wood is more difficult since the chemicals can not be broken down, but instead must be solubilized in the wood so that they can be removed in subsequent steps. A number of fungi have been shown to render the metals susceptible to subsequent leaching treatments and there is considerable interest in these technologies in Europe. The primary drawbacks of both chemical and biological extraction are cost and the inability to completely eliminate preservative. The resulting process leaves a much reduced volume of preservative-contaminated residue of dubious value that will likely wind up in a MSW facility. The Future It is clear that all materials (not just treated wood) will face ever more stringent disposal requirements and this is clearly illustrated by more rigorous regulations to minimize packaging waste imposed in parts of Europe. Despite these concerns, most treated wood appears to be a desirable product for other applications. Utilities would be wise to develop educational materials to provide with their poles or restrict donations or sales to contractors, but disposal does not appear to be a major deciding factor for pole use. Disposal of treated dimension lumber poses a much greater challenge because of the overall lack of collection sites and technologies capable of handling the volumes that could be generated. In some regions, however, disposal will become an issue due to diminished landfill capacities and lack of recycling options. Fortunately, there appear to be a number of emerging solutions to these problems as we will see in the remainder of this meeting. Literature Cited


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Alderman, D.R., Jr. and R.L. Smith. 2000. Solid wood received and marketed by Virginia landfill facilities. Forest Products Journal 50(6):39-44. American Wood Preservers’ Association (AWPA). 1999. Annual Book of Standards. AWPA, Granbury, TX. 466 p. American National Standards Institute (ANSI). 1992. Specification and dimensions for wood poles. ANSI 05.1-1992. ANSI, New York, NY. 26 p. Anonymous. 1992. Salvaging utility poles: Turning poles into wood and paper products. Electrical World October:70-71. BioCycle. 1997. Woody materials recycling: Recovering treated lumber. BioCycle 38(7):34-37. Cahill, J. and D. Parry. 2002. Retired poles make good fencing products. In: Proceedings Northeast Utility Pole Conference, October 22-23, Binghamton, NY. Conlon, P. 1992. Crosstie disposal problem or opportunity? Proceedings of the Treated Wood Life-Cycle Management Workshop, American Wood Preservers Institute, Vienna, Va. p.18-26. Cooper, P.A. 1993. The potential for reuse of treated wood poles removed from service. In: Proc. 2nd Inter. Symp. on Wood Preservation. Doc. No. IRG/WP 93-50001. Inter. Res. Group on Wood Preservation, Stockholm Sweden. p. 251-264. Electric Power Research Institute (EPRI). 1990. Pentachlorophenol (PCP)-treated wood poles and crossarms: Toxicity characteristic leaching procedures (TCLP) results. Prepared by the Environmental Management Services, Interim Report EPRI EN 7062, EPRI, Palo Alto, CA. Felton, C.G. and R.C. DeGroot. 1996. The recycling potential of preservative-treated wood. Forest Prod. J. 46(7/8):37-46. Geimer, R.L. 1982. Feasibility of producing reconstituted railroad ties on a commercial scale. Res. Pap. FPL-411. Madison, WI: USDA Forest Service, Forest Products Laboratory. 8 p. Goodrich-Mahoney, J. 1992. TCLP test data on utility pole and crossarms treated with penta and creosote. In: Treated Wood Life-Cycle Management Workshop Proceedings, American Wood Preservers' Institute, Vienna, Virginia Pages 195-213. Hess, R. 1988. Handling and disposal practices of Northwest utilities. In: Proceedings, Wood Pole Conference, October 20-21, Portland, Oregon. p. 26-27. Huang, C. and P.A. Cooper. 2000. Cement-bonded particleboards using CCA-treated wood removed from service. Forest Prod. J. 50(6):49-56. Karakash, J. and G. Lipinski. 1998. Disposal of pentachlorophenol-treated wood by combustion, report of recent compliance testing and project status. Proceedings Northeast Utility Pole Conference. Binghamton, New York. p. 60-62.


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Kempton, C.C. 1992. Life cycle management of treated wood products: issues & answers. Proceedings of the Treated Wood Life-Cycle Management Workshop, American Wood Preservers Institute, Vienna, Va. pp. 54-105. King, S.A. and D.K. Lewis. 2000. Solid wood products from used utility poles: an economic feasibility study. Forest Products Journal 50(11/12):69-78. Labat, G. 1998. Alternative technologies for wood waste recycling. Document No. IRG/WP 98-50101, International Res. Group on Wood Preservation, Stockholm Sweden. p. 205-220. Lamar, R.T. 1995. Use of wood-decay fungi for disposal of PCP-treated wood. In: Proc. 3rd Inter. Symp. on Wood Preservation. Doc. No. IRG/WP 95-50040. Inter. Res. Group on Wood Preservation IRG Secretariat, Stockholm Sweden. p. 441-449. Lamar, R.T. and D.M. Dietrich. 1992. Use of lignin-degrading fungi in the disposal of pentachlorophenol-treated wood. J. of Industrial Microbiology 9:181-191. Levien, K.L., J.J. Morrell, S. Kumar, and E. Sahle-Demessie. 1994. Process for removing chemical preservatives from wood using supercritical fluid extraction. U.S. Patent No. 5, 364, 475. Washington, DC. Malecki, R.L. 1992. The utility perspective on treated wood life-cycle management. Proceedings of the Treated Wood Life-Cycle Management Workshop, Am. Wood Preservers Institute, Vienna, Va. p. 27-50. Mankowski, M., E. Hansen, and J. Morrell. 2002. Wood pole purchasing, inspection and maintenance: a survey of utility practices. Forest Products Journal 52(11/12):43-50. Messner, K. and S. Bohmer. 1998. Evaluation of fungal remediation of creosote treated wood. Paper IRG/WP 98-50101, International Res. Group on Wood Preservation, Stockholm Sweden. Morrell, J.J. 1999. Pole disposal in the Pacific Northwest . In: Proceedings Utility Pole Structures Conference and Trade Show, Reno, NV, October 21-22. p. 53-59. Morrell, J.J. and R. James.1997. Pole disposal in the Pacific Northwest . In: Proceedings Utility Pole Structures Conference and Trade Show, Reno, NV, November 6-7. p. 27-36. Morrell, J.J. and S. Lopath. 2000. Treated wood waste in the recycling stream. Proceedings American Wood Preservers’ Association 96:44-47. Munson, J.M. and D. Kamden. 1998. Reconstituted particleboards from CCA-treated red pine utility poles. Forest Prod. J. 48(3):55-62 Murarka, I.P., R. Malecki, B. Taylor, B. Hensel, and J. Roewer. 1996. Release, migration, and degradation of pentachlorophenol around in-service utility poles. Proceedings American Wood Preservers' Association 92:180-187.


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Portier, R.J. and J.N. Kressbach. 1992. Recovery of wood fiber from treated wood products by combined physical, chemical, and biological approaches. Proceedings of the Treated Wood Life-Cycle Management Workshop, Am. Wood Preservers Institute, Vienna, VA. p. 148-160. Roliadi, H., C.Y. Hse, E.T. Choong, and T.F. Shupe. 2000a. Gluability of out-of-service utility poles. Forest Prod. J. 50(10):76-81. Roliadi, H., C.Y. Hse, E.T. Choong, and T.F. Shupe. 2000b. Decay resistance of out-of-service utility poles as related to the distribution of residual creosote content. Forest Prod. J. 50(11/12):64-68. Ruddick, J.N.R. and F. Cui. 1995; Extraction of toxic organic contaminants from wood and photodegradation of toxic organic contaminants. U.S. Patent 5476975. Smith, G. 1992. Reduction, handling and burning of treated wood. Proceedings of the Treated Wood Life-Cycle Management Workshop, American Wood Preservers Institute, Vienna, Va. p. 139-143. Solo-Gabriele, H.; T. Townsend, J. Penha, T. Tolaymat, and V. Calitu. 1999. Disposal end management of CCA treated wood. Proceedings American Wood Preservers’ Association 95:65-74. Vassou, Z, A. Satanakis, C. Koutsikopoulus, and J. Petinarakis. 1998. The rate of losses of creosote from power transmission poles during storage. International Research Group on Wood Preservation, 4th International Symposium on Wood Preservation. Document No IRG/WP/98-50101. Stockholm, Sweden. p.311-320. Vick, C.B., R.L. Geimer, and J.E. Wood, Jr. 1996. Flakeboards from recycled CCA-treated southern pine lumber. Forest Prod. J. 46(11/12):89-91. Webb, D.A. and D.E. Davis. 1992. Spent creosote-treated railroad crossties – alternatives and their reuse. Proceedings of the Treated Wood Life-Cycle Management Workshop, American Wood Preservers Institute, Vienna, Va. p. 109-138.


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EU Directives and National Regulations for the Recycling and Disposal of Waste Wood

Peek, R.-D.

Federal Research Center for Forestry and Forest Products (BFH) Leuschnerstr. 91, D-21031 Hamburg, Germany

ABSTRACT Waste wood or 'reclaimed wood' is produced in numerous areas of private and public life, in trade and in commerce. Its re-use increasingly poses problems in Germany since the construction sector produces large amounts of waste wood, particularly within the framework of the new building and reconstruction measures in the new federal states. This development has been reinforced in Germany as a result of national legislation, such as the German Waste Circle Act (KrW-/AbfG), and the European definitions of hazardous waste as well as accompanying regulations of the combustion of wastes. In order to meet these challenges Germany has issued the ‘Ordinance on the requirements for the recycling and disposal of waste wood’, which is put into force, March 2003 in order to guarantee an orderly, environmentally correct and thus harmless disposal of timber treated with preservatives. Aim of the ordinance is to avoid, to reduce, to re-use or to recycle waste wood. This paper gives an overview about the European definitions and classification principles for hazardous wastes as well as the regulation of the combustion of treated wood waste on the European and German level. Further, it describes the assessment of treated wood waste properties and the classification system of wood wastes applied in the German Ordinance of waste wood. Finally, it presents an overview about the main actives in treated wood wastes, their classification according to the established European and German codification and the problems arising thereof for the German impregnation industry.

LEGAL ASPECTS Referring to the Council Frame-Directive 75/442/EEC3 on waste of 15 July 1975, the Commission Decision 2000/532/EC4 on a waste catalogue and a list of hazardous wastes of

3 Amended by the following measures:

Council Directive 91/156/EEC of 18 March 1991; Council Directive 91/692/EEC of 23 December 1991; Commission Decision 96/350/EC of 24 May 1996; Council Directive 96/59/EC of 16 September 1996

4 Replacing Decision 94/3/EC establishing a list of wastes pursuant to Article 1(a) of Council Directive 75/442/EEC on waste and Council Decision 94/904/EC establishing a list of hazardous waste pursuant to Article 1(4) of Council Directive 91/689/EEC on hazardous waste


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22 January 2001, and the Council Frame-Directive 2001/77/EC5 on Renewable Energies of 27 September 2001, Germany implemented several subsidiary legal measures in order to ensure the orderly and harmless disposal of wastes. The most important regulations referring to recovered wood are: The German Closed Substance Cycle and Waste Management Act (Kreislaufwirtschaftsgesetz - KrW-/AbfG), the Ordinance on Incineration Plants and other Combustible Substances (Seventeenth Ordinance on the Implementation of the Federal Emission Control Act), the Ordinance on the Requirements Pertaining to the Recovery and Disposal of Waste Wood (Ordinance on the Management of Waste Wood - (Altholzverordnung - AltholzV), the Act on Granting Priority to Renewable Energy Sources (Erneuerbare-Energien-Gesetz - Renewable Energy Sources Act - EEG), the Ordinance on Generation of Electricity from Biomass (Biomass Ordinance – Biomasseverordnung für klimaschonende Energieerzeugung - BiomasseV) of 21 June 2001, and the Ordinance on a Harmonised Waste List (Verordnung über das Europäische Abfallverzeichnis - Abfallverzeichnis-Verordnung - AVV) of 01. January 2002. On the basis of these legal regulations, in Germany recovered wood is mainly ruled by the waste regime and it is subdivided into five property-based categories.

German Closed Substance Cycle and Waste Management Act6 The German ‘Act for Promoting Closed Substance Cycle Waste Management and Ensuring Environmentally Compatible Waste Disposal’ (Waste Avoidance, Recovery and Disposal Act (KrW-/AbfG) of 27 September 1994, (latest changes: 21. August 2002) determines the objectives and fundamental rules of German waste management. It aims at the protection of natural resources and eco friendly waste disposal. The general principles for the waste management are

• To AVOID • To REDUCE • To REUSE or to RECYCLE • To ELIMINATE

German Ordinance on Incineration Plants In Germany the Ordinance on Incineration Plants and other Combustible Substances – 17th BImSchV (Seventeenth Ordinance on the Implementation of the federal Emission Control 5 Directive on the promotion of electricity produced from renewable energy sources in the internal

electricity market 6 As amended by the Act on the Expedition of Licensing Procedures

(Genehmigungsverfahrensbeschleunigungsgesetz) of 12 September 1996 (Federal Law Gazette I p. 1354), the Act for the Conservation of the Soil (Gesetz zum Schutz des Bodens) of 17 March 1998 (Federal Law Gazette I p. 502), the Act on the Reform of Road Haulage Law (Gesetz zur Reform des Güterkraftverkehrsrechts) of 22 June 1998 (Federal Law Gazette I p. 1485) and the Act on the Implementation of the Protocol of 7 November 1996 to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter of 1972 (Federal Law Gazette I p. 2455) This Act implements Council Directive 91/156/EEC of 18 March 1991 for amendment of Directive 75/442/EEC on waste (EC Official Journal no. L 78 p. 32) and of Council Directive 94/31/EC of 27 June 1994 for amendment of directive 91/689/EEC on hazardous waste (EC Official Journal no. L 168 p. 28).


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Act) - of 23. November 1990 establishes a limitation of air emissions and further appropriate conditions for combustion in waste incineration and co-incineration plants. It was changed on 14. August 2003. The ordinance fixes the conditions for the incineration of solid and liquid waste and other substances which are not regular fuel according to the 4th BimSchV (Fourth Ordinance on the Implementation of the Federal Emission Control Act – Ordinance on Installations subject to Licensing (4. BImSchV) of 14. March 1997, changed 14. August 2003). Having regard to the potential hazardous waste, the 17th BImSchV requires more stringent conditions concerning the limitation of air emissions, the operation and monitoring of waste incinerators and co-combastion plants. In the case of industrial plants practising co-incineration by mixing regular fuels with waste wood, the co-incineration shall not be allowed to cause higher emissions of polluting substances than those permitted for conventional waste incinerators. That means that the limit values for the combustion of regular fuel will be determined in accordance with the 13th BImSchV (Thirteenth Ordinance Implementing the Federal Immission Control Act - Ordinance on Large Firing Installations) or TA Luft (First General Administrative Regulation Pertaining the Federal Immission Control Act - Technical Instructions on Air Quality Control) of 1986, changed 30. July 2002. For the partial use of waste the stringent emission limit values apply to that fraction of the combustion gasses derived from incineration of waste according to the 17th BimSchV. On European level the Directive 2000/76/EC on the Incineration of Waste of 4 December 2000 establishes legal requirements for the incineration and co-incineration of waste. The Directive was approved by the Conciliation Committee at the begin of October 2000 and entered into force with its publication on 4 December 2000. Germany had to transpose the Directive into national laws within two years. As a consequence the German 17th BimSchV had to be amended (s. above).

German Ordinance on the Management of Waste Wood

General The Closed Substance Cycle and Waste Management Act (KrW-/AbfG) considerably extended the scope of the waste law as compared to earlier legislation. Under the heading “closed substance cycle” the Act also includes all waste recovery measures relevant to the waste sector. The provisions in the Closed Substance Cycle and Waste Management Act that in many cases had to be kept general, need to be specified for individual waste flows by means of more detailed provisions in order to ensure legal and investment certainty in the enforcement of the law. Furthermore, the Ordinance shall guarantee a binding and nationwide standard for waste wood management and thus leading to greater equality of competition, in particular for the small to medium waste management companies primarily active in this field. From both an ecological and an economic point of view, the Waste Wood Ordinance represents an important step towards the sustainable further development of the closed substance economy. On 1 March 2003 the Ordinance on the Management of Waste Wood entered into force. This Ordinance is considered a pilot project for such material-specific ordinances. It laid down specific requirements pertaining to the recycling and energy recovery as well as for the disposal of waste wood on the basis of the Closed Substance Cycle and Waste Management Act. These requirements


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provide a sustainable support for the environmentally sound recovery of waste wood and ensure that pollutants are eliminated from the economic cycle. In this context, waste wood was particularly suitable as a model substance because

• It is a significant volume flow for waste recovery, • It is suitable for both substance recycling and energy recovery, • The environmental compatibility of some of the recovery paths for waste wood currently in

practice is questionable, and • There is an urgent need for standard nationwide regulation in view of the different

regulations of the German Länder. The Ordinance defines specific requirements for substance recycling and energy recovery and for the disposal of waste wood on the basis of the Closed Substance Cycle and Waste Management Act. At the same time, these requirements are harmonised with the requirements to be adhered to for the management of waste wood pursuant to chemicals and hazardous substances law as well as the provisions governing the keeping of waste recovery and disposal records. The following regulations are particularly relevant:

• Both residual wood from industry and wood products that have become waste are classified as waste wood in this Ordinance. Generally speaking, waste wood includes residues from the working and machining of wood and derived timber products as well as used products such as wood packaging, palettes, furniture and waste wood from demolition. The prerequisite here is firstly, in the case of composite materials, that the wood content is greater than 50 percent by mass, and secondly, that the waste wood qualifies as waste. This means, for instance, that residual wood classified as a tie-in product or a by-product (e.g. wood chips from saw mills or forest thinning) is not included in the scope of application.

• The Ordinance identifies and covers all the common methods of waste wood management such as preparing waste wood for the production of derived timber products, the production of active carbon or industrial charcoal and synthesis gas and the energy recovery of waste wood as a substitute fuel. Other possible recovery paths are not regulated by the Ordinance but are also not excluded so that this does not stand in the way of incorporating new recovery paths and innovative recovery procedures for waste wood. Whether these are permissible according to waste law is then assessed not on the basis of the Waste Wood Ordinance but instead directly on the basis of the requirements in the Closed Substance Cycle and Waste Management Act. If waste wood cannot be recovered, it must be disposed of using thermal processes. Land filling is not permitted

The requirements in the Waste Wood Ordinance define high-quality substance recycling and energy recovery procedures. There is no regulation in the Ordinance on priority for substance recycling or energy recovery pursuant to the Closed Substance Cycle and Waste Management Act, since in the case of wood as a renewable raw material there are no clear advantages or disadvantages for the one or the other type of recovery. The waste holder thus has the choice between substance recycling and energy recovery, although the prerequisites for permissibility stipulated in the Closed Substance Cycle and Waste Management Act are to be given due consideration in the case of energy recovery.

Specific regulations for waste wood in Germany Definition of Terms


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For the purposes of this Ordinance the following terms are used in Germany in connection with wood preservation and the disposal of wood wastes. The same terms might be used in a different way in other countries and might have an other meaning

Waste wood: Residual wood from industry and used wood, insofar as these constitute waste7 within the meaning of the Closed Substance Cycle and Waste Management Act; Residual wood from industry: Wood residues accumulating in woodworking and machining plants, including derived timber residues accumulating in the derived timber product industry as well as composite products consisting mainly of wood (over 50% by mass); Used wood: Used products made from solid wood, derived timber products or from composite materials consisting mainly of wood (over 50% by mass); Waste wood containing PCBs: Waste wood which constitutes waste wood containing PCBs within the meaning of the PCB/PCT Waste Ordinance [PCB/PCT-Abfallverordnung] and is to be disposed of in accordance with the provisions of this Ordinance, in particular insulating board and sound insulating board treated with agents containing polychlorinated biphenyls; Wood preservatives: Substances used in woodworking and machining having a biocidal effect against hylophagous insects and fungi as well as fungi which discolour the wood, as well as substances for reducing the flammability of wood; Substance recycling of waste wood: a) Processing of waste wood to wood chips for the manufacture of derived timber products, b) Production of synthetic gas for further chemical use and c) Manufacture of active carbon/industrial charcoal; Energy recovery from waste wood: Recovery of waste wood within the meaning of the Closed Substance Cycle and Waste Management Act8; 7 "Waste" means all movable property, which the holder discards, or intends or is required to discard.

"Waste for recovery" is waste that is recovered; waste that is not recovered is "waste for disposal". 8 Energy recovery shall mean the use of waste as a substitute fuel; the priority for energy recovery

does not affect thermal treatment of waste for disposal, especially household waste. The main purpose of a measure in question shall be taken as the criterion for differentiation. For a given waste sample that has not been mixed with other substances, the type and extent of the waste's impurities, and the additional waste and emissions occurring as a result of its treatment, shall be the criterion for determining whether the relevant waste management measure's main purpose is energy recovery or treatment.


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Waste wood treatment installation: Installation used for substance recycling or energy recovery from waste wood and installations for sorting or other treatment of waste wood including any attendant storage; Interfering substances: Inorganic or organic substances which damage wood, particularly soil, stones, concrete, metal parts, paper, cardboard, textiles, plastics or foil which are stuck to, added to or attached to the waste wood, insofar as they prevent recovery.

Waste Wood Categories Waste wood must be assigned to one of four of the following waste wood categories depending on the level of pollution. • Waste wood category A I:

Waste wood in its natural state or only mechanically worked which, during use, was at most insignificantly contaminated with substances harmful to wood,

• Waste wood category A II: Bonded, painted, coated, lacquered or otherwise treated waste wood with no halogenated organic compounds in the coating and no wood preservatives,

• Waste wood category A III: Waste wood with halogenated organic compounds in the coating, with no wood preservatives,

• Waste wood category A IV: Waste wood treated with wood preservatives, such as railway sleepers, telephone masts, hop poles, vine poles as well as other waste wood which, due to its contamination, cannot be assigned to waste wood categories A I, A II or A III, with the exception of waste wood containing PCBs.

Implications for the German industry The assignment of waste wood to category A IV can pose difficulties to the wood industry. Waste timber can be contaminated to different extents with paint, lacquer, coatings and wood preservatives. Some active ingredients can represent a particular risk potential. Among these are pentachlorophenol, mercury, arsenic and/or chromium compounds, as well as creosotes (Table 1).


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Table 1: Kind of impurities* and estimated quantity of wood waste from different origin (Voss, Willeitner 1995, changed)

Assortment (possible) impurity

Retention Estimated quantity

(*1000 to/a)

Sleepers Creosote, CKB1

45 kg/m3 – 175 kg/m3

n.d.i. ca. 60 – 85

Poles CKB, CKF, CKA creosote, HgCl2

6-12 kg/m3 ca. 90 kg/m3

0,6-1,0 kg/m3

ca. 15 – 25

Landscaping CKB, CKF Cu-HDO-salts creosote tar oil derivates/ formulations LOSP

6-8 kg/m3 3-4 kg/m3 ca. 80 kg/m3 250-400 g/m2

n.d.i.

ca. 220

Hop-poles CKB, CKF, CKA creosote HgCl2

ca. 6-8 kg/m3

ca. 90 kg/m3

ca. 0,4-0,8 kg/m3

present stock (pcs): 150.000 – 270.000

Vineyard posts CKA, CKF CKB creosote HgCl2 CFA

5-6 kg/m3

ca. 10 kg/m3

50-100 kg/m3

ca. 0,6-1,0 kg/m3

5-6 kg/m3

ca. 9 – 14

Wood from demolition of buildings, building sites

all WPs except creosote, chloronaphthaline and HgCl2; coatings, varnishes, impurities etc.

No specification possible ca. 500 – 2.000

Wood for packaging/ palettes

rarely -:- ca. 470 – 970

Cable drums CKB, CKF, CK (CKA?)

6-8 kg/m3 31 – 45

Furniture varnishes, glues, coatings

Unknown ca. 2.500

Industry residues2 rarely, known if applied No specification possible ca. 8.000

Total treated Untreated Grand total

1.300 – 3.400 10.500

11.800 – 13.900

* Voss, A., Willeitner, H. 1994; Bucki, C., Willeitner, H. 1994; old German states. 1 Privat railways in some cases may use chromium containing salts (only pine). 2 Industry residues are solid wood cut-offs, chips, shavings, dust, bark. N.d.i. No definite information available


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CLASSIFICATION CONCEPT With regard to inspections and monitoring, the Waste Wood Ordinance is geared towards strengthening the personal responsibility of the installations, supplemented by moderate independent inspections and monitoring. The focus is on the operators of waste wood treatment installations that are obligated to allocate the waste wood to the given recovery paths. This allocation process is to be monitored regularly. This system of internal and independent monitoring is supported by documentation and reporting obligations. This provision produces a high level of precautionary environmental protection with the greatest possible personal responsibility while at the same time being enforcement-friendly. Instead of elaborate and uncertain sampling and analysis provisions, assignment to the respective category can occur on the basis of origin and in accordance with strict requirements for keeping waste wood separate and bans on mixing waste woods. To simplify assignment, the Ordinance contains a general rule to be assumed for the common types of waste wood. In the case of a mixture of different waste wood categories, the mixture must always be assigned to the category subject to the most stringent provisions. In order to ensure safe recovery, the waste wood categories A I to A IV are then allocated to the individual substance recycling paths; energy recovery is governed by the provisions of the Federal Immission Control Act and the statutory ordinances issued on the basis thereof. Waste wood containing PCBs is classified, as a “special category” if it’s PCB content is more than 50 mg/kg. Waste wood containing PCBs must be disposed of in accordance with the PCB/PCT Waste Ordinance – only thermal treatment procedures come into question.

RE-USE/RECYCLING The waste wood categories A I to A IV may be used for the manufacture of active carbon/industrial charcoal and the production of synthetic gas as well as in incineration and gasification plants that are licensed pursuant to the Fourth Ordinance on the Implementation of the Federal Immission Control Act and with regard to emissions are subject to the Seventeenth Ordinance on the Implementation of the Federal Immission Control Act (cf.). During these procedures, the organic pollutants contained in the waste wood are completely destroyed due to the high temperatures. Heavy metals are bound as solid in the residues or dispersed during waste gas purification. Only certain pollution-free or low-pollution waste woods can be considered for use in manufacturing derived timber products. Compliance with this requirement is guaranteed by binding pollutant limit values (cf Table 3), including relevant sampling and analysis provisions, for the wood chips produced for use as raw materials for the manufacture of derived timber products (cf Table 4). Waste wood processed in this manner for the derived timber products industry ceases to be waste and can be processed there as a primary raw material.


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Table 2: Methods for the substance recycling of waste wood Permissible waste wood categories

Recovery method A I A II A III A IV Special requirements

Processing of waste wood to wood chips for the manufacture of derived timber products

Yes Yes (Yes)

The processing of waste wood from category A III is only permissible if varnishes and coatings have been largely removed by pre-treatment or will be largely removed during processing.

Production of synthetic gas for further chemical use Yes Yes Yes Yes

Recycling is only permitted in installations licensed for this purpose under Article 4 of the Federal Immission Control Act.

Manufacture of active carbon/industrial charcoal Yes Yes Yes Yes

Recycling is only permitted in installations licensed for this purpose under Article 4 of the Federal Immission Control Act.

Table 3: Limit values for wood chips used in the manufacture of derived timber products

Element/compound Concentration (milligrams per kilogram dry mass)

Arsenic 2

Lead 30

Cadmium 2

Chromium 30

Copper 20

Mercury 0,4

Chlorine 600

Fluorine 100

PCP 3

Polychlorinated biphenyls 5


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Table 4: General classing of waste timber arising from regular assortments (examples). Common types of waste wood (examples) Usual

assignment Waste, cuttings, shavings from solid wood in its natural state

A I

Wood waste from woodworking and machining Waste, cuttings, shavings from derived timber products and other treated wood (with no harmful contaminants)

A II

Palettes made from solid wood such as: Euro palettes, industrial palettes made from solid wood

A I

Palettes made from derived timber products A II Pallets

Other pallets with composite materials A III Transport cases, crates made from solid wood A I Boxes for fruit, vegetables and ornamental plants as well as similar boxes made from solid wood

A I

Ammunition boxes A IV Cable reels made from solid wood (made before 1989) A IV

Packaging

Cable reels made from solid wood (made after 1989) A I Solid wood in its natural state A I

Waste wood from building sites Derived timber products, barked wood, treated solid wood (with no harmful contaminants)

A II

Boards, false ceilings, planks from interior works (with no harmful contaminants)

A II

Door leafs and frames (without harmful contaminants)

A II

Profile boards for the fitting out of rooms, ceiling panels, ornamental beams etc. (without harmful contaminants)

A II

Heat and sound insulating board treated with agents containing polychlorinated biphenyls

Disposal

Chipboard used in construction A II Wood used in construction for load-bearing elements A IV Timber framework and rafters A IV Windows, window posts, outer doors A IV

Waste wood from demolition and restoration work

Impregnated wood used in external structures A IV

Waste wood from the construction industry

Wood from construction and demolition work containing harmful contaminants A IV Railway sleepers A IV Transmission poles A IV Various wood used in horticulture and landscaping, impregnated garden furniture

A IV Impregnated waste wood used in external structures

Various wood used in agriculture A IV Furniture, solid wood in its natural state A I Furniture, with no halogenated organic compounds in the coating

A II Furniture

Furniture, with halogenated organic compounds in the coating

A III

Waste wood from bulky refuse (mixed) A III Waste wood from industrial use (e.g. industrial flooring, cooling towers) Waste wood from hydraulic engineering Waste wood from dismantled vessels and goods wagons Waste wood from damaged structures (e.g. burnt wood) Fine fraction from the processing of waste wood to make derived timber products

A IV


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ENERGY RECOVERY In the context of the energy recovery of waste wood, use of waste wood in installations where fodder is dried in direct contact with the installation’s exhaust and flames is restricted to waste wood category A I. This ensures that fodder contamination is ruled out. Priority must be given to energy recovery from such kind of waste wood, which cannot be used for the production of derived timber products (and). The energy recovery from waste wood treated with heavy duty wood preservatives is strongly regulated by e.g. the Fourth Ordinance on the Implementation of the Federal Emission Control Act – Ordinance on Installations subject to Licensing (4. BImSchV), Thirteenth Ordinance Implementing the Federal Immission Control Act - Ordinance on Large Firing Installations (13. BImSchV) of 22. June 1983, and the Seventeenth Ordinance Implementing the Federal Immission Control Act - Ordinance on Incinerators for Waste and similar Combustible Material (17. BImSchV) of 23. November 1990. At present, only waste timber of contamination group A I may be processed in furnaces of a nominal thermal output of less than 50 kW (). Furnaces with a nominal thermal output of more than 50 kW and less than 1 MW may use waste timber of contamination group A II but only in woodworking and wood manufacturing companies. Furnaces with less control of harmful substances may only process waste timber of contamination groups A I and A II. Furnaces, which fulfil higher requirements with regard to the control of harmful substances, may only process waste timber of contamination groups A I, A II and A III. If the furnace fulfils the highest requirements of the Seventeenth Ordinance Implementing the Federal Immission Control Act - Ordinance on Incinerators for Waste and similar Combustible Material, it is then also possible to process waste timber of contamination groups A III and A IV.


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Table 5: Emission limit values for cement kilns (TA Luft) and for waste incinerators (17. BImSchV) as well as emissions detected (values given in mg/m3, Dioxins and Furans given in ng/m3 TEQ); Wiedemeier 1999, changed

Emission Experiments

Cement kiln1) Waste incinerator2)

Coal power plant (melting chamber

combustor)3)

TA Luft4)

17 BImSchV5)

Total dust n.t. 1 – 44 0,5 – 1 5 – 10 50 10 Total C ≤ 1 – 7,7 0,9 – 94 1 – 2 <10 --- 10 CO 35 – 301 1350 – 3750 10 – 25 13 – 181 --- 50 HCl 0,3 – 8,3 0,7 – 10 0,5 – 2 3 – 11 30 10 HF 0,3 – 29,6 0,7 1,5 <0,5 >2,5 5 1 SO2 n.t. 9 – 730 5 – 8 <250 400 50 NOx 131 – 791 740 1.200 65 – 120 <200 1300 200 Cd+TI n.t. 0,0003 – 0,05 <0,01 0,0007 – 0,0016 0,2 0,05 Hg n.t. 0,00014 – 0,017 <0,02 0,004 – 0,011 0,2 0,05 Sb+As+Co+Ni+ Se+Te+Pb+Cr+ Mn+V+Sn+Cu

0,1 – 1,9 0,002 – 0,106 <0,2 0,015 – 0,023 1 0,05

Dioxins and Furans

0,018 – 1,415 <0,03 <0,03 <0,002 --- 0,1 TEQ

1) according to Reiter and Stroh 1995 2) values by RZR-Herten, 1997 avi-Twente/NL 1999 3) Technical Supervision Association (TÜV) North, coal power plant Ibbenbühren, June 1999 4) Technical Guidance Air (TA Luft) 5) Ordinance on Incinerators for Waste and Similar Combustible Materials (17th BImSchV), same limit values as in the draft EU proposal for the emissions from waste incinerators (COM(98)0558 – C4-0668/98 – 98/0289(SYN)) with the exception of NOx = 500 mg/m3 (EU proposal).


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Figure 1: Classing of untreated and treated waste timber with furnaces of different standard (Anonymus 1998)

A I A II, A IV

untreated wood Wood, wood based material glued, coated, painted, lacquered without

wood preservatives

wood treated with wood preservatives without and with halogen organic compounds in the coating without

halogenorganic compounds in the

coating

With halogenorganic

compounds in the coating

furnaces < 1 MW

furnaces 50 kW < 1 MW

furnaces ≥ 100 kW

furnaces ≥ 100 kW

1. BImSchV 4. BImSchV, Nr. 1.2

4. BImSchV, Nr. 1.3

only in wood working and wood manufac-turing companies

furnace has to fulfil the highest requirements of the 17th Federal Emis-sion Protection Act (BImSchV)

material re-use possible, e.g. particleboard industry


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WASTE MANAGEMENT FOR TREATED WOOD IN THE DIFFERENT EUROPEAN COUNTRIES

The waste management for treated wood is different in the European countries and varies between strongly regulated and no regulation at all. On the occasion of the 6th Workshop 21 - 23 September 2003 Zagreb, a survey was carried out among the signature countries of the EU COST Action E22 ‘Environmental Question 1: How much waste wood (to) do you produce in your country annually?

Thereof: treated waste* Thereof: treated with CCA

*wood treated with any kind of preservative, including CCA Question 2: What is your country doing with waste wood? Question 3: What is the legal situation for waste wood in your country (legislation/regulation)? Please tick the respective box and note the related regulations, directives etc that you are aware of.

The following tables (Table 6, Table 7 and Table 8) present the results received. Further information on this topic can be found at URL http://www.bfafh.de/cost22.htm . Please note that the figures presented can only be considered as preliminary and are still a matter of improvement as soon as new results are available.

CONCLUSIONS The German Waste Wood Ordinance (AltholzVO) is intended to considerably increase the re-use of waste wood, thus to ensure its orderly and harmless disposal and to prevent the transporting of waste into those states which have the "easiest" way of disposal. In Germany the disposal of waste wood led to great uncertainty at those owning waste wood as well as at the approval authorities. With the Waste Wood Ordinance Germany is breaking new ground. Thus far there are no European regulations in this field. This Ordinance promotes the environmentally sound management of waste wood. It ensures a binding and nationwide standard for waste wood management and thus leads to greater equality in competition, in particular for small and medium-sized recovery and disposal enterprises. From the standpoint of its structure and system, this Ordinance is also intended to serve as a pilot ordinance for future requirements specific to material flows for waste recovery.


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Table 6: Production of wood wastes

Country Untreated

amount [to]

treated amount

[to]

CCA treated amount

[to] B 1,200.000 N/D 200.000 CH N/D N/D N/D D 8,000.000 1.900 – 2.800 - FIN (VTT) 530.000 10.000 9.000 GR 90.000 - 100.000 10.000 1.000 IRL N/D N/D N/D NL N/D 400.000*** 120.000*** NO 1,200.000 100.000 15.000 RO* 2,320.000 42.300** - UK 7,300.000 80.000 40.000

* Unfortunately there are no available data (N/D) concerning the amount of treated wood

waste (including those treated with CCA). There are no collects (recoveries) of treated wood waste organized at national level.

** This quantity has resulted from the sawdust and shaves, which were obtained from some wood, based products manufacturing. (In their manufacturing we use also different chemicals – not preservatives)

*** Figures in m3 * 0,5 (~ to)


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Table 7: Kind of waste wood reuse Kind of reuse/Country untreated

amount [to] Treated

Amount [to] CCA treated Amount [to]

B 816.000 156.000 N/D CH N/D N/D N/D D N/D N/D - FIN (VTT) 5.000 N/D N/D GR 50.000 N/D N/D IRL* N/D N/D N/D NL 844.000 127.000 5.100 NO N/D N/D N/D RO 260.000 - -

Recycling / reuse e.g. particle board

UK 0.63 Mto reused

0.84 Mto recycled to panel prodn

80.000 40.000

B N/D N/D N/D CH banned banned banned IRL* N/D N/D N/D D banned banned banned FIN (VTT) 5.000 N/D N/D GR N/D 5.000 N/D NL 0 0 0 NO 20 % 30 % (?) 0 % (?) RO 110 000 - -

Landfill

UK ca 5,530.000 80.000 to All - ~ 40.000 B 336.000 164.000 N/D CH N/D N/D N/D D N/D N/D N/D FIN (VTT) 295.000 10.000 9.000 GR 20.000 2.000 N/D IRL* N/D N/D N/D NL 200.000 1.200 500 NO 80 % 70 % (?) 100 % (?)* RO 1,520.000 - -

Energy production

UK unknown B N/D N/D N/D CH N/D N/D N/D D - - - FIN (VTT) 225.000 N/D N/D GR N/D N/D N/D IRL* N/D N/D N/D NL 0 0 0 NO 1,200.000 100.000 15.000 RO 430.000 - -

Special dumps

UK Very little * IRL - Again, N/D available. However, much of construction waste currently goes into landfill. There are re-cycling programmes underway to reduce this. At present, there is, to my knowledge, any separation of any wood waste. There is a lot of interest at present at sawmill level to use wood waste for energy production and it is expected that this is a good possibility. At present, sawmill wood residue gose to the various particle-board plants (chipboard, OSB, MDF, hardboard). There is at least one company which will go to a factory to grind up waste wood eg pallets into chips. We have no special dumps. If something is classified as a harazdous wood wastel, it will be shipped to eg Finland for high temperature incineration – at a high cost!


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Table 8: Waste wood regulations Regulation

Kind of use Exists Does not exist In preparation Coming into

force (year) B CH X D X FIN (VTT) X GR X IRL X (in principle) NL X NO X No RO* X

Recycling / reuse e.g. particle board

UK X 2004 B X CH banned D X FIN (VTT) X GR X IRL X NL X NO X RO* X

Landfill

UK X 2004 (I think - maybe 2007)

B X CH + D X FIN (VTT) X GR X IRL X NL X NO X X 1 - 3 years RO*

Energy production

UK X B X CH banned D X FIN (VTT) X G N/D IRL X NL X NO X RO* X

Special dumps

UK X * In RO there is no specific legislation concerning the use of wood waste as you have indicated.

In accordance with EU legislation that covers that field, respectively the Council Directive 75/442/CEE – the European Catalogue for Waste, published by Council Decision 94/3/CE and reviewed by the Decision 2000/532/EC, the following regulations have been issued: G 155/8.03.1999 – Decision regarding the introduction of waste management and of the European Catalogue for Waste; OUG no. 78/16.06.2000 – Regulation regarding waste (storage, manipulating, utilization, destruction); HG 128/14.02.2002 – Decision regarding the waste incineration.


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Electrodialytic Remediation of CCA-Treated Wood In Larger Scale

*Iben Vernegren Christensen, Anne Juul Pedersen, Lisbeth Moelgaard Ottosen, and **Alexandra Ribeiro

Abstract A pilot plant for electrodialytic remediation of CCA-treated wood in larger scale has been designed and tested at DTU. Several process parameters were investigated, and it was found that the use of collecting units and soaking of the wood prior to the electrodialytic process had a positive influence on the remediation process. There is a tendency towards easier remediation of wood chips < 2cm, than larger wood size fractions. The influence of the electrode distance could not be fully investigated due to the experimental setup but it is expected that the use of collecting units will keep any influence to a minimum. The best remediation efficiency was obtained in an experiment with an electrode distance of 60 cm, and 100 kg wood chips. In this experiment 87% Cu, 81% Cr and >95% As was removed. Only one other experiments was analysed for As and here 95% was removed. The electrode distance was 1.5 m and the results indicate that As may be the easiest removable of the Cu, Cr and As investigated here. This is very encouraging since As is the CCA components of most environmental concern. Keywords CCA-treated waste wood, electrodialytic remediation, oxalic acid, phosphoric acid, pilot plant _____________ *Iben Vernegren Christensen, Anne Juul Pedersen, Lisbeth Moelgaard Ottosen, Department of Civil Engineering, build. 204, The Technical university of Denmark, DK-2800 Lyngby, Denmark **Alexandra Ribeiro DCEA- Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal. *Corrosponding author. Email: [email protected]


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Figure 1 Proposed life cycle for CCA treated wood Introduction The service life of wood treated with CCA (Chromated Copper Arsenate) may be 30 years or even more due to the strong fixation of CCA in the wood. The strong fixation also means that when the wood is removed from service, a large proportion of the copper (Cu), chromium (Cr) and arsenic (As) is still present and will enter the waste stream unless actions are taken to prevent this. The amount of treated wood being removed from service is expected to increase dramatically over the next few decades, making an environmentally safe handling of the wood desirable. In figure 1 a proposed life cycle for CCA-treated wood is presented. The CCA treated waste wood is chipped and the Cu, Cr and As are removed using electrodialytic remediation. Afterwards the wood may be used as bio fuel since it no longer contains CCA, thereby utilising the energy resource of the wood. The removed Cu, Cr and As may be used for the production of new CCA. Since the use of CCA is being restricted in most of the world, the metals may be used in other parts of the industry instead or stabilized for safe disposal. Electrodialytic remediation is a method developed and patented at the Technical University of Denmark (DTU). Initially the method was developed for removing heavy metals from polluted soil. The method uses a direct electric current as a cleaning agent and combines it with the use of ion exchange membranes to separate the electrolytes from the soil. Good results have been obtained, and subsequently the method has been tested on a wider range of materials including fly ash, sludge, harbour sediments and impregnated waste wood. In laboratory scale experiments CCA-treated waste wood has been remediated both as sawdust and wood chips with encouraging results. In sawdust app. 95% Cu, 90% Cr and more than 96% As


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Figure 2 Schematic presentation of an electrodialytic cell. Compartment I and III is the anode and cathode compartment respectively, the wood chips are placed in compartment II. AN: Anion exchange membrane, CAT: Cation exchange membrane has been removed [1] and in remediation of wood chips, removal results of more than 90% Cu and app. 85% of both Cr and As has been obtained [2]. Based on the good results obtained in the laboratory, the upscaling of the electrodialytic remediation has now been started. In the experiments presented here, between 94 kg and 469 kg wood chips was used in each experiment, compared to the 50-70 grams used for experiments in laboratory scale. Electrodialytic remediation (EDR) EDR uses a direct electric current as a cleaning agent and combines it with the use of ion exchange membranes to separate the electrolytes from the wood. The laboratory cell consists of three compartments: an anode compartment (I), a cathode compartment (III) and a middle compartment (II) containing the wood chips (figure 2). The catholyte is separated from the middle compartment by a cation exchange membrane, a membrane that only allows positive ions – cations - to pass. The anolyte is separated from the middle compartment by an anion exchange membrane, a membrane that only allows negative ions – anions- to pass. When an electric potential is applied to the electrodes, the current in the cell will be carried by ions in the solutions. Accordingly Cationic species will migrate towards the cathode and anionic species will migrate towards the anode. With ion exchange membranes placed as described above, no current carrying ions can pass from the electrode compartments into the middle compartment, while ions can be transported from the middle compartment into the electrode compartments. In this system the current is thus prevented from carrying highly mobile ions from one electrode compartment through the middle compartment into the other electrode compartment. Furthermore competition between such highly mobile ions from the electrode compartments and the ions in the middle compartment is avoided. The electrodialytic remediation method is described in further details in [3] & [4]


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Experimental Wood The wood used in the experiments was supplied by RGS90, the largest recycling company in Denmark. From a large pile of demolition wood waste app. 10 m3 of impregnated wood was collected. By visual inspection it can be very difficult to see if old (weathered) wood is impregnated or not, therefore Chromazurol S, a colour reagent turning blue in contact with Cu was used to identify the impregnated wood. After sorting, the wood was chipped and divided into three size fractions (< 2cm, 2-4 cm and > 4cm) by sieving. In table 1 the mean concentration of Cu, Cr and As in the wood is given. Table 1 Mean Concentration ±95% CL of Cu, Cr and As in Waste Wood

ppm (mg/ kg wood) [Cu] 1279 ± 66 [Cr] 1334 ± 91 [As] 837 ± 114

Mean values are based on 179 samples for Cu and Cr and 95 samples for As. Pilot plant

Figure 3 The pilot plant in use. Wood chips in yellow plastic nets are placed between collecting units, where the Cu, Cr and As from the wood is collected. The end units contains the electrodes, and are named electrode units.


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A pilot plant has been designed for the remediation of up to 2 m3 treated wood waste. Figure 3 shows the pilot plant in use. It consists of a box that is app. 3 meter long, 1 meter wide and 1 meter high. Inside the box, there are ribs for every 35 cm and at these ribs it is possible to place a collecting unit or an electrode unit. When the full capacity of the plant is in use, the electrode units are placed in each end of the box, thereby giving a distance between the electrodes of 3 meters. The electrode units may also be placed at the ribs, thereby allowing the distance between the electrodes to vary from 30 cm to 3 meters. The pilot plant is in principle only an upscale of the laboratory set up, but some adjustments have been made in the up scaling. Due to the larger size, the distance between the electrode compartments (where the ions are collected in laboratory scale experiments) may become a limiting factor on the remediation time or efficiency. To compensate for this, collecting units are introduced. Collecting units are placed between the electrode units and have a cations exchange membrane on one side and an anion exchange membrane on the other side. The membranes make it possible to trap the ions inside the units. By introducing the collecting units, the distance the ions have to travel before being captured can be reduced to 30 cm. The amount of wood to be treated may vary between app. 300 l and 2 m3. A total of seven pilot plant remediation experiments are presented here, and in table 2 the experimental conditions for the experiments are outlined Table 2 Experimental Conditions. Exp. 1 Exp. 2 Exp. 3 Exp. 4 Exp. 5 Exp.6 Exp. 7 Electrode distance (cm)

60 60 60 60 90 150 270

Wood (kg) 94 106 97 99 178 248 469 Duration (days)

11 11 21 15 15 21 21

Wood fractions

M M M M F/M/L M F

Collecting units

1 0 1 1 2 4 8

Current (A)

1.4-2 2 2-5 0.2-3 2-3 2-3 1-1.5

Voltage (V)

24-25 14-18 30-58 14-60 23-29 40-63 23-39

Additive Water Water Water 5% oxalic acid

Water Water Water

Soaking solution /duration (hours)

5% oxalic acid/48

5% oxalic acid/48

0,5 M H3PO4/18 5% oxalic acid/24

- 0,5 M H3PO4/18 5% oxalic acid/24




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In Exp. 4 oxalic acid was used as electrolyte solutions. In all other experiments 0.01 M NaNO3 was used. Wood fractions: Fine (F) <2 cm, Medium (M) 2-4 cm, Large (L) >4 cm. In all the experiments the current strength was kept as high as possible. In exp. 1 and 2 the max current strength possible was 2 A. For exp. 3-7 the power supply was replaced and the max. current strength was 5 A. In all experiments the current strength was initially kept constant, but due to increasing resistance the current strength had to be reduced during the experiments. In all experiments but exp. 4, the wood was soaked before remediation. After soaking the wood was placed in the pilot plant and covered with tap water and the current was applied. In the electrode units and collecting units 0.01 M NaNO3 was circulated. During the remediation, the pH was kept below pH 2 in the units to prevent precipitation. After remediation the distribution of Cu and Cr was measured in all seven experiments. The content of Cu and Cr was measured in the soaking solutions, the units, in the middle compartments and in the wood. Wood samples were analysed using microwave assisted acid digestion and the concentration of Cu and Cr was measured on AAS. The distribution of As was only measured in exp. 3 and exp. 6 due to the fact that the analysis had to be made outside the department and at high costs. Results The influence of different parameters on the remediation result has been investigated. The interpretation are here based on only seven experiments in total, ad no two experiments are alike. It is therefore emphasised that it is to be regarded as tendencies rather than definite conclusions on the matter of remediation in larger scale. In figure 4 the concentration of Cu, Cr and As in the wood after remediation is shown.

0

200400

600

800

10001200

1400

1600

1 2 3 4 5 6 7

experiment

ppm

CuCrAs

Figure 4 The concentration of Cu, Cr and As in the wood after remediation. Concentration of As is only measured in exp. 3 and exp. 6. Horizontal lines indicate initial concentration.


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As seen in figure 4 the content of all three metals have been reduced in the wood in all seven experiments. In the following sections the results are discussed in relation to different process parameters. Collecting Units In experiment 1 and 2 the setup is similar except for the use of a collecting unit in exp.1. The purpose was to illustrate the influence of the collecting unit on the remediation by comparing the two experiments. In figure 4 the concentration of Cu and Cr in the wood after remediation is illustrated by comparing exp. 1 and 2. It seems that the remediation of Cu is improved by the use of a collecting unit to shorten the way the ions have to travel before being collected. On the other hand, no effect is seen for Cr. To further investigate the differences in Cu remediation, the distribution of removed Cu after remediation in the two experiments is compared in figure 5. As can be seen in figure 5, a larger amount of Cu was removed in the experiment where a collecting unit was placed (exp. 1). The amount of Cu found in the units after remediation is more than three times larger in experiment 1 and the amount of Cu present in the middle compartments is higher in exp. 2, where the ions have to travel a greater distance before being captured in a unit. The reason for the large difference in Cu removal is not connected with the use of a collecting unit alone. In stead it may be connected with the fact that the soaking liquids from exp. 1 were reused in exp. 2. The Cu removed during soaking is more than four times larger in exp. 1. The possibility of reusing soaking solutions have been tested in laboratory scale and the results (not shown) indicated that it may be used up to 4 times without any influence on the remediation efficiency. Thereby no influence by the reuse of the soaking solution was anticipated. However, the apparent reduced removal of Cu during soaking, when the soaking solution has been used before seems to point in the other direction. Further investigation is needed to verify if the reuse of soaking solutions have an influence on the remediation efficiency in larger scale. For the present series the soaking solutions has been used and reused three times in total in all experiments except exp. 1 and 3.

0

5000

10000

15000

20000

25000

30000

35000

soaking units middlecomp.

total

mg

Cu Exp. 1Exp. 2

Figure 5 Distribution of removed Cu in experiment 1 (with collecting unit) and experiments 2 (without collecting unit). The term “units” in the figure covers both collecting unit and electrode units.


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Soaking In exp. 4 the wood was not soaked before remediation, but placed directly in the pilot plant. Oxalic acid was used as an additive in the middle compartments and in the units. The experiment had to be stopped after 15 days because of technical problems. The resistance increased dramatically, forcing the current strength to a value below 0.2 A. It was later discovered that the anode was broken. During the experiment the current strength had to be decreased due to extreme gas evolution in the cathode compartment that resulted in malfunction of the circulating pump. As seen in figure 4 the remediation of Cu was greatly reduced in this experiment (exp. 4) compared to exp. 1 where the oxalic acid was used in the soaking procedure, and not during the electrodialytic remediation process. In the remaining experiments, soaking was used. Two different soaking solutions were tried in this series. In the first two experiments oxalic acid was used, and in the subsequent experiments dual soaking in phosphoric acid and oxalic acid was used. The change in soaking solution was based on a series of laboratory experiments with different acids and combinations of acids, and the use of phosphoric acid, followed by oxalic acids gave the best results in laboratory scale. By comparing exp. 1 and 3 it seems that the change in soaking solution had a profound impact on the remediation (see figure 4). In figure 6 the distribution of Cu and Cr after remediation are shown for exp. 1 and exp. 3. The remediation is increased for both metals by the dual soaking and larger proportions have been removed during soaking in exp. 3 compared to exp. 1 Size Fraction In exp. 5 all three wood size fractions have been remediated at the same time. The different sizes where evenly distributed all over the pilot plant and after remediation, 24 wood samples from each of the three fractions where analysed for Cu and Cr. The concentration of both metals was significantly lower in the fine fraction than in the medium and large fraction, indicating that it may

0%

20%

40%

60%

80%

100%

Exp. 1 Exp. 3 Exp. 1 Exp. 3

Cu Cr

soakingMiddle comp.coll. Unitanolytecatholytewood

Figure 6 Distribution of Cu and Cr after remediation in exp. 1 (oxalic acid soaking) and exp. 3 (dual soaking of phosphoric and oxalic acid).


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be easier to remediate wood chips with a size < 2 cm. The concentration of Cu was reduced to 127 ± 12 ppm in the fine fraction, 368± 67 ppm in the medium fraction and 515 ± 176 ppm in the large fraction. Overlap of the 95% CL in the medium and large fraction indicates that the difference between these two fractions is not statistically significant. However the relatively high 95% limits in the same fractions indicate a high variation. For Cr the variation is high in the large fraction where the concentration after remediation was reduced to 771 ± 294 ppm. In the medium fraction the concentration of Cr was 629 ± 95 ppm and 462 ± 35 ppm in the fine fraction. As for Cu, the concentration of Cr is significantly lower in the fine fraction, compared to the medium fraction, indicating an easier remediation of the fine fraction. The high variation in the large fraction does not make the difference between the Cr content of this fraction and each of the other two fractions statistically significant. Electrode Distance The electrode distance has been varied between 60 cm and 270 cm, but to evaluate the influence of electrode distance on the remediation exp. 3 and 6 are used. The two experiments are of the same duration, and the same wood size fraction and soaking solution was used in the two experiments. The electrode distance was 60 cm in exp. 3 and 150 cm in exp. 6. In figure 4 it is seen that increasing the electrode distance by factor 2.5 results in a decrease in the remediation of app. the same magnitude for both copper and chromium. The same is not true for the remediation of As. In both experiments more than 95% of the As has been removed. The limiting factor when increasing the electrode distance may be the current strength and voltage drop. It is likely that the increase in amount of wood and electrode distance may require an increase in electric charge and voltage drop. This was not possible in these experiments due to the limitations of the power supply and the all ready mentioned fact that the current was kept as high as possible in all experiments. In exp. 6 only the medium fraction was used and in exp. 7 only the fine fraction was used. In figure 4 it is seen that the remediation in the two experiments seems unaffected by the fact that the electrode distance is 150 cm in one experiment and almost twice as long (270) cm in the other experiment. The reason for this may have more to do with the difference in wood fraction as discussed earlier than on the difference in electrode distance. Discussion A series of seven electrodialytic remediation experiments has been presented here and different process parameters have been investigated. Due to the limited amount of experiments it is important to emphasis that the results may be viewed as trends or indications rather than absolute results. The use of collecting units to shorten the way the ions have to travel before being captured proved useful, especially in exp. 6 and 7 where the electrode distance was 150 cm and 270 cm respectively. In all but one experiment the wood was soaked before the electrodialytic remediation process. When soaking was not used, the remediation efficiency decreased and in addition to that, major technical problems were encountered. The purpose of soaking is to remove the most available Cu, Cr and As first and then use the electric current to remove the less available fractions. Soaking solutions contain acid and/or complexing agents in the form of ions that will move in the electric field. If the oxalic acid or phosphoric acid was used directly in the pilot plant a large proportion of


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the current would be wasted on removing these ions from the middle compartment instead of Cu, Cr and As. By introducing soaking, the wood and CCA comes into contact with the acids prior to that, and the concentration of the acid (ions) in the electrodialytic remediation is reduced. In this series the soaking in phosphoric acid followed by soaking in oxalic acid proved to be most effective. The reuse of the soaking solutions was initially presumed to have no influence on the remediation, but when the exp. 1 and 2 was compared it seems that the removal of especially Cu during soaking was reduced. It is possible that the soaking solutions have become saturated and that some of the Cu precipitated as CuOx during the soaking in exp. 2. Thereby the amount of Cu removed during soaking in exp. 2 may be underestimated in figure 5. Even if this is the case, the measured concentration in the wood after remediation is still higher in exp. 2 than exp. 1 indication that the remediation in total was more successful in exp. 1. It may also be interpreted as an indication of precipitation of CuOx in or on the wood chips, and maybe that the precipitate dissolves to a certain extend during the remediation where the wood chips are covered with tap water. The main conclusion based on these experiments is that the soaking is desirable for the process, but the reuse of the soaking solutions has to be investigated further. Three different wood size fractions have been remediated and the results indicate that the remediation efficiency increases with decreasing wood size. The remediation of wood chips < 2 cm was significantly better than the remediation of the larger wood sizes. Further investigations are needed to locate the reason but lack of total soaking of the inner part of the larger fractions may be part of it. If the wood is not soaked all the way through, then it is not expected that the current will pass here, since this is believed to be the part of the chip with highest electric resistance. If the soaking solution does not reach the inner part and the current does not pass though, then the CCA will not be removed. To further investigate this possibility, laboratory experiments are planned using vacuum soaking of the wood to insure total soaking prior to the remediation. In the upscaling process the electrode distance was one of the main factors to be evaluated. The results obtained here indicated that the remediation efficiency decreased with increasing electrode distance. The main problem in estimating the influence of the electrode distance is that the current and voltage drop was similar in all experiments since the current was kept as high as possible in the experiments. It is believed that the voltage drop has an influence on the remediation efficiency and since the voltage drop is similar in the two extremities it may not be comparable. Instead a power supply with a higher voltage range is needed for these experiments, to ensure that the V/m may be the same in the experiments to be compared. The use of collecting units is expected to insure that the remediation time is unaffected by the electrode distance, since the distance the ions have to travel before being collected may be the same. This theory has to be verified with the above mentioned power supply. The highest removal of both Cu, Cr and As was obtained in exp. 3, where 87% Cu, 81% Cr and more than 95% As was removed during remediation. In this experiment the electrode distance was 60 cm and just under 100 kg wood chips of medium size fraction (2-4 cm) was used. When the electrode distance was increased, the removal of Cu and Cr was decreased. In exp. 6 where the electrode distance was 150 cm and 250 kg wood was remediated, 58% Cu and 54% Cr was removed. On the other hand the remediation of As didn’t decrease with increasing electrode distance. In the same experiment 96% As was removed. This is a very encouraging result since As is the CCA component of most concern and the main reason why incineration of CCA-treated wood is not allowed in Denmark. In the life cycle presented here, the wood is used as a bio fuel. In order


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to use CCA-treated waste wood, it is assumed that the concentration of Cu, Cr and As must be reduced to practical zero value first. Instead it is possible that remediated wood, where As has been removed and the concentration of Cu and Cr are reduced can be used in a conventional waste incineration plant. Thereby the energy resource of the wood may still be utilised. Acknowledgements The financial contribution of the LIFE financial instrument of the European Community are greatly appreciated. References [1] Ribeiro, A.B. et al. (2000) Electrodialytic removal of Cu, Cr and As from chromated copper arsenate-treated timber waste. Environmental Science and Technology (34) pp. 784-788 [2] Kristensen, I.V. et al. (2001) Electrochemical removal of Cu, Cr and As from CCA-treated waste wood. 3rd Symposium and Status Report on Electrokinetic Remediation, Karlsruhe 18.-20. April 2001. Proceedings.’ [3] Ottosen, L.M. et al. (1997) Electrodialytic remediation of soil polluted with copper from wood preservation industry. Environmental Science and Technology (31) pp. 1711-1715 [4] Hansen, H.K. et al. (1999) Electrodialytic rmediation of soil polluted with heavy metals, key parameters for optimization of the process. Trans IchemE (77) part A, pp. 218-222


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Recovery and Reuse of The Wood and Chromated Copper Arsenate (CCA) from CCA Treated Wood – A Technical Paper

Kazem Eradat Oskoui ABSTRACT Chromated Copper Arsenate (CCA) impregnated waste materials are generated during the treating process and from treated wood removed from service. This material is currently land-filled, which creates concerns because of the bulky nature of wood and the potential for leaching of some Cr, Cu and As components of the preservative. A recycling process has been developed whereby up to 99% of the CCA components are extracted from the waste material. CCA treated wood waste is chipped and reacted with a proprietary lixivient which mobilizes the CCA components and brings them into solution. The Aclean@ wood and other residues pass the TCLP test and can be reused for paper or composite products or disposed of in a normal landfill. The pregnant solution is then passed through another proprietary process to separate the CCA components from the Clean water. The extracted solution, containing Cr , Cu and As can be reprocessed to a condition where it is compatible with CCA treating solutions and could be re-used for treating new wood. Keywords: Arsenic Contamination, CCA Treated Wood, Wood Disposal and Recycle, CCA Extraction Director, Engineering Services, West Central Environmental Consultant, Inc. 11253 - 91st Avenue North, Maple Grove MN55369. Tel. 763 425 7496 Fax. 763 425 7235 e-mail: [email protected]


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INTRODUCTION There was a rapid expansion of the use of chromated Copper arsenate (CCA) wood preservative between 1975 and 1990, as a result of high consumer acceptance of the product for decks, fences and other residential applications. It is therefore expected that in the next two decades, the amount of CCA treated wood that will be removed from service will expand greatly. Approximately 65.3 Million kilograms (144 Million pounds) of chemicals were used in US during 1997 to produce 12.7 Million m3 (450 Million ft3 ) of treated wood products (1). Currently, American and Canadian environmental regulations allow the disposal of CCA treated lumber in landfills, and most of the out-of-service or Aspent@ treated wood ends up in landfills. In the future, treated wood will use increasing volumes of landfill space. In addition to leaching and environmental impacts, there are considerable human and animal health implications associated with the use of CCA treated wood. According to a document published by Origen Network (2), A It is incredible, but a single 12 foot 2 x 6 contains about 27 grams of Arsenic - enough Arsenic to kill 250 adults.@ In order to avoid the adverse environmental impact of increased CCA treated wood waste as well as its impact on human and animal health and, reduce the burden on the nation’s landfills, finding an economical, environmentally friendly and, cost effective recycling and disposal method is becoming more important everyday. A practical, simple and cost effective process for removing up to 99% of the CCA components from CCA contaminated waste is described LITEATURE CITED During the past few decades, several attempts been made to propose a cost effective and environmentally sound process for recycling the CCA contaminated waste products. The literature describing the disposal methods for the CCA contaminated waste is voluminous. A simple search using the keywords “CCA Disposal” resulted in 4985 returns in the World Wide Webb. Similar search using “CCA Extraction” resulted in 2896 returns. Since it is impractical to present and cite all the literature relevant to this subject here, only a few are mentioned. Omission of any such work does not diminish its importance or relevance to this subject. Extensive and exhaustive review of the CCA issue has been described in numerous articles and publications by Florida Center for Solid and Hazardous Waste Management (3). Several procedures such as acid extraction, burning, pyrolysis, re-using in composite wood products, and biological detoxification have been proposed. Among these processes extraction of CCA components have been both prominent and most promising. Extraction alone (4,5) and extraction combined with biological detoxification (6) have produced substantial removals of (up to 99%) the CCA components from the CCA contaminated waste. Although the extraction have provided viable results, very limited cost information is available on these process. Some researchers estimate the extraction cost at over US$300 per metric ton of wood extracted (5). Pyrolysis (7) has also been proposed as a process for recycling CCA contaminated wood. Although the technology has shown satisfactory CCA components removal efficiency, no cost information has been provided.


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OBJECTIVES The main objective of this article is to introduce a cost effective, simple, practical, and environmentally benign technology which can be used by waste management industry to remove CCA components from CCA contaminated waste products prior to disposal or recycling. MATERIALS AND METHODS Samples of commercially available CCA pressure treated wood (0.25 pcf) was obtained and ground to a mean particle size of 10 to 20mm. The protocol adopted in the previous bench scale study (not published) was used for the data reported here. Mean particle sizes selected are much larger than those used in the previous study. To obtain a baseline characterization of the contaminated wood, a 100g dry treated sample ( sample ID: SW1) was sent to the laboratory for analysis to determine the Cr, Cu and As contents in the wood. A series of proprietary compounds “lixivients” were used to demobilize the CCA components in the wood into solution. These compounds are non-corrosive, organic, and biodegradable proprietary compounds which can extract CCA salts from spent wood or sludge with a very high efficiency. The five different protocols used are identified as follows:

$ WT1WH $ WT2ED-H $ WT3ED-HD $ WT4ED-D $ WT5ED-A

Each protocol represents a specific temperature-lixivient-wood combination. Intellectual property protection restricts further explanation of these combinations. The extraction is a 4 hour process which consists of the following steps:

• Particle size reduction • Hydrolysis and reaction • Settling • Decanting • Solids Separation • Water treatment

Particle Size Reduction

Waste wood is ground or chipped to a mean particle diameter of about 10 to 20 mm (1/2 to 1 inches) using a commercial grinder or chipper. Size reduction can be conducted as needed or in a batch form where ground wood is stored in a covered area for use in the extraction process.


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5.1 Hydrolysis and Reaction Size reduced particles are conveyed to the reaction tank. In this tank water is introduced while is being mixed with appropriate amount of lixivient. Typical water:solids ratio is 0.25:1 by volume. Introduction of heat has shown an increase in the performance of the lixivient. An optimum (economical) temperature of 40oC has yielded the best extraction efficiency. Upon introduction of the water and lixivient, the mixture is agitated by mixing air which also introduces heat to the mixture to maintain the desired temperature. This process continued for 2 hours.

Settling

After two hours the mixture is allowed to settle where the clean wood is settled at the bottom of the tank and pregnant solution (solution containing the CCA components) is stratified at the top. Setting is typically carried out over a one hour period.

Decanting The supernatant is decanted using a floating decanter. This solution has a light green color and contains a mixture of lixivient and CCA components. Up to 3000 ppm of As, 2000 ppm Cu and 3000 ppm of Cr was measured in the decanted solution.

Solids Separation

Upon Completion of the decanting process, the settled solids are conveyed to a screw press which separates the solids from the residual liquid. This process removes the most of the residual contaminants from the solids thus leaving a clean semi-dry (55% to 65% moisture content) wood cake which can be used for reprocessing or disposal.

Water Treatment

Both the decanted water and the pressate from the screw press are directed to the water treatment plant where the CCA component are separated from the lixivient using a patented technology. The technology uses a zirconium based exchange medium with strong affinity to CCA components. Upon saturation of the medium, it is regenerated. CCA components are separated in a concentrated sludge form.

ECONOMIC ANALYSIS Despite its failure of TCLP tests, CCA contaminated waste is currently exempted from the Environmental Protection Agency’s hazardous waste characterization. Due to this exemption, these wastes can be disposed of in Construction and Demolition (C&D) landfills in most States in the US and Canada. Most European countries and other industrial nations as well as some States in US (Minnesota) however, have more stringent rules governing these wastes. The exemption from hazardous waste classification has considerably reduced the cost of disposal of these wastes in the US and Canada and have removed the incentive from finding a more environmentally benign disposal process. Disposal cost varies from as low as $20/ton in Midwestern States to as high $160/ton in some East Coast and California Cities. These costs of course, do not include the possible environmental clean-up costs, future liability litigation costs as well as any potential human and animal health costs. Individual and class action law suits are increasing which make the landfill owners more cautious in accepting CCA contaminated waste products. For example most landfills


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in the Twin Cities of Minneapolis and St. Paul area have started refusing to accept CCA contaminated waste products fearing future liabilities. The system described here is simple, practical, and environmentally sound as well as economical and cost effective. The cost of processing one ton of CCA contaminated waste wood is between US$120 to US$150. This cost may seem high when compared to low cost of C&D landfill tipping fees but once all the other costs as describe above are included in the equations, it becomes more comparable to the actual cost of lanfilling. This cost does not include the revenue from the recycled wood which may be between US$15 to US$25/ton depending on the final use. There is also a small amount of income (US$6/pound) from the recovered CCA components.

RESULTS AND DISCUSSION

Extraction Results Following the completion of the reaction process, a mixed sample of cleaned wood and the liquid containing the extracted solution was sent to the Laboratory for analysis. Solution from each sample was strained using 1F screen and solids were dried to be used for testing. The filtrate was analyzed for Cr, Cu, Cd, and As. The dried baseline sample was also tested for these elements. Results are tabulated in Table 1. The baseline sample indicated no trace of Cd thus, subsequent samples were not tested for this elements. As it can be seen from the table, there is a considerable amount of Cr, Cu, and As in the initial wood sample. The values are expressed in mg/kg or parts per million (ppm). Amount of Arsenic in the base sample (SW1) was 3020 ppm or 0.3% , Chromium was 3380ppm or 0.34%, and Copper was 1991ppm or 0.2%. These levels are higher than the allowable level in the environment by several orders of magnitude. Results from the wood samples indicate about 80% to 90% removal of Arsenic, 78% to 82% removal of Chromium and 95% to 99% removal of total Copper concentration. TABLE 1. Sample Extraction Results (solids) Sample ID Arsenic Chromium Copper

Baseline

Value

Removal

Baseline

Value

Removal

Baseline

Value

Removal

ppm ppm % ppm ppm % ppm ppm % WT1WH 3020 203 93.28 3380 525 84.47 1991 88.73 95.54 WT2ED-H 110 96.36 309 90.86 32.83 98.35 WT3ED-HD 118 96.09 308 90.86 04.88 99.75 WT4ED-D 374 87.62 375 90.89 78.50 96.06 Average 201 93.34 379 89.27 51.24 97.43 As it can be seen in Table 2., levels of Arsenic in the filtrate ranged from 22,800 parts per billion (ppb) to 57,600 ppb considering that the current drinking water Arsenic level is 50ppb which is under revision and may be reduced to as low as 10ppb. Copper levels in the filtrate was in


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general 3 to 4 times of the Arsenic except in one sample where Copper concentration was slightly less than the Arsenic concentration. Levels of the Chromium in the solution were about 1/4 of the levels of Arsenic. This is due to the fact that Chromium is less soluble than the other two elements at a give pH level. These concentration levels will vary with varying wood:liquid ratios during the extraction process. TABLE 2. Sample contaminant concentration levels in the extracted solution

Sample ID Contaminants (mg/l) Arsenic Chromium Copper WT1WH 22.80 4.00 79.00 WT2ED-H 29.80 5.67 69.60 WT3ED-HD 57.60 19.60 40.00 WT4ED-D 24.00 6.86 120.00

Toxic Characteristic Leachability Process (TCLP) Test Since the cleaned wood still contained some residual CCA compounds, additional tests were conducted in order to determine the leachability of cleaned wood. A series of cleaned samples were then tested for TCLP (Toxic Characteristic Leachability Procedure) by EPA SW846-1311 and SW846-351 method. Average TCLP levels for the cleaned wood samples were 0.737 mg/kg for Arsenic, 0.06 mg/l for Copper and 0.18 mg/l for Chromium. These levels are well below the maximums levels set for hazardous waste characterization for these elements.

CONCLUSIONS The results of this study and previous bench scale studies indicate that, in a suitable environment, almost 90% of the CCA components leach to the environment in less than 2 hours. It also indicates that most of these components (up to 99%) can be removed from the waste stream before its disposal into the environment. This can be done economically, safely and in an environmentally sound manner. REFERENCES

1. American Wood Preserver’ Institute, 1997. 1996 wood preserving industry production statistical report. American Wood Preserver’ Institute, Fairfax, Virginia.

2. Martin, R., 2002. Arsenic and CCA Wood. Published at http://www.origen.net/ccawood.html by Richard Martin of 2525 Hartford Road, Austin, Texas, USA 78703.

3. Solo-Gabriele, H. 1999. Disposal of CCA treated wood: An evaluation of existing and

alternative management options. Report#99-6. Florida Center for Solid and Hazardous Waste


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Management. 2207 NW 13th Street, Suite D. Gainesville, FL 32609. Also Available at:

http://www.ccaresearch.org/publications.htm.

4. Cooper, P.A. and Y.T. Ung. 1989. Assessment of preserved wood disposal practices. Report prepared for Environment Canada. Contract No. KE 144-8-2015, 85 pages. Also presented at: http://www.awpa.com/papers/Cooper_2003.pdf

5. Cooper, P.A., T. Ung, J.P. Aucoin and C. Timusk. 1996. The potential for reuse of preservative treated utility poles removed from service. Waste Management and Research. 14:263-279.

6. Clausen, Carol A. 2000. CCA removal from treated wood using a dual remediation process. Waste Manage Res. 18: 485–488. Printed in UK. Also Available at. http://www.fpl.fs.fed.us/documnts/pdf2000/claus00d.pdf

7. Helsen, L., Van den Bulck, E., Van den Broeck, K. and Vandecasteele, C. 1997. Low temperature pyrolysis of CCA treated wood waste: Chemical determination and statistical analysis of metal in- and output; mass balances. Waste Management, Vol 17, No 1, pp.79-86. Also presented at: http://people.mech.kuleuven.ac.be/~lieve/publications/1997P15.pdf


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Bioremediation of waste copper/chromium treated wood using wood decay fungi

MIHA HUMAR*, FRANC POHLEVEN,

Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Slovenia, SI-1000 Ljubljana

* Phone: (+38614231161) Fax: (+38614235035) Email: [email protected] SAM O. AMARTEY

Forest Products Research Center, Buckinghamshire Chilterns, University College, UK, HP11 2JZ

Abstract

The expected service life of copper/chromium (CCA or CCB) treated wood is about 20 - 50

years. After that period, the treated wood is discarded as waste. Due to the toxic elements in such treated wood, burning and landfill disposal are not considered as environmentally friendly solutions. Extraction and recycling of the preservatives from the waste wood is a much more promising and environmentally friendly solution, which is based on the conversion of the fixed biocides in the wood into soluble forms which can subsequently be leached out of the wood. In order to elucidate the mechanism of this process, copper/chromium treated wood samples were leached after exposure to copper tolerant (Antrodia vaillantii and Leucogyrophana pinastri) and copper sensitive wood decay fungi (Gloeophyllum trabeum and Poria monticola). Furthermore, the ability of fungal hyphae to penetrate and overgrow the wood samples was investigated using following methods. Small stick of unimpregnated wood (r = 1.5 mm, l = 25 mm) was inserted into a hole, bored in the center of the samples, and after that sealed with epoxy sealer. Sterilized, leached and non-leached impregnated and unimpregnated specimens were exposed to brown rot fungi for one, two, five, eight or twelve weeks. After respective period, the inserted wood pieces were removed form the specimens and put onto nutrient medium containing petri dish. Possible growth of the hyphae from those pieces was than visually determined. Rate of colonization was determined by measurement of CO2 production as well. The fungal growths were stimulated by immersing of the specimens into aqueous solution of glucose or corn step liquor prior to exposure to fungi. Followed exposure the fungi, specimens were leached and concentrations of copper and chromium leached were determined. Afterwards, EPR measurements of leached and non-leached samples were performed in order to determine the paramagnetic complexes that were formed. The fastest colonization of impregnated wood was found at copper tolerant A. vaillantii. Addition of nutrients onto the surface of the specimens increased the colonization of the specimens. All wood decay fungi investigated as copper tolerant as well as copper sensitive increased heavy metals leaching from the treated wood. These fungi influenced the de-fixation process via oxalates formation. EPR measurements indicates that the transformation of copper into copper oxalate by the fungi was found to be essential but not the only mechanism responsible for copper tolerance by these fungi However, from our results, it seems that other acids were also responsible for increased copper and/or


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chromium leaching. These results are important in elucidating copper toxicity by wood decay fungi and at using of these fungi for bioremediation of treated wood wastes. Keywords: Copper tolerant fungi, Waste treated wood, Remediation, Wood colonization, Detoxification, leaching, EPR, INTRODUCTION CCA or CCB as wood preservatives are the most important wood preservatives, as CCA and CCB-treated lumber have been proven to be effective in deterring insects and fungal decay. For example, approximately 212 million m3 of CCA treated lumber was produced annually in the USA alone [i]. Additional 1.5 to 2.0 million m3 of wood containing about 1000 tons of chromium and 600 tons of copper are preserved annually in the area of the former Federal Republic of Germany [ii]. We can foresee huge amounts of preserved wood removed from service in future years, in most of developed countries. The presence of copper and chromium, as well as arsenic causes problems in the later disposal of this impregnated wood. Because of the toxic elements in such treated wood, it is very important to find an effective and environmentally sound recycling solution for preserved wood when removed from service. Landfill disposal is not an environmentally sound option since it only postpones dealing with the problem to future generations. Furthermore, the heavy metals in the wood may diffuse into the surrounding soil, resulting in significant environmental damage [iii]. In addition, capacities of special dumps are limited and public approval for new facilities is extremely low. Burning of CCA/CCB waste preserved wood is only permitted in approved incinerators under extremely controlled conditions in many countries, since emitted gases have been found to contain high concentration of arsenic compounds [iv]. The cost of destruction, such as by incineration, can be very expensive: about 500 EUR/t [v]. A number of environmentally sound disposal options have been investigated in recent years, including biological methods using either copper tolerant fungal strains [ii] or bacteria [i]. The principle underlying methods is to convert the insoluble heavy metals in the waste wood into a soluble form through acidification with organic acids. The soluble heavy metal complex can then be leached from the wood. Thus, both the remediated wood fiber and the metals can be reclaimed and recycled. The most important acid involved in this process is oxalic acid [i]. Oxalic acid is a small organic acid with two low pK values (pK1 = 1.27; pK2 = 4.26) [vi]. It is often produced by brown rot fungi in great quantities [vii,viii,ix] and is associated with brown rot colonization of wood [ x ]. The most efficient oxalic acid producers and consequently the most tolerant fungi include the genus Antrodia [xi]. Other wood decaying fungi produce significantly less oxalic acid. Instead of oxalic acid, these fungi excrete other organic acids in order to optimise pH value of the substrate [viii,xii]. Oxalic acid can react with insoluble chromium in wood to form chromium oxalate, which is soluble and can be leached out of wood. On the other hand, copper oxalate, which is formed between copper and oxalic acid, is insoluble and can only be leached with an ammonia solution [iii,ix]. The aim of this study was to elucidate the ability of a selected copper tolerant fungal strain as well as copper sensitive ones to colonize wood preserved with copper and chromium


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based preservatives and to describe their influence on leaching of copper and chromium from treated wood samples. Finally, changes to the active ingredients (Cu, Cr) in the treated wood after exposure to the fungi, and leaching, were studied using electron paramagnetic resonance (EPR). MATERIALS AND METHODS

Preparation of the samples

Norway spruce (Picea abies) samples of dimensions (15 × 25 × 50 mm) were vacuum impregnated with 5 % CCB solution according to the EN 113 procedure [xiii]. The treatment resulted in a preservative uptake of about 18 kg/m3. The samples were later conditioned for four weeks, the first two weeks in closed chambers, the third week in half closed and the fourth week in open ones. The conditioned samples were then oven dried (75 °C) for five days in order to ensure complete reduction of chromium. Following conditioning, the samples were leached according to the EN 84 procedure for 14 days [xiv]. Afterwards, the samples were oven dried (103 °C) and their masses were determined, then conditioned and finally steam- sterilized. Prior to exposure to the fungi some samples were immersed for five minutes to 4 % aqueous solution of corn step liquor (Sigma) or 4 % aqueous solution of glucose or to the mixture of 4 % aqueous solution of corn step liquor and glucose (Sigma) or to water only. Glucose was used as easy available carbon source and CSL as nitrogen one.

Baiting experiment

Experiment was performed according to the procedure described by Kleist and co-workers [xv]. This experiment was designed to determine whether fungal hyphae can penetrate the center of the wood sample or they can only be found in the surface region. Samples impregnated as described above, were prepared as follows prior to exposure to the fungi. Holes (diameter = 3 mm, depth = 20 mm) were bored in longitudinal direction into the center of the sample. A small toothpick was then inserted into the hole as the bait and the hole sealed with epoxy sealer, as shown in Figure 1. The epoxy sealer has no effects on fungal growth. Afterwards, the samples were sterilized and exposed to the fungi as described later. After one, two, or four weeks of exposure, the toothpicks were in carefully removed from the specimens under sterile conditions and put onto a sterilized solid nutrient medium (PDA, Difco). Any fungal growth from the sticks was monitored for a period of two weeks.


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Figure A Sketch of the specimen for baiting experiment.

Table A Brown rot fungi used. Copper tolerance is described with marks according to the results of POHLEVEN et al. (2002). Mark 1 describes the highest copper tolerance; and 5 describes the highest copper sensitivity.

Fungi Abbreviation Origin Estimated Cu tolerance

Antrodia vaillantii Pv2 University of Ljubljana ZIM L037 Cu tolerant 1

Leucogyrophana pinastri Yf Buckinghamshire Chilterns University

College Cu tolerant 2

Poria monticola Pm2 BAM 102, Germany Cu sensitive / Cu tolerant 3

Gloeophyllum trabeum Gt2 University of Ljubljana ZIM L017 Cu sensitive 5

Exposure to the fungus

Sterilized and air dried samples were exposed to the following brown rot fungi: Gloeophyllum trabeum (Gt2) (ZIM L017), Antrodia vaillantii (Pv2) (ZIM L037), Poria monticola (Pm2) (BAM 102) and Leucogyrophana pinastri (Yf) (HPT 595) [xvi]. The A. vaillantii and L. pinastri strains have been shown to be copper tolerant in previous investigations [viii,xvii]. Cultures were grown and maintained on a 3.9 % potato dextrose agar medium (PDA, Difco). Jars with PDA medium were inoculated with small pieces of fungal mycelium. One treated and one untreated wood sample was placed on a sterilized plastic grid in each inoculated jar and exposed to fungal decay for certain period of time in the growth chamber (25 °C, RH = 75 %).

Respiration measurements

Infested wood blocks were after five weeks of exposure carefully removed from the fungal mycelia and put into empty experimental jars where they were subjected to measurement of CO2 production. The jars were sealed with the ventilation lids, using silicon vacuum paste


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to enhance the seal. Afterwards the initial concentration of CO2 and the final one after one hour were measured using an equipment that consisted of membrane pump (flow rate 0.5 l/min), IR carbon dioxide sensor (0-3000 ppm, accuracy = 5 ppm) and 16-bit A/D converter for computerized data acquisition (ECHO d.o.o. Slovenia). The ECHO system was a closed-circuit system and permitted measurements of changes in CO2 concentrations over time [xviii].

Leaching procedure

Leaching of Cu and Cr from the samples was conducted according to the modified European standard EN 1250 [xiv]. Three conditioned samples per each treatment were put on a shaker and positioned with a ballasting-device. After that, 250 g of leaching solution was added. The leaching solution was replaced every 24 hours over four days. Half of the samples were later leached with aqueous solution of ammonia (cNH3 = 1.25 %) following the same procedure. Concentrations (%) of Cu and Cr in the leachates were determined using atomic absorption spectroscopy (AAS). Leached and non-leached decayed samples were oven dried (103 °C) and mass losses were determined. After drying, they were stored for EPR measurements (20 °C and 65 % RH).

Electron paramagnetic resonance (EPR) measurements

EPR experiments were performed at room temperature using Bruker ESP-300 X-band spectrometer (Microwave Frequency = 9.62 GHz, Microwave Power = 20 mW, Modulation Frequency = 100 kHz, Modulation Amplitude = 0.1 mT). Four matchstick like samples (40 × 1 × 1 mm) were cut from each wood sample and inserted one at a time into the resonator. Thus, EPR measurements of each observation were performed in twelve parallels per each treatment. The various components of EPR parameters (tensor g, and hyperfine splitting tensor A) were determined directly from the spectra, where possible for the respective paramagnetic species. RESULTS AND DISCUSSION

Colonization of the specimens

The fastest overgrowth of the control-unimpregnated specimens was by G. trabeum followed by P. monticola. Hyphae of G. trabeum reached the bait in the center of specimens after one week of exposure for two thirds of the exposed specimens. However, specimens exposed to the rest of brown rot fungi investigated apart from L. pinastri were completely colonized after two weeks of exposure. L. pinastri took more weeks to achieve 100 % colonization of the specimens (Table A). This data correlates well with the respiration measurements of the infested wood specimens. G. trabeum and P. monticola that showed the highest ability to penetrate the wood specimens produced the highest levels of CO2 after four weeks of exposure. The copper sensitive G. trabeum produced on the average, 1127 ppm of CO2 in one hour, which is


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almost double the amount produced by the copper tolerant A. vaillantii (560 ppm of CO2/h) (Table B). These results are comparable with the respiration rates described by Tavzes and co-workers [xviii] (Figure B). Addition of nutrients did not increase the ability of fungi to reach the centers of the unimpregnated samples. However, at he presence of the CSL and/or glucose even lower portion of the fungal hyphae reach the bait in the samples (Table B). Copper tolerant strain A. vaillantii needs two weeks of exposure to colonize all control specimens that were prior to exposure immersed to water only. On the other hand, only 75 % of samples that were immersed to aqueous solution of CSL and/or glucose were colonized. Similar relationship was observed at other fungal species as well. We presume that the reason for this originates in the fact, that after immersion to nutrient solution, fungi have food source available on the surface of the specimens, thus there were less need for colonization of the central parts of the wood. This presumption was further supported by respiration measurements as well (Figure B).

Table B Percentages of colonized untreated specimens exposed to the fungi for one, two and five weeks. Prior to the fungal exposure samples were immersed into water (C) or aqueous solution of glucose (G) or corn step liquor (CSL) or glucose (G) and corn step liquor (CSL+G).

Percentages of colonized specimens [%]

1 week 2 weeks 5 weeks fungus C G CSL CSL+G C G CSL CSL+G C G CSL CSL+G

Pv2 0 33 0 33 100 75 75 75 100 100 100 100 Yf 0 0 0 0 100 100 75 75 100 100 100 100

Pm2 33 33 0 33 100 100 75 100 100 100 100 100

Gt2 66 66 0 0 100 100 75 75 100 100 75 100


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Figure B Respiration of infested unimpregnated wood samples (Control) and impregnated (Treated) and specimens exposed to the fungi for five weeks. Prior to the fungal exposure samples were immersed into water (C) or aqueous solution of glucose (G) or corn step liquor (CSL) or glucose (G) and corn step liquor

(CSL+G).

Respiration measurements indicates more clearly than baiting experiment, that in some cases addition of nutrients have positive influence on fungal growth (Pv2, Yf), sometimes there were no influence (Pm2) and sometimes nutrients can even have negative influence (Gt2) on surface overgrow by wood decay fungi (Figure B). In general, samples that were immersed to glucose were more overgrown by fungi than the others. For example, fungi A. vaillantii growing on unimpregnated specimens immersed to glucose produce 744 ppm CO2/h, while during growing on specimens immersed to water the production of 505 ppm CO2/h was measured. In contrast, at the samples immersed to CSL and exposed to G. trabeum significantly less extensive surface overgrow were determined. The production of carbon dioxide by G. trabeum while overgrowing samples immersed to CSL is more than six times lower than at the ones immersed to water only (Figure b).


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Table C Percentages of colonized impregnated specimens exposed to the fungi for two, five, eight and twelve weeks. Prior to the fungal exposure samples were immersed into water (C) or aqueous solution of glucose (G) or corn step liquor (CSL) or glucose (G) and corn step liquor (CSL+G).

Percentages of colonized specimens [%] 2 weeks 5 weeks 8 weeks 12 weeks fungus

C G CSL CSL+G C G CSL CSL+G C G CSL CSL+G C G CSL CSL+G

Pv2 0 0 0 0 33 66 33 33 66 66 66 33 100 100 100 100

Yf 0 0 0 0 0 0 0 0 33 0 0 66 100 100 100 100

Pm2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Gt2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Not all the fungal isolates were able to penetrate the center of the impregnated specimens after one and two weeks of exposure. After five weeks, the first hyphae of A. vaillantii reached the bait in the center of the exposed treated specimens. However, the complete colonization were observed seven weeks later, after 12 weeks of exposure. Colonization of the impregnated specimens by the copper tolerant A. vaillantii is not surprising, as this strain was found to exhibit high copper tolerance [xvii]. First hyphae of the other copper tolerant fungi L. pinastri reached the bait in the impregnated samples after eight weeks of exposure. 100 % colonization was observed after 12 weeks of fungal overgrow. However, none of the copper sensitive fungal species did not reached the center if the impregnated specimens even after 12 weeks of the exposure. Respiration measurements were performed after 5 weeks of exposure of the impregnated specimens to fungi. Higher overgrowth of control specimens compared to impregnated ones was evident visually as well as from the CO2 measurements. The highest surface overgrowth of treated specimens was found at CCB impregnated specimens exposed to the copper tolerant A. vaillantii followed by L. pinastri. Production of CO2 from the leached impregnated specimens exposed to A. vaillantii was approximately 66 % of that from the control samples. On the other hand, exposure of the impregnated samples to the copper sensitive species G. trabeum resulted in 100 times lower CO2 production than the control ones. However, both visual and by CO2 measurement showed insignificant growth on the impregnated wood exposed to the copper sensitive P. monticola (Table ?). As well as observed at unimpregnated samples, immersion of impregnated specimens to CSL and/or glucose did not influence the fungi to reach the center of the impregnated wood block (Table C). On the other hand, immersion to nutrients significantly improve ability of fungi to overgrow the surface of impregnated specimens (Figure B). This is even more evident at copper sensitive fungal strain. At specimens immersed to water and exposed to Pm2, there was no growth observed, in contrast when the specimens were immersed to CSL and glucose, the production of 247 ppm CO2/h were determined. Although, the highest respiration rates were observed at impregnated specimens that were prior to exposure immersed to aqueous solution of CSL and glucose (Figue B). Respiration and the


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baiting results indicate that wood decay fungi are able to colonize the surface of the treated specimens when immersed to nutrients but they have difficulties to reach the center of the wood specimens.

Mass losses and leaching of the Cu and Cr from Impregnated wood

Mass losses of the impregnated samples indicated that heavy metals present in wood was quite toxic against both copper sensitive and copper tolerant strains. In all cases, mass losses between 1.3 and 1.9 % were obtained. Nevertheless, mass losses did not reflect all the changes that might have taken place in the wood samples. After eight weeks of exposure of CCB samples to wood rotting fungi, the moisture content of the treated samples increased from an initial value of 9 % to values between 97 % (Pm2) and 104 % (Pv2). In addition, blue deposits were observed on the surfaces of the CCB treated samples

exposed to the copper tolerant strains (Pv2 and Yf) (Figure E). Figure E : End view of the CCB treated samples exposed to the copper tolerant fungus Antrodia vaillantii. Please note the blue deposits on the bottom left corner.

Table D: Leaching of active ingredients from fungi infected samples with water for 4 days and leaching with water followed by leaching with 1.25 % solution of ammonia for 4 days. Standard deviations are given in the parenthesis.

Water Water + ammonia Fungus Leached Cr [%] Leached Cu [%] Leached Cr [%] Leached Cu [%]

Pv2 12.4 (2.1) 13.2 (1.1) 17.9 (2.0) 23.1 (0.9) Yf 7.4 (0.6) 10.0 (0.6) 9.6 (0.4) 18.5 (0.5) Pm2 6.5 (0.1) 7.8 (0.7) 8.7 (0.2) 13.6 (0.5) Gt2 0.6 (0.0) 1.1 (0.1) 1.8 (0.1) 5.7 (0.2) None 0.3 (0.0) 1.0 (0.1) 2.5 (0.1) 2.0 (0.2) Leaching of the samples immediately after exposure to the fungi resulted in further mass losses. For example, treated samples exposed to the copper tolerant A. vaillantii (Pv2) which had average mass losses of 1.7 %, when leached, had significantly higher average mass losses (5.3 %). Similar, higher mass losses were obtained for leached samples decayed by the other brown rot fungi. These results support the finding that brown rot fungi depolimerise wood components into water-soluble simple sugars which can be leached from the wood [xix]. Leaching with ammonia solution caused even higher mass losses of the partially decayed samples, e.g. samples decayed by copper sensitive G. trabeum (Gt2) for


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four weeks, had an average mass loss of 1.3 %. Leaching with water and a 1.25 % aqueous solution of ammonia increased the mass loss three times to 6.1 %. For the impregnated wood, the highest leaching of Cr and Cu was obtained for samples exposed to A. vaillantii. From those samples, 12.4 % of Cr and 13.2 % of Cu were leached respectively (Table D). As expected, the lowest heavy metals losses for the CCB-treated samples were found for samples decayed by G. trabeum. This copper sensitive fungus also caused the lowest mass loss of the CCB-treated (Table D). The Cr and Cu losses from those samples were comparable to those from the control-unexposed samples. We believe, that with the optimization of the fungal exposure, significantly higher levels of heavy metals leaching could be achieved. Additional leaching of the samples with the aqueous solution of ammonia increased the amount of copper leached from the decayed treated samples. For example, leaching of the Cu from treated samples exposed to A. vaillantii resulted in 13.2 % copper loss. Additional leaching with ammonia solution increased Cu loss to 23.1 %. Though the influence of ammonia on the leaching of Cu from the samples decayed by the other fungi was comparable (Table D).

EPR observation of decayed and leached impregnated wood

Exposure of the CCB-treated samples to the copper tolerant A. vaillantii and L. pinastri resulted, that the intensity of Cu(II) EPR signal (g┴ = 2.076,) and Cr(III) (g = 1.98; ∆h = 48 mT) Cr(V) (g0 = 1.978) decreased and a broad EPR signal overlapped with Mn(II) (g0 = 2.003 a0 = 9.6 mT) signal appeared (Figure C). The parameters of this broad signal, with a measured g0 value of 2.175 and linewidth about 43 mT, correlate well with that reported in the literature for copper oxalate [ix,xx,xxi]. This proves, that during exposure new complexes of copper oxalate between copper in wood and oxalic acid were formed. The reasons for decrease of chromium EPR signals are similar. In the cited literature [xxi,xxii] it is suggested that water environment affects chromium reduction, which could have lead to the disappearance of Cr(V) signal. In addition, a significant decrease of Cr(III) signal was observed as well and this could be due to the formation of chromium oxalate and the leaching of chromium. Chromium oxalate compounds cannot be resolved from the EPR spectra [xxiii].


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Figure c: EPR spectra of CCB-treated samples (a), exposed to the fungus A. vaillantii for 8 weeks (b), and later leached with water (c), and aqueous solution of ammonia (d). Hovewer, the shape and the parameters of preserved samples exposed to G. trabeum do not significantly differ from the unexposed ones, indicating that there was no chemical change of the active components in the wood. Result is acceptable, as this copper fungus is known as copper sensitive strain that excretes low amounts of oxalic acid [viii,xii].The only observed change is the decrease of Cr(V) EPR signal, which could be due to the high moisture content of the exposed samples as already mentioned (Figure D). After leaching of the impregnated specimens exposed to the A. vaillantii with water, the manganese signal disappeared, but two EPR signals, Cu(II) EPR signal (g┴ = 2.077) and a broad EPR signal assigned to copper oxalate remained on the EPR spectra. The intensity of the Cu oxalate EPR signal decreased after leaching as well. We believe that this broad signal belongs to the copper deposits present on the surface of the wood samples. As there were no interactions between these deposits and the wood some of the crystals were washed from the surface during leaching, and thus the decrease in intensity of the copper oxalate EPR signal. Furthermore, during exposure leaching increased acidity may unfix bounded copper and soluble copper(II) sulfate could have diffused to the surface layers of the wood samples, resulting in a higher intensity of the Cu(II) sulfate EPR signals (g┴ = 2.077). These results shows that the amount of oxalic acid excreted by the copper tolerant fungi (Pv2 and Yf) in eight weeks, was not enough to transform all the copper in the copper-treated wood to copper oxalate. And that there are some other acids excreted as well Described changes can be clearly seen from the EPR spectra in Figure c.

250 300 350 400 450

Cu oxalate EPR signal

Cu(II) EPR signal

Cr(III) EPR signal

Cr(V) EPR signal

Free radical EPR signal

d

c

b

a

Field width [mT]


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Figure d: EPR spectra of CCB-treated samples (a), exposed to the fungus G. trabeum for eight weeks (b), and later leached with water (c), and aqueous solution of ammonia (d). Ammonia leaching influences on the copper in impregnated wood. As already described, it can be well resolved from the EPR that not all the copper in the treated samples was transformed into copper oxalate. Thus, the ammonia reacted with both the copper oxalate and the remaining copper sulfate in the wood. From Figures c and d, it is clear that there are no copper oxalate/ammonia complexes (g┴ = 2.067, gII = 2.286 and AII = 15.7 mT) [ix] resolved in the spectra, thus they must have been leached from the wood leaving only copper (II) sulfate/ammonia (g┴ = 2.060, gII = 2.256 and AII = 17.0 mT). Cu(II) sulfate/ammonia complexes have been reported to be less soluble [xxii,xxiv] and are even capable of forming chemical bonds with wood components [ix,xxii], which could reduce leaching of the Cu. However, copper/ammonia/oxalic acid complex is more soluble and thus it was leached from the wood and thus it can not be resolved from the EPR spectra any more.

Conclusions

Immersion of the samples to nutrients (Corn step liquor and/or glucose) significantly improves the ability of copper tolerant, as well as copper sensitive wood decay fungi to overgrow the surface of copper/chromium/boron treated specimens. On the other hand, nutrients do not contribute to the capability of the fungi to reach the central parts of the impregnated wood specimens.

The fastest overgrow of the surface and the fastest penetration to the center of the specimens were observed at copper tolerant fungus Antrodia vaillantii. However, none of the copper sensitive

250 300 350 400 450

Cr(III) EPR signal

Cu(II) EPR signal

Cr(V) EPR signal

d

c

b

a

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fungi did not reach the bait in the central part of the impregnated samples even after 12 weeks of exposure.

Exposure of the impregnated specimens to wood decay fungi considerably influence the leaching of heavy metals from impregnated specimens, due to formation of chromium oxalate and defixation of copper. Addition of ammonia to leaching solution resulted in increased leaching of Cu and Cr as well.

Acknowledgements

The authors would like to thank Biffaward, Protimsolignum-Osmose, Arch Timber Protection, CSI Timber Protection and the British Council Partnership for Science program for financial support.

Literature

[1] Clausen C.A., Smith R.L., 1998. Removal of CCA from treated wood by oxalic acid extraction, steam

explosion, and bacterial fermentation. Journal of Industrial Microbiology and Biotechnology 20, 251-257.

[2] Stephan, I., Peek, R.D., Nimz, H., 1996. Detoxification of Salt impregnated wood by organic acids in a pulping process. Holzforschung 50, 183-187.

[3] Stephan, I., Peek, R.D., 1992. Biological detoxification of wood treated with salt preservatives, The International Research Group for Wood Preservation, IRG/WP 92-3717, 12.

[4] Honda, A., Kanjo, Y., Kimoto, A., Koshii, K., Kashiwazaki, S., 1991. Recovery of Copper, Chromium and Arsenic compounds from the waste preservative treated wood. The International Research Group for Wood Preservation. IRG/WP91-3651, 8.

[5] Ribeiro, A.B., Mateus, E.P., Ottosen, L.M., Bech-Nielsen, G., 2000. Electrodialytic removal of Cu, Cr, and As from chromated copper arsenate treated timber waste. Environmental Science and Technology 34, 784-788.

[6] Skoog, D.A., West, D.M., Holler, F.J., 1992. Fundamentals of Analytical Chemistry, Saunders College Publishing, Fort Worth USA, 118-143.

[7] Green III, F., Larsen, M.J., Winandy, J.E., Highley, T.L., 1991. Role of oxalic acid in incipient brown-rot decay. Material und Organismen 26, 191-213.

[8] Humar, M., Petrič, M., Pohleven, F., 2001. Changes of pH of impregnated wood during exposure to wood-rotting fungi. Holz als Roh- und Werkstoff 59, 288-293.

[9] Humar, M., Petrič ,M., Pohleven, F., Šentjurc, M., Kalan, P., 2002a. Changes of copper EPR spectra during exposure to wood rotting fungi. Holzforschung 56, 229-238.

[10] Jellison, J., Connolly, J., Goodell, B., Doyle, B., Illman, B., Fekete, F., Ostrfsky, A., 1997. The role of cations in the biodegradation of wood by the brown rot fungi. International Biodeterioration & Biodegradation 39, 165-179.

[11] Tsunoda, K., Nagashima, K., Takahashi, M., 1997, High tolerance of wood-destroying brown-rot fungi to copper-based fungicides. Material und Organismen, 31: 31-44.

[12] Takao, S., 1965. Organic acid production by basidiomycetes, I. Screning of acid-producing strains. Applied Microbiology 13, 732-737.


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[13] European Committee for Standardization, 1989. Wood preservatives; Determination of the toxic values against wood destroying basidiomycetes cultured an agar medium, EN 113, Brussels, 14.

[14] European Committee for Standardization, 1994. Wood preservatives – Methods for measuring losses of active ingredients and otherpreservative ingredients from treated timber – Part 2: Laboratory method for obtaining samples for analysis to measure losses by leaching into water or synthetic sea water. EN 1250, Brussels, 16.

[15] Kleist, G., Morris, I., Murphy, R., 2002, Invasion and colonisation of bamboo culm material by stain and decay fungi. IRG/WP 02-10453, 10.

[16] Raspor, P., Smole-Možina, S., Podjavoršek, J., Pohleven, F., Gogala, N., Nekrep, F.V., Rogelj, I., Hacin, J., 1995. ZIM: zbirka industrijskih mikroorganizmov. Katalog biokultur; Biotehniška fakulteta, Katedra za biotehnologijo, Ljubljana: 98.

[17] Pohleven, F., Humar, M., Amartey, S., Benedik, J., 2002, Tolerance of Wood Decay Fungi to Commercial Copper Based Wood Preservatives. IRG/WP 02-30291, 12.

[18] Tavzes, C., Pohleven, J., Pohleven, F., Koestler, R.J., 2002. Anoxic eradication of fungi in wooden objects. Art, biology, and conservation: biodeterioration of works of art: New York, The Metropolitan museum of art, 116-117.

[19] Green III, F., Highley, T.L., 1997. Mechanism of brown rot decay: Paradigm or paradox. International Biodeterioration & Biodegradation 39, 113-124.

[20] Srivastava, P.C., Banerjee, S., Banerjee, B.K., 1980. Magnetic & spectroscopic behaviour of some copper oxalate complexes. Indian Journal of Chemistry, 19 A, 77-79.

[21] Humar, M., Pohleven, F., Šentjurc, M., Effect of oxalic, acetic acid and ammonia on leaching of Cr and Cu from preserved wood. Wood Science and Technology. In press

[22] Hughes, A.S., Murphy, R.J., Gibson, J.F., Cornfield, J.A., 1994. Electron paramagnetic resonance (EPR) spectroscopic analysis of copper based preservatives in Pinus sylvestris. Holzforschung 48, 91-98.

[23] Lahiry, S., Kakkar, R., 1982. Single-crystal magnetism of sodium magnesium chromium(II) oxalate, NaMgCr(C2O4)3×9H2O. Chemical Physics Letters 88, 499-502.

[24] Hartford, W.H., 1972. Chemical and physical properties of wood preservatives and wood preservative systems. In Wood deterioration and its prevention by preservative treatments. Vol. 2, Preservative and preservative systems, Syracuse University Press, Syracuse, 154.


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Bioremediation and Degradation of CCA-Treated Wood Waste

Barbara L. Illman* and Vina W. Yang

USDA Forest Service, Forest Products Laboratory, Madison, WI, USA ABSTRACT

Bioprocessing CCA wood waste is an efficient and economical alternative to depositing the waste in landfills, especially if landfill restrictions on CCA waste are imposed nation wide. We have developed bioremediation and degradation technologies for microbial processing of CCA waste. The technologies are based on specially formulated inoculum of wood decay fungi, obtained through strain selection to obtain metal tolerant fungi. Two strains of Meruliporia incrassata and two strains of Antrodia radiculosa were selected for capacity to degrade CCA wood, thereby reducing the waste volume. Formulation of the fungal inoculum requires a lignocellulose substrate and a nutrient supplement to optimize fungal establishment and growth on the waste wood. The inoculum can be prepared in standard sterile containers or small to intermediate scale bioreactors, applied to the waste wood and maintained in an aerated and hydrated environment having temperature conditions sufficient to allow fungal growth. Oxidation states of chromium, copper and arsenic remained constant during wood processing as determined earlier by synchrotron-based technologies. The criteria for selecting fungal strains, nutrients, lignocellulose substrate, optimum growth conditions and wood analysis provided the basis for developing a fungal processing system to degrade CCA-treated wood waste while removing the metals. Keywords: Bioremediation, CCA, wood waste, Meruliporia incrassata INTRODUCTION Wood treated with chromated copper arsenate (CCA) in service in the United States was estimated to be over 85 million metric tons in 1997, with 8 million metric tons being produced each year [1]. CCA-treated wood removed from service is primarily sent to landfills. Large volumes of CCA-treated wood waste are expected be added to the solid waste stream in the next 20 years, causing potential problems for landfills [1,2,3]. Historically, economic, regulatory and environmental pressures stimulate development of alternative disposal methods and lead to recovery of waste wood. Between 1990 and 1999, 42.3 million tons of recoverable wood waste dropped to 29.6 million tons, primarily due to diversion of the waste to new uses or new materials [4]. Alternative strategies are being developed to decrease the volume of CCA-treated wood waste from landfill disposal. Several strategies will be useful in meeting the demands of differing collection methods, __________ *Dr. Barbara L. Illman, Research Project Leader, USFS Forest Products Laboratory, One Gifford Pinchot Dr, Madison, WI, USA 53726. Phone: +608-231-9231, FAX: +608-231-9262. Email: [email protected]


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use categories, current urban and rural waste management systems, and desired end products. An economically feasible method for reducing the volume of CCA-treated waste and recovering the metals will serve small-scale niche markets.

As a nonspecific preservative, CCA has been highly effective in protecting wood against decay for many years. Most species of decay fungi are not CCA-tolerant and do not degrade the metal-treated wood. With long-term selection pressures on a population, however, it is possible for a fungal strain to develop resistance to preservatives, including CCA. We have screened hundreds of fungi in search of these rare strains as they have putative roles in the clean up of toxic waste sites and in the disposal of preservative-treated wood waste. The objective of this research was to develop a method for fungal remediation and degradation of CCA-treated wood waste by (1) isolating and characterizing CCA-tolerant fungi, (2) defining economical materials and methods to prepare and package viable inoculum of metal-tolerant decay fungi, (3) establishing treatment procedures for the remediation and degradation process, and (4) conducting a laboratory scale-up to evaluate the method on solid lumber treated with CCA. This paper presents new and summarizes past research [5,6,7]. MATERIALS AND METHODS Wood Decay Fungi

Isolation and culture conditions Fungi were collected from field test sites or selected from the extensive fungal library at the Center for Forest Mycology Research, Forest Products Laboratory (FPL), Madison, WI, USA. The FPL fungal library was screened for isolates (identified to species but not to strain) that were collected from preservative-treated wood products, such as decks, poles and test stakes that had visible signs of decay. Additional isolates were taken from 20-30 year-old preservative-treated wood stakes taken from the FPL field test plots in Gulfport, Mississippi and Picnic Point, Madison, WI. Fungi were cultured on 2% malt extract agar (DifcoBacto) or a modified Taylor’s medium at 27o C and 70% relative humidity (RH). Mycelium was stored on 2% malt extract agar test tube slants or in Petri dishes at 4 o C.

Metal Tolerance Assay Fungal tolerance to CCA was determined by two methods, an in vitro bioassay described as

a


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Figure 1. Collecting field stakes to isolate fungi. ‘choice test’ by Leithoff et al. [8] and a growth response bioassay of in vitro exposure to metals. Briefly, for the ‘choice test’ assay a 9 mm fungal disk from a freshly grown malt agar culture was placed in the center of a Petri dish (14 cm diameter) containing 12 ml of a 2% agar medium with a CCA-treated and a non-treated southern yellow pine wood sample (1.5 cm x .3 cm) placed at opposite edges of the plate. Fungi were kept in an incubator at 27oC and 70% relative humidity (RH) for 14 days, observed for growth response to the treated wood. Metal tolerance was rated as fungal growth toward and/or on the treated wood. For the metal exposure assay, copper, chromium or arsenic were incorporated into 2% MEA in Petri plates and inoculated in the center with Meruliporia incrassata (TFFH-294) and Meruliporia incrassata (TFFH-295). Cupric sulfate, potassium dichromate or sodium arsenate (Aldrich) were added to MEA at levels of 0, 0.1, 1 10 and 100 mM of Cu, Cr, or As. Mycelium was measured from the center of the plate on day 14 to determine metal effect. Response was expressed as % of growth without metals in the medium. Optimum Growth Conditions Temperature: Four disks (9 mm) of freshly grown fungal cultures were removed from 2% MEA plates and inoculated into 125 ml Erlenmeyer flasks containing 25 ml of 2% malt extract liquid medium (DifcoBacto). Flasks were placed in an incubator at 20, 27, 32 or 37o C at 70% RH in the dark for 12 days. Mycelium was harvested by straining the liquid culture through previously weighed Whatman No. 1 filter paper, allowing the mycelia to air dry on the paper, reweighing and calculating biomass dry weight. Light conditions: Liquid cultures and biomass dry weight were prepared as described above for temperature. Flasks were kept stationary in an incubator at 27o C and 70% RH for 12 days under one of the following light regimes: 24 hours of light, 12 hours of light with 12 hours of darkness, or 24 hours of darkness. Oxygen and chemically defined medium: Four disks (9 mm) of freshly grown fungal cultures were removed from 2% MEA plates and inoculated into 125 ml Erlenmeyer flasks containing 25 ml of Bailey’s medium [9] or BIII medium [10]. Flasks were kept stationary in an incubator at 27o C and 70% RH in the dark for 21 days, with or without an exposure to a 20 second oxygen flush on alternate days [9]. Mycelia were harvested and biomass dry weight determined as above with temperature and light. There were three replicate flasks per medium per oxygen treatment. Fungal Inoculum


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Nutrient Supplement Disks (9 mm) of freshly grown fungal cultures were removed from 2% MEA culture plates and inoculated into 125 ml Erlenmeyer flasks containing 25 ml of 2% malt extract liquid medium supplemented with or without 1% sterile corn steep liquor (CSL) from corn processing (ADM, Cedar Rapids, Iowa). Flasks were kept stationary in an incubator at 27 C and 70% RH for 3 weeks. Mycelium was separated from liquid culture by filtration through previously weighed Whatman No. 1 filter paper, allowed to air dry on the paper and reweighed. Biomass dry weight of CSL fed mycelium was expressed as % dry weight of mycelium grown without CSL.

Lignocellulose substrate The lignocellulose substrates sawdust, wood chips, rice straw, corn stalks, and wheat straw, were

evaluated for effectiveness as a long-term food source in the fungal inoculum and as a matrix for inoculum storage and handling. Similar methods apply to all. Sawdust and wood chips were steam-sterilized and cooled at room temperature prior to mixing with the fungal nutrient supplement mixture. Steam sterilization of the lignocellulose substrate is preferred as the steam provides both sterility and moisture content. Moisture from steam-sterilization enhances fungal growth. Wood degradation

Wood decay test Blocks of southern yellow pine (1 x 1 x 0.3 inches) were treated with CCA to 6.4 kg/m3 (.40-pounds/cubic foot) according to American Wood Preserver's Association (AWPA) standards [11]. Treated blocks were inoculated with Meruliporia incrassata (TFFH-294), Antrodia radiculosa (MJL-630), Meruliporia incrassata (Mad-563) or Antrodia radiculosa (FP-90848-T) according to the ASTM standard soil bottle decay test [12]. Briefly, CCA-treated blocks (2.5 by 2.5 by 0.9 cm) were inoculated with fungi in soil-bottles, incubated for 12 weeks at 27 C and 70% RH, and weight loss determined. Treated and nontreated control blocks were incubated without exposure to fungi. The test was replicated 5 times. Decay was expressed as per cent weight loss.

Effect of supplements on decay A fungal inoculum amended with nutrients and lignocellulose supplements was prepared with minor modification of the method described in the section above. Fungal mycelium was transferred from stock culture to 10 ml 2% MEA in a glass bottle (2 x 2 x 5 inches) and incubated in the dark at 27 C and 70% RH for 2 weeks. The resulting mycelium was mixed in the bottle with 10 g of sterile sawdust, 20 ml sterile water, and 20 ml sterile 1% CSL or 0.25 g of a 50/50 mixture of sterile wheatbran and cornmeal, incubated in the dark at 27 C and 70% RH for 6 weeks. Names of fungal isolates are listed in Table 6. Laboratory Scale-up

Fungal Inoculum The inoculum preparation described in the sections above was modified to evaluate the

effectiveness of the method on larger volumes of solid lumber and particulate, flaked, or chipped CCA-treated southern yellow pine. Sawdust (350 g) was sterilized in an aluminum tray (9 x 13 x 2.5”), cooled to room temperature, mixed with 700 ml 1% CSL. Meruliporia incrassata (TFFH-294)


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was cultured in seven Petri dishes (14 cm diameter) containing 2% MEA, incubated at 27o C and 70% RH for 2 weeks. The resultant culture was cut into pieces (approximately 1.5 in square), mixed with the solid substrate in the tray, incubated at 27 o C, 70% in the dark for 8 weeks. If not used for processing right away, the inoculum should be stored at 4 o C.

Bioprocessing The bioprocessing method was evaluated in a laboratory scale-up with CCA-treated and

nontreated southern yellow pine lumber. Several large metal chambers (33 x 6 x 8 inches) with sliding covers were custom-made for the decay test on lumber. A 2-inch layer of moistened soil with a water content of 35% lined the bottom of the chamber. Test samples of CCA-treated and nontreated wood (2 x 4 x 12 inch) were placed on top of the soil and steam sterilized. After the chambers had cooled to room temperature, wood was completely covered with the Meruliporia incrassata TFFH-294 inoculum. The closed chamber was placed in the dark in an incubator at 27 o C and 70% RH for 12 weeks. Weight loss of wood was calculated as described for the decay test above. RESULTS Wood Decay Fungi

A total of 150 brown- and white-rot wood decay fungi were obtained from metal-treated wood.

The isolates that exhibited CCA-tolerance in the ‘choice test’ are listed in Table 1. Most fungi grew toward nontreated wood with no growth toward CCA-treated wood. The 18 fungal isolates in Table 1 grew toward and/or on CCA-treated wood. The brown-rot fungus, M. incrassata (TFFH-294) exhibited the most tolerance and was selected for the growth response studies. Two isolates of M. incrassata were tolerant to 1mM copper, chromium and arsenic (Table 2). The response of M. incrassata (TFFH-294) to temperature and light was the same as reported for most wood decay fungi, known to be metal-sensitive [10]. The optimum temperature range for M. incrassata (TFFH-294) biomass production was between 27 o C. and 32 o C, with declining production at the higher and lower temperatures of 35 o C and 20 o C (Table 3). Light inhibited fungal growth (Table 4). The fungus produced 33% more biomass when incubated in the dark for 24 hr per day than for 24 hr per day in light. M. incrassata (TFFH-294) exhibited a similar growth response on chemically defined medium and exposure to oxygen as that reported for many brown-rot fungi and for the white-rot fungus, Phanerochaete chrysosporium [13,10]. Biomass production was slightly higher on Bailey’s than on BIII medium and production was enhanced on both media when exposured to oxygen (Table 5).


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Table 1. Wood decay fungi tolerant to CCAa ________________________________________________________________________

SPECIES ISOLATE COLLECTION SITE ________________________________________________________________________ Antrodia radiculosa L-11659-sp FPL-MCb Gloeophyllum subferrugineum FRI 417/R FPL-MC Polyporus sp. FP134933 FPL-MC Trichaptum byssogenum FP105308-R FPL-MC Gloeophyllum trabeum Boat 228 FPL-MC -- TLH-1 FPLc Antrodia radiculosa MJL-630 FPL-MC Neolentinus lepideus HHB 1 3625 FPL-MC Antrodia xantha MB268 FPL-MC -- CAC-1 FPL -- P6G FPL-ppd -- P71H FPL-pp -- UpK FPL -- UpL FPL Meruliporia incrassata FFH-294 FPL Meruliporia incrassata Mad-563 FPL Antrodia radiculosa FP-103272-sp FPL-MC Antrodia radiculosa FP-90848-T FPL-MC _______________________________________________________________________ aCCA toleranc determined by ‘choice test’ bFPL-MC Forest Products Lab Center for Forest Mycology Research cFPL-RWU4502 Forest Products Lab Biodeterioration Unit dFPL-PP Forest Products Lab Picnic Point

Table 2. Growth response of Meruliporia incrassata TFFH-294 and MAD-563 on malt extract agar amended with copper, chromium or arsenic Inhibition of growth (%) M. incrassata (TFFH-294) M. incrassata (MAD-563) Metal (mM) 0 0.1 1.0 10 100 0 0.1 1.0 10 100 Copper 0 0 0 100 100 0 0 0 100 100 Chromium 0 0 0 100 100 0 0 0 100 100 Arsenic 0 0 13.3 80.3 100 0 0 0 100 100


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Table 3. Meruliporia incrassata (TFFH 294) response to light ____________________________________ Light condition weight (mg) 24 hours of light 66 ± 8* 12 hours of light 70 ± 6 24 hours of dark 88 ±13

_________________________ * ± Standard error

Table 4. Meruliporia incrassata (TFFH-294) growth response to oxygen and culture medium _____________________________________________________________ Medium O2 weight (mg) pH__ Bailey + 23 ±1 2.73 – 20 ±1 3.04 BIII + 21 ±2 2.96 – 18 ±2 3.61 _____________________________________________________________

Fungal inoculum Fungal growth and biomass production were enhanced by the addition of 1% CLS to the growth medium, but was adversely affected by higher concentrations (Table 5). Lignocellulose provided a solid, organic matrix for the fungal inoculum. Wood Decay Four isolates, Meruliporia incrassata (TFFH-294), Antrodia radiculosa (MJL-630), Meruliporia incrassata (Mad-563) and Antrodia radiculosa (FP-90848-T), degraded the CCA-treated wood more than 20% of the original dry weight of the wood (Table 6). Supplements enhanced degradation of CCA-treated wood (Table 7). Laboratory Scale up

M. incrassata (TFFH-294) degraded CCA-treated lumber by 28%. Fungal growth is slower on treated vs. nontreated wood, but mycelia are clearly visible on the outer surface and interior of the wood (Figure 3).

Figure 3. Meruliporia incrassata (TFFH 294) decay of CCA-treated wood. Top lumber is nontreated southern yellow pine and bottom is CCA-treated.

Table 5. Effect of corn steep liquor on biomass production of metal-tolerant Meruliporia incrassata (TFFH-294) _____________________________________________ CSL concentration % Dry weighta 0 100 1.0 % 321 2.5 % 256 5.0 % 196 _____________________________________________ a% dry weight of mycelium grown without CSL


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Table 6. Fungal Degradation of Preservative-Treated Wood* _________________________________________________________________________________ UNTREATED CCA Weight (mg) Fungal species Avg (SD) Avg (SD) __________________________________________________________________________________ Meruliporia incrassata (TFFH-294) 62.2 (2.9) 36.8 (2.7) Antrodia radiculosa (MJL-630) 32.6 (4.8) 26.6 (2.9) Meruliporia incrassata (Mad-563) 62.5 (2.5) 23.7 (3.2) Antrodia radiculosa (FP-90848-T) 39.5 (4.1) 20.1 (7.7) Antrodia radiculosa (FP-103272-sp) 24.6 (6.0) 6.5 (4.7) Antrodia radiculosa (FP-105309-R) 27.2 (3.0) 2.3 (0.8) Antrodia radiculosa (L-11659-sp) 23.1 (2.7) 1.3 (1.3) Neolentinus lepideus (Mad-534) 38.8 (5.3) 0.7 (0.4) ___________________________________________________________________________________ * ASTM D-1413-76 Standard Method of Testing Wood Preservatives by Laboratory Soil-Block Cultures Table 7. Effect of inoculum supplements on Meruliporia incrassata TFFH 294 degradation of CCA-treated wood Inoculum Supplements _____________________________________________________________ No CMWBb CSLc Fungal Species Isolate supplementa weight (mg) ________________________________________________________________________________________________________________ Antrodia radiculosa L-11659 32.0 150% 446% Meruliporia incrassata TFFH 294 34.0 32% 208% ________________________________________________________________________________________________________________ aInoculum with no CMWB or CSL bCorn meal and wheat bran amended inoculum cCorn starch liquor amended inoculum dWeight of CCA-treated wood inoculated with no supplements eDegradation expressed as % of wood weight loss with no supplements


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DISCUSSION

This paper describes the development of a method for the fungal degradation and/or bioremediation of CCA-treated wood waste, providing a product with reduced waste volume and the capacity for reuse of waste metals. A market analysis confirmed the economic feasibility of the method (unpublished). An ICP/MS analysis of residual metals in the wood waste will be reported elsewhere. Early results indicate that residual metal concentrations decrease during the processing.

Unique, natural mutants of wood decay fungi were taken from FPL collections or isolated from field test samples, characterized and reintroduced into CCA-treated wood to determine if they degraded wood, testing Koch’s postulates. Fungal isolates identified as CCA-tolerant and as degraders of CCA-treated wood include Meruliporia incrassata (TFFH-294), Antrodia radiculosa (MJL-630), Meruliporia incrassata (Mad-563) and Antrodia radiculosa (FP-90848-T), Antrodia radiculosa (L-11659).

An advantage of the bioprocessing method is that the CCA-tolerant fungi do not require genetic

alteration to grow in the presence of and degrade CCA-treated wood. Thus, the introduction of the fungi into the environment provides no new, non-naturally occurring organisms. However, the method is designed for contained waste management facilities where fungal viability and growth can be altered with temperature, water, oxygen, light, nutrients and other conditions. Metal-tolerant isolates such as M.. incrassata (TFFH 294) thrive only in optimum conditions. It is a slow growing isolate that would not be expected to compete in nature with faster growing microorganism such as molds, bacteria or the decay fungi Postia placenta and Gleophyllum trabeum. M. incrassata (TFFH 294) has the advantage over other microorganisms during the bioprocessing because it has extensive mycelia growth in the inoculum and because competing microorganisms do not tolerate CCA on the lumber.

The inoculum in this method has many advantages. It is cost effective, utilizing agricultural waste products and waste products from saw mills and urban chipping. These products provide a quick and low cost food source for the fungus, stimulate rapid and extensive fungal growth, and provide a readily storable and transportable solid matrix. The inoculum should limit the disadvantage experienced by various fungal strains, such as M. incrassata (TFFH-294), which are typically disadvantaged by a slow growth that limits their competition with other dominant fungi in nature. The metal-tolerant strains can be easily grown as indicated by the optimum growth and nutrient conditions identified in this study. Fungal growth is substantially enhanced with aeration and nutrients added to the culture medium.

Another advantage is that the inoculum and its method of use are particularly well suited for wood

waste such as pressure-treated lumber from buildings, decks, utility poles and railroad ties. The solid matrix of the fungal inoculum provides a wood environment for fungal growth, which is similar to that of the wood waste. The fungal strain is, therefore, readily adapted to the waste wood upon inoculation and does not require a period of adjustment before degradation and bioremediation begins.

The bioprocessing method is designed for remediating and degrading solid pieces of lumber, not

costly chipping or flaking that may require environmental oversight in the future with increased concerns about worker exposure to airborne particles; can be conducted on a small scale without costly transportation to larger, distant disposal sites; is designed for a wood use category that will not require extensive sorting, i.e. wood from docks, decks or landscaping can be kept separate more easily than mixed grades of wood from building demolition; and . The CCA-treated wood in this study was not wood waste; therefore we expect higher yields with spent wood taken out of service.


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A major component of the inoculum proved to be the lignocellulose substrate. Sawdust or wood chips are preferred for several reasons: (1) they provide a long-term food source for the fungus while providing fungal growth in a wood environment similar to the CCA-treated waste wood environment experienced during inoculation; (2) they permit the production of a large quantity of fungi in a single container; (3) they provide a substrate for easily storing and transporting the fungi; (4) they provide a matrix for convenient and even distribution of the fungus at the inoculation site; and (5) they provide a low cost use of a waste product from saw mills.

Several aspects of the procedure will need to be addressed for pilot level scale-up. Potential contamination, especially mold contamination at later stages of the procedure warrants an evaluation of specific mildewcides to be added with the inoculum and/or applied during the incubation. Procedures for various sizes of lumber need to be identified and schedules developed for incubation on a pilot scale. SUMMARY An economical fungal bioprocessing method was developed in which a fungal inoculum is prepared by culturing a CCA-tolerant fungus on 2% MEA under aerobic conditions in the dark at a temperature range of 27 – 32o C and 70% RH for 2 weeks; combining the fungal culture with a heat-sterilized mixture of 1% nutrient supplement (CSL), a lignocellulose substrate (sawdust) and water at 2-3 volumes per volume substrate; incubating the mixture under aerobic conditions in the dark at a temperature range of 27 – 32 o C and 70% RH for 6 weeks. The inoculum can be transferred to bioprocessing containers or stored at 4o C. Large quantities of inoculum can be stored in trays or large durable plastic bags, loosely packed to allow aeration. Trays and bags can be transported easily to the field sites and applied to the wood waste. Inoculum can be prepared directly in a truck bed or in a truck loaded container. ACKNOWLEDGEMENTS

The authors would like to thank Les Ferge for technical assistance. REFERENCES [1] Cooper, P.A. 2003. TECH SESSION I - Status and Future of CCA. American Wood Preservers’ Association Annual Meeting, Boston, MA. http://www.awpa.com/papers/Cooper_2003.pdf [2] Falk, Bob. 1997. Opportunities for the wood waste resource. Forest Products Journal 47(6)17-22. [3] Solo-Gabriele, H., M. and Townsend, T. 1999. Disposal practices and management alternatives for CCA treated wood waste. Waste Management and Research, 17:378-389. [4] McKeever, D.B. 1999. How woody residuals are recycled in the United States. Biocycle. JG Press, Inc. Emmaus, PA. pp. 33-44. [5] Illman, B.L. and Highley, T.L. 1996. Fungal degradation of wood treated with metal-based preservatives: Fungal tolerance. International Research Group on Wood Preservation, Stockholm, Sweden. IRG/WP 96-10163. [6] Yang, V.W., and Illman, B.L. 1999. Optimum growth conditions for the metal-tolerant wood decay fungus, Meruliporia incrassata TFFH294. International Research Group on Wood Preservation, Stockholm, Sweden. IRG/WP 99- [7] Illman, B.L., Yang, V.W., and Ferge, L. 2000 Bioprocessing preservative-treated waste wood. International Research Group on Wood Preservation, Stockholm, Sweden. IRG/WP 00-50145. [8] Leithoff, H., Stephan, I., Lenz, M.T., Peek, R-D. 1995. Growth of the copper tolerant brown-rot fungus Antrodia vaillantii on different substrates. International Research Group on Wood Preservation, Stockholm, Sweden. IRG/WP95-10121. [9] Bailey et al., Cellulase (B-1,4-Gucan,4-Glucanohydrolase) from wood-degrading fungus Polyporus Chweinitzii, Fr. I. Purification. Biochem. Biophys. Acta, 185:381-391(1969)


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[10] Kirk T.K., Croan S., Tien, M., Murtagh, K.E., Farrell, R.L. 1986. Production of multiple ligninases by Phanerochaete chrysosporium: Effect of selected growth conditions and use of a mutant strain. Enzyme Microb. Technol., 8:27-32. [11] American Wood Preservers' Association: Book of Standards. American Wood-Preservers Association, Woodstock, MD, 1991. [12] ASTM. 1998. Standard Test Method for Wood Preservatives by Laboratory Soil-Block Cultures. Designation D 1413-76. Annual Book of ASTM Standards, Vol. 04.10 Wood. American Society for Testing and Materials, West Conshohocken, PA. [13] Forest Products Laboratory. 1999. Wood handbook: Wood as an engineering material. Gen. Tech. Rep. FPL-GTR-113. USDA Forest Service, Forest Products Lab, Madison, WI. pp.13.1-13.17.


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Compression Tests on Wood-Cement Particle Composites Made of CCA-Treated Wood Removed From Service

An Gong Donatien P. Kamdem Ronald Harichandran

ABSTRACT

This research investigates the compressive properties of wood-cement particle composites made of CCA-treated wood retired from service. A total of 22 specimens were fabricated using Portland cement (type I) and wood particles from CCA-treated southern yellow pine retired from service. The specimens were made as rectangular short columns with different column aspect ratios (height/width). The cement to wood ratios by weight of the specimens were 1.5 and 1.0.

The load-deformation curves display significant nonlinearity, and indicate that the wood-cement

particle composite has the capability to absorb energy. Further, the mechanical properties were not isotropic and indicate directional dependencies due to the orientation of the wood particles caused by the pressing during the manufacturing process. Short column specimens failed predominantly in shear under compressive loading irrespective of the orientation of the particles in the specimens.

The wood-cement particle composites exhibited a compressive strength comparable to that of

normal concrete material. However, the strain at peak load was at least ten fold higher than that of normal concrete. The ability of such composite to sustain large plastic deformations implies that it can be used for applications where energy dissipation is highly required.

An Gong, Research Assistant, Department of Civil and Environmental Engineering, 3546 Engineering Building, Michigan State University, East Lansing, MI48824. Donatien P. Kamdem, Professor, Department of Forestry, 126 Natural Resources; Ronald Harichandran, Professor and Chairperson, Department of Civil and Environmental Engineering, 3546 Engineering Building, Michigan State University, East Lansing, MI48824 INTRODUCTION

In 1993, an estimated 5 billion board feet of wood were CCA treated and will be removed from service after approximately 27 years in 2020. This figure does not include the 72 million utility poles or


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15 million ties treated annually with creosote or pentachlorophenol or other oilborne preservatives [1, 2]. A major challenge facing the wood preservative industry today is how to deal with this massive waste wood in the near future.

Based on a 30-year service-life, researchers at the Forest Products Laboratory (FPL) in Madison,

Wisconsin estimate that 2.5 billion board feet per year (6 million m3/year) of treated-wood products (all types of preservative treatments) are currently entering the solid-waste stream, and that level will increase to 8 billion board feet per year (19 million m3/yr) by the year 2020 [3].

Recently, the U.S. Consumer Product Safety Commission (CPSC) released a risk assessment of CCA-treated wood on playground structures [4]. This assessment concluded that children playing on playground equipment built with CCA-treated wood might have a slightly increased risk of developing cancer. However, at this time, no further action has been recommended by the CPSC .

For general public, on the one hand, the landfill disposal may produce environmental problems. It is

increasingly difficult to landfill solid wood because it is a high volume material and deterioration is questionable when necessary requirements for biodegradation are not met. On the other hand, Stalker [1] reported a quoted cost by landfill operators of $150 US per utility pole. The cost of landfill and the current level of environmental awareness will reduce land filling as an attractive alternative [5,6] for disposal of treated wood.

As a result, the disposal of preservative-treated wood products removed from service is problematic.

Therefore an attractive solution for the after service disposal of treated wood is reconstituted wood products. Recycled treated wood, if properly managed, can be a good fiber source for engineered wood products such as hardboard, fiberboard, adhesive bonded and cement-bonded particleboard. Recycling wood into wood composite products becomes increasingly attractive because it not only benefits the environment but also has economic value.

A wood-cement particle composite is composed of wood particles, Portland cement and water. The wood-cement composites have a history of several decades in the United States. The flexural strength of the wood-cement composites has been investigated extensively. Little to negligible information is available on the compression strength of cement bonded wood particle composites. The use of wood-cement particle bricks in load bearing walls where the compression is solicited will require information on the compressive load-deformation and toughness as well.

Wolfe [7,8] reported that the characteristics of the compressive load-deformation curve were similar

to those for the bending. In their study, the load displacement plots exhibited linear behavior up to 60 - 75% of the maximum load, at which point the rigid cement matrix began to crack. As the material began to fail, the material exhibited elasto-plastic behavior. Research on hardwood-cement particle composites by Blankenhor [9], revealed that as the amount of red maple and hardwood pulp increased in wood cement particle composite (WCPC), the compressive strength decreased. Sorfa [10] reported that WCPC bricks developed for structural supports in mines exhibited compression properties similar to those of wood loaded at direction perpendicular to the grain. The load-deformation curves were initially linear until the matrix cracking, after which they softened.

Up to now, WCPC were assumed to be isotropic, few studies proposed the evaluation of the

properties with the orientation of the particles. We propose to laboratory manufacture cement bonded wood particle composites from CCA treated

wood removed from service. The compressive properties of the WCPC in directions parallel and


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perpendicular to wood fiber, the compressive failure modes, compressive stress-strain correlations, and the energy dissipation will be investigated. MATERIAL AND PROCEDURES Southern yellow pine boards with CCA and used for 21 years as decking were removed in service in Lansing, Michigan. A wiley mill was used to reduced the boards into particles with size varying from 2 to 8 mm in length by 1 mm in diameter. A sieve was used to screen the particles.

The wood-cement composite specimens were made by mixing wood particles with cement at a ratio of cement to wood of 1.0 and 1.5 by weight. The amount of wood particles, water and cement required to produce particleboard measuring 35 mm in thickness by 315 mm wide by 315 mm long were calculated for a each given cement/wood ratio. The mixtures were placed in a mold and pressed using manual hydraulic press for 24 hours. After curing in room temperature for 28 days, the particleboards were cut into rectangular short column specimens for compression test.

The composite short column specimens were tested in compression parallel and perpendicular to the thickness of the board. The specimens were soaked in water at 20 + 3o C for 24 hour before the test and were tested immediately upon removal from the water. The test matrix of the compression tests is shown in Table 1. COMPRESSION TESTING

The compressive tests were conducted on INSTRON machine at a loading rate of 0.15 cm per minute. The sizes of the specimens used for testing are listed in Table 1. The specimens were tested with load parallel and perpendicular to the board thickness. The procedures in ASTM D1037-78 [11] were followed in the compression tests.

RESULTS AND DISCUSSION Compressive Strength

Figure 1 shows the failure mode of specimens loaded parallel and perpendicular to the fiber

directions with a column aspect ratio of 2.0 and a cement/wood ratio of 1.5. The failure modes on all samples were irrespective of the cement to wood ratios and column aspect ratios used in this study. The compressive failure typically occurred along diagonal bands similar to compression-shear failure on concrete columns. It can be concluded that short column specimens failed predominantly in shear under compressive loading irrespective of whether the wood particles were oriented along the direction parallel or perpendicular to the thickness.

Figure 2 shows the stress-strain curves of wood-cement particle composites for parallel and

perpendicular compressions. The stress-strain curves obtained in the tests display significant nonlinearity, and indicate that the wood-cement particle composite has the capability to absorb energy. Further, the mechanical properties were not isotropic and indicate directional dependencies. The directional anisotropy were due to the orientation of wood particles caused by pressing during the manufacturing process.


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In general, based on strain-stress test results, three significant findings can be reported: WCPC in direction parallel the particle orientation is much more stiffer than it in the perpendicular direction. Second, the deformation of the specimens in the perpendicular direction is much larger than in the TABLE 1 TEST MATRIX FOR COMPRESSION ON SPECIMENS

Short column speciemens

Cement/wood ratio 1.5 1.0

Column aspect ratio (h/d) 2.0 3.0 2.0

Parallel 4 4 3 Number of

specimens Perpendicular 4 4 3

Dimensions (d×d×h), (mm) 17 x 17 x 34 11.7 x11.7 x 35 15 x15 x 30

a. Parallel loading b. Perpendicular loading Figure 1. Compression failure mode (h/d =2.0, cement/wood ratio = 1.5) parallel direction. Third, the compressive strength of specimens with cement to wood ratio of 1.5 was higher than that a cement/wood ratio of 1.0 for both parallel and perpendicular directions.

The compressive strength of WCPC was comparable to that of normal concrete. The strains at maximum stress and at failure were much larger than that of normal concrete. In general, a concrete with a compressive strength of 3000 psi is considered as normal concrete, and the strain in concrete when it reaches its peak compressive stress is about 0.002.

WCPC made with a column aspect ratio 2.0 and a cement/wood ratio of 1.5 yield the compressive

strength of 2600 psi at the direction parallel to particle fiber direction, which is comparable to that of normal concrete, the strain at peak stress is about 0.02, which is ten times larger than it is for concrete; for the specimens loaded in compression perpendicular to the fiber direction, the compressive strength is about 2500 psi, which is also comparable to that of normal concrete, the strain at peak stress is about 0.11, which is over fifty times larger than it is for concrete.


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For specimens made with cement/wood ratio of 1.5 and with a column aspect ratio (h/d) of 3.0, the compressive strength in the direction parallel to the fiber direction is about 1650 psi, which is half of the value of normal concrete, the strain at peak stress is about 0.017, which is over eight times larger than it is for concrete. The specimens in compression perpendicular to the fiber direction exhibited a compressive strength value of 2000 psi, which is also comparable to that of normal concrete, the strain at peak stress is about 0.09, which is over forty five times larger than it is for concrete. At 1.5 cement to wood ratio and 3.0 column aspect ratio, the value of the compressive strength and strain at peak stress were lower than that of the composite with a cement/wood ratio of 1.5 and with an aspect ratio of 2.0. The difference may be attributed to the column aspect ratio because column with a higher aspect ratio could create stable problem.

Specimens with a cement/wood ratio of 1.0 and with an aspect ratio (h/d) of 2.0, the compressive

strength parallel to the fiber direction is about 700 psi, about 23% of the value for normal concrete, the strain at peak stress was about 0.035, which is seventeen times larger than it is for concrete; In compression perpendicular to the fiber direction, the compressive strength was about 1800 psi, which is about 60% of that of normal concrete, the strain at peak stress was about 0.28, which is about 140 times larger than that of concrete.

Figure 2. Stress-strain relationships of the wood-cement composite short columns

The ability of the composites to sustain such large plastic deformations implies that it has a strong potential to dissipate energy. Toughness

The toughness is a measure of the energy absorbed per unit area of material; it is also defined as the area under load deformation curve. ASTM C1018 [12] is often used to calculate the toughness indices. ASTM C1018 defines a set of toughness indices for fiber reinforced concrete, which is defined as the area under the load-deformation curve up to the deformations of 3, 5.5 and 10.5 times the deformation at first crack divided by the area under load-deformation curve up to the first crack. In concrete industry, the

-3000

-2500

-2000

-1500

-1000

-500

0-0.45-0.4-0.35-0.3-0.25-0.2-0.15-0.1-0.050

strain in/in

stre

ss

ps

1

3 6

5

4

2 1: Parallel, C/w =1.5, h/d = 2.0. 2: Perpendicular, C/w =1.5, h/d = 2.0. 3: Parallel, C/w =1.5, h/d = 3.0. 4: Perpendicular, C/w = 1.5, h/d = 3.0. 5: Parallel, C/w =1.0, h/d = 2.0. 6: Perpendicular, C/w =1.0, h/d = 2.0.


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toughness index of plain concrete is 1.0 and the toughness index of steel fiber reinforced concrete is about 5.0. In this study ASTM C1018 procedure for toughness index (I5) was used to define the compressive toughness of the wood-cement composites. The toughness index (I5) is defined by the following equation:

δ

δtoupndeformatioloadtheunderAera

toupcurvendeformatioloadtheunderAreaI−

−=

35 (1)

Where, δ is the deformation up to the first crack.

Table 2 shows the calculated toughness index I5 for wood-cement particle composites with two cement/wood ratios under uniaxial compression tests. The calculated toughness indexes (I5) of the

Table 2 Compressive toughness of wood-cement particle composites

wood-cement particle composites are closed to 7.0. In Figure 2, apparently, the energy dissipation ability of the wood cement composite in perpendicular to fiber direction is stronger than that of the composites in the direction parallel to fiber direction. The toughness index I5 for sample with a cement wood ratio of 1.5 was 6.98 irrespective of the orientation. Same results were obtained for samples with a cement/wood ratio of 1.0. The toughness index (I5) of the composites with cement/wood ratio of 1.5 was lower than that of the composites with the cement/wood ratio of 1.0.

CONCLUSION

Compressive tests conducted on wood cement particle composites show a tremendious nonlinearility. the composite specimen fails in shear under compressive loading in either doirection parallel to or perpendicular to wood fiber direction. Composites with a cement/wood ratio of 1.5 exhibited a compressive strength comparable to that of normal concrete, the strain at peak load was more than ten to fifty times larger than the strain at peak load for normal concrete depending on the direction of the compressive loading. The ability of the composites to sustain such large plastic deformations suggests that WCPC has a strong potential to dissipate energy. The toughness index I5 for the composites with either a cement/wood ratio of 1.5 or 1.0 was about 7.0, which is seven times larger than that of normal concrete.

Cement/wood ratio

1.5 1.0

Mean 6.99 7.03 Toughness

I5 St. Dev. 0.41 0.37


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This study suggests that CCA-treated wood removed from service can be used for manufacturing wood cement particle composites for use in applications where compressive strength and energy dissipation are desirable properties.

REFERENCES

1. Stalker, I. N. 1993. Disposal of treated wood after service. Proceeding CWPA: 159-174. 2. Micklewright, J. T. 1993. Wood Preserveation Statistics, 1991. American Preserver’s Association.

Woodstock, MD. 3. Environmental Building News, Disposal: The Achilles’ Heel of CCA-Treated Wood. Vol. 6, No.3, March

1997. 4. U.S. Consumer Products Safety Commission (COSC) Web site http://www.cpsc.gov/. 5. Cooper, P.A. 1994. Disposal of treated wood removed from service: The issues in environmental

considerations in manufacture, use, and disposal of preservative-treated wood, Forest Products Society(Madison, Wisconsin), pp. 85-90.

6. Marer, P.J. and Grimes, M. 1992. Wood Preservation. University of California Statewide integrated pest management project. Division of Agriculture and Natural Res. Pub. 3335.

7. Wolfe, Ronald W., 1997, “The use of recycled wood and paper in building applications,” Proceedings No.7286, Forest Products Society

8. Wolfe, Ronald W., 1999, “Durability and strength of cement bonded wood particle composites made from construction waste,” Forest Products Journal, 49(2): 24-31

9. Blankenhor, P.R. 1994, “Compressive strength of hardwood-cement composites”, Forest Products Journal, Vol. 44, No. 4, pp. 59-62

10. Sorfa, P. 1984, “Properties of wood-cement composites”, Journal of Applied Polymer Science, Applied Polymer Sym. 40, pp. 209-216

11. American Society for Testing and Materials, 1996, Standard method of evaluating the properties of wood-based fiber and particle panel materials. ASTM Standard D1037-78.

12. American Society for Testing and Materials, 1996, Standard Test Method for Flexural Toughness and First Crack Strength of Fiber-Reinforced Concrete. ASTM Standard C1018.


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Review of Thermochemical Conversion Processes as Disposal Technologies for Chromated Copper Arsenate (CCA) Treated Wood Waste

Lieve Helsen and Eric Van den Bulck ABSTRACT Several alternative methods for the disposal of chromated copper arsenate (CCA) treated wood waste have been studied in the literature, and these methods are reviewed and compared in this paper. Extraction experiments have been carried out on CCA treated wood and evaluated as a method to recover the metal compounds into either fresh wood preservatives or other useful industrial materials. Recycling and recovery processes of the metals in the metallurgical industry have also been studied, but not yet all metal products are transformed to usable forms. A study about biorecycling of CCA treated wood through bioremediation and biodeterioration has been initiated. Numerous studies and experiments have been carried out on burning contaminated wood. Direct electrodialytic removal of the metals from CCA treated wood, as well as electrochemical cleaning processes for ash resulting from combustion of CCA treated wood, are under study. Pyrolysis processes (both slow and flash pyrolysis) have been investigated as a major process for the disposal of cellulosic wastes, also CCA treated wood waste. The authors performed a lot of experimental and theoretical work to get more insight in the metal behaviour during the low-temperature pyrolysis of CCA treated wood waste. Experiments were carried out with CCA treated wood samples, as well as with arsenic model compounds and mixtures of arsenic oxides and reducing agents (glucose or activated carbon). The most important conclusion is that zero arsenic release during pyrolysis of CCA treated wood seems to be impossible since the reduction reaction (As2O5 → As2O3 + O2) can not be avoided in the reducing environment, created by the presence of wood, char and pyrolysis vapours. Once the trivalent arsenic oxide is formed, it is released. This release is driven by a vapour pressure controlled volatilisation process: the higher the temperature, the faster the release. The insights gained through these studies are used to evaluate other thermochemical conversion processes (flash pyrolysis, gasification and combustion) with respect to their applicability to the disposal of CCA treated wood waste. This evaluation is compared with observations and calculations reported by other researchers in the literature. Finally, the most appropriate thermochemical disposal technology is identified. Keywords: chromated copper arsenate (CCA), wood waste, disposal, thermochemical conversion ------------------- Katholieke Universiteit Leuven, Dept. of Mechanical Engineering, Div. Applied Mechanics and Energy Conversion, Celestijnenlaan 300A, B-3001 Heverlee, Belgium Email address: [email protected], Phone number: 00-32-16-32.25.05 Fax number: 00-32-16-32.29.85


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INTRODUCTION It is estimated that world-wide the wood preservation industry presently treats approximately 30 million cubic metres of wood each year, consuming some 500 000 tonnes of preservative chemicals. Approximately two-thirds of this volume is treated with chromated copper arsenate (CCA) [1]. CCA has been used to preserve wood from insects, fungi and water damage for many years, and is still used today (almost exclusively as oxides), albeit restricted to a limited number of industrial applications. Substantial amounts of CCA remain in the wood for many years and the disposal of scrap wood is a growing problem in Europe, the United States, North America and Japan. The quantities of discarded CCA treated wood will increase significantly in the future [2]. With respect to CCA treated wood at the end of its service life, the wood is classified as hazardous in some member states of the EU and subject to stringent requirements and classified as not hazardous in other member states and therefore subject to much less stringent requirements. Current legislation in the classification of waste is thus imprecise thereby creating a lack of consistency. For several wood products it has been concluded that the waste stage has a very significant impact on the Life Cycle Assessment results [3].

Future waste minimisation focuses on the use of alternative wood treatment preservatives that do not contain arsenic. However, these alternatives leach more copper than CCA treated wood. From a regulatory perspective, they pose a lower risk than CCA treated wood within the disposal sector and within terrestrial environments. Slightly higher risks are expected in aquatic environments due to the toxicity of copper to aquatic organisms [2]. A number of technical issues still have to be resolved with several potential alternative treatments, including corrosion effects, weathering properties and fixation characteristics. Viable alternatives are available for CCA treated wood for the lower retention levels (4 - 6.4 kg/m3).

Besides the use of alternative wood treatment preservatives other waste abatement, elimination or

reduction methods could be [4]:

• substitution of CCA treated wood by other materials such as untreated cedar, teak, plastic lumber, concrete, steel, aluminium, brick, … for which complete and quantitative full life cycle assessments are needed,

• wood modification treatments (such as high temperature nitrogen or steam exposure or thermal oil submersion) for which research on durability and weathering performance is needed,

• optimisation of preservation treatment for specific end-use conditions (better quality control, selection of wood species),

• designing details that will minimise the potential for decay and thereby the overuse of preserved wood,

• service life enhancing technologies such as the use of stains and other surface protection coatings and water repellents,

• design to minimise waste during construction (reduction in off-cuts and other wastes from reprocessing).

Regardless of waste minimisation efforts, improved disposal-end management practices will play a key role in minimising the impacts of CCA treated wood upon disposal within the short term (25-40 y). The authors had the idea to give a critical overview of the different methods suggested in literature as solutions for the disposal of CCA treated wood waste. While reviewing the papers already published, an extensive review paper with a list of selected references, published by Cooper [5] in 2003, was found. Because a good review already exists, the aim of this paper is not to repeat this work. Therefore, in this paper the authors give a more detailed analysis of the thermal processes and try to identify the most appropriate thermochemical disposal technology for CCA treated wood waste. First, a short overview of


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the different methods under study is given, based on the material published by Cooper [4,5,6] and other researchers. LITERATURE REVIEW: OPTIONS FOR MANAGING CCA TREATED WOOD WASTE A first question that arises when looking for disposal-end management options for CCA treated wood waste is whether or not the CCA treated wood should be separated from mixed wood sources. In Florida, for example, construction and demolition (C&D) wood can contain up to 30 wt% CCA treated wood [2]. Sorting technologies have been studied [2,7,8,9,10,11,12,13,14] and will become a greater challenge as more alternative preservatives are introduced. Visual sorting based on the green colour is known to be not very effective, although it can potentially reduce the amount of CCA treated wood entering waste streams by 15-20%. Chemical stains (e.g. PAN indicator (C15H11N3O) producing an orange colour if sprayed on untreated wood and a magenta colour if sprayed on CCA wood) were found to be effective for sorting small quantities (< few tonnes/y) of CCA treated wood. Both laser and X-ray systems were shown to be very promising technologies for sorting large quantities (> 8000 tonnes/y) of wood in a more automated way. The detection limit of XRF is found to be 3-5% CCA treated wood. Moskal and Hahn [8] designed, implemented and made a field evaluation of an online detector system using laser-induced breakdown spectroscopy (LIBS) for the analysis of CCA treated wood. Discrimination between CCA wood and untreated wood was based on the atomic emission signal of chromium. The accuracy of the LIBS-based analysis ranged from 92% to 100% for sorting the waste at a construction and demolition (C&D) debris recycling centre. The LIBS system did not prove reliable for the detection of severely rotted wood samples or samples that were completely soaked with water. Morak et al. [9] reported a very high spatial resolution for laser-induced plasma emission spectrometry (LIPS) and found that the influence of the humidity and the species of the wood on the results of the analysis is negligible. The application of a permanent identification marking system similar to but more persistent than for grade stamping may become a requirement. Whether this be indelible stamp, bar code or embedded chip, it must be able to survive the service life exposure conditions to be of any use [6]. Industrial treated products, such as poles and railway ties, are easily recovered but CCA treated residential lumber presents a challenge to collection and transportation because of the increasing quantities and its widespread distribution. Eventually, it will be necessary to have a collection, transportation and processing infrastructure for this material. Since at European level the sale of arsenic-treated wood to consumer is banned and its use is restricted to a limited number of essential industrial applications, the collection and transportation of CCA treated residential lumber will be only a problem of the near future. When looking for disposal-end management options for CCA treated wood waste, a hierarchy of options should be considered with some options being more acceptable than others. The acceptability can differ from location to location, e.g. in Europe a lot of treated wood waste is incinerated while in North America almost all treated wood waste is landfilled. However, a general order of preference can be defined: 1. waste abatement or elimination 2. waste reduction 3. waste reuse 4. waste refining for recycling 5. waste treatment and destruction 6. waste disposal


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The first two points (abatement or elimination and reduction) have already been mentioned in the introduction, the existing and emerging technologies for managing CCA treated wood waste are summarised in Table 1, together with their barriers and prognosis with respect to implementation [4,5,6,15,16,17,18,19,20,21,22,23,24,25,26,27]. Table 1 Existing and Emerging Technologies for Managing CCA Treated Wood Waste management option barriers prognosis reuse wood waste is bulky and

inefficient to transport; contaminated sawdust may be generated

good for industrial products but of limited potential for residential treated products

• used as garden borders, posts, land piling, retaining walls, …

high contamination with nails and other fasteners; high cost to dismantle; low quality wood

• remanufacture – fence components

high contamination with nails and other fasteners; high cost to dismantle; low quality wood

material would have to be refinished to even out differences in weathering discoloration

• salvage and reuse through waste exchange

high cost of handling sorting, transportation and storage

limited potential

refining for recycling • wood based

composites issue of using metal containing and contaminated wood and loss of ownership of treated wood (product should be identified as one containing treated wood); landfill disposal is only deferred, not avoided; CCA tends to interfere with the adhesives

the market is not in favour of using CCA wood in conventional wood composite manufacturing, questions about safety of workers and environmental problems

− wood-cement composites

CCA wood fibre cement products are unlikely to be used since pulping of treated wood releases the CCA components into the spent pulping liquor, unless it is mechanically pulped; slow process due to long curing time of the composite; potential for hexavalent chromium release

excellent potential for the development of new composite products; benefit from inclusion of decay resistant wood fibre; stabilisation of metals within a cement matrix; improvement in bending strength and stiffness, internal bond strength, water absorption and thickness swelling performance

− wood-polymer composites

leaching, recyclability, decay resistance, emissions during processing and impacts on physical and mechanical properties should be evaluated

benefit from inclusion of decay resistant wood fibre; low cost and high strength to weight ratio

− thermosetting adhesives bonded

it makes little sense to use CCA wood since the decay hazard is

unproven and unlikely to be a significant factor in the near


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composites, particleboard

too low to justify it, except in the presence of termites; in that case the identification of the amount and distribution of CCA particles is required; an addition of 50% CCA wood does not significantly affect the board properties

term

− wet processed fibreboard and MDF

it makes little sense to use CCA wood since the decay hazard is too low to justify it; use of CCA wood would complicate the cleanup of process water

unproven and unlikely to be a significant factor in the near term

− exterior flakeboard products, oriented strand board (OSB)

OSB is made from high quality flakes; lumber products can not be flaked properly; the presence of CCA lowers all property values substantially; however, physical and mechanical properties were enhanced by spraying the flakes with a primer just before spraying and blending of the resin

unproven and unlikely to be a significant factor in the near term

• biodegradation by fungi part of the contaminants left in the wood and loss in fibre quality; absence of end use for extracted wood and chemicals; problems with contamination of the system by other organisms

not economically feasible

• extraction of CCA components

not 100% effective and slow; recycling of CCA components is not proved; not cost-effective at this time; high cost of size reduction

some potential for treatment of minor amounts of treated wood such as that produced as a by-product of milling

− biological almost complete extraction, only if combined with solvent extraction = dual remediation; several constraints that limit efficiency and cost-effectiveness

technically feasible but slow and expensive (high cost of the nutrient culture medium)

− chemical huge amounts of chemicals are used; multistage extraction is required to ensure complete removal of CCA; technology to recover CCA chemicals is not disclosed (re-oxidation + elimination of extracting compounds), but mixing of recovered solution and fresh CCA solution is promising

more research and development is needed to improve, optimise and evaluate the process; effects of extraction on combustion characteristics of wood residue are not reported; extraction has negative effect on the properties of particleboard prepared from extracted wood; economic feasible for surface removed treated wood or sawdust by-products of a re-sawing operation to recycle CCA chemicals

− steam explosion does not increase the extractability of the chemical components if used as a pre-treatment prior to extraction; leave some residual material in the extracted wood (only 90% removal of CCA)

not economically feasible


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− electro-dialytic no field tests performed (pilot scale is now being tested); expected cost is high; after treatment the metals are distributed over the electrolyte solution, the membrane and as a precipitate on the electrode; total removal of metals not achieved, Cu/Cr/As ratio in the electrolyte differs from the ration in the fresh CCA solution

not yet economically feasible; difficult to compete with solvent extraction

• use for mulch, compost or animal bedding

more leaching due to increased surface area (less than 0.1% CCA wood causes a mulch to exceed risk-based direct exposure standard for arsenic); CCA chemical is dispersed into the environment; products will become untraceable

clear policies and regulations that prohibit inclusion of CCA wood in mulch should be developed

treatment and destruction • wood liquefaction only initial lab-scale experiments;

only 85% of the CCA is removed much more research is needed to improve, optimise and evaluate the process

• thermal destruction advantage of energy recovery and significant reduction of waste volume, but ash is considered as hazardous waste and arsenic compounds are volatile (modifications, controls and monitoring are needed to meet air quality standards); chipping or grinding is required increasing the energy consumption and cost

potential if the metals collected in the ash are dealt with and arsenic is trapped from the flue gas; most common method in Europe but strong resistance in Canada; more favourable climate for this option is expected in the future

− controlled environment incineration / combustion / cogeneration

cost of grinding dirty material; presence of arsenic in the emissions; collection of metals in the ash where it must be collected and dealt with (metal stabilisation or metal extraction through chemical or electrochemical processes or cyclone melting); general resistance in some countries to consider these options for disposal

some potential, but requires further development; lessens the dependence on fossil fuels; metal concentrations can be diluted by mixing with other waste streams (such as household waste) or fuels (such as coal)

− cement kilns Portland cement standards have limitations on metal levels, chromium being the limiting element; cost of collection, transport, removal of metal contaminants, getting a permit

potential is limited to a fraction of wood generated; appropriate for milling residues and low retention residential wood

− controlled pyrolysis arsenic is distributed over the three products (charcoal, bio-oil and pyrolysis gas); no time-temperature threshold found for zero arsenic volatilisation

besides elimination of dioxins and furans formation and possibly easier metal recovery, no additional advantages over the other thermal destruction methods

− high temperature gasification in a metallurgical furnace

high cost of pure oxygen; removal of pure metallic arsenic in the vapour not yet proven on a large scale; arsenic emissions during start-up and shutdown

pilot plant tests still have to be performed; more research is needed to evaluate the process


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• energy and raw materials recovery by metallurgical processes

plant has to be well designed to scrub all volatile and particulate arsenic from the stacks; relatively low CCA concentrations in the lumber make CCA recycling economically infeasible; not yet all metal products are transformed to usable forms

excellent potential if infrastructure for collection and transportation of CCA wood waste is developed; further research is needed to examine the maximum amount of CCA wood that can be mixed with copper concentrates without interfering the process

landfill disposal CCA chemical can leach from CCA wood (both unburned and as ash) in quantities that exceed regulatory thresholds; monofill results in the highest metal concentrations in the leachate compared to C&D debris landfill and MSW landfill; cost of landfilling (hazardous waste sites, lined landfills); shortage of landfill space

not a preferred option because it does not recover any value from the used product; may not be acceptable at individual landfill sites (by 2005 no organic wastes will be accepted at landfills in the EU)

As shown in Table 1 there are many technological options to manage waste of CCA treated wood, but all have their limitations and problems. Instead of importing (the major part from China and Mexico) considerable quantities of arsenic to Europe, it would be more reasonable to utilise the arsenic recovered in whatever way (recycling process at the wood preservation sites, in the metallurgical industry, arsenic containing solutions resulting from remediation processes, …). However, the metals must be converted to their proper valence state before reuse. Such additional processing adds to the cost of recycling which renders the current technologies not economically feasible at this time. The main restriction on commercial exploitation of reuse or recycling technology is the highly diffuse nature in which redundant treated timber enters the waste chain. In the following sections the authors focus on thermochemical conversion processes as possible alternatives for the treatment of waste of CCA treated wood. Thermal utilisation of the wood waste offers the advantage of providing energy and concentrating wastes for recycling or disposal. THERMOCHEMICAL CONVERSION PROCESSES: OBSERVATIONS While the CCA preservative chemicals are relatively simple, inorganic reactions during the wood preservation process produce complicated inorganic compounds and complexes. The thermal decomposition behaviour of these inorganic compounds and complexes is unknown and difficult to determine. The reactions and thermal decomposition of a system containing a volatile compound, such as arsenic oxide, in a gas flow cannot be predicted solely based on equilibrium data. Therefore, in practical disposal of CCA treated wood by thermal decomposition, the reaction kinetics will likely determine the ultimate fate of arsenic in the system [28]. Thermogravimetric (TG) experiments with model compounds have been used to predict the thermal behaviour of the CCA treated wood system by Helsen et al [29] and Kercher and Nagle [28]. The main conclusions are listed below. 1. Volatile As2O3 loss occurs below practical wood pyrolysis and combustion temperatures (Tonset =

200°C), due to the high vapour pressure of As2O3. 2. Pure As2O5 does not reduce nor volatilise at temperatures lower than 600°C in air or nitrogen

atmosphere. Oxygen content of the atmosphere shows no effect on volatile loss, which suggests a


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weight loss mechanism based on vapour pressure, not on the decomposition As2O5 → As2O3 + O2. A hydrogen containing atmosphere (5% H2) causes As2O5 to volatilise at much lower temperatures (order of 425°C) which suggests that reducing gases from thermal decomposition of wood (e.g. CO), which behave similar to hydrogen, likely would decompose As2O5 at lower temperatures.

3. The thermal decomposition of copper (II) oxide strongly depends on the oxygen content in the atmosphere (Tonset is 775°C versus 1050°C in respectively nitrogen and air), indicating that solid-state oxygen diffusion may be the limiting step. The onset of weight loss in a hydrogen/nitrogen mix is around 200°C, which is confirmed by the Ellingham diagram showing a driving force for the reduction of copper oxides by hydrogen (or carbon monoxide).

4. Chromium (III) oxide does not undergo any significant reactions during heating in inert or air atmosphere.

5. When a mixture of copper (II) oxide and arenic (V) oxide is heated, part of arsenic (V) oxide simply volatilises at slightly lower temperatures than in the pure As2O5 experiments; the remainder of arsenic (V) oxide reacts with copper (II) oxide to form mixed copper arsenates (2CuO.As2O5 and Cu3(AsO4)2). The atmosphere exhibits a strong effect on the thermal decomposition of the copper arsenates; in air no weight loss is observed up to 900°C. During thermal decomposition of CCA treated wood the formation of copper arsenates may be a mechanism to limit arsenic loss up to 900°C.

6. When a mixture of chromium (III) oxide and arsenic (V) oxide is heated, free arsenic (V) oxide is volatilised; some As2O5 reacts with Cr2O3 to form chromium arsenate (CrAsO4), which however does not exhibit any temperature range of zero weight loss.

7. In CCA treated wood, the thermal decomposition of the inorganic components can be influenced by interactions with wood and its decomposition products. Therefore the influence of the presence of glucose and activated carbon has been studied. The thermal decomposition of As2O5 is highly influenced by the presence of glucose, both in a nitrogen atmosphere and in a mixed nitrogen – oxygen atmosphere. The presence of glucose gives rise to a faster decomposition, the effect being more pronounced the higher the oxygen concentration in the purge gas is. The interaction of glucose and As2O5 is probably a combination of three effects: mutual acceleration of the decomposition reaction, oxidation-reduction reactions and the formation and decomposition of arsenate esters. Oxygen concentrations up to 10% are sufficient to accelerate the decomposition of both As2O5 and glucose, but insufficient to reverse the reaction As2O5 → As2O3 + O2. Also activated carbon influences the thermal behaviour of As2O5, by promoting arsenic volatilisation at temperatures higher than 300°C. Extrapolation of the behaviour of these model compounds to the real thermal decomposition of CCA treated wood indicates that the reduction of pentavalent arsenic to trivalent arsenic is favoured by the reducing environment, created by the presence of wood, char and pyrolysis vapours. Therefore, the most important conclusion is that zero arsenic release during thermal decomposition of CCA treated wood seems to be impossible since the reduction reaction (As2O5 → As2O3 + O2) can not be avoided in the reducing environment. Once the trivalent arsenic oxide is formed, it is released, obeying a temperature controlled solid-vapour equilibrium.

8. For a mixture of arsenic (V) oxide and yellow pine sawdust it was found that the products from inert pyrolysis of wood promote the volatilisation of As2O5. By heating at 5°C/min interaction between both compounds can be observed from 370°C, indicating that arsenic volatilisation occurs above 370°C. However, if the mixture is held for longer time periods at temperatures between 250°C - 370°C, it is observed that arsenic volatilisation occurs, the rate of arsenic volatile loss increasing with dwell temperature.

9. For a mixture of copper (II) oxide and yellow pine sawdust inert pyrolysis causes the reduction of copper (II) oxides at low temperatures (around 305°C).

These studies with model compounds may not take all effects into account, for example the formation of complexes and hydrates of arsenic (V) oxide during preservative fixation that may help to prevent arsenic loss below 400°C. Therefore thermal decomposition studies with real CCA impregnated wood samples


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are necessary. A lot of researchers have studied the pyrolysis, gasification or combustion / incineration of CCA treated wood and evaluated the fraction of arsenic, copper and chromium released to the atmosphere and retained in the solid residue. This work has varied in scale from laboratory to industrial installations and has included 100 % CCA treated wood and mixtures with other waste timber sources or other industrial wastes. Both experimental and modelling work have contributed to new insights. Percentages of arsenic volatilised have been reported to range between 8 and 95 % [16,30,31,32,33,34,35,36,37,38]. These percentages depend on temperature, residence time, extended period of ash heating, presence of chlorine and/or sulphur, oxygen partial pressure, air flow rate and the impregnation process. Amounts of copper and chromium volatilised are not well documented, but are found to be much lower than for arsenic. In all studies arsenic is identified as the problematic compound with respect to volatilisation. If working conditions can be determined for which arsenic losses are predicted to approach zero, extensive flue gas cleaning equipment (scrubbers and filters) is not required, resulting in a less expensive system. Therefore, a threshold temperature, below which the arsenic volatilisation is zero, has been looked for. Hata et al. [30] state that at 300°C already 20% of the total arsenic is volatilised, which is ascribed to part of the arsenic being unreacted (as As2O5 compound) after impregnation of the wood. The remainder of the arsenic has reacted during the impregnation process resulting in chromium arsenate (Cr2As4O12) that decomposes only at temperatures higher than 700°C. Helsen et al. [16] conclude that metal (Cr, Cu and As) release seems to be “zero”, but is inconclusive (because of the high experimental uncertainty) at a temperature of 300°C which is held for 20 minutes. Residence times of 40 minutes already result in non negligible arsenic releases. Furthermore, they show that the major part of arsenic in the solid pyrolysis residue (350°C, 20 minutes) is present in trivalent state [39]. Pasek and McIntyre [31] reported that arsenic volatilisation is predicted (through linear extrapolation) to approach zero under conditions of limited air flow and high combustion temperature in excess of 1100°C. No volatilisation of copper or chromium was observed. The residual ash is indigestible even under the strongest acidic conditions, which is thought to be due to the formation of transition metal arsenides at the higher combustion or calcination temperatures. The results from this work are contrary to other studies. Moreover, arsenic balances were far below 100%, which is suspected to be due to incomplete sampling and/or analysis of the metals released, a problem also appearing in several other studies [37,38,40,41,42,43]. These studies show that a threshold level (temperature-time) below which zero arsenic release is guaranteed will be very difficult or even impossible to reach in large industrial installations without flue gas cleaning. The mechanism responsible for arsenic release during the thermal decomposition of CCA treated wood is not yet fully understood, although a lot of researchers have tried to identify the arsenic compounds released and to postulate some hypotheses. McMahon et al. [36] reported that negligible amounts of arsine (AsH3) are formed during CCA wood combustion. Essentially all of the volatilised arsenic recovered was found in the condensed (particulate) form and consisted of both arsenites and arsenates. The volatile arsenic trioxide, however, could not be trapped efficiently. They stated that arsenic release is not so much a function of how the fuel is burned, but rather how long the residual ash is exposed to high temperature. Hirata et al. [40] stated that arsenic compounds are first reduced to As2O3 with heating, after which it is gasified according to the equilibrium 2As2O3 ↔ As4O6 and generally accepted to be As4O6 for temperatures up to 1073°C. For minimising gaseous toxicants from arsenic, CCA treated wood must be burned at low temperatures with reduced air supply. Cornfield et al. [44] did not detect arsine or other metal compounds in volatile nonparticulate form. They suggested that the metals released are all present in particulate form. Helsen and Van den Bulck [45] concluded that the release of arsenic during pyrolysis of CCA treated wood is controlled by the reduction of pentavalent to trivalent arsenic, which is accelerated by the presence of reducing compounds originating from the pyrolysing wood. Once arsenic trioxide is formed, it will be released at temperatures as low as 200°C. In freshly treated wood arsenic is fixed in pentavalent state, but in weathered wood the arsenic may be partly reduced to the trivalent state. The only way to avoid or limit arsenic release (at low temperatures) is to control the reduction reaction.


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Once arsenic trioxide is formed, it is not easy to re-oxidise it. For example, during combustion with a high air/fuel ratio oxygen is present in the flue gas, but arsenic trioxide does not get oxidised into arsenic pentoxide as the reaction is known to happen only under pressure [46]. Besides experimental studies modelling contributes to a deeper understanding of the metal behaviour during thermal decomposition of CCA treated wood. Sandelin and Backman [47] studied the high temperature equilibrium chemistry involved when CCA treated wood is burned by utilising an equilibrium model based upon minimising the Gibbs free energy of a hypothetical combustion system. They revealed that partial pressures of arsenic-containing compounds dominate in the temperature range from 500 to 1600°C. At temperatures between 500 and 1150°C, As4O6(g) is the dominating species, but at higher temperatures AsO(g) takes over. The following explanation was given: arsenic pentoxide is stable at low temperatures but ''forms'' gaseous As4O6 at about 580°C. They concluded that chromium and copper in impregnated wood are unlikely to volatilise at common combustion temperatures. At 1200°C only 0.05 % of the total chromium and 0.51 % of the copper was found in the gas phase. Arsenic was more volatile, existing 86.89 % in the gas phase at the same temperature. Supplementary calculations showed that magnesium, copper and chromium compounds may prevent arsenic from volatilising. In addition, reducing conditions within the char particle may affect the tendency of the metals to vaporise. Conclusions with respect to low-temperature chemistry were not given. Kitamura and Katayama [48] combined experimental studies and thermodynamic analyses and concluded that the higher retention of arsenic in charcoal (after pyrolysis in nitrogen atmosphere) compared to ash (after combustion in air) is due to absorption of arsenic in the charcoal. Thermodynamic calculations resulted in the identification of vaporised arsenic species in nitrogen and air atmosphere: As4, As2 and As3 dominate up to 1100 K in nitrogen atmosphere, while AsO2, AsO, As, As4O7 and As4O6 appear at temperatures above 1100 K in air. These results do not agree with the results published by Sandelin and Backman [47]. Since thermal processes inherently lead to volatilisation of arsenic, appropriate arsenic capturing devices have to be installed. These devices are said to be commercially available, but very few tests have been carried out on industrial scale for the specific case of thermal conversion of CCA treated wood that is characterised by the production of submicron aerosol fumes which are difficult to effectively collect. Even on lab-scale it is very difficult to obtain arsenic mass balances of 100%. The most important conclusions drawn from an extensive literature review are given elsewhere [49]. Syrjanen and Kangas [38] emphasised the need to change existing flue gas cleaning equipment when impregnated timber is burned. A venturi scrubber was found to be insufficient in combination with a grate boiler; the average arsenic concentration in the exhaust gas was 2.8 mg/Nm3 [41]. Additional investments are needed for better cleaning systems, tuned in to the type of burner, gasifier or pyrolyser, and for measurements to control emissions. Industrial experience with other feedstocks can be helpful in the design of an appropriate arsenic capturing device. When incinerating arsenic containing waste an efficient filter (electrostatic filter) does not succeed in capturing all the arsenic. Around 5.4% of the arsenic originally present in the waste passes the electrostatic filter and is captured in the downstream wet scrubber (using lime and NaOH) by absorption and/or chemisorption [50]. Sorbent injection is a very attractive method to reduce arsenic emission during coal combustion [46,51,52,53]. Arsenic reacts, while still in the vapour state, at high combustion temperatures, with various sorbents to form larger particles which can be collected effectively by particulate collection devices. The sequestering action of the sorbents reduces the vapour form and/or fine particle form of the metal [51]. These sorbents can be fly ash, activated carbon or mineral material. Hydrated lime (Ca(OH)2) and limestone (CaCO3) are found to be very effective. While Ca is responsible for the reaction of As with these solids, it is the availability of active Ca sites at the surface of these solids that determines the rate of reaction [53]. At temperatures below 600°C tricalciumorthoarsenate (Ca3As2O8) is formed, while temperatures between 700 and 900°C give rise to the formation of dicalciumpyroarsenate (Ca2As2O7), which is unstable and therefore responsible for a decrease in As capture at higher temperature [46]. Sterling and Helble [53], however, reported a maximum capture of As with calciumoxide at 1000°C.


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Besides the mechanism responsible for arsenic release and options available for arsenic capture, the characteristics of ash resulting from combustion of CCA treated wood and combustion of a mixture of untreated and CCA treated wood have been studied. It is concluded that the environmental impact of the ashes investigated (bottom ash, boiler ash, fly ash) is remarkable, none of them meeting the requirements for above-ground disposal [54,55]. Leachates concentrations according to the DIN 38414 part 4 leaching standard exceed the limits for arsenic and chromium. Moreover, chromium is present in the toxic hexavalent state [54]. Bottom ash from wood mixed with minimum 5% CCA treated wood is characterised as hazardous waste under US regulations [55]. To dispose the ash in an environmentally sound manner two options exist: 1. the elements enriched in the ash after the combustion process are recycled; 2. the ash is landfilled after pretreatment, e.g. solidification with cement, concrete, … Different theories exist about the formation of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF), but about the role of copper in the pathways all researchers are unanimous: copper is identified as a catalyst for PCDD/F formation [34,56,57,58,59,60,61]. Due to the presence of copper in CCA treated wood, the formation of toxic PCDD/Fs has to be taken into account [61]. Wunderli et al. [62] examined solid residues (bottom ash and fly ash) from wood (native and waste) combustion and concluded that wood burning is always accompanied by unwanted production of PCDD/F, the amount being dependent on the type of wood burned and the construction of the combustion system. Low carbon burnout and zones with low temperatures seem to support the formation of PCDD/F strongly [60,62]. Consequently, grate boiler fly ashes contain higher levels of PCDD/F than either bubbling or circulating fluidised bed boiler fly ashes [63]. One way to avoid the formation of PCDD/F in incinerators is by blocking the catalytically active sites of copper species by poisoning, for example through the addition of small amounts of sulfamide to the fuel [58]. Since PCDD/F formation is the combination of the elements C, H O and Cl under favourable conditions, another way is to ensure working conditions that eliminate one or more of the essential elements (C, H, O, Cl) or essential parameters (temperature 250-400°C), for example pyrolysis is performed in an oxygen-free environment or flue gases are immediately quenched to very low temperatures. In this aspect pyrolysis has an advantage over gasification and combustion. BEST AVAILABLE THERMOCHEMICAL CONVERSION TECHNOLOGY For an inert pyrolysis process to be a reasonable disposal method for CCA treated wood, volatile arsenic loss has to be controlled and the solid pyrolysis product must be suitable for recuperating the inorganic compounds. SEM-EDXA studies have shown [30,64], that during pyrolysis the metal compounds form agglomerates, which suggests that the metals can be easily recuperated from the charcoal in a dry way [65]. However, arsenic losses are already observed for temperatures as low as 275°C [28]. Lower temperatures give rise to very slow wood decomposition rates and thus extremely long reaction times. Therefore, in practice pyrolysis leads to non zero arsenic volatilisation. However, the amount of arsenic volatilised is much less compared to gasification or incineration and therefore the arsenic released may be easier captured by for example chemisorption. The use of flue gas cleaning equipment that captures all arsenic volatilised can thus not be eliminated. With respect to the formation of PCDD/Fs and maybe to recovery of the metals, pyrolysis could be a better option than gasification or combustion. Flash pyrolysis, that aims at producing as much pyrolysis oil as possible, is not an option for CCA treated wood since a non negligible percentage of arsenic (between 5 and 18% [42]) is collected in the oil. The advantage of pyrolysis oil is that it can be stored, but substantial concentrations of arsenic make it useless.


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Incineration of CCA treated wood can be coupled to a recycling process, provided that an extensive gas cleaning system is used to control air emissions. The arsenic containing solution, collected in the scrubber, is recycled to the CCA solution production unit and the ash containing arsenic, copper and chromium is processed in a copper smelter [38,66] or recycled through chemical or electrochemical processes [67]. The arsenic trioxide dust collected in filters still poses problems with respect to occupational health. As far as occupational health is concerned the use of wet methods to capture arsenic is preferred. Incineration is thus an option for the disposal of CCA treated wood waste or mixed wood waste if three requirements are satisfied: 1. the arsenic and PCDD/F emissions are avoided by using an appropriate gas cleaning system and

appropriate cooling trajectories for the flue gas, 2. the arsenic captured (scrubber solution and filter dust) can be recycled in a safe way, 3. an environmentally sound ash treatment technology is available. A disadvantage of incineration is that it generates heat that has to be used immediately or converted to electricity (efficiency is relatively low), instead of producing a secondary fuel. Co-incineration is often presented as the best solution for the treatment of wood waste. Advantages are: • the attraction of co-incineration is the economy of scale; power stations are huge compared to

incineration plants. • low investment cost since the incineration plant already exists, only the gas cleaning equipment has to

be extended or adjusted. In Norwegian waste incinerators, for example, the combination of bag filters with activated carbon and wet scrubbers is used [68].

• the installation can be designed and installed on a short term. • the availability of CCA treated wood waste is not an issue since co-incineration is highly flexible with

respect to the fuel used. • if different waste streams are mixed, e.g. CCA treated wood waste and municipal solid waste (MSW),

arsenic may be scavenged by the calcium present in the other waste stream. • it is easier to comply with emission legislation due to the dilution effect. However, it is not advisable to mix CCA treated wood with other fuels, such as coal, since CCA treated wood contains much more arsenic than coal. Consequently, the incineration process would deliver more bottom ash that has a higher concentration of water-soluble arsenic and the volatile arsenic has to be removed from a larger amount of flue gas [66]. Moreover in some countries (like Denmark) legislation prescribes that impregnated wood waste must be sorted out and treated separately. For these countries co-incineration is not an option. In other countries, like the Netherlands, a mixture of coal and up to 40% of wood waste (including CCA treated wood) can be used as input fuel for power plants, receiving green certificates [69]. In the European waste classification system, however, CCA treated wood waste is defined as dangerous waste and excluded form the biomass category for which green certificates can be handed out. Most European countries, except the Netherlands, follow this EU directive. Gasification is characterised by higher energetic efficiencies (electricity generation efficiency is enhanced by burning a combustible gas in a gas turbine instead of fuelling a boiler) and lower environmental impact compared to incineration. If CCA treated wood is used as feedstock, appropriate gas cleaning equipment is still needed [43], but the amount of gas to be cleaned is lower than for incineration. During high temperature gasification the arsenic may be totally converted to metallic arsenic, which is much easier to capture than arsenic trioxide since metallic arsenic does not go through a liquid phase upon cooling and has a higher sublimation temperature than arsenic trioxide [15]. It is essential that the total amount of arsenic is released from the CCA treated wood and reduced to the metallic form. A cleaning system that captures all the arsenic is a very critical point in this gasification unit. Due to the high temperature (1100-1500°C) all organic compounds are cracked, eliminating the danger for PCDD/F formation. When a metallurgical furnace is used the chromium and copper can be caught in a slag, which can be applied as


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abrasive. The syngas (H2 + CO, diluted by CO2 + H2O + N2) can be used or sold as fuel and the pure metallic arsenic can be recycled in the CCA impregnation process. A disadvantage of the process is the high temperature needed, but the heat required can be recovered from the gas produced. This process has still to be proven at pilot scale. The authors conclude that the best available thermochemical conversion technology for the treatment of CCA treated wood waste is: • on the short term: co-incineration as long as CCA treated wood waste has not to be treated separately

and dilution is allowed. • on the long term a sustainable solution has to be found: preference is given to recycle as much

material as possible but it has do be done in a cost-effective way. Dependent on the results of further research work one of the following methods will be identified as best available technology:

1. low-temperature (380°C) pyrolysis in a moving bed [70]; 2. high temperature gasification (1100-1500°C) in a metallurgical furnace [15].

Both technologies aim at recuperating the metals and the energy (as secondary fuels: combustible gas and charcoal or syngas) contained in the CCA treated wood waste, but both technologies still have to be proven.

The optimal scale of application is determined by a balance between the high investment cost of the reactor and flue gas cleaning equipment on one hand and the high transport cost to collect the waste timber on the other hand. The important issue is whether or not it is better to transport the wood waste over long distances to gain economy of scale for the operation of large thermal treatment plants. ACKNOWLEDGEMENTS L. Helsen is a post-doctoral research fellow of the Fund for Scientific Research of Flanders (Fonds voor Wetenschappelijk Onderzoek - Vlaanderen) (Belgium). The authors are grateful to the company ARCH Timber Protection Limited (UK) for the financial support of the research work. REFERENCES 1. D.G. Humphrey, The chemistry of chromated copper arsenate wood preservatives, Reviews in

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26. J. Jambeck, T. Townsend and H. Solo-Gabriele, The disposal of CCA treated wood in simulated landfills: potential impacts, Presented at the 34th Annual IRG Meeting, Brisbane, Australia, May 18-23, 2003, IRG/WP 03-50198.

27. R.J. Shiau, R.L. Smith and B. Avellar, Effects of steam explosion processing and organic acids on CCA removal from treated wood waste, Wood Science and Technology, 34 (5), 2000, 377-388.


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29. L. Helsen, E. Van den Bulck, M.K. Van Bael and J. Mullens, Thermal behaviour of arsenic oxides (As2O5 and As2O3) and the influence of reducing agents (glucose and activated carbon), submitted for publication in Thermochimica Acta, 2003.

30. T. Hata, P.M. Bronsveld, T. Vystavel, B.J. Kooi, J.Th.M. De Hosson, T. Kakitani, A. Otono and Y. Imamura, Electron miscroscopic study on pyrolysis of CCA (chromium, copper and arsenic oxide)-treated wood, J. Anal. Appl. Pyrolysis, 68-69, 2003, 635-643.

31. E. A. Pasek and C. R. McIntyre, Treatment and recycle of CCA hazardous waste, Presented at the 24th annual IRG meeting, Orlando, USA, 1993, IRG/WP 93-50007.

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33. A.J. Dobbs, D. Phil and C. Grant, The volatilization of arsenic on burning copper-chromium-arsenic (CCA) treated wood, Holzforschung, 32 (1), 1978, 32-35.

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35. J.E. Kramer, J.W.A. Lustenhouwer, J.C. Van Weenen and M.A.C. Brinkkemper, Gebruik van afvalhout, Ministerie van Volksverhuizing, Ruimtelijke Ordening en Milieubeheer, Leidschendam, Nederland, Nr. 17, 1985.

36. A.K. McMahon, P. B. Bush and E. A. Woolson, Release of copper, chromium and arsenic from burning wood with preservatives, Presented at the 78th annual meeting of the air pollution association, Detroit, MI, 1985, paper 85-56.3.

37. Tauw Infra Consult B.V., Verbranding van afvalhout, Deel 1, Nationaal Onderzoeksprogramma Hergebruik van Afvalstoffen (NOH), Nederland, 1987, project 51766.01.

38. T. Syrjanen and E. Kangas, Recycling of pressure impregnated timber and preservatives – incineration techniques, Presented at the IRG Symposium Environment and wood preservation, Cannes-Mandelieu, France, February 5-6, 2001.

39. L. Helsen, E. Van den Bulck, M. Van Bael and J. Mullens, Arsenic release during pyrolysis of CCA treated wood waste: current state of knowledge, Journal of Analytical and Applied Pyrolysis, 68-69, 2003, 613-633.

40. T. Hirata, M. Inoue and Y. Fukui, Pyrolysis and combustion toxicity of wood treated with CCA, Wood Sci. Technol., 27, 1993, 35-47.

41. L. Lindroos, Recycling of impregnated timber. Part 2: Combustion trial, Presented at the 30th annual IRG meeting, Rosenheim, Germany, 1999, IRG/WP 99-50132.

42. T. Hata, D. Meier, T. Kajimoto, H. Kikuchi and Y. Imamura, Fate of arsenic after fast pyrolysis of chromium-copper-arsenate (CCA) treated wood, In A.V. Bridgwater (ed.) Progress in Thermochemical Biomass Conversion, Blackwell Science, Oxford, UK, 2001, 1396-1404.

43. A.J. Nurmi, Disposal of CCA treated waste wood by combustion: an industrial scale trial, Presented at the 27th Annual IRG Meeting, Guadeloupe, France, May 19-24, 1996, IRG/WP 96-50068.

44. J.A. Cornfield, S vollam and P. Fardell, Recycling and disposal of timber treated with waterborne copper based preservatives, Presented at the 24th Annual IRG Meeting, Orlando, FL, 1993, IRG/WP 93-50008.

45. L. Helsen and E. Van den Bulck, Metal behaviour during the low-temperature pyrolysis of chromated copper arsenate treated wood waste, Environmental Science & Technology, 34 (14), 2000, 2931-2938.

46. R.A. Jadhav and L.S. Fan, Capture of gas-phase arsenic oxide by lime: kinetic and mechanistic studies, Environmental Science & Technology, 35 (4), 2001, 794-799.

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48. T. Kitamura and H. Katayama, Behaviour of copper, chromium and arsenic during carbonization of CCA treated wood, Mokuzai Gakkaishi, 46 (6), 2000, 587-595.

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58. D. Lenoir, A. Wehrmeier, S.S. Sidhu and P.H. Taylor, Formation and inhibition of chloroaromatic micropollutants formed in incineration processes, Chemosphere, 43, 2001, 107-114.

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60. T. Salthammer, H. Klipp, R.D. Peek and R. Marutzky, Emissions from the combustion of wood treated with organic and inorganic preservatives, Presented at the 25th annual IRG meeting, Nusa Dua, Indonesia, May 29-June 3, 1994, IRG/WP 94-50019.

61. N.W. Tame, B.Z. Dlugogorski and E.M. Kennedy, Increased PCDD/F formation in the bottom ash from fires of CCA treated wood, Chemosphere, 50 (9), 2003, 1261-1263.

62. S. Wunderli, M. Zennegg, I.S. Dolezal, E. Gujer, U. Moser, M. Wolfensberger, P. Hasler, D. Noger, C. Studer, G. Karlaganis, Determination of polychlorinated dibenzo-p-dioxins and dibenzo-furans in solid residues from wood combustion by HRGC/HRMS, Chemosphere, 40, 2000, 641-649.

63. A.V. Someshwar, Wood and Combination Wood-Fired Boiler Ash Characterization, J. Environ. Qual., 25, 1996, 962-972.

64. L. Helsen and E. Van den Bulck, The microdistribution of copper, chromium and arsenic in CCA treated wood and its pyrolysis residue using energy dispersive X-ray analysis in scanning electron microscopy, Holzforschung, 52 (6), 1998, 607-614.

65. L. Helsen, E. Van den Bulck, K. Van den Broeck and C. Vandecasteele, Low-temperature pyrolysis of CCA treated wood waste: chemical determination and statistical analysis of metal input and output: mass balances, Waste Management, 17 (1), 1997, 79-86.

66. L. Lindroos, Balance of arsenic and recycling, Presented at the 33rd Annual IRG Meeting, Cardiff, Wales, UK, May 12-17, 2002, IRG/WP 02-50189.

67. O. Kristensen, Gasification of CCA impregnated wood, Presented at the Symposium Handling of Impregnated Waste Wood, Silkeborg, Denmark, September 25, 2002.

68. E. Kjerschow, Incineration of CCA wood waste in Norwegian Waste Incinerators, Presented at the Symposium Handling of Impregnated Waste Wood, Silkeborg, Denmark, September 25, 2002.


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69. A.M.L. Van Rooij, Open brief aan Voorzitter R. Prodi van de Commissie van de Europese Gemeenschap, June 2003, http://www.sdnl.nl/prodi-5.htm

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Characterization of Residues from Thermal Treatment of CCA Impregnated Wood. Chemical and Electrochemical Extraction

*Lisbeth M. Ottosen, Anne Juul Pedersen, Iben V. Christensen Abstract Thermal treatment of CCA impregnated waste wood is a way to utilize the energy resource of the wood and at the same time to reduce the volume of the waste. An issue of concern in relation to the thermal treatment is As emission to the air. Meanwhile there is still a matter to cope with when methods to avoid As emission are implemented; the residues with increased concentrations of Cu, Cr and As. In the present paper two different residues after thermal treatment are characterized: mixed bottom and fly ash from combustion of CCA impregnated wood and coke from pyrolysis of treated waste wood. By SEM/EDX it was found that the coke still showed wood structure and that Cu, Cr and As was to be found inside this wood structure. Cu was found alone while Cr and As was often found together. By chemical analysis it was found, too, that the coke contained high concentration of Zn, probably from paint. Chemical extraction experiments in acids were conducted with the coke and it was found that the order of extraction (in percentage) was Zn > Cu > Cr (As not measured). A similar investigation of the ash from combustion showed presence of small pieces with wood structure, too, though most particles were without sign of the material combusted. Cr was found build into the structure of some matrix particles, Cu, too, but Cu was also found condensed on the surface of some larger ash particles. As on the other hand was found associated to Ca in particles with an open structure. Chemical extraction with inorganic acids showed the order of percentages mobilized as: As > Cu > Cr. Electrodialytic extraction was tested with the ash. The aim was to test if this method could separate the ash from the mobilized parts of Cu, Cr and As and the method showed promising. As much Cr and Cu as solubilized by chemical extraction at pH below 1 was removed and only 8% As was left in the ash. Keywords

Waste wood, combustion, pyrolysis, residues, extraction, CCA _____________ *Lisbeth M. Ottosen, Anne Juul Pedersen, Iben V. Christensen Department of Civil Engineering, build. 204, The Technical university of Denmark, DK-2800 Lyngby, Denmark *Corrosponding author. Email: [email protected]


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Introduction In many countries an increased amount of chromated copper arsenate-treated wood (CCA) waste is expected in the years to come. CCA has been widely used for wood preservation since the early 1950s and because the fixation of CCA in the wood is good, the concentration of CCA is still high, when the wood is at the end of service. In some countries e.g. Denmark and Norway, the use of As for wood preservation has recently been forbidden. However, there will still be a lot of older impregnated wood that needs handling. To utilize the energy resources of the impregnated waste wood thermal treatment is beneficial. Meanwhile, thermal treatment must be done with cautions to avoid emission of toxic compounds to the surrounding environment, and it is especially As that is identified as the problem compound with respect to metal release during thermal treatment of CCA treated waste wood e.g. [1]. The behaviour of the preservation chemicals under thermal conversion should be examined with consideration to the environment. It is generally said that As compounds change to volatile As or Arsenious acids and cause air pollution. On the other hand, Cr and Cu compounds are considered to remain in the ash as water-insoluble solids on the heating of CCA-treated waste wood [2]. That emission of As to the air must be subjected to further investigation may be illustrated with the fact that field tests and laboratory studies have revealed the existence of trace elements in submicron particles emitted from power stations and that As are present in these sub-microns. The sub-microns are most likely to escape particulate control devises [3]. Thus even from thermal treatment of coal with typical As concentrations of less than 5 mg/kg [3] As emission occur. Two main groups of thermal treatment are combustion and pyrolysis and the As emission from the two methods are expected to vary considerably. An example of this experimentally obtained was given by Zeng et al. 2001 [3]. Pyrolysis experiments with coal were performed at temperatures from about 1400K to 1700K and the percentage of As retained in the coarse particles (particles not in sub-micron size) increased with decreasing temperature (to a maximum of 63%). Combustion experiments were conducted, too. At 2200K and a bulk oxygen concentration of 20% less than 10% As was retained in the coarse ash fraction and at higher temperatures and oxygen concentrations even less As was retained. A literature study performed by Helsen et al. (2003) [4] clearly showed that the mechanism of metal, and in particular As, volatilisation during the thermal decomposition of CCA treated wood is not yet completely understood. While the CCA preservative chemicals are relatively simple, inorganic reactions during the wood preservation process produce complicated inorganic compounds and complexes and the thermal decomposition of these is unknown and difficult to determine [5]. Helsen et al. 2003 [1] illustrated this experimentally. Pure As2O5·aq does not decompose nor volatilise at temperatures lower than 500ºC. On the other hand, during pyrolysis of CCA treated wood, arsenic is already released at a temperature of 320ºC, though As is present in the pentavalent state in the wood. Moreover, in the pyrolysis residue trivalent As is found. It can be concluded that the presence of wood, char and pyrolysis vapours may influence the thermal behaviour of As-oxides [1]. Hata et al. (2003) [2] followed the changes in As content as a function of temperature for CCA-treated wood after pyrolysis and found that already at 300ºC


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about 20% of the As was lost. A very careful control of process parameters during pyrolysis will be required to ensure a “zero” arsenic emission (if possible) [1] Even when a thermal treatment method that ensures no emission of As to the air is developed there is still a serious matter of concern: handling of the residues containing high concentrations of Cu, Cr and As. The present paper is focused on these residues. A coke residue from pyrolysis and a mixed bottom and fly ash from combustion are characterized and different extraction experiments are conducted. Residues from thermal treatment of CCA treated wood Cu, Cr and As will be heavily concentrated in the residues after thermal treatment of CCA impregnated wood, only. The more other waste treated together with the CCA treated wood the more dilution of Cu, Cr and As will be found in the residues but at the same time the impregnation chemicals are spread to a higher volume and thus handling of a higher amount of ash with less Cu, Cr and As is the result. In some countries it have been decided to sort out the impregnated waste wood from other waste to avoid increased As emission from waste incineration plants. Different systems for sorting out the waste wood are used. In Denmark all treated wood is sorted out by demolition companies and from private persons a special container is placed for treated wood at places for collection and recycling of household waste. In Finland impregnated waste wood can be returned at the stores where new wood are bought. The company that collects the waste wood is called Demolite Oy and is owned by the Finnish Wood Preservation Asociation. Also in Germany the wood preservation association (DHV) is actively taking part in collecting the impregnated wood waste. The opposite philosophy, where it is investigated how much CCA impregnated wood it is possible to add to the other waste for incineration before the emission criteria for As is exceeded, is also investigated in e.g. Norway at present by Norsk Energi. Another study by Solo-Gabriele et al. 2002 [6] have indicated that ash from combustion of a wood mixture with more than 5% CCA treated wood leached enough As (and sometimes Cr) to be characterized as hazardous waste under US regulations. Ash that originates from burning pure wood (without any impregnation) contains small amounts of chromium, and even the combustion of pure wood can produce ash whose leachate may not meet the requirement for Cr(VI) in the German “”Technische Anleitung Siedlungsabfall” [7]. Pohlandt et al (1993) [8] compared leachate from different ash types originating from impregnated wood and neither of the ashes met the requirements for above-ground disposal in the German “TA Abfall” regulations of the 17.12.1990. A pyrolyse residue (from pyrolysis experiment at 350ºC for 20 min.) was subjected to two successive extraction steps to determine the oxidation state of As. This speciation study showed that the major part of As was present in the trivalent state. If the pyrolysis residue would be disposed on a landfill, mainly As(III), which is the more toxic form, will be liberated into the


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environment. Hence, the pyrolysis residue of CCA treated wood waste cannot be landfilled without pretreatment [1]. Experimental section For this investigation two different residues from thermal treatment of impregnated wood is used: coke from pyrolysis and a mixed bottom and fly ash from combustion. A description of the origin of the ashes can be found in Table 1. Coke from pyrolysis Mixed ash from combustion The wood originated from “Kommunale sorteringsanlæg” and the wood was sorted by visual inspection, only. Since visual sorting of wood is very difficult, it can be expected that a fraction of the wood was not CCA impregnated. Pyrolysis experiment conducted at Kommunekemi A/S, Denmark, 2003.

The ash was obtained from a combustion experiment performed in Ås, Norway, in August 2000. 378.1 kg wood waste was burned, and 6.1 kg ash was produced, corresponding to a weight reduction of 98 %.

Temperature during the pyrolysis: 300 - 400ºC The cyclone temperature was 800-900oC during the combustion experiment.

Table 1: Origin of the residues for the experiments Visually the ash looked like every other ash, whereas the coke most of all looked like black wood chips in the size of about 2-5 cm. Characterization of the residues

The residues were characterized with respect to content of Cu, Cr, As for both and Zn, too, for the coke, loss on ignition, water content and pH. Furthermore the residues were subjected to an SEM/EDX investigation. The ash was dried and the coke dried and crushed by hand in a mortar before the characterization. The heavy metal content was found by FAAS (atomic absorption spectrophotometry in flame) after microwave assisted pressurized digestion of ash: 0.4 g dry sample in 10 ml concentrated HNO3 (135 Psi, 30 minutes). Loss on ignition was found as weight loss at 550oC, and pH was measured with a combined pH electrode (Radiometer, Copenhagen) in 1 M KCl after 1hour contact. For the ash a L/S (liquid to solid) ratio of 2.5 was used for the pH measurement, but for the coke the L/S ratio was increased to 8 to have enough liquid phase to place the pH electrode in for the measurement. The coke could contain a lot of water. The samples for SEM/EDX investigation were prepared by gluing a small amount of dry, powdered sample to a sample holder, which fitted into the SEM/EDX. The samples were coated with carbon prior to the analysis.

CHEMICAL EXTRACTION EXPERIMENTS

• Coke: Extraction experiments were made with 5.0 g dry, crushed material and 40 mL of

varying concentrations of HNO3 (concentrations between 0.01 M to 1.0 M). Furthermore


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extraction was made with 0.2 M H2SO4, 0.4 H2SO4, 1% oxalic acid and 2.5% oxalic acid. Cu, Cr and Zn release were measured in the extractions.

• Ash: Extraction experiments were made with 5.0 g dry ash and 25 mL HNO3 or NaOH of different concentrations. The concentrations of HNO3 and NaOH varied between 0.01 M and 1.0 M. An extraction with 0.75 M H2SO4 was made, too. Cu, Cr and As release were measured in the extractions.

Electrodialytic extraction

After a chemical extraction separation of fine-grained material and solution with the unwanted components is difficult. A separation method that may be used for extraction of these components from the suspension of ash could be the electrodialytic method. This method was first developed for removal of heavy metals from soils [9], [10]. The method is based on applying an electric DC field to the soil to be decontaminated and a combination of ion exchange membranes is used to separate the processing solutions around the electrodes from the soil. The method was patented in 1995 (PCT/DK95/00209). During the recent years the method has been tested for removal of heavy metals from other porous, solid waste products [11] such as harbour sludge [12], impregnated waste wood [13], sewage sludge [14] and different ash residues [15], [16]. It was found that it is beneficial to treat the ashes in a stirred suspension by this method [16]. The principle of a laboratory cell for electrodialytic extraction is shown in Figure 1. It consists of three compartments. In the central cell compartment the suspension of ash is placed and stirred during the experiment. The electrodes are placed in the outer compartment and ion exchange membranes separate the cell compartments. When the DC voltage is applied across the cell the ions in the ash suspension will be transported into the electrode compartments with the electrode of opposite sign as the ion itself.

AN CAT

Cu2+

Cr3+H+OH-

Figure 1: Principle of a laboratory cell for electrodialytic extraction (AN = anion exchange membrane, CAT = cation exchange membrane)

A laboratory experiment was made with electrodialytic treatment of the mixed bottom and fly ash from combustion of impregnated wood in a cell as shown in Figure 1. The cell had an internal diameter of 8 cm and the length of the central cell compartment was 10 cm. In each of the electrode compartments 500 mL 0.05 M H2SO4 was circulated. In the central compartment a suspension of 40 g ash and 235 mL 0.5 M H2SO4 was placed and a stirrer was placed in the


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compartment from the top of the compartment. The current density was kept constant at 0.8 mA/cm2 throughout the 5 days the experiment lasted and the voltage varied between 3.6 V and 2.7 V. At the end of the experiment the concentrations of Cu, Cr and As was measured in the different parts of the cell: in the ash, the solution of the central compartment, in the membranes, in the solutions in the electrode compartments and at the electrodes.

Results and discussion Characterization of residues

The results from the chemical characterization of the two residues are shown in Table 2.

As (mg/kg) Cu (mg/kg) Cr (mg/kg) Zn (mg/kg) Loss on

ignition (%) pH

Coke 990 690 2500 NA 89% 7.0 Ash 35000 69000 62000 9250 2.9 11.5

Table 2: Characteristics of the two residues: Coke from pyrolysis and ash from combustion (NA = not analysed)

As it can be seen from Table 2 the difference between the parameters of the two residues investigated is pronounced. The concentrations of As, Cu and Cr is much less in the coke than in the ash. This is probably a result of a combination of less CCA in the wood that was pyrolysed and a smaller weight reduction during the process. The loss on ignition shows that in neither of the thermal treatments, the decomposition of organic matter has been completed, but the coke has a very high loss on ignition, whereas it is much less for the ash. From the SEM/EDX investigation of coke (Figure 2) it is noticed that the wood structure in the particles, and this is in consistency of what was found by Hata et al. (2003) [2] and Helsen and Bulck (1998) [17] with other pyrolysis residues. From Figure 2 (A-C), showing some SEM images of the coke the wood cell structure can clearly be seen.


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FIGURE …

FIGURE 2: SEM/EDX IMAGES OF COKE FROM PYROLYSIS OF IMPREGNATED WOOD. CU, CR AND/OR AS WAS IDENTIFIED IN THE LIGHT PARTS MARKED IN THE CIRCLES: (A) AS AND CR, (B)

CU, AND (C) AS

In image 2(A) the particle has been cut lengthwise. In the long ares lightning in white in the left part of the picture Cr and As was identified. In the two light areas of the marvstråle shown in the circle Cr and As was exclusively found. In image 2(B) it can be seen that the cut of the particle is oppositely to image 2(A) i.e. transversely. In the two larger white areas in the central part of the image Ca was found. Cu was identified in the grey spot shown in the circle. In image 2(C) the edge of the same particle as in image 2(B) is shown. At the coke particle surface some


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small particles are concentrated and in this layer of small particles As was identified in the white area shown in the circle. At the images in Figure 2 only coke particles where Cu, Cr or As was identified was shown. Meanwhile this was not the case for all particles investigated. In some particles Zn and Mn was identified and these particles may originate from painted wood not vacuum impregnated.


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Figure 3 show a typical SEM/EDX image of the mixed top and bottom ash from the combustion experiment. It is first noticed, that the wood structure is broken down to a much higher extent than it was the case in the coke residue. Meanwhile some particles in the ash also show wood structure, e.g. particle 1, where Cu and Cr were identified. No As was found in this particle and this does not necessary mean, that As was not present in the original wood for this particle but As probably evaporated during the combustion. In the light grey areas of the larger matrix particles of the ash (e.g. particle 2) Cr and Cu was identified. Cu was found condensed at some of the matrix particles, too, see the white layer of varying thickness at the surface of particle 2. This layer consists almost exclusively of Cu. As was often found associated to Ca in particles with open structure like particle 3.

FIGURE 3: SEM/EDX IMAGE OF MIXED BOTTOM AND FLY ASH AFTER COMBUSTION OF CCA TREATED WOOD.

Chemical extraction of Cu, Cr, As and Zn from the residues The result from the chemical extractions of Cu, Cr and Zn from coke is shown in Figure 4 as percentage solubilized of the total concentrations given in Table 2. Since there are variations in the total concentrations of each metal this will influence the graph in Figure 4, but an overall tendency can be seen.

12

3


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The Zn of the wood is expected to originate from paint. Zn was also found to be present in higher average concentration (350 mg/kg) than Cu (32 mg/kg) in Swedish waste wood and forest residues [18] and thus it may generally be relevant, to include Zn in investigation of residues from thermal treatment of waste wood.

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Cu (HNO3)Zn (HNO3)Cr (HNO3)Cu (H2SO4)Cr (H2SO4)Zn (H2SO4)Cu (oxal.)Cr (Oxal.)Zn (Oxal.)

Figure 4: Percentage Cu, Cr and Zn solubilized at different pH and in different acids (As not measured)

Figure 4 shows that Zn is the heavy metal of the three investigated that is extractable to the highest extent in the inorganic acids followed by Cu and then Cr. For Cu and Cr there is no clear difference between solubilisation with HNO3 and H2SO4. It seems as if less Zn is solubilized in H2SO4 but this may also relate on differences in total concentrations. For the extractions with oxalic acid, on the other hand, there is a huge difference at pH 2.5 compared to the inorganic acids. About 60% Zn and 20% Cu was extracted in HNO3 but less than 1% and 6%, respectively, was extracted in oxalic acid. For Cr the oxalic acid extraction was on the contrary the most efficient. In oxalic acid at pH 2.5 about 10% Cr could be extracted compared to less than 1% in HNO3. For extractions of Cr from wood chips oxalic acid has shown the most efficient [19] among different inorganic and organic acids, but Cu extraction from wood chips has shown relatively poor because of precipitation of Cu oxalates [19], and precipitation of Cu and Zn oxalates is probably also responsible to the pronounced decrease in extraction in oxalic acid from coke seen in Figure 4. That Cr is little extractable from the pyrolysis residue is in consistency of what was observed by Helsen et al. 1998, where it is noticed that Cr is stronger bound in the pyrolysis residue than in the original wood. Figure 5 shows the solubilized percentage of Cu, Cr and As from the ash as a result of pH. Extractions were made with both HNO3 and H2SO4. The extractions with H2SO4 were generally made with a lower pH than the extractions with HNO3, but extractions were made with both acids with a pH of the suspension of about 2.4. At this pH there is no pronounced difference in the result obtained with the two acids.


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It is seen from Figure 5 that the As compounds in the ash was most soluble of the three and up to about 70-100% As could be extracted at pH below 2. Less Cu (at maximum about 30%) and almost no Cr (max. 5%) could be extracted in the two acids. Neither Cu nor Cr was solubilized at high pH whereas As was solubilized to a small extent of about 12%.

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pH i suspension

Solu

biliz

ed (%

) Cr (HNO3)Cu (HNO3)As (HNO3)Cr (H2SO4)Cu (H2SO4)As (H2SO4)

Figure 5: Percentage Cu, Cr and As solubilized at different pH and in different acids That there is no difference in the extraction result of Cu, Cr and As in HNO3 and H2SO4 is important knowledge when designing the electrodialytic extraction experiment, which is described in the next chapter. When the ash is suspended in H2SO4 the Ca2+ ions are expected to precipitate as gypsium and this precipitation of Ca will decrease the electric conductivity of the ash suspension. Meanwhile it is only the conductivity from Ca2+ that is decreased, meaning that to waste electric current in removing Ca2+ from the suspension during the electrodialytic treatment is avoided, see [20]. Electrodialytic extraciton of Cu, Cr and As from mixed ash The distribution of Cu, Cr and As in the different parts of the laboratory cell for electrodialytic extraction is shown in Figure 6. In black colour is shown the percentage left in the ash after the treatment and it can be seen that this counts for most of Cu and especially for most Cr. This corresponds well to the finding from the SEM/EDX investigation where it was seen that these two heavy metals were found build into the matrix structure of the ash particles to a high extent and can thus be expected to be hard to extract. Only 3% Cr was actually mobilized during the electrodialytic experiment. For Cu about 30% was removed and this percentage could correspond to the Cu precipitated at the surface of the matrix particles (seen from the SEM/EDX investigation). Cu was removed towards the cathode, probably as Cu2+, where it electro-


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precipitated at the cathode. The 30% also corresponds well to the maximum percentage of Cu that could be chemically extracted by suspension in H2SO4. On the contrary to the removal of Cu and Cr, the removal of As from the ash in the electrodialytic experiment was quite successful. Only 8% As was left in the ash at the end of the experiment. As was removed both in cationic and anionic species since As was found in both sides of the cell. In the cathode end As electro-precipitated at the cathode together with Cu and this solid layer consisted thus of highly concentrated Cu and As. The As removed towards the anode was concentrated in the anolyte.

Cr

97%

1% 2%

AnolytAN. MembranMidterkammerAskeKAT. MembrankatolytKatode

Cu1%

2%

70%

27%AnolytAN. MembranMidterkammerAskeKAT. MembrankatolytKatode

As

32%

1%

17%8%

12%

30% Anolyt

AN. Membran

Midterkammer

Aske

KAT. Membran

katolyt

Katode

Figure 6: Distribution of Cu, Cr and As in the cell for electrodialytic extraction at the end of a 5 days experiment.

The aim of the electrodialytic extraction experiment was to remove As and soluble fraction of Cu and Cr from the ash to make the ash less toxic to the environment. In the ash was left 8% As


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at the end of the experiment, but it is expected that more As could be removed if the experiment had lasted longer. CONCLUSIONS The characteristics of residues from thermal treatment of CCA impregnated waste wood depend of several factors. Important is of course the degree of sorting out not-impregnated waste wood from the impregnated wood, because wood not containing CCA result in dilution of Cu, Cr and As concentrations in the residues. The residues from the thermal treatment also depend highly on the thermal method used, whether it is combustion or pyrolysis, and on several parameters regarding the thermal treatment. The differences of the two residues after thermal treatment of waste wood that were included in the present investigations varied considerably. By SEM/EDX it was found that the wood structure was almost intact after the pyrolysis (which had not been optimal) but also in the mixed bottom and fly ash after combustion small, almost intact wood pieces were observed. Meanwhile the mixed ash mainly consisted of ash particles that showed full decomposition of the wood. SEM/EDX investigations gave an overall picture of where Cu, Cr and As were present in the two residues. In the ash Cr was found inside the structure of the matrix particles and to a small extent in some micro-wood pieces in the ash. Cu was found in these places, too, together with Cr, but Cu was also found condensed at the surface of some of the coarser ash particles. As was almost exclusively found associated with Ca in the ash. In the coke Cu, Cr and As was found inside the preserved wood structure. Cr and As was found associated whereas Cu was found without the two other elements. As was also identified in some very small particles at the surface of a wood particle. The concentrations of Cu, Cr and As in the two residues were very different, but similar extraction patterns were found for Cu and Cr in inorganic acids regardless differences in concentration and matrix. Cu could be extracted with about 30% at pH less than 1 in both residues and not more than about 5% could be extracted from either of them. The As extraction was measured in the ash only, and As was far most mobile of the three. In the coke Zn extraction was found and a higher percentage of Zn could be extracted than Cu and Cr. In an electrodialytic extraction experiment it was shown possible to remove 92% As, 30% Cu and 3% Cr from the ash. The removed amounts of Cu and Cr are probably as the amounts that are not built into the matrix structure and thus the remaining fraction of these elements are expected to be relatively immobile, since this fractions are similar to the fractions that could not be extracted chemically at pH values of less than 1. REFERENCES [1] Helsen, L., Van den Bulck, E., Van Bael, M.K., Mullens, J. (2003) Arsenic release during pyrolysis of CCA treated wood waste: current state of knowledge. J. Anal. Appl. Pyrolysis, 68-69, 613-633


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[2] Hata, T., Bronsveld, P.M., Vystavel, T., Kooi, B.J., De Hosson, J.Th.M., Kakitani, T., Otono, A., Imamura, Y. (2003) Electron Microscopic study on pyrolysis of CCA (chromium, copper and arsenic oxide)-treated wood. J. Anal. Appl. Pyrolysis. 68-69, 635-643 [3] Zeng, T., Sarofim, A.F., Senior, C.L. (2001) Vaporization of Arsenic, Selenium and Antimony during Coal Combustion. Combustion and Flame, 126, 1714-1724 [4] Helsen, L., Van den Bulck, E., Cooreman, H., Vandecasteele, C. (2003) Development of a sampling train for arsenic in pyrolysis vapours resulting from pyrolysis of arsenic containing wood waste. J. Environ. Monit. 5, 758-765 [5] Kercher, A.K., Nagle, D.C. (2001) TGA modeling of the thermal decomposition of CCA treated lumber waste. Wood Science and Technology, 35, 325-341 [6] Solo-Gabriele, H., Townsend, T.G., Messick, B., Calitu, V. (2002) Characteristic of chromated copper arsenate-treated wood ash. J. Haz. Mat. B89, 213-232 [7] Pohlandt-Schwandt, K. (1999) Treatment of Wood Ash Containing soluble chromate. Biomass and Bioenergy 16, 447-462 [8] Pohlandt, K., Strecker, M., Marutzky, R. (1993) Ash from the combustion of wood treated with inorganic preservatives: Element combustion and leaching. Chemosphere 26, 2121-2128 [9] Ottosen, L.M., Hansen, H.K., Laursen, S., Villumsen, A. (1997) Electrodialytic Remediation of Soil Polluted with Copper from Wood preservation Industry. Environ. Sci. Technol. 31, 1711 [10] Hansen, H.K., Ottosen, L.M., Kliem, B.K., Villumsen, A. (1997) Electrokinetic Remediation of Soils Polluted with Cu, Cr, Hg, Pb and Zn. J. Chem. Tech. Biotech. 70, 67-73 [11] Ottosen, L.M., Kristensen, I.V., Pedersen, A.J., Hansen, H.K., Villumsen, A., Ribeiro, A.B. (2003) Electrodialytic Removal of Heavy Metals from Different Solid Waste Products. Separation Science and Technology, 38(6), 1269

[12] Nystrøm, G.M., Ottosen, L.M., Villumsen, A. (2003) The use of Sequential Extraction to Evaluate the Remediation Potential of Heavy metals from Contaminated harbour Sediment. J. Phys. IV France. 107, 975 [13] Ribeiro, A.B., Mateus, E.P., Ottosen, L.M., Bech-Nielsen, G. (2000) Electrodialytic Removal of Cu, Cr and As from CCA Treated Timber Waste. Environ. Sci. Technol. 34, 784 [14] Jakobsen, M.R., Fritt-Rasmussen, J., Nielsen, S., Ottosen, L.M. Electrodialytic Removal of Cadmium fro Wastewater Sludge. Accepted for publication in J. Haz. Mat. [15] Hansen, H.K., Ottosen, L.M., Villumsen, A., Houmøller, S. (1999) Electrodialyitc Removal of Cadmium from Straw Ash. Proceedings 2. Symposium on Heavy Metals in the Environment and Electromigration Applied to Soil Remediation, Lyngby Denmark, 7. - 9. July 1999, 130-134. [16] Pedersen, A.J. (2003) Characterization and Electrodialytic treatment of Wood Combustion Fly Ash


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for the Removal of Cadmium. Biomass and Bioenergy 25 447-458 [17] Helsen, L., Van den Bulck, E., Hery, J.S. (1998) The Microdistribution of Copper, Chromium and Arsenic in CCA Treated Wood and its Pyrolysis Residue using Energy Dispersive X-Ray Analysis in Scanning Electron Microscopy. Holzforschung, 52, 607-614 [18] Jermer, J., Ekvall, A., Tullin, C. (2001) Analysis of contaminants in waste wood. IRG/WP 01-50179 [19] Ottosen, L.M., Kristensen, I.V. (2002) Electrochemical reuse of CCA from wood. Report, BYG.DTU, Technical University of Denmark (In Danish) [20] Ottosen, L.M., Pedersen, A.J., Kristensen, I.V., Ribeiro, A.B. (2003) Removal of arsenic from toxic ash after combustion of impregnated wood. J. Phys. IV France. 107, 993-996


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Tehcnical Papers Supplementing Poster Presentations


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A Complete Industrial Process To Recycle CCA-Treated Wood

Jean-Sebastian Hery

"Chartherm" R&D Department, THERMYA, Bordeaux, France ABSTRACT

Concerned by the evolution of the EU regulations on wood waste, Xavier Beaumartin, President and General Manager of Beaumartin SA, a Family Group, leader of the wood impregnation industry in France, decided in 1992 to equip its 10 running plants with: "treated wood waste recycling systems". That decision was in direct line with the historical tradition of innovation of this company, which started producing mine posts and railway ties in the early years of the Nineteenth Century.

If, when we started to study the problem, ten years ago, the recycling of treated wood waste was just the concern of a manager, looking for the future of his company, it has become today the concern of many people. In fact, in the meantime, it has indeed been a big evolution of rules and mentalities. Today, people is concerned by the use of Arsenic to treat wood and the rules on treated wood and wood waste have changed. Today, the treated wood waste is classified as "dangerous waste" in the EU and the use of creosote or CCA is restricted to a few very specific professional uses. The same evolution can be observed in the US.

Today, "the Chartherm process" is developed at an industrial level, with an industrial plant able to recycle CCA-Treated wood or any other kind of wood waste, whichever be its type or level of contamination, at a rate of 1500kg (3000 pounds) per hour, 10,000 MT per year, producing a "clean graphitic carbon powder" at a minimum rate of 425 kg (850 pounds)per hour, 3000 MT per year.

Which is why, the problem of the treated wood waste becoming huge every day and Chartherm Process being today recognized worldwide as the only system developed at an industrial level, able to recycle CCA-treated wood and any other kind of treated or contaminated wood waste, we receive every month requests from everywhere to know about our system. We have serious contacts with people interested by Chartherm, who come from all over Europe but also from America. We are currently negotiating the building of a new Industrial Chartherm plant in France and two license agreements with wood waste operators of the EU.

KEYWORDS: CCA - Treated Wood - Wood Waste –CHARTHERM – Recycling

Jean-Sebastian Hery. Mailing address: THERMYA, 144, ave de la Republique, F33200 BORDEAUX France. Phone: +33 (0)556 240 901. Fax: +33 (0)556 240 995. Email: [email protected]

INTRODUCTION The "Chartherm" project started from scrap at the end of 1993, when Xavier Beaumartin, General

Manager of a Family Company dedicated to the making and preservation of wooden poles and railway sleepers, since the 1830's, hired Jean-Sebastian Hery, an Industrial Automation Engineer.

Xavier Beaumartin was concerned by the evolution of the European rules on wood waste. He decided to put in place a treated wood waste recycling solution, to have it ready when the European Commission


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will require the wood treaters to recover the old treated wood (as a condition to be allowed to sale new treated wood).

HYSTORY The initial idea was to adapt an existing wood waste recycling system to the needs of Beaumartin

Group. After a fully dedicated nine months study of all the available wood recycling technology existing in Europe, America, Japan and Australia, we had to accept the evidence: the offer of wood waste recycling systems was unsatisfactory and totally unable to solve the problem at an industrial level. Then J-S Hery was commissioned to develop and build a new complete solution, able to recycle every treated wood waste, whatever be the kind of treatment, particularly CCA.

Observing the most difficult task was to recycle CCA treated wood, we decided to make a strong research on that particular subject. We collected and studied the published experiments already carried out on that matter and met different Authors of these works all around Europe and North America. A first theory was then built and an agreement was reached with Prof. Van den Bulk of the KUL (Leuven Catholic University) in Belgium, to carry on some experiments. The first trials were made on a laboratory scale pilot by Mrs. Lieve HELSEN.

By the end of 1994, after six months of trials, the encouraging results Mrs. Lieve HELSEN obtained, on our idea to "mineralize the wood at low temperature", served as base to built a second more sophisticated laboratory scale pilot at the Bordeaux University of Sciences. After several modifications the "Chartherm Process" could be developed and a Patent was registered by May 1995.

Then, to continue the development of the process, one first working scale prototype was built at a Beaumartin plant, near Bordeaux, quickly replaced by a second one of a bigger size and a lot of technical improvements. During one year, a dedicated team made trials and modifications on the prototype, on an everyday base. By September 1996, a prestigious French Engineering Company (Bertin Technologies) qualified the "Chartherm" process, by ending a three months complete study of the whole system. Based on that study, the Beaumartin Company decided to pass to the next step: the fabrication and set up of a "Chartherm" industrial plant.

It took one year to build the first "Chartherm" industrial plant. Nine more months to tune it and by September 1999, we were able to start the working trials.

Unfortunately, by December 1999, with the dismissal of Xavier Beaumartin as President and General Manager of the Group, for personal reasons, and in the absence of any heir interested in continuing the management of the Company, the Beaumartin family group decided to sell "all their industrial activities", to concentrate their efforts on forestry (more than 100,000 thousand acres) and vineyards (several "Chateaux" in the Bordeaux region). As a consequence,. "Chartherm" project was put on standby.

Trials and tuning started again by September 2000, with a reduced team, to get the industrial "Chartherm" plant to an operational level, in order to sell it. Tests and analysis done in October 2002 show the industrial "Chartherm" plant was operational. Ready to be sold. Put on standby.

In the meantime, an EU Directive, classified all the treated wood waste, including poles and railway sleepers, as a "dangerous waste" in all EU. This Directive coming in to force on Jan 1st, 2002

Some months later start the talks with different candidates interested to buy it and in January 2003, THERMYA acquired from Beaumartin Group the whole "Chartherm" project, including patents, brands, prototypes and the industrial plant, located at Saint Médard d'Eyrans, near Bordeaux.


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HOW CHARTHERM WORKS ? The "Chartherm Process" is basically a "wood waste recycling system", able to operate with any

contaminated wood waste, whichever be the kind of toxic contaminating the wood and the concentration level of this contamination. This means "Chartherm Process" is able to recycle wood even if it is contaminated with different toxics at the same time, like a painted CCA and Creosote treated wood piece.

"Chartherm Process" is a wood waste recycling system which doesn't need a previous sorting to classify the wood by type of contamination. I does not either requires a previous withdraw from the wood the eventual metallic inclusions it may have.


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Three steps complete the Chartherm process:: "wood crushing", "thermal treatment" and "separation" (to clean the carbon).

The Crushing

We have developed our own crusher to be able to work with all kinds of wood, whatever be their length or hardness, even if they include small metallic parts like bolts, screws or small steel plates.

In only one step, the crusher reduces the wood from its original size to two inch long splinters, able to be introduced in the thermal processor.


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The crusher is able to work at a rate of 12 MT to 18 MT per hour, depending on the transverse section and the hardness of the wood.


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The Thermal process

Coming from a heat generator, hot gases (370°C), with a low oxygen content (<1.5%), are injected thru a grid, at the bottom of a thermal reaction column, full of crushed wood.

By controlling the difference of pressure at the top and bottom of the column, a decreasing stratified gradient of pressures and temperatures is obtained, from bottom to top of that column. So the temperature at the top of the column is always below 65°C.

The thermal choc produced by the contact of hot gases on to the crushed wood, at the bottom of the column, breaks the Hydrogen bonds, which liberates groups of organic molecules and causes the evaporation of the organics of the wood.

These mix of gases and vapors of organic molecule groups, are pushed up thru the column, where the crushed wood cools them and provokes their condensation.

When all the organics are evaporated from the mineral matrix of the wood, at the bottom of the column, it only remains, a mineral residue with a high content of carbon (95 to 99%), which holds all the other minerals present in the wood at the beginning of the process, including heavy metals and other toxic minerals.

This mineral residue is recuperated thru the grid at the bottom of the column, as the top of the column is refilled with more crushed wood.

By progressing in its way down into the column, the crushed wood heats and part of the organics, already condensed on it, crack and evaporate to condense again at a higher step in the column. This phenomenon is repeated and repeated again until the organics become so light they do not condense again and make their way to the top of the column.

Which is why, only the lighter organic gases, with a high content of hydrocarbons, can reach the top of the column.


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From the top of the column the hydrocarbon gases are dried and sent back to the heat generator. That way the wood generates enough hydrocarbon gases to maintain the system in auto-combustion. The Separation step

The mineral residue is grounded to a thin powder (<15µm) and introduced into a pneumatic centrifugal, where the carbon is separated from the other minerals.

The clean carbon is packed into airtight big-bags of 800 kg, while the other minerals are put into metallic drums.


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THE CARBON PRODUCT


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The clean carbon issued from the Chartherm process is 99% pure. It has a graphitic structure and a

calorific power of 6500 kilocalories per kilo. These characteristics allow to use it in a wide range of applications, from fuel powder to fireworks.

The application makes the price. Each particular application of the carbon powder requires a specific characteristics particle size curve.

The separation step of the Chartherm industrial plant allows to modify the characteristics of the clean carbon particle size curve, to adapt it to a specific application.

The most obvious (but not the best) application for the Chartherm clean carbon being to replace, with advantage, Carbon Black in some particular applications.

In 2002, the World market demand for Carbon Black was 3,500,000 MT In 2002, the average World market price of the Carbon Black was $0.82 / kg. (€728 / MT) The Chartherm industrial plant is able to recycle 1,500 kg/hour of wood waste.(10,000 MT/year) For each 1,000 kg of wood waste, Chartherm produces 280/320 kg of clean carbon.( 3,000 MT/year)

Jean-Sebastian Hery. Mailing address: THERMYA, 144, ave de la Republique, F33200 BORDEAUX France. Phone: +33 (0)556 240 901. Fax: +33 (0)556 240 995. Email: [email protected]


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Impacts of Wood Preservatives (CCA, CCB, CDDC, ACZA, ACQ and ACC) on the Settlement and Growth of Fouling Organisms

B. Tarakanadha1*, Jeffrey J. Morrell2, and K. Satyanarayana Rao1

1Institute of Wood Science & Technology, Malleswaram, Bangalore 560 003, India

2 Department of Wood Science & Engineering, Oregon State University, Corvallis, Oregon-97331, USA

ABSTRACT

The effects of wood preservatives on settlement, abundance, growth and biomass development of fouling organisms (Non-target organisms) was studied on treated panels exposed at an Indian harbour, Krishnapatnam (Lat.13028’ to13059’ N; Long: 800 10’ to 800 16’E). Panels of Bombax ceiba treated with copper chrome arsenic (CCA), copper chrome boric acid (CCB), ammoniacal copper zinc arsenate (ACZA), ammoniacal copper quaternary (ACQ), or ammoniacal copper citrate (CC) and hem-fir panels treated with copper dimethyldithiocarbamate (CDDC) were exposed over a 24 month period. There was considerable variation in abundance and biomass of fouling organisms among the preservatives. Algal and bryozoan settlement was common on all the treated and untreated panels during the initial stages (up to one month), but these communities were replaced due to heavy settlement of calcareous organisms such as barnacles, oysters and serpulids. A greater variety of fouling assemblages were recorded on control, CCB and CCA treated panels compared to CDDC, ACZA, CC and ACQ treated panels. CCA treated panels had heavier settlement of barnacles followed by oysters and bryozoans, while CCB treated panels had heavier settlement of oysters followed by barnacles and bryozoans. Serpulid settlement was negligible on treated panels, but heavy on control panels. The preservatives tested appeared to have a positive impact on settlement of barnacles, oysters and bryozoans. CDDC panels experienced heavier bryozoan settlement followed by barnacles, oysters and serpulids. The fouling assemblages that developed on ACZA, ACQ and CC panels consisted of fewer species that were less abundant than those found on other panels indicating that these preservatives negatively impacted settlement of fouling organisms. Biomass levels were found to be highest on CCB treated panels, while the lowest levels of fouling occurred on ACQ treated panels. The results illustrate the differential effects of wood preservatives on surface colonizers of wood in marine environments.

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• Corresponding Author. Mailing address: Institute of Wood Science & Technology, 18th

Cross , Malleswaram, Bangalore -560 003, India. Phone No.0091-80-3346811-14. Fax

No.0091-80-3340529. Email: [email protected]

Keywords: Impact of wood preservatives, Fouling settlement (Non target organisms), Marine

environment and Bombax ceiba.


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INTRODUCTION:

While we no longer depend upon wood for our sailing vessels, wood continues to play an important

role in the marine infrastructure supporting the many docks, wharves and other features of our harbors

and ports. As in olden times, this wood remains susceptible to attack by fungi, insects and marine borers.

This attack can be minimized by the use of naturally durable timbers, but the supplies of these materials

are limited and their cost can be prohibitive. As a result, we often depend on the use of non-durable

timbers that are supplementally protected with preservatives (Kumar and Morrell, 1993).

Marine wood preservation provided the impetus for our current wood treating practices and remains

an important component of this industry. For decades, creosote was the preferred treatment, but a

number of inorganic arsenicals (primarily chromated copper arsenate) have also emerged as important

marine wood preservatives. Preservative treatment is an extremely effective method for extending the life

of wood used in marine environments, however, the preservative levels required to achieve this protection

are often 2 to 4 times those required for protecting wood in terrestrial environments. The use of such high

chemical loadings was of little concern to users as ports sought to increase capacity and maximize their

investment, but an ever-increasing environmental ethic has led to a reexamination of chemical use in

sensitive environments including the use of chemically preserved wood.

While all chemicals have experienced increased public scrutiny, CCA, by virtue of its dominance in

world commerce, has received the greatest attention (Solo-Gabriele et al., 2003; Townsend et al., 2001).

One of the primary advantages of CCA as a preservative is its ability to react with and become fixed to

the wood following treatment. The reactions by which this process occur have been extensively studied

and these data have been used to develop procedures for minimizing the risk of metal loss into the

surrounding environment as well as the creation of models that can be used to predict the relative risk of

treated wood use under varying harbor conditions. Despite these efforts, it is virtually impossible to

completely fix the CCA components or, for that matter, those of any other metal-based preservative to the

wood. Metal-based preservatives appear to function, in part, by always having a small amount of each


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metal component in solution within the wood cell lumens. The rates of metal release into the surrounding

environment have been studied in a number of applications, but the most intensively studied have been

aquatic applications because of the sensitivity of many marine organisms to elevated copper levels.

While there have been a number of studies examining the potential metal losses in aquatic environments,

relatively few have examined the effects of these losses on marine fouling organisms and even fewer have

examined the effects of the CCA replacement chemicals on these organisms. Marine fouling organisms

should be especially sensitive to preservative leaching since these organisms must settle and grow on the

chemically treated wood and since this wood is treated to such high chemical levels. Chemical losses

create the potential for both acute and chronic effects on the settling organisms that may result in either

reduced abundance of specific organisms or wholesale shifts in fauna and flora. These effects may be

minimal in well-flushed areas, where any chemical releases are quickly diluted, but metals can buildup to

high concentrations in more stagnant waters, especially when very large volumes of treated wood are

employed (Weis and Weis, 1992a).

Previous studies indicate that communities which develop on CCA treated wood have lower

species diversity, abundance of certain species and biomass levels compared to untreated panels (Weis

and Weis, 1992a, b; 1996) and adverse impacts have been found on the physiology of some organisms in

close proximity to CCA treated surfaces (Weis et al., 1992). These studies quantitatively examined the

effects of CCA treated wood on the early successional stages of epi-biotic development.

A number of studies have examined the effects of wood preservatives on settlement patterns,

growth and biomass development of epi-biota in temperate and sub-tropical environments (Albuquerque

and Cragg, 1995a, b; Baldwin et al., 1996; Brown, 1998; Brown and Eaton, 1997; 2001; Brown et al.,

2000, 2001, 2002, Cookson et al., 1996; Marchall and Manton, 1997; 1998; Weis and Weis, 1999), but

there is little data on the effects of these treatments in tropical waters. Since temperature can influence

the toxicity of some metals (Bryer et al., 1985), examining treatments under a variety of environmental

conditions should be any important component of any environmental assessment.


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In this report, we describe the effects of preservative treatment on settlement of fouling organisms

on hardwood and softwood panels treated with various metallic wood preservatives and exposed in

tropical waters in India.

MATERIALS AND METHODS:

Bombax ceiba panels (37.5 by 37.5 by 150 mm long) were pressure treated with copper chrome

arsenic (CCA), copper chrome boric acid (CCB), ammoniacal copper zinc arsenate (ACZA), ammoniacal

copper quaternary (ACQ) or ammoniacal copper citrate (CC) to a target retention of 40 kg/m3. Actual

retentions ranged from 28 to 35 kg/m3. Similarly, Hem-fir (a mixture of species of Abies and Tsuga sold

commercially in the U.S.) panels (19 by 87.5 by 300 mm long) were treated with copper

dimethyldithiocarbamate (CDDC) to a target retention of 10.9 kg/m3. Treatment procedures can be found

elsewhere (Tarakanadha et al., 2003; Narayanappa et al., 1999). All panels were labeled and holes were

drilled at both ends then attached to ropes for immersion at the test site. Treated panels along with

untreated controls were exposed one meter below the low tide level from a jetty at Krishnapatnam harbor.

Panels were examined for barnacles, serpulids, bryozoans and oysters (dominant fouling

organisms on test panels) after 1, 3, 6, 12, 18 and 24 months. Barnacles, serpulids and oysters were

counted individually, while levels of encrusting bryozoans were estimated by counting the total number

of colonies and measuring colony spread (diameter) on each panel. Fouling species were identified to

species wherever possible. At each observation, fouling settlement on each preservative treated panel was

removed and placed into a tared plastic container. The panels were then resubmerged. While fouling

removal at each time point disrupted the normal colonization patterns on the wood, it also created an open

surface that provided a measure of the suitability of the panel at any given time to settlement and

establishment by fouling organisms. The fouling organisms collected from each panel surface at each

time point were weighed and the container weight subtracted to provide total wet biomass. The

containers were oven-dried at 600C to constant weight then weighed again to estimate total dry biomass

on each panel.


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RESULT AND DISCUSSION

A variety of organisms settled on the various panels over the test period including: algae

(Enteromorpha intestinalis, E. compressa, Ulva lactuca); serpulids (Serpula vermicularis, Hydroides

elegans, Mercierella enigmatica, Pomatoceros triquetor); oysters (Crassostrea madrasensis, Saccostrea

cucullata); barnacles (Balanus amphitrite, Megabalanus tintinnabulum); bryozoans (Membranipora

amoyensis, Hippoporina americana, Alderina arabianensis) and bivalves (Modiolus striatulus, Perna

indica and P. viridis) (Table 1). Control panels were colonized by a wide array of organisms in the short

time before they were destroyed. Of the 17 species found on the panels at the site, only M. amoyensis, A.

arabianensis, and P. indica were absent from the control panels. These results illustrate the role of woody

debris as habitat in the marine environment. CCB treated panels contained all but one of the 17 species

(P. viridis) over the 24 month period, while CCA treated panels were colonized by all but S. vermicularis

and P. triquetor. These results suggest that CCB and CCA treatments did not adversely affect

settlement or establishment of most fouling organisms. Panels treated with CDDC had a somewhat

reduced diversity of organisms, with only 11 of the 17 organisms present over the test period; however,

even fewer species were present on the panels treated with ACZA, ACQ or CC. These results suggest

that surface conditions were unsuitable for settlement on panels treated with these chemicals. It is

unclear how this diminished flora might affect the surrounding environment; however, it is clear that

ammoniacal based treatments produce a different, less diverse species mixture on the wood. This reduced

diversity is of relatively little consequence when the wood is used in isolated structures, but could become

important where large amounts of timber treated with one chemical were employed.

Biomass levels on the panels increased steadily over the exposure period for all of the

treated panels (Figure 1). Panels treated with ammonia-based systems (ACZA, ACQ and CC)

had the lowest biomass levels while CCB treated panels had the highest. Panels treated with

CCA also developed high levels of total biomass at each inspection. Biomass level serves as an

indicator of receptivity of the panel surface to settle and colonization. Leaching of chemical


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from the panels would be expected to play a major role in this process. Ammoniacal-copper

treated (ACZA, ACQ, CC) panels will tend to lose copper at a faster rate than acid-based

systems (CCA, CCB, CDDC) and contain much higher loadings of copper (Archer et al.,1994).

This combination would be expected to produce higher metal losses that would affect settlement

to a greater degree and this trend was evident in our biomass results.

Settlement of specific groups of organisms varied with treatment. Barnacle levels were

highest on CCA treated panels followed by CCB and CDDC treated panels (Figure 2a). ACZA,

ACQ and CC treated panels all had uniformly low levels of barnacle colonization, suggesting

that some component of the treatments had inhibited settlement. Oysters exhibited a similar

trend to the barnacles for the first 3 months of exposure, then the levels on CCA treated panels

declined to levels similar to those found with the other treatments (Figure 2b). Oyster levels on

CCB treated panels declined between 12 and 24 months. Oyster levels on the other treatments

were similar, although ACQ and CC treatments tended to have lower levels of colonization at all

time points.

Serpulid levels were extremely high on the untreated panels, but were uniformly low on

all treated panels. These results suggest that treatment will inhibit settlement or colony

establishment by these organisms (Figure 2c). Bryozoan levels on control, CCA and CDDC

treated panels tended to be elevated for the first 3 months of exposure, then levels in CCA treated

samples declined to level similar to those found on panels treated with the other systems (Figure

2d). Panels treated with CDDC continued to have the highest levels of bryozoans after 24

months of exposure. The reasons for these differences are unclear. Similar results have been

demonstrated in earlier studies from temperate waters (9) where bryozoan settlement, especially by

Bugula turrita, was enhanced on CCA treated panels. Aggregation of the bryozoan B. turrita on CCA

treated panels (Weis and Weis, 1992) and of B. neritina on copper treated panels (Wisely, 1962) have


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also been observed. Aggregation was apparently initiated by copper ions progressively restricting the

swimming movements of the larvae passing over the painted surfaces. Larvae that are unable to swim

descend on the surfaces, resulting in greater accumulation of larvae on treated surfaces. Brown et al.,

(2001) reported heavy settlement of bryozoans, Electra pilosa and Bugula fulva on CCA treated wood

after 6 months of submergence, but bryozoan abundance was reduced after 12 months of immersion.

DISCUSSION

CCA treatment had a negligible impact on epi-biotic community. The total number of individuals,

biomass and growth were actually higher on CCA, CCB and CDDC treated panels compared to controls

although the loss of untreated control after 3 months limits direct comparisons. . This suggests that

leached components of these preservatives had no adverse effect on fouling organisms. These results

support earlier field studies conducted in temperate regions (Albuquerque, 1998; Alburquerque and

Cragg, 1995a; Baldwin et al., 1996; Brown and Eaton, 2001; Brown et al., 2000, 2001, 2002; Cragg et al.,

1998).

Generally, the rates of metal loss from treated structures are highest soon after submersion in the

sea water, then gradually decrease with time. The impact of leachate is higher on fouling organisms in

confined conditions, while leached metals may be rapidly diluted by the surrounding seawater in natural

environments, minimizing the effects of the initial leaching surge. Brooks (1996) reported that the

leaching of metals was most rapid during the first 5 or 6 days after installation in an aquatic environment,

then leaching rates halved on each successive day after immersion. A number of studies have reported

that chromium and arsenic emissions were low and always below the toxic levels (Brown and Eaton,

2001; Beslin and Ivanbrook, 1998; Lebow et al., 1999). On the other hand, Weis and Weis (1992a, b;

1996) suggested that leached metals from treated wood were a source of both chronic and acute

pollution to marine biota which resulted in significantly lower numbers of species, diversity indices and

biomasses. These experiments were performed in poorly flushed, relatively stagnant waters where


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327

concentrations of leachate could build up to high levels. These tests also used relatively short exposures

(one month). The absence of marked effects on biomass and species diversity after 3 months in our tests

suggest that any biological effect of leachate from CCA treated wood was short term relative to the

service life of timber (Albuquerque, 1998).

Heavy settlement of barnacles, bryozoans, oysters and moderate settlement of serpulids on CCA

and CCB treated panels indicates that these preservatives had minimal impact on fouling organisms or

that the organisms may be somewhat tolerant of these components.

The heavy settlement of bryozoans and barnacles on CDDC treated panels implies that the material

had little effect against fouling organisms. Moreover, Bryozoans tolerate a wide range of toxicants and

were among the major organisms that initially settled on the treated panels. Oysters, appeared to be

unaffected by treatment, although large quantities of metals, especially copper, can accumulate in body

tissues with no adverse effect (Tarakanadha and Rao, 2002).

The lower intensity, biomass and growth of fouling organisms on ACZA, ACQ and ACC treated

panels compared to CCA and CCB suggests that panels treated with ammoniacal preservatives probably

release higher quantities of metals, that may deter or repel fouling larvae. The consistently lower levels of

fouling on the ACZA treated panels may be either due to higher levels of metal loadings in these panels

or greater bio availability of metals on panel surfaces (Tarakanadha et al., 2003).

Albuquerque (1998) studied mussel settlement and biomass on panels treated with CCA, ACQ or

creosote and found the lowest values on ACQ treated panels. Mussel biomass was similar for all chemical

types, suggesting that settlement was affected by the type of preservative, but that growth of successful

settlers was less affected by the chemicals.

A lower abundance of barnacles on control panels compared to CCA treated panels indicates that

the surface of control panels may be unattractive to barnacle larvae or reduced recruitment might have

occurred in the early stages of surface colonization. Lower barnacle level may also reflect the relatively

rapid degradation of the untreated panels, which created limited opportunities for settlement. Cragg et al.

(1998) found that recruitment of barnacle larvae after 3 weeks of exposure was much higher on CCA


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328

treated panels than on untreated panels and suggested that high levels of recruitment could ultimately

result in greater abundance of foulers. It is unclear why the treated wood allows for more successful

colonization, although changes in the chemical environment near the wood surface may stimulate

settlement (Brown and Eaton, 1997).

Settlement of serpulids tended to be lower on treated panels compared to the controls.

Albuquerque et al., (2001) also reported significant reductions in Pamatoceros triquetor on CCA treated

panels in Portugal. Heavy settlement of serpulids on untreated panels suggests that these tubeworms

select surfaces based upon nutritional potential much in the same way that polychaete larvae show species

specific settlement responses to particular surface polysaccharides or glycoproteins in the bacterial films

on the wood surface (Kirchman et al., 1992). Treatments may have altered this bacterial flora to produce a

different nutritional potential that was less attractive to the serpulids in our test site..

The effect of ammoniacal-based systems on settlement is particularly important since many of these

chemicals have been developed as CCA replacements. It is clear that these systems have a much greater

effect on the fouling community and merit further study. Albuquerque and Cragg 1995a) reported lower

species richness, abundance and biomass on ACQ treated panels compared to CCA and creosote. The

present study indicates that the effect of conventional preservatives on non-target organisms are

moderate or negligible compared to ammoniacal preservatives like ACZA, ACC and ACQ.

ACKNOWLEDGEMENTS:

The authors like to express their gratitude to the Director General, ICFRE, Sri.R.P.S.Katwal, IFS.,

for his keen interest and constant support. This work was financially supported under the World Bank

aided FREEP component at the Institute of Wood Science & Technology, Bangalore.


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REFERENCES:

Albuquerque, R. 1998. The environmental effects of CCA treated wood use in the Sea. Ph.D. Thesis, Forest Product Research Centre, Buckinghamshire College, London: 1-203 pp. Albuquerque, R., Brown, J., Cragg, S. and Eaton, R.A. 2001. Effects of CCA preservative treatment on the settlement of barnacles and serpulid worms on wood. Proceedings, 10th International Congress on Marine Corrosion and Fouling Pages 1-10. Albuquerque, R. and Cragg, S. M. 1995b. Evaluation of Impact of CCA treated wood on the marine environment In: Third International Symposium on Wood Preservation; the Challenges, Safety-Environment, Cannes, France International Research Group on Wood Preservation. Pages 224-236. Albuquerque, R. and Cragg, S.M 1995a. Fouling organisms as indicators of the Environmental impact of marine preservative treated wood. The International Research Group on Wood Preservation Document No. IRG/WP/50063. Stockholm, Sweden. 14 pages.. Archer, K., Preston, A., Chittenden, C. and Page, D. 1994. Depletion of wood preservatives after 4 years marine exposure in Mt. Maunganui Harbour, New Zealand. The International Research Group on Wood Preservation Document No. IRG/WP/50036. Stockholm, Sweden. 16 pages. Baldwin, W.J., Pasek, E.A. and Osbourne, P.D. 1996. Sediment toxicity study of CCA-C treated marine piles. Forest Products Journal 46 (3): 42-50. Breslin, V.T. and Adler Ivanbrook, L. 1998. Release of copper, chromium and arsenic from CCA-C treated lumber in estuaries. Estuaries, Coastal and Shelf Sci. 46: 111-125. Brooks, K.M. 1996. Evaluating the environmental risks associated with the use of chromated copper arsenate treated wood products in aquatic environments Estuaries 19(2A):296-305. Brown, C. 1998. The impact of copper chrome arsenic (CCA) wood preservative on non target marine organisms. Ph.D. Thesis. University of Portsmouth, UK. Brown, C.J., Albuquerque, R., Cragg, S. and Eaton, R.A. 2001. Effects of CCA (copper chrome arsenic) preservative treatment of wood on the settlement and recruitment of barnacles and tube building polychaete worms. Biofouling 15 (1-3): 151-164. Brown, C.J. and Eaton, R.A. 1997. Settlement of fouling organisms on CCA treated Scots pine in the marine environment. The International Research Group on Wood Preservation Document No. IRG/WP/97-50094. Stockholm, Sweden. 15 pages. Brown, C.J. and Eaton, R.A. 2001. Leaching of copper chrome arsenic (CCA) wood preservative in sea water. Material und Organismen 33: 213-231. Brown, C., Eaton, R.A., Cragg, S., Philippe.G., Artemis. N., Maria Joao, B., John, I., Geoffrey, D., Thomas, N., Andrew, P. and Sawyer, G. 2002. Fouling assemblages on CCA treated timber submerged in European waters. The International Research. Group on Wood Preservation, Document No. IRG/WP/02-50181. Stockholm, Sweden. 18 pages.


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Brown, C.J., Eaton, R.A. and Thorp, C.H. 2000. Effects of Chromated copper arsenate (CCA) wood preservative on early fouling community formation. Mar. Pollu. Bull. 42 (11): 1103-1113. Bryan, V., Newbery. D.M., McLusky, D.S. and Campbell, R. 1985. Effects of temperature and salinity on the toxicity of Arsenic to 3 estuarine invertebrates (Corophium volutator, Macoma balthica, Tubifex costatus). Marine Ecol. Prog. Series 24: 129-137. Cookson, L.J., Scown, D.K. and Schmalzl, K.J. 1996. Pile surface coverage and copper, chromium, arsenic content of barnacles growing on experimental mooring piles. Presented at the 25th For. Prod. Res. Conf. Clayton, Victoria. 18-21 November. Pages 1-13. Cragg, S. M., Brown, C., Albuquerque, R., Eaton, R. A. and Goulletquer, 1998. Effects of CCA treatment on settlement and growth of barnacles under field conditions. The International Research Group on Wood Preservation Document No. IRG/WP/50116. Stockholm, Sweden. 9 pages. Dong, H.L., Dong won, S., Myung Jae, L., Chang Ho, K., Cheon Ho, K. and Eui Bae, J. 2003. Biological safety evaluation of animal contact of preservative treated wood. The International Res. Group on Wood Preservation Document No. IRG/WP/03-50196. Stockholm, Sweden. 10 pages. Kirchman, D., Graham, S., Reish, D. and Mitchell, R. 1982. Bacteria induce settlement and metamorphosis of Janua (Dexospira) brasiliensis (Grube). Journal of Exp. Mar. Biol. and Ecol. 56: 153-163. Lebow, S.T., Foster, D.O. and Lebow, P.K. 1999. Release of copper, chromium and arsenic from treated Southern pine exposed in seawater and Freshwater. Forest Products Journal 49(7/8): 80-89. Marchall, P. and Martin, C. 1997. Environmental behaviour of Treated wood in (semi) permanent contact with Fresh or Sea water, 248-262: 4th International Symposium on Wood Preservation. Cannes, France, International research Group on Wood Preservation Document No. IRG/WP/5010. Stockholm, Sweden. Pages 1-10. Marchall, P. and Martin, C. 1998. Assessment of treated wood leachates genotoxicity with a bacterial test. International Research Group on Wood Preservation, Document No. IRG/WP/98-50101 Stockholm, Sweden. Pages 248-262. Narayanappa, P., A.B. Chang, and J.J. Morrell. 1999. Treatment of two Indian wood species with waterborne inorganic wood preservatives. J. Tropical Forest Products 5(2):149-153. Satish Kumar and Morrell, J.J. 1993. Wood preservatives – The next generation. J. Timber Dev. Association (India) 39(3): 5-22. Solo-Gabriele, H., Townsend, T.G., and J. Schert. 2003. Environmental Impacts of CCA Treated wood: A Summary from Seven years of Study focusing on the U.S. Florida Environment. The International Research Group on Wood Preservation. Document No. IRG/WP/03-50205. Stockholm, Sweden. 13 pages. Tarakanadha, B. and Satyanarayana Rao, K. 2002. Effects of two wood preservatives and one water repellant on the settlement of fouling communities in a tropical marine environment. International Research. Group on Wood Preservation Document No. IRG/WP/02-30293. Stockholm, Sweden. 14 pages.


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Tarakanadha, B., Rao, K.S., Morrell, J.J., Rhatigan, R.G. and D.B.Thies. 2003. Performance of ACZA and CDDC treated conifers in tropical marine exposures in Krishnapatnam, India. Journal of Tropical Forest Products 9 (1 & 2) : 134-144. Townsend, T., Stook, K., Ward, M. and Solo Gabriele, H. 2001. Leaching and Toxicity of CCA treated and Alternative Treated Wood Products. Draft Technical Report #02-4. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL. Walker, C.H., Hopkins, S.P., Sibly, R.M. and Peakall, D.B. 1996. Principles of Ecotoxicity. Taylor and Francis Ltd. London. 321 pp. Weis, J.S. and Weis, P. 1992b. Transfer of contaminants from CCA treated lumber to aquatic biota. J. Exp. Mar. Biol. & Ecol. 161: 189-199. Weis, J.S. and Weis, P. 1992a. Construction materials in estuaries: reduction in the epibiotic community on chromated copper arsenate (CCA) treated wood. Mar. Ecol. Prog. Ser. 83: 45-53. Weis, J.S. and Weis, P.S. 1996. Reduction in toxicity of chromated copper arsenate (CCA) treated wood as assessed by community study. Marine Environmental Research 41(1): 15-25. Weis, P. and Weis, J.S. 1999. Accumulation of metals in consumers associated with Chromated copper arsenate treated wood panels. Marine Environmental Research 48: 73-81. Weis, P., Weis, J.S., Greenberg, A. and Nosker. J.T. 1992. Toxicity of construction materials in the Marine environment: A comparison of Chromated copper arsenate - Treated wood and recycled plastic. Arch. Environ. Cont. Toxicol. 22: 99-106. Wisely, B. 1962. Effects of antifouling paints on settling larvae of the Bryozoa Bugula neritina. Australian J. of Marine and Freshwater Research. 14: 44-59 pp.


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Table 1. Settlement of various fouling organisms on test panels treated with different wood preservatives and exposed for 24 months in India.

INCIDENCE OF SPECIES (+/-) Fouling species

GROUP NONE CCA CCB CDDC ACZA ACQ CC

Enteromorpha intestinalis Algae + + + + + + + E. compressa Algae + + + + - + + Ulva lactuca Algae + + + + + - + Serpula vermicularis Serpulid + - + - - - + Hydroides elegans Serpulid + + + + + - - Mercierella enigmatica Serpulid + + + + + + - Pomatoceros triquetor Serpulid + - + + - - - Crassostrea madrasensis Oyster + + + + - + + Saccostrea cucullata Oyster + + + - - - - Balanus amphitrite Barnacle + + + + + + + Megabalanus tintinnabulum Barnacle + + + + + - - Membranipora amoyensis Bryozoan - + + - - - - Hippoporina americana Bryozoan + + + + + + - Alderina arabianensis Bryozoan - + + + + - + Modiolus striatulus Bivalve + + + - - - - Perna indica Bivalve - + + - - - - P. viridis Bivalve + + - - - - -


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Figure 1. Relative levels of biomass (dry weight basis) produced on panels treated with selected preservatives and exposed in an Indian harbor for 24 months.

05

101520253035404550

0 5 10 15 20 25 30

Exposure Period (Months)

Biom

ass

(kg

dry

wt/m

2 )ControlCCACCBCDDCACZAACQCC


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Figure 2. Incidence of a.) barnacles, b.) oysters, c.) serpulids, or d) bryozoans on panels treated with various preservatives and exposed in an Indian harbor for 1 to 24 months.

0

50

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300

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/Pan

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ulid

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Table 2 Incidence of selected fouling organisms as assessed by settlement, growth and biomass accumulation on control and treated panels exposed for 1 to 24 months in a harbor near Krishnapatnam, India.

ORGANISM FREQUENCY/PANEL Average Colony Diameter (mm.) EXPOSURE TIME (Months)

Treatment Barnacles Oysters Serpulids Bryozoans Barnacles Oysters Serpulids Bryozoans

Biomass DRY WT. (Kg/m2)

1 Control 29 (15) 29 (7) 185 (11) 43 (12) - - - - 1.51 CCA 129 (39) 31 (10) 12 (4) 45 (12) - - - - 1.32 CCB 55 (12) 84 (19) 7 (12) 23 (6) - - - - 1.91 CDDC 21 (8) 9 (5) 5 (3) 30 (4) - - - - 1.17 ACZA 21 (14) 11 (4) 9 (2) 8 (3) - - - - 1.10 ACQ 6 (2) 7 (3) 5 (2) 4 (0) - - - - 0.40 CC 6 (1) 7 (3) 4 (1) 9 (3) - - - - 0.44 3 Control 49 (2) 84 (30) 344 (79) 22 (8) 12 (2) 12 (1) 27 (59) 17 (4) 11.60 CCA 248 (43) 143 (27) 17 (3) 51 (16) 13 (3) 22 (3) 18 (47) 20 (2) 12.70 CCB 35 (16) 186 (23) 13 (5) 16 (7) 13 (2) 22 (3) 20 (64) 17 (2) 14.20 CDDC 26 (12) 34 (19) 21 (6) 36 (6) 11 (3) 14 (1) 12 (42) 27 (4) 5.20 ACZA 24 (6) 27 (8) 8 (2) 8 (3) 10 (3) 17 (3) 18 (21) 15 (3) 2.90 ACQ 13 (2) 21 (6) 6 (1) 8 (3) 12 (3) 18 (4) 15 (33) 21 (2) 1.71 CC 13 (5) 17 (4) 8 (2) 8 (2) 15 (4) 20 (2) 18 (53) 19 (2) 1.87 6 CCA 336 (39) 61 (11) 7 (2) 31 (13) 11 (4) 23 (3) 16 (33) 24 (3) 14.90 CCB 91 (28) 197 (7) 17 (3) 11 (5) 15 (4) 24 (5) 17 (43) 23 (3) 17.80 CDDC 123 (32) 46 (6) 28 (3) 24 (4) 13 (3) 18 (3) 18 (32) 34 (5) 8.80 ACZA 30 (16) 42 (1) 9 (2) 13 (3) 15 (4) 29 (5) 15 (40) 21 (2) 4.76 ACQ 14 (4) 24 (6) 12 (3) 7 (2) 13 (2) 21 (3) 16 (35) 18 (4) 2.93 CC 22 (8) 26 (7) 8 (1) 8 (2) 14 (3) 21 (3) 10 (25) 22 (5) 3.12 12 CCA 185 (55) 43 (13) 14 (3) 25 (6) 21 (4) 22 (4) 17 (30) 30 (8) 19.40 CCB 70 (20) 130 (16) 19 (3) 10 (2) 19 (3) 35 (5) 18 (25) 21 (4) 23.10 CDDC 37 (13) 56 (7) 21 (3) 48 (3) 13 (3) 12 (3) 16 (24) 41 (4) 13.60 ACZA 25 (15) 49 (10) 11 (3) 11 (2) 16 (2) 22 (3) 16 (31) 25 (5) 7.82 ACQ 20 (4) 32 (9) 10 (2) 13 (5) 14 (1) 18 (3) 14 (24) 16 4) 4.90 CC 19 (5) 22 (6) 10 (4) 9 (2) 17 (4) 21 (4) 15 (49) 24 (2) 5.17 18 CCA 231 (39) 27 (5) 15 (2) 13 (3) 24 (1) 33 (5) 18 (38) 22 (5) 22.40 CCB 97 (24) 95 (35) 17 (8) 14 (4) 18 (3) 44 (9) 17 (34) 26 (4) 32.10 CDDC 122 (12) 86 (24) 16 (3) 68 (4) 14 (3) 14 (4) 12 (23) 42 (4) 18.30 ACZA 28 (12) 34 (5) 9 (4) 16 (3) 17 (3) 40 (7) 12 (22) 20 (4) 9.20 ACQ 18 (3) 20 (4) 6 (1) 8 (2) 16 (2) 23 (4) 12 (1) 24 (6) 5.11 CC 31 (9) 19 (5) 12 (4) 12 (2) 19 (2) 22 (3) 14 (27) 21 (2) 5.70 24 CCA 299 (55) 39 (8) 10 (4) 19 (5) 27 (4) 39 (10) 18 (38) 28 (8) 30.50 CCB 95 (35) 77 (15) 11 (3) 12 (4) 21 (2) 47 (7) 17 (36) 32 (8) 43.60 CDDC 69 (28) 59 95) 27 (9) 42 (6) 11 (2) 19 (3) 18 (17) 67 (26) 21.60 ACZA 27 (11) 66 (13) 15 (6) 8 (4) 19 (4) 23 (4) 13 (24) 23 (2) 14.20 ACQ 24 (4) 23 (6) 9 (1) 9 (2) 19 (5) 30 (5) 14 (16) 25 (5) 7.10

CC 20 (6) 21 (8) 10 (4) 5 (1) 13 (1) 27 (5) 12 (3) 27 (5) 7.90


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Leachable and Dislodgeable Arsenic and Chromium from In-Service CCA-Treated Wood

Tomoyuki Shibata1, Helena M. Solo-Gabriele1, Lora Fleming2, Stuart Shalat3, Yong Cai4,

and Timothy Townsend5

1University of Miami, Department of Civil, Architectural, and Environmental Engineering, P.O. Box 248294, Coral Gables, Florida, 33124-0630 USA

2 University of Miami, NIEHS Marine and Freshwater Biomedical Sciences Center,

Rosensteil School of Marine and Atmospheric Science, 4600 Rickenbacker Causeway, Virginia Key, FL 33149

3The Environmental and Occupational Health Science Institute (EOHSI), Robert Wood Johnson Medical School Rutgers University of Medicine and Dentistry of New Jersey,

170 Frelinghuysen Road, Rm 318, Piscataway, NJ 08554

4Florida International University, Department of Chemistry & Biochemistry and Southeast Environmental Research Center (SERC),

11200 S.W. 8 St., University Park, Miami, Florida 33199

5University of Florida, Department of Environmental Engineering Sciences, 333 New Engineering Building, Gainesville, Florida, 32611-6450 USA

Corresponding Author: Helena Solo-Gabriele

University of Miami, Department of Civil, Architectural, and Environmental Engineering, P.O. Box 248294, Coral Gables, Florida, 33124-0630 USA

Telephone: 305-284-3489, FAX: 305-284-3492, e-mail: [email protected] ABSTRACT

Leachable and dislodgeable arsenic and chromium from CCA (chromated copper arsenate)-treated wood were studied to evaluate the fate of these CCA-chemicals and possible human exposures when the chemicals have been released to the environment. To evaluate the leachable component, two full sized decks were constructed. One was made of CCA-treated wood, and the other was made of untreated wood. Rainfall, runoff water from the top surface of the deck, and infiltrated water through 70 cm of soil below the deck had been monitored for 408 days. Soil below the decks was collected 6 months and 13 months after deck installation. The results of the deck monitoring showed that a significant portion of arsenic could be leached to environment during the service life of the CCA-treated wood product when exposed to rainfall. During the monitoring period, the average concentration in the runoff water from the CCA-treated deck was 1,000 ug/L for arsenic and 99 ug/L for chromium. Release of these metals to the surface soil was


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also observed. The surface arsenic concentrations increased from 4.5 mg/kg for the 6 month soil sample to 11.5 mg/kg for the 13 month sample. The impacts of the releases were also observed in the infiltrated water samples collected from below the experimental decks. The arsenic concentrations below the CCA-treated deck increased from a background level of 2 ug/L to 20 ug/L during the 408 day monitoring period; the chromium concentrations were more consistent at concentrations typically between 3 to 4 ug/L.

The dislodgeable components from CCA-treated wood were quantified through wipe tests, which were designed to evaluate the effects of different wood retention levels, sapwood versus heartwood, repetitive wipes, and long-term weathering. This part of the study demonstrated that significantly larger amount of dislodged arsenic and chromium could be removed from higher retention CCA-treated wood. The average mass of dislodged arsenic from the 40 kg/m3 CCA-treated wood sample was 1200 ug/wipe, and 74 ug/wipe for the 4 kg/m3 CCA-treated wood sample. The amount of dislodged arsenic and chromium from the sapwood side of CCA-treated wood was larger than from the heartwood side, and these differences were significant for the first repetition of wipe samples collected. Furthermore, the amount of dislodged arsenic and chromium significantly decreased as the number of consecutive sets of wipes increased on the same area. The average quantities of dislodged arsenic and chromium decreased from 6 months to the 12 month study period, however these averages were not statistically different.

Overall, this study confirmed that CCA-chemicals are released from the wood products through both leaching and dislodging. These releases result in environmental contamination, and may serve as a source of arsenic and chromium exposure for humans. Keywords; leachable CCA, dislodgeable CCA, arsenic, chromium, and CCA-treated wood INTRODUCTION

CCA is a chemical mixture consisting of three metal/metalloid compounds (i.e. arsenic, chromium, and copper) registered for wood preservative uses. CCA is the most common wood preservative utilized in the US, representing over 75% of the wood preservation market since the 1970s (Micklewright 1998). During this time, CCA has been used to treat lumber used for decks, playgrounds, docks, and other outdoor uses. Arsenic, one of the element contained within CCA, is well known for its toxic nature and its toxicity depends upon its chemical form (WHO 1996).

Earlier studies have shown that a significant portion of the CCA chemicals could be leached into the environment during the service life of the treated wood products when exposed to rainfall and low pH solutions (Warner and Solomon 1990; Cooper, 1991). Other studies have shown that the surface soils below CCA-treated wood decks can become contaminated with arsenic. For example, an average of 76 mg/kg (3 ~ 305 mg/kg) of arsenic in soils was observed in Connecticut (Stilwell and Gorney 1997), and 28.5 mg/kg (1 ~ 217 mg/kg) in Florida (Townsend et al., 2001). Leachable arsenic from the CCA-treated wood increases arsenic soil concentrations under CCA-treated wood products, and may result in potential groundwater contamination. It has been noted that children are exposed to environmental chemicals, such as pesticides, and often in greater quantities than adults. In the case of many pesticides, a major route of exposure is non-dietary ingestion; significant correlations between the levels of pesticides on the hands of young children and in urine have been reported (Shalat 2001). A study reported that total urinary arsenic excretion was significantly increased in children living in a community with high levels of arsenic in soil compared with a community with low levels in soil (Binder et al. 1987). Studies have shown that


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arsenic can be dislodgeable by contacting or rubbing on the surface of CCA-treated wood (U.S. CPSC 1990). Therefore, these studies suggest that particularly young children could have potential exposure to leachable and dislodgeable arsenic through normal behavior on and around CCA-treated wood products.

Currently, the U.S.EPA is reassessing CCA as part of its ongoing re-registration program for older pesticides. On February 12, 2002, U.S.EPA Administrator Whitman announced a voluntary decision by the Industry to move away from consumer use of CCA-treated lumber by December 31, 2003, in favor of new alternative wood preservatives (U.S.EPA 2002). As of January 1, 2004, the U.S.EPA will not allow the new use of CCA to treat wood intended for most residential uses (U.S.EPA 2002). However, as of November 2003, the U.S. EPA had not yet recommended that consumers replace or remove existing structures made with CCA-treated wood or the soil surrounding those structures. Recommendations concerning existing playground equipment are pending an on-going study sponsored by the U.S. EPA and the U.S. Consumer Products Safety Commission.

The primary objective of this study was to obtain essential information on leachable and dislodgeable arsenic and chromium from CCA-treated wood. The intent was to incorporate these data into a contaminant transport model and a risk analysis for evaluating possible human exposures associated with CCA releases to the environment.

MATERIALS AND METHODS

This study consisted of two sampling efforts. One focused on leachable arsenic and chromium, and the other focused on dislodgeable arsenic and chromium.

Sample Collection Leachable arsenic and chromium: Two decks (with a 3 m2 top surface area of deck sitting on a 6 m2 surface area of sand base) were installed to monitor leachable arsenic and chromium during in-service use of wood (Figure 1). One deck was constructed of CCA-treated wood retention level of 4 kg/m3 (= 0.25 pcf) as indicated upon purchase of the wood. The other served as a control, and was constructed of untreated wood. The sand was from local rock mining activities in south Florida which is formed during the excavation of the local limerock within the area. The total bulk volume of soil below each deck was 4.2 m3 soil (sand: porosity of 35%, soil particle density of 2,690 kg/m3), resulting in a depth of 0.7 m of soil. Sawdust samples were collected from each deck by drilling approximately 1.5 cm depth from the top deck boards, sideboards, and legs in order to confirm treatment with the CCA-chemicals, and to determine the initial concentration and retention level of the CCA-chemicals in the wood boards if initially positive for CCA chemicals. The results of sawdust analysis confirmed that all boards used for the untreated deck were not treated wood. For the CCA-treated deck, only the top surface boards were CCA-treated wood. The sideboards and legs were confirmed as ACQ (Alkaline Copper Quat)-treated wood. The concentrations of arsenic, chromium, and copper in the CCA-treated deck top boards were 1,460, 1,586, and 729 mg/kg respectively, with a resulting 3.2 kg/m3 CCA retention level.


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Figure 1: Deck used to evaluate leachable arsenic and chromium

Figure 2: Outdoor wipe stations to evaluate dislodgeable arsenic and chromium

Water Sample Collection: The two decks had been monitored for a 13-month period since September 7, 2002 through October 20, 2003 for a total of 408 days. Three types of water samples were collected from each deck: rainwater, runoff water from the deck surface, and infiltrated water through sand below the deck. The water samples from each deck were collected in 100 ml plastic bottles everyday for the first month and then twice a week (Monday and Thursday) thereafter. pH and oxygen reduction potential (ORP) was measured (525A, Orion Research Inc., Beverly, MA, USA) immediately after sample collection for all water samples collected from the two decks. All water samples, after being measured for pH, were acidified by adding 1 ml of 1:1 nitric acid (HNO3) and stored in a refrigerator until sample analysis. Rainfall depth and rainwater sample collection was facilitated through the use of a set of standard rain gages located 1.2 m above each deck. A total of 84 rainfall measurements resulting in 1,850 mm of rainfall were measured at the gage located above the CCA-treated deck. The mean rainfall measured at the gage above the untreated deck was statistically equivalent to the mean rainfall measured above the CCA-treated deck (alpha 0.05, p = 0.996) thus all subsequent computations requiring rainfall depth were based upon data collected at the rain gage located above the CCA-treated deck. Rainwater samples from each of the gages were collected from the first rainfall event for each month resulting in a total of 26 rainwater samples with 13 collected per deck. The runoff water collection system consisted of a gutter that drained the lowermost board from each deck. The gutter was covered with a polyethylene liner to prevent rainfall from entering the gutter. Water from the gutter was collected in a plastic reservoir located below each deck. A total of 51 runoff samples were collected from the CCA-treated deck and 49 samples were collected from the untreated deck. The mean runoff water volumes collected from each deck were statistically the same (alpha = 0.05, p = 0.983) and the amount of runoff water collected was strongly correlated with rainfall (r = 0.855). Every runoff water sample collected from each deck was analyzed for arsenic and chromium with the exception of the samples collected during the last 5 months from the untreated deck. During the last 5 months, only the first runoff sample was analyzed due to the consistently low concentrations observed in the runoff from the untreated deck.


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The infiltrated water was collected from below a 0.7 m sand layer. The drainage system below the sand layer consisted of a felt liner underlaid by gravel and an impervious liner which facilitated the drainage of the water towards a graduated plastic reservoir. The volume of water collected was measured directly from the graduated reservoir and infiltrated water samples were collected from the reservoirs during the pre-determined sampling intervals, which were consistent with the sampling intervals used for runoff water collection. The mean volumes of infiltrated water collected from each deck were statistically the same (alpha 0.05, p = 0.519). The amount of infiltrated water was strongly correlated with rainfall (r = 0.883) and runoff water volume (r = 0.871). A total of 98 infiltrated water samples were collected from the CCA-treated deck and 82 samples were collected from the untreated deck. All samples collected from below the CCA-treated deck were analyzed for arsenic and chromium and all samples collected during the first 5 months of monitoring were analyzed from the untreated deck. After the first 5 months only the first sample during each month from the untreated deck was analyzed for arsenic and chromium.

Soil Sample Collection: Sand samples from below each deck were collected using a 28.6 mm diameter unslotted stainless probe fitted with a pre-acid washed plastic liner (Forestry Supplier, Inc., Jackson, MS, USA). Samples were collected after six months and one year from the installation date of the decks. The collected sand samples were divided into 2.5 cm depth intervals, and kept in a Ziploc bags until analysis. Dislodgeable Arsenic and Chromium: In order to study dislodgeable arsenic and chromium, wipe samples were collected from CCA-treated wood boards. The wiping device was 8 cm in diameter and weighed 1.1 kg, consistent with the device used by the U.S. Consumer Products Safety Commission (U.S. CPSC. 2003). Between samples, the device was covered with a new piece of parafilm and polyester cloth (static reutilizing cloth, VWR International, West Chester, PA, USA). The wipe cloth and parafilm were fixed to the sampling device with a rubber band. In advance of wiping action, a surface area of 400 cm2 (50 x 8 cm) on the wood sample was measured, and the area was marked using tape. The sampling device was moved by pulling the attached strings five times forward and backward (forward and backward counted as one stroke). The sampling device was rotated 90 degrees, and then another five strokes were applied. The wiped cloth was carefully removed from the sampling device and stored in a Ziploc bag until analysis. Wipe samples were collected from three different sets of wood boards. These sets included a set that was kept inside the laboratory (4 kg/m3 as indicated upon purchase of the wood), one that was placed outside (untreated, 4 kg/m3 and 40 kg/m3 as indicated upon purchase) (Figure 2), and another set consisting of preselected boards from the constructed decks as described above (i.e.untreated and the 3.2 kg/m3 confirmed CCA-treated deck). The wood boards were used to evaluate 4 different factors: the effects of wood retention level, sapwood versus heartwood, repetitive wipes, and long term weathering. The effect of retention level was evaluated on: a set of 3 unweathered wood boards, 1 untreated board, 1 CCA treated at 4 kg/m3, and 1 CCA treated at 40 kg/m3. Each board was separated into 6 sections, and 1 wipe sample was collected from each section for a total of 6 wipes per board. Only the sapwood portions of the boards were wiped (with the exception of the untreated board where 3 wipes were collected from the sapwood side and 3 wipes collected from the heartwood side of the board). Efforts also focused on comparing the wipe data collected from the heartwood side of CCA-treated wood versus the sapwood side since CCA-retention, in general, is small within the heartwood side due to the higher density of the wood within this region (Figure 3). A total of 36 wipes were collected for comparison between the sapwood and heartwood portions of CCA-treated wood. Eighteen wipes were collected from an unweathered 4 kg/m3 wood board which was


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separated into 6 wiping sections. Three sections corresponded to the sapwood side of the board and three corresponded to the heartwood side. Three wipes were collected from each section for a total of 18 wipes collected from the unweathered board (9 from the sapwood side and 9 from the heartwood side). The remaining 18 wipe samples were collected from 3 preselected boards from the CCA-treated decks described above. Two of these deck boards were heartwood and one deck board was sapwood. After a 6-month period of weathering, each of the deck boards was wiped 3 times for a total of 6 heartwood wipes and 3 sapwood wipes. The same procedure was followed after a 12-month period of weathering with another 9 wipes collected (6 heartwood wipes and 3 sapwood wipes). Untreated wood controls from an unweathered board and from the untreated wood deck were also carried through the analysis. Wipes collected from the unweathered wood boards were processed in duplicate by splitting the wipes into quarters, with 2 of the quarters per wipe analyzed separately. The effects of repetitive wipes were evaluated on the same set of samples as used to evaluate the possible differences between heartwood and sapwood. Thus a total of 36 wipes were used for this analysis. Eighteen wipes were collected from 6 sections on the unweathered 4 kg/m3

wood board and 18 were collected from 3 weathered deck boards (after 6 months and 12 months of weathering). Given that each section was wiped consecutively 3 times, the effects of the first wipe could be compared to the second wipe and to the third wipe.

The effects of long-term weathering were evaluated by comparing the results from the deck samples described above, with the results corresponding to 6 months of weathering compared to the results after 12 months of weathering. A total of 9 wipes were available for the 6 month period and 9 wipes were available for the 12 month period. Wipes were also collected from untreated wood as controls.

Figure 3: Photograph of CCA-treated wood METALS ANALYSIS

Sample matrices analyzed in this project included sawdust, water, soil, and wipes. Each sawdust and soil sample was split into 4 sub-samples. All subsamples were digested in hydrogen peroxide and hot acid according to U.S. EPA Method 3050B (U.S. EPA 1996). Two sub-samples were digested in nitric and hydrochloric acid (suitable for subsequent chromium and copper analyses), whereas only nitric acid was used in the remaining two subsamples (consistent with the requirements of the procedure for arsenic analyses). Once digested, sawdust digestates were analyzed for arsenic, chromium, and copper using an atomic absorption spectrometer (AA) using flame atomization (Perkin Elmer Model AA800, Wellesley, MA, USA) and soil digestates were analyzed using the same instrument except graphite furnace atomization was used due to lower concentrations. Water samples were initially processed by acidifying to a pH less than 1 with 1:1 concentrated nitric acid. These samples were then quantified for arsenic, chromium, and copper using an AA with graphite furnace atomization. Each sub-sample was analyzed in triplicate with flame atomization analysis, and in duplicate with graphite furnace atomization analysis. Two extraction methods were evaluated for wipe sample processing and compared as part of the preliminary work associated with this study. These methods included a hot acid digestion (U.S. EPA 1996, Method 3050B) and a diluted acid extraction method based upon the use of a 10% solution of HNO3 heated to 60 oC (U.S. CPSC 2003). In order to evaluate these methods, a set of 18 samples was collected by wiping six different sections of a 4 kg/m3 wood board in triplicate. Each

Heartwood Side

Sapwood Side


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wipe sample was then split by cutting the wipe samples into quarters. Two of the quarters were subjected to the digestion method and the remaining two were subjected to the dilute acid extraction method, for a total of 36 pairs. A pair consisted of 2, ¼ wipe samples, one processed using the concentrated acid digestion method and the other processed using the diluted acid extraction method. Due to the slightly different digestion methods required for chromium versus arsenic, the entire process was repeated for subsequent chromium analysis. A total of 34 pairs of samples were analyzed for arsenic and 23 pairs were analyzed for chromium. Statistical analysis indicated that the diluted acid extraction and hot acid digestion method provided statistically the same values (alpha, a = 0.05, T-test, p = 0.105 for arsenic and 0.274 for chromium). The extraction method was chosen for processing all subsequent wipe samples given that it was a simpler procedure providing statistically the same results as the digestion method. RESULTS

Leachable Arsenic and Chromium Water Samples: Physico-chemical data (Table 1) collected from the untreated and CCA-treated decks were statistically the same. The mean pH values between the rainfall, the runoff water, and the infiltrated water were significantly different from each other (alpha 0.05, t-Test, p < 0.001). The pH of the rainwater at 4.8 was the lowest; the pH of the runoff water was higher at 6.2 and for the infiltrated water the mean pH was at 7.9 to 8.1, indicating that rainwater contact with wood increases the pH of the water. Subsequent contact with the soil results in further increases in pH. The ORP of the rainwater (120 mV) decreased as it came into contact with the wood (40 mV) and as it was collected from below the soil (-70 to -75 mV), indicating that the water becomes more reduced as it passes through the system. The mean metals concentrations observed in the water samples (Table 2) indicated that rainwater collected from above the untreated and CCA-treated deck was consistently below the 1 ug/L detection limit for both arsenic and chromium. The mean arsenic and chromium concentrations in the runoff water for the CCA-treated deck were 1001 + 770 ug/L for arsenic and 99 + 79 ug/L for chromium. The highest concentrations observed during the monitoring period were 4,660 ug/L (Figure 4) for arsenic and 470 ug/L for chromium. The concentrations observed in the runoff water from the CCA-treated deck contrasted with the concentrations observed in the untreated deck which were consistently below the 1 ug/L detection limit for both chromium and arsenic. At the beginning of the monitoring period, the arsenic and chromium concentrations in the infiltrated water below the treated deck were at or near detection limits. As time progressed, the concentrations increased (Figure 4). The highest concentrations observed from below the CCA-treated deck were 24 ug/L for arsenic and 10 ug/L for chromium. Neither arsenic nor chromium were detected above the level of 1 ug/L from most all infiltrated water samples at the untreated deck. Including the below detection limit samples, which were set at 0.5 ug/L, the average arsenic concentration in the infiltrated water below the treated deck was 6.6 + 6.4 ug/L and 3.1 + 1.9 ug/L for chromium. Soil Samples: The highest concentrations of arsenic within the soils were found at the surface (0 ~ 2.5 cm depth) below the CCA-treated deck with concentrations decreasing notably with depth. Arsenic concentrations in surface soils collected after the 13 months were considerably larger than those observed in the six-month surface soil samples (Figure 5). The surface concentration was 4.5 mg/kg of dry soil for the six month sample and 11.5 mg/kg for the 13 month sample.


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Concentrations decreased to less than 1 mg/kg below a 5 cm depth for the 6 month sample and below a 7.5 cm depth for the one year sample. All arsenic soil concentrations collected under the untreated deck were less than 1 mg/kg of dry soil in both the six-month sand samples and 13 month sand samples.

Table 1: Summary of physico-chemical parameters in water samples Rainfall Runoff Infiltrated Water

Parameter untreated deck

treated deck

untreated deck

treated deck

untreated deck

treated deck

Mean 13 mm 13 mm 581 ml 584 ml 42 L 48 L Standard Deviation

Depth/Volume 23 mm 23 mm 1174ml 1174 ml 73 L 73 L

Mean 4.78 4.83 6.18 6.25 7.91 8.10 Standard Deviation

pH 0.81 0.81 0.65 0.65 0.89 0.89

Mean 121 117.6 42 37.9 -70 -74.8 Standard Deviation

ORP, mV 55 55 32 32 30 30

Table 2: Summary of arsenic and chromium concentration in water samples

Rainfall, ug/L Runoff, ug/L Infiltrated Water, ug/L

Metal

untreated deck

treated deck

untreated deck

treated deck

untreated deck

Treated deck

Mean < 1 < 1 < 1 1,001 < 1 6 Standard Deviation

As < 1 < 1 < 1 770 < 1 6

Mean < 1 < 1 < 1 99 < 1 3 Standard Deviation

Cr < 1 < 1 < 1 79 < 1 2


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Figure 4: Arsenic concentrations (ug/L) in runoff and infiltrated water from the CCA-treated wood Deck

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Figure 5: Arsenic in soil under the decks Dislodgeable Arsenic and Chromium Retention Level Effect: Wood with increasing retention level resulted in greater amounts of dislodged arsenic (Table 3). The average amount of arsenic for the 4 kg/m3 wood samples was 74 + 32 ug/wipe. This increased to 1200 + 245 ug/wipe for the 40 kg/m3 wood samples. These differences were statistically significant (p < 0.001).

Table 3: Dislodged arsenic from different retention levels

Sample IDa

Retention Level

(kg/m3) Arsenic

(ug/wipe) Sample

ID

Retention Level

(kg/m3) Arsenic

(ug/wipe)Sample

ID

Retention Level

(kg/m3) Arsenic

(ug/wipe)WA-0S 0 <0.5 WA-4S 4 45 WA-40S 40 970 WB-0S 0 <0.5 WB-4S 4 52 WB-40S 40 1,152 WC-0S 0 <0.5 WC-4S 4 42 WC-40S 40 1,606 WD-0H 0 <0.5 WD-4S 4 112 WD-40S 40 1,112 WE-0H 0 <0.5 WE-4S 4 90 WE-40S 40 1,307 WF-0H 0 <0.5 WF-4S 4 105 WF-40S 40 949 Mean <0.5 74 1183

Std dev --- 32 245 a W corresponds to outdoor wipe stations but these data were collected before the wood was placed outside.

Sapwood Versus Heartwood: Results from the 36 wipe samples showed that the amount of arsenic dislodged from the sapwood side of CCA-treated wood (81 + 79 ug/wipe) was greater than from the heartwood side (50 + 47 ug/wipe (Table 4). Although the quantity of dislodged arsenic on the sapwood side was relatively greater than the heartwood side, the mean dislodged arsenic from these two surfaces were statistically the same for all of the data collectively (p = 0.064). When the data for the first repetition only were compared, the amount of dislodged arsenic was significantly greater from the sapwood side as compared to the heartwood side (p = 0.021). Effects of Repetitive Wipes: The amount of dislodged arsenic and chromium notably decreased as the number of consecutive sets of wipes increased on the same area (Table 4). The amounts dislodged from the first set of wipes decreased significantly after the second set of wipes (p < 0.001

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for arsenic; p < 0.001 for chromium). From the second set of wipes to the third set of wipes, the amounts dislodged also decreased significantly (p = 0.004 for arsenic; p = 0.002 for chromium). Although the mass of arsenic and chromium dislodged decreased with repeated wipes, the masses were much higher in the first wipe taken after 12 months compared to the third wipe taken after 6 months (Table 5), indicating the replenishment of the wood surface with the CCA chemical. Results for a subset of the data evaluated are shown in Figure 6. Effects of Long Term Weathering: The amount of dislodged arsenic was 52 + 43 ug/wipe from the CCA-treated deck after 6 months of weathering, and 41 + 26 ug/wipe after 12 months of weathering (Table 5, Figure 7). For chromium, the mean amount of dislodged arsenic was 75 + 56 ug/wipe for the 6-month period and 54 + 29 ug/wipe for the 12-month period. The mean amounts of dislodged chromium were significantly larger than arsenic (p < 0.024) for both sampling periods. The average quantities of dislodged arsenic and chromium decreased from the six-month to the 12-month period. However, the mean amount of dislodged arsenic and chromium collected after six months versus 12 months was statistically the same (p = 0.140 for arsenic; p = 0.041 for chromium). The amounts of arsenic and chromium collected by wiping action on the surface of the untreated deck were below 1 ug/wipe in both the six month and 12-month samples.


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LA-4HLB-4SLC-4HLD-4SLE-4HLF-4S

All samples correspond to 4 kg/m3

Table 4: Dislodged arsenic (ug/wipe) from sapwood versus heartwood Sapwood Side Heartwood Side

Sample ID Retention Level

(kg/m3)

Repetition Number

As (ug/wipe)

Cr (ug/wipe)

Sample ID

RetentionLevel

(kg/m3)

Repetition Number

As (ug/wipe)

Cr (ug/wipe)

LB-4Sa 4 1 174 132 LA-4Ha 4 1 109 11 2 31 56 2 27 15 3 21 31 3 11 12 LD-4Sa 4 1 254 12 LC-4Ha 4 1 169 10 2 50 17 2 32 8 3 11 12 3 24 4 LF-4Sa 4 1 303 LE-4Ha 4 1 169 2 32 2 69 3 16 3 26 DB6-4S 3.2 1 123 162 DA6-4H 3.2 1 130 175 2 34 48 2 47 69 3 23 29 3 30 43 DB12-4S 3.2 1 100 94 DA12-4H 3.2 1 52 105 2 44 59 2 39 52 3 39 49 3 32 40 DC6-4H 3.2 1 41 83 2 23 39 3 15 26 DC12-4H 3.2 1 37 46 2 13 21 3 13 19 Mean 84 58 53 43 Std. Dev. 91 48 49 43 aData shown are the average from two splits from the same wipe.

Figure 6: Effects of repetitive sets of wipes on dislodged arsenic


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Table 5: Dislodged arsenic and chromium after long-term weathering

Arsenic, ug/wipeb Chromium, ug/wipeb Sample IDa

Repetition Number 6 months 12 months 6 months 12 months

1 130 52 175 105 2 47 39 69 52 DA-4H 3 30 32 43 40 1 123 100 162 94 2 34 44 48 59 DB-4S 3 23 39 29 49 1 41 37 83 46 2 23 13 39 21 DC-4H 3 15 13 26 19

Mean 52 41 75 54 Std dev. 43 26 56 29

aThe letter “D” in the Sample ID corresponds to the CCA-treated deck. The letter “H” in the Sample ID corresponds to Heartwood Side and the letter “S” corresponds to Sapwood. bResults for the untreated control were below the 0.5 ug/wipe detection limit for the 6 and 12 month samples.

Figure 7: Dislodged arsenic after 6 and 12 months of weathering

DISCUSSION AND CONCLUSION

The results of this study were consistent with other studies that show that metals leach from CCA-treated wood throughout its in-service use (Townsend et al. 2000; Stilwell and Gorney 1997; and others). The mean concentrations of arsenic in the runoff and infiltrated water were

Error Bars correspond to 1 std. dev.

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significantly greater than the concentrations of chromium, although the initial retention level of chromium was greater.

The average arsenic concentrations of 1.0 mg/L in the runoff water from the CCA-treated deck were significantly higher than the U.S. EPA drinking water standards (U.S. EPA 1974) which includes a Maximum Contaminant Level Goal (MCLG) of 0 mg/L and the Maximum Contaminant Level (MCL) of 0.050 mg/L (0.010 mg/L as of January 23, 2006, U.S. EPA 2002). The arsenic concentration in the runoff water was also higher than the Florida Criteria for Surface Water Quality Classifications (FDEP 1996), which includes a maximum permissible concentration of 0.050 mg/L for all water classes (I to V). The average chromium concentration in the runoff water from the CCA-treated deck (0.1 mg/L) was near the U.S. EPA drinking water standard of 0.1 mg/L (MCL and MCLG) and higher than the Florida Criteria for Surface Water Quality Classifications of 0.05 mg/L for Class II, III (fresh), and V (predominantly marine) and 0.011 mg/L for Class I, III (marine), IV, and V (predominantly fresh). The arsenic and chromium leached from the CCA-treated wood drained into the soil below the deck. Arsenic concentrations in the surface soil below the CCA-treated deck after 6 and 13 months of leaching were 4.5 mg/kg and 11.5 mg/kg, respectively. These concentrations are higher than the U.S. EPA soil screen level (SSL) of 0.4 mg/kg (U.S.EPA 1996) and Florida’s Soil Cleanup Target Levels (SCTLs) (FDEP 1999) of 0.8 mg/kg for residential areas and 3.7 mg/kg for industrial areas. The arsenic concentrations observed in the surface soils were relatively smaller than earlier studies that showed an average of 76 mg/kg (3 to 305 mg/kg) in Connecticut (Stilwell and Gorney 1997) and 28.5 mg/kg on average (1 to 217 mg/kg) in Florida (Townsend et al. 2001). The arsenic concentration in the soil did not exceed the Florida SCTLs of 29 mg/kg for leaching to groundwater. It should be noted that in this study, the soil was sandy and had been receiving runoff from the CCA-treated deck for only 1 year. The 1 year study period was significantly shorter than the age of the decks (2 to 19 years) used in the Florida study (Townsend et al. 2001). Given the increasing trend for arsenic concentrations in the surface soil between 6 and 13 months, it is likely that the surface soil concentrations may increase with time to higher levels as observed in other studies. Arsenic (7 ug/L on average) and chromium (6 ug/L on average) were also detected in the infiltrated water located below the CCA-treated deck. Overall the concentrations increased from detection limits at the beginning of the study to upwards of 20 ug/L. Although the majority of the arsenic introduced from the CCA-treated deck was sorbed by the sand, “break-through” of the metals was still observed through the 2 foot sand layer, resulting in concentrations that could present a threat to groundwater drinking water supplies. This study supported earlier studies that showed that arsenic and chromium could be dislodged by wiping the surface of CCA-treated wood (U.S. CPSC 1990; Stilwell et al. 2003). The average mass of dislodged arsenic from the rated 4 kg/m3 wood was 72 ug/wipe. This value was larger than the 39 ug/wipe measured by the U.S. CPSC (2003). The current study also showed that the amount of dislodgeable arsenic decreased with repeated rubbing for wood that had been weathered up to 1 year. It would be of interest to evaluate whether repeated wipes result in reduced dislodgeable arsenic levels for wood that has been weathered for longer periods of time.

Overall this study provided important information that could be used in the development of risk assessments for possible human exposures to leachates and dislodgeable metals from CCA-treated wood. CCA-treated wood will be phased-down for residential applications in the future; however, many CCA-treated structures currently exist. It will be important to evaluate the impacts of these existing structures, as well as the impacts of the CCA-treated wood that will continue to be produced for non-residential uses and for residential uses exempted from the EPA mandated CCA phase-down. The results of this study may be helpful in identifying feasible recommendations concerning mitigations efforts aimed at existing playgrounds and other CCA-treated structures.


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Additional work should concentrate on documenting further the potential impacts of CCA-treated wood leachates to groundwater as an additional environmental and human exposure risk. ACKNOWLEDGMENT

Funding for this project has been received from the Florida Center for Solid and Hazardous Waste Management, the Institute of Hazardous Materials Management, and the National Institute for Environmental Health Sciences (Grant No. S11 ES11181). We thank Gary Jacobi and Dr. Wimal Suaris for assistance with the design and construction of the structures used to contain the CCA-treated decks. REFERENCES

Binder, S., Forney, D., Kaye, W., and Paschal, D., 1987. Arsenic exposure in children living near a copper smelter. Bull Environ Contam Toxicol, 39: 114-121. Cooper, P.A., 1991. Leaching of CCA from treated wood; pH effects. Forest Product Journal, 41: 1: 30-32 Florida Department of Environmental Protection (FDEP), 1996. Chapter 62-302.530, Criteria for Surface Water Quality Classifications. FDEP, Tallahassee, FL. Florida Department of Environmental Protection (FDEP), 1999. Chapter 62-777, Contaminant Clearn-up Target Levels. FDEP, Tallahassee, FL Micklewright J.T., 1998. Wood Preservation Statistics 1997. American Wood Preservers’ Association, Granbury, TX Shalat, S.L., Donnelly KC., Ramesh, S., Freeman, N., Jimenez, M., Black, K., Needham, L., Barr, D., Ramirez, J., 2001. Ingestion of pesticides by children in an agricultural community on the U.S./Mexico border: preliminary report. Annual Meeting of the International Society for Exposure Analysis. Charleston, SC Stilwell, D.E. and Gorney, K.D, 1997. Contamination of soil with copper, chromium, and arsenic under decks built from pressure treatment wood. Bulletin of Environmental Contamination and Toxicology, 58: 22-29 Stilwell, D.E., Toner, M., and Sawhney, B., 2003. Dislodgeable copper, chromium, and arsenic from CCA-treated wood surface. The Science of the Total Environment, 312: 123-131 Townsend, T., Stock, K., Tolaymat, T., Song, J.K., Solo-Gabriele, H., Hosein, N., Khan, B., 2001. New Lines of CCA-treated Wood Research: In-Service and Disposal Issues. Draft Technical Report #00-12. Florida Center for Solid and Hazardous Waste Management, Gainesville, FL U.S. Consumer Products Safety Commission (CPSC), 1990. Estimate of Risk of Skin Cancer from Dislodgeable Arsenic on Pressure Treated Wood Playground Equipment. U.S. CPSC, Washington, DC


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U.S. Consumer Products Safety Commission (CPSC), 2003. Briefing Package, Petition to Ban Chromated Copper Arsenate (CCA)-Treated Wood in Playground Equipment (Petition HP 01-3). U.S. Consumer Products Safety Commission, Washington D.C. U.S. Environmental Protection Agency (EPA), 1974. Safe Drinking Water Act. U.S. Environmental Protection Agency, Washington, DC. U.S. Environmental Protection Agency (EPA), 1996. Soil Screening Guidance: User’s guidance. Environmental Protection Agency, Washington, DC. U.S. Environmental Protection Agency (EPA), 1996. Method 3050B: Acid Digestion of Sediments, Sludges, and Solids. U.S. Environmental Protection Agency, Washington, DC. U.S. Environmental Protection Agency (EPA), 2002. Implementation Guideline for the Arsenic Rule and Clarifications to Compliance and New Source Contaminants Monitoring. U.S. Environmental Protection Agency, Washington, DC. Warner, J.E., Solomon, K.R., 1990. Acidity as a factor in leaching of copper, chromium and arsenic from CCA-treated dimension lumber. Environmental Toxicology and Chemistry, 9: 1331-1337. World Health Organization (WHO) 1996. Guideline for drinking water quality, 2nd edition, Vol. 2, Health criteria and other supporting information: Arsenic. World Health Organization, Geneva, Switzerland


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Poster Abstracts


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Arsenic speciation in soils and CCA-treated wood leachate

Myron Georgiadis1*, Yong Cai1 and Helena M. Solo-Gabriele2

1Department of Chemistry & SERC, Florida International University, University Park, Miami, FL 33199; 2 University of Miami, Dept. of Civil, Arch., & Environ. Engineering

Coral Gables, FL 33124 Abstract The evaluation of the extraction efficiency and arsenic speciation in soil was performed by using phosphate as extractant. PACS-2, a standard reference material (marine sediment) was used as the model sediment/soil for the study. The primary results indicated that only a small percent (<20%) of arsenic, including both arsenite (AsIII) and arsenate (AsV), could be extracted from PACS-2 using 10 to 100 mM phosphate solutions. We observed the conversion from AsIII to AsV or readsorption of arsenic back to the solid phase during extraction and storage before analysis for both spiked and non-spiked samples. In order to gain real arsenic speciation information in soils, we have been conducting several experiments to preserve the arsenic species during the extraction. Phosphate with EDTA: EDTA has been used to preserve AsIII in water samples for arsenic speciation analysis. It was used in our study in an effort to stabilize arsenic species during extraction from soils. It was found that the use of EDTA at this concentration level (50 mM) did not improve much the decline of AsIII concentration with extraction time. In other words, EDTA did not prevent AsIII from conversion or readsorption. This is probably due to the large amounts of metal ions extracted from the sample. Greater concentration of EDTA interfered with the HPLC analysis; therefore it could not be used in the extraction. Phosphate with hydroxylamine hydrochloride: Hydroxylamine was chosen as an extractant because of its mild reducing characteristics, which may be helpful in preserving AsIII from oxidation. The results shows that AsIII concentrations still decrease with prolonged extraction times. However, the decreasing rate and magnitude were much smaller compared to those observed using phosphate alone. The decline in AsIII concentration occurred with extraction periods above 12 hours. The total amount of arsenic extracted was about 28%, indicting that hydroxylamine helped arsenic release from soil/sediment. Phosphate with sodium diethyldithiocarbamate(NaDDC): NaDDC is a chelating agent that complexes AsIII, therefore may prevent its conversion to AsV and/or reduce its readsorption to the solid phase. PACS-2 was extracted with 0.5% NaDDC + 10mM phosphate. It was observed that much more AsIII and less AsV were extracted with the NaDDC/phosphate mixture than with phosphate alone. AsIII concentration was found to be higher than AsV in PACS-2 under these experimental conditions, suggesting that PACS2 may contain more AsIII than AsV. It seems likely that NaDDC can complex AsIII as soon as its extraction occurs.


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Beyond the Lumberjack: Managing Wood Pallets and Industrial Wood Wastes

Miriam Zimms and Shane Barrett

Kessler Consulting Inc. Tampa, Florida, USA

Early log homes; covered wagons; construction of the first transcontinental railroad--the importance of wood in the building of America is undisputed. Today wood is still an integral part of residential home construction and wood ties can still be found supporting the country's railroad tracks. However the popularity of treated wood in its many modern applications has led to concerns about the impact of wood waste on the environment and how major users of wood and wood products can be part of the solution. One modern day use of wood that could not have been imagined by our early ancestors is the wood pallet. It is safe to say that the material that helped build America is now the material essential to helping move American products. The pallet industry acknowledges that 42 percent of all hardwood lumber harvested is used in pallet manufacture. And almost half of all pallets produced are designed for only one use. Since pallets are bulky and difficult to dispose of, and landfill restrictions on the disposal of wood waste are becoming more common, it's not surprising that the industry has taken steps to facilitate internal recycling programs. Even so, KCI’s research found that obstacles still exist such as difficulty dealing with contaminated wood, the lure of low tipping fees, and the absence of established end markets. The remanufacture or repair of wood pallets has been embraced by the wood pallet industry as a major waste reduction initiative. Pallet repairs are generally done in-house, contracted out to repair facilities, returned to manufacturers or suppliers, or in some cases pallets are pooled in a local partnership. The Reusable Pallet and Container Coalition (RPCC) reports that seven million tons of low quality wooden pallets are disposed of each year in the United States at a cost of about $400 million dollars. Companies like Home Depot, Procter and Gamble, and WalMart have initiated a reusable pallet program for at least part of their pallet usage however reusable pallets nationally still only comprise three percent of the total marketplace. RPCC promotes the program as allowing businesses to utilize stronger pallets, realize improved safety, and spend less operational time focusing on pallet management issues. A National Wood Pallet and Container Association (NWPCA) survey in 1997 showed the percentage of pallets being landfilled had dropped to 28 percent compared to 60 percent just four years earlier. The survey also revealed that, on average, pallets are reused nine times by the same pallet user. For pallets that have passed the point of repair or reuse, approximately 41 percent were used for fuel while just over 38 percent were being processed for mulch, compost, particleboard material or other use. Since the study was completed, the pressure treated lumber industry has come under fire in Florida, as well as other areas, regarding the potential health risks in certain applications of arsenic-treated wood. According to the University of Miami, over 28 million cubic feet of chromated copper


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arsenate (CCA) treated wood was sold within Florida during 1996. Sixty-two percent of this treated wood was produced at the 27 treatment plants in the state. Even in the absence of regulatory requirements, Florida solid waste managers are focusing their concern primarily on the use of pressure treated wood for playgrounds and the potential environmental hazards associated with improper handling and disposal of wood waste by end users. The FDEP feels that the majority of treated lumber in the state is contained within construction and demolition processing sites where it is not burned but could leach into groundwater. These concerns prompted additional studies and research by the university community as well as private industry. Amidst all this attention, the American Wood Preservers Institute (AWPI) points out that treated wood has been tested for decades and the industry has established procedures and guidelines for disposal and use of the product. And the Environmental Protection Agency (EPA) has evaluated the use of treated wood in playgrounds and other applications with the conclusion that it does not pose an acute or chronic toxic hazard. Pressure treated wood has been produced for well over a hundred years and the CCA type of treated wood has been around since the 1930s. And beginning in 2001, the AWPI began working more closely with the EPA to enhance their consumer awareness program and disseminate information to businesses and individuals about the proper use and handling of treated wood products. In 2002, many wood preservative manufacturers decided to seek and amend their respective registrations with the EPA to transition from CCA to a new generation of wood preservatives for use in the consumer and residential treated wood markets by December 31, 2003. CCA will continue to be produced for industrial end applications such as highway construction, utility poles, and pilings. A year 2000 survey of Florida counties, conducted by KCI, revealed that 71 percent do not offer a wood recycling program for large generators even though 33 percent of the counties surveyed indicated they had received inquiries from the commercial/industrial sector about wood pallet or wood waste disposal alternatives. Wood waste management and recovery is should be Florida’s next planning phase. Program development is critical now and it is time to begin taking practical action for wood waste recovery and proper disposal. More recently, attention to pressure treated wood and wood waste handling issues has been enhanced by increased coverage in industry trade and mainstream publications. Attention is also focused on a pilot project in Sumter County, Florida involving countywide separation of treated and untreated wood prior to disposal. A Wood Reuse & Exchange Center was constructed to house separated, useable wood for community reuse at no charge. This program, funded by an FDEP innovative grant in the amount of $269,000, will develop and implement best management and handling practices for wood waste as well as encourage business, government and residents to separate treated and untreated wood for proper reuse, recycling or disposal. A good corporate model is Florida Power and Light Corporation (FPL) of Juno Beach, Florida, which has taken an aggressive in-house approach to dealing with untreated wood products. The company operates a wood recycling facility, which produces two grades of mulch. In addition, an in-house pallet reuse program is operated along with the management of re-use agreements involving reel recovery operators and wire and cable vendors. FPL also captures a variety of other wood waste including vegetative material from line clearing projects as well as crates and broken furniture. In 2000, the company recovered or reused about 3,600 wood reels and scrapped or mulched another 1,100 reels. In addition, the company processed nearly 5,500 tons of wood


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waste—all part of a continuing program of combining reuse and recycling to capture as much material as possible. For the management of wood waste by consumers or commercial entities, a number of workable options are available. Waste reduction or reuse is effectively illustrated by local Habitat for Humanity ReStores, which accept, used wood and other construction materials, which are resold or used in construction projects. Unused wood and other materials can also be donated to local Habitat building projects. Some of the more successful Habitat ReStores around the country have reported generating enough revenue and materials to build as many as 10 or more houses each year. Habitat affiliates are encouraged to establish a specific area on each construction site dedicated to recycling and reuse. In addition, a number of entrepreneurs across the country have established furniture building cooperatives and businesses using scrap wood and old pallets as a primary material source. Since pallets are constructed largely of hardwoods, skilled hobbyists also find them useful in building quality items. In fact, FDEP’s Bill Hinkley, Chief of the Bureau of Solid and Hazardous Waste, developed an interest in pallets after seeing huge piles of them discarded at landfills. Hinkley says he “discovered pallets made from oak, maple, hickory, cherry, mahogany and many other hardwoods and has made them into furniture, jewelry boxes, picture frames and other items.” He points out that intensive labor is involved in breaking down the pallet, planing, sanding and finishing the wood “but the results can be extraordinarily beautiful.” Another waste reduction option involves the use of alternative materials such as plastic or steel pallets and recycled plastic lumber. Many vendors claim over 100 trips with a single plastic pallet. These pallets now can offer better fire resistance with a new resin recently developed by GE Plastics. And steel pallets, although heavy, are extremely durable and strong. Also gaining in popularity with businesses are collapsible or reusable containers, which reduce waste and save space. Even with such marketable advantages, these alternative containers are in many cases still a small percentage of the marketplace. Several of the recycling options available could be utilized in many communities through partnerships with various local entities or through agreements with public sector solid waste recovery programs. Many of the innovative and effective recycling options for wood waste involve partnerships creating a new market or utilizing wood in place of a non-renewable feedstock. Understanding that economic and geographic considerations can impact the feasibility of markets, Table 1 lists a few of the common recycling options available for wood waste.


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Table 1: Wood Waste Recycling Options Landscape mulch or groundcover

Animal bedding or litter Compost or soil amendment

Landfill cover or road stabilization Wood-Plastic composite material

Wood as a renewable resource-Fuel Concrete fill or road barriers

Wood pellets for fuel or kitty litter Pulp and paper

Hardboard and fiberboard Particleboard

Densified wood products such as logs or charcoal Packaging filler (sawdust and shavings)

Landfill cover The expansion of wood waste recovery programs in Florida should ultimately be promoted through the established network of recycling coordinators and solid waste managers. However, many counties are not making wood management a priority until the State's regulatory position becomes more clearly defined. At the appropriate time and depending on available funding, recycling coordinators are well positioned to provide the most cost-effective means of disseminating information about wood waste disposal to local communities. In addition, coordinators are in a unique position to help forge useful public-private partnerships to strengthen traditional markets and help develop new market opportunities. Over 19 million tons of industrial wood output was received by Florida wood-using facilities in 1997. Proper wood waste management is clearly a priority as Florida's population, and waste generation levels, continues to rapidly expand with increased construction and movement of goods and services. For more than a decade, the easily collected residential recyclables in Florida have received all the funding and recovery promotion. As pressure mounts to further increase recovery of high volume materials such as wood, states will be called upon to provide direction and funding to facilitate the proper handling and marketing of such targeted materials. This will require a better understanding of quantities and types of material, the regulatory climate, and the available options for wood waste management. Even though disposal options continue to present economic and environmental challenges, the groundwork has been established for solid waste managers to evaluate the waste reduction and reuse options for this high volume material, which is vital to the nation’s economy. We started with Creosote, then Pentachlorophenol, went to CCA, now it looks as if we are headed for another treatment solution, ACQ; but will researchers find potential health hazards and leaching issues with this new alternative treatment? It’s time to stop looking for the solutions to our disposal concerns in more research that continues to challenge itself. It is now time to take active, practical approaches to develop recovery programs and better informed consumers who dispose of these materials.


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Characterizing Properties and Products of Spent CCA from Residential Decks

Bob Smith, Dave Bailey, Phil Araman

The amount of CCA treated wood being removed from spent residential decks is increasing at a tremendous rate. While most spent CCA treated wood is being disposed in landfills, further useful and environmentally beneficial alternatives have to be met. If the volume of CCA treated wood reaching landfills continues to rise, stricter disposal regulations and thus higher disposal cost may soon follow. This research estimated the percentage of recoverable lumber from spent CCA decks that can be recycled into other usable products. Six residential decks were removed from service, by either demolition or deconstruction procedures. It was found that 86% of the CCA treated wood from the residential decks could be recovered as reusable CCA treated lumber. It was also found that deconstruction of a residential deck, rather than demolition, was not a factor in the volume of CCA treated wood recovered. The joists and decking were the most successful material recovered, at 95% and 93% respectively. Chemical and mechanical properties of the removed CCA treated wood were also analyzed. The chemical retention of the deck material, through chemical assay, proved that most of the spent CCA treated wood could be used in above ground applications. The stiffness of spent CCA treated wood from residential decks was approximately equal to that of recently treated CCA wood. The strength properties were slightly lower than recently treated CCA wood probably due mainly to physical and climatic degradation. Products were then produced that could be successfully utilized by recycling centers or community and government organizations, to reduce the burden of landfills and extend the useful life of CCA treated lumber. Products made included; pallets, picnic tables, outdoor furniture, residential decks, and landscaping components. Waste management, recycling, and government organizations were interviewed to determine what markets and barriers exist for recycled CCA treated products. Most landfill and recycling facilities do not currently sort or recycle CCA treated wood, citing the main reason is lack of a viable market, or were deterred to recycle due to the recent media assault of CCA treated wood. The results of the research should reduce the burden on landfills and on timber harvesting by extending the useful life of removed CCA treated wood from residential decks.


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COST Action E31: Management of Recovered Wood

Gerfried Jungmeier1, Bengt Hillring2

1Joanneum Research, Elisabethstrasse 5, A-8010 Graz, Austria

Tel: +43-316-8761313, Fax:+43-316-8761320, e-mail: [email protected] 2Swedish University of Agricultural Sciences, P.O. Box 7060, SE-75007 Uppsala, Sweden

Call for Papers “Environmental Impacts of Preservative-treated Wood”, February 8 - 10 of, 2004, Orlando, Florida, USA

Overview The COST (European Co-operation in the Field of Scientific and Technical Research) Action E31 (2002 to 2006) is a multi-disciplinary forum for the exchange of information on “Management of Recovered Wood” with the main objective to improve the European management of recovered wood towards a higher common technical, economic and environmental standard. Researchers of 15 European countries – Austria, Belgium, Bulgaria, Finland, Germany, Greece, Ireland, Italy, Netherlands, Norway, Rumania, Slovenia, Spain, Sweden, United Kingdom - are involved in the Action, which is subdivided in 2 Working Groups:

1) European management of recovered wood: analyse the current systems of wood recovery in Europe, i.e. technical and legal aspects, environmental impacts, recovered wood potential

2) Treatment options for recovered wood: Analysis of different current and future treatment options for recovered wood based on technical, economic and environmental criteria

Main Objectives - further enhancement of the integration of the management systems for recovered wood - examination of the technical potentials of recovered wood as secondary raw materials and as

energy sources - improvement of the quality of the European databases on the technical, economical and

statistical information for recovered wood - analysis of different management approaches for recovered wood in the European countries to

establish a reliable basis for strategic decisions - broadening of the knowledge basis and improvement of assessment procedures to advance the

common understanding and to promote the development of appropriate wood recovery systems at the European level to further optimise recovered wood use

- further development of methodologies to analyse different recovered wood management systems to achieve a common description of the recovered wood management sector in European Countries

- improvement of the methods to monitor the implementation of new systems for the management of recovered wood

Scientific innovation - development of new methods including guidelines for the management of recovered wood - improvement of the methods to evaluate existing and possible new treatment options for wood

recovery - improvement of the methods to generate energy from recovered wood


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- development of a common method for technical, economic and environmental comparison of different recovered wood treatment options

- improvement of the methods to assess the use of recovered wood in (new) materials and products

- investigation of possibilities to increase the use of wood recovered as a secondary material - development of methods to improve the data collection concerning the (regional) amount of

recovered wood taking into consideration the different collection systems and treatments applied to wood recovery.

Outcome - bring together a multi-disciplinary and multi-cultural ‘team’ discipline under one umbrella - establish a European forum for the management of recovered wood - give a comprehensive overview of the different management options for recovered wood - give an overview on available data and stimulate new data acquisition on the different

recovered wood assortments in Europe - expand the relevant data base - provide strategic information for possible European Commission frameworks - contribute to the harmonisation of corresponding legalisation - reduce environmental loads by creating recovered wood management options that minimise

landfill and incineration without energy use - mobilise additional biomass as a sustainable energy source - advance the methodology for environmental, technical and economical evaluation of different

recovered wood treatment options - develop tools for the comparison of different management options for recovered wood - initiate possible common proposals to European Community framework programs. Further information is available on: http://cost.cordis.lu/src/action_detail.cfm?action=e31 Gerfried Jungmeier Bengt Hillring Chair Person of Cost Action E31 Vice Chair Person of Cost Action E31 March 12, 2003


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Copper Fixation Using A Pyrolytic Resin

D. Mourant, X. Lu, D.Q. Yang, B. Riedl and C. Roy

Abstract: CCA will be banned for residential use as a wood preservative in North America at the end of 2003. The alternatives will be copper based chemicals, such as Ammonium Copper Quad (ACQ) or Copper Azole (CA). Leaching of copper from treated wood into the environment will become one of the most important issues for the wood preserving industry. So far, no wood treatment with the new copper alternatives offers a long term fixation of copper in wood to last as long as CCA does. As a mean to improve the fixation of copper in treated wood, the formulation of a resin designed to penetrate and immobilize copper in the wood cells was undertaken. The use of pyrolytic oil in the composition of this resin as a percentage of the total phenol base can reduce the environmental problems associated with the use of petroleum-born phenol. Leaching tests have been conducted with 3 different formulations of resins, containing different ratios of pyrolytic oil in total phenol. The leachates were analyzed for the presence of copper by using atomic absorption techniques. A reduction of leaching copper of around 20 times was observed when comparing the treatment with and without the resin. Variations were observed between wood species as well as between the resins containing different concentrations of pyrolytic oil. The organic leachate was measured using gas chromatography and mass spectroscopy (GC/MS). Trace amounts of organics, mostly acetic acid, were found in the leachate. Keywords: Leaching, copper, pyrolysis oil, resin, fixation, wood, preservation


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Deportment and Management of Metals Produced During Combustion of CCA-treated Timbers

Mary Stewart, Joe Rogers, Ashley Breed, Brian Haynes and Jim Petrie

CRESTA, Department of Chemical Engineering, University of Sydney, NSW 2006, AUSTRALIA

ABSTRACT

The management of chromated copper arsenate (CCA) treated timber wastes is a significant issue for the treated timber industry at present. Currently most treated timber is disposed to landfill; this equates to a loss of valuable resources (energy and metals) and represents an environmental hazard due to the potential mobility of the metals used. Thermal treatment of CCA-treated timber thus represents an opportunity to recover the energy content of the wood, and to recover the impregnated metals; for reuse or subsequent disposal. A first order technology assessment of the thermal treatment of these wastes based on their efficiency at delivering the desired products guaranteeing that the products are not contaminated with metals and manageability of the wastes suggested that high temperature combustion might fulfil these requirements.

The combustion of CCA-treated wood at temperatures in excess of 400°C results in the volatilisation of some of the arsenic (the proportion of arsenic reporting to the off-gas increases with increasing temperature) whereas the copper and chrome report to the ash product. To date the fate of arsenic and its valence state has limited interest in the high temperature thermal treatment of these wastes. This is in spite of technologies for the management of arsenic in fumes and off-gases within the minerals processing industry being well developed. The research being performed is thus aimed at determining whether the thermal treatment of CCA-treated timber wastes can be used to recover both its energy content and the copper-, chrome- and arsenic-containing compounds in environmentally stable residues.

In this poster we report the results from the initial laboratory work conducted in a 2” tube furnace. These results focus on the effects of combustion temperature and fuel:air ratio on:

• the recovery of metals to the gas stream, • the stability of the residues from the system

o ash residue o solid residue recovered from the combustion off-gases

Using this information we suggest preferred combustion conditions for different technology drivers, most notably:

• maximising energy recovery • maximising metals recovery for potential recycling to CCA formulations

Keywords: CCA treated timber, Combustion conditions, energy recovery, metals recovery


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Energy Recovery from Shredded Waste Railroad Ties

Karl E. Lorber

Institute of Sustainable Waste Management & Technology, Montan-University Leoben,

Peter-Tunner-Straße 15, A-8700 Austria. E-mail: [email protected], Tel: +43-(0)3842-402-5101, Fax: +43-(0)3842-402-5102

Abstract: Railroad ties are produced by treating beech- and oak wood raw ties with creosote in autoclave-drums after the so-called RÜPIG process. About 14 kg of creosote are consumed per impregnated tie, which has a volume of about 0.1 m³. Usually the life-time of railroad ties is between 30-40 years, but in the Europeans Union (EU), wooden railroad ties are more and more replaced by concrete ones, resulting in relative large amounts of scrap ties coming on the market for waste management. Due to pollutants like polycyclic aromatic hydrocarbons (PAH) and odor problems, in Austria and other EU countries, scrap railroad ties are classified as hazardous waste, which is expensive to treat and dispose. In this contribution, energy recovery from shredded waste railroad ties in industrial fluidised bed boilers as well as cement works is reported and the results on flue gas emission measurements and combustion residues analyses are depicted. Up to 1 tonne/h (i.e. 1,000 kg/h) of shredded scrap ties, particle size < 50 mm, have been fed into fluidised bed at a combustion temperature between 800-900 °C. There was no significant increase in flue gas emissions which could meet the EU as well as national limit values, but a relative high concentration of lead (Pb) was found in bed ash, caused by lead containing metal pieces (embossments) not sufficiently removed during shredder operations. No significant adverse environmental impacts could be observed when shredded scrap ties have been used as alternative fuel during clinker production in cement works, when around 750 kg/h of this RDF (refuse derived fuel) material was fed at the secondary burner side into the rotary kiln inlet at about 900-1000°C. There was no increase in flue gas emissions and also no impairment of operating conditions and product quality. All the results obtained so far are indicating, that energy recovery from shredded waste railroad ties in cement works and industrial fluidised bed utility boilers is an environmentally sound and economically feasible waste management option.


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Extent of CCA-Treated Wood in Consumer Mulches

Gary Jacobi1, Helena Solo-Gabriele 1, Timothy Townsend2, Brajesh Dubey2, and Laura Lugo1

1University of Miami, Department of Civil, Architectural, and Environmental

Engineering, P.O. Box 248294, Coral Gables, Florida, 33124-0630 USA

2University of Florida, Department of Environmental Engineering Sciences, 333 New Engineering Building, Gainesville, Florida, 32611-6450 USA

Preliminary studies have shown that some commercially available mulches leach excessive amounts of arsenic. The objective of this ongoing study is to determine the extent to which the consumer purchases mulch that is contaminated with CCA-treated wood in Florida. The study also focuses on determining the effectiveness of visually inspecting the mulch for CCA. Once collected, samples are analyzed two different ways. First, the wood is visually inspected for the presence of engineered, and/or dimensional wood. Second, two sub-samples are processed for chemical analyses. One of those sub-samples is ashed, digested and analyzed for total recoverable metals, to determine the fraction of CCA-treated wood within each mulch sample. The second sub-sample is subjected to a SPLP test to determine the amount of leachable arsenic, chromium, and copper. To date 35 samples have been subjected to the SPLP test and 22 samples have been ashed, digested, and analyzed for metal content. Results to date show that some of the samples are positive for arsenic. Of the 35 samples subjected to the SPLP test, 15 tested positive for arsenic. The concentrations range from 13 to 167 µg/L. Nine samples exceeded the 50 ug/L Florida’s groundwater cleanup target level for arsenic. Of the 22 samples ashed, digested and analyzed, 8 tested positive for arsenic. The arsenic concentrations ranged from 4 to 196 mg/kg. These concentrations exceed Florida’s soil cleanup target levels which are 0.8 mg/kg for residential areas and 3.7 mg/kg for industrial areas. Of the 8 positive samples, 7 were red colored. Two of the positive red mulches were collected from playgrounds. All of the red mulches had plywood mixed in which indicates that the mulch was made up of recycled dimensional wood. More results are pending and a final report will be released during the Fall of 2004.


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Forecast of future uses for CCA outside USA

Ian N Stalker: Abstract: In USA, the voluntary program in place will mean a marked reduction in use of CCA It will lose most of the non-industrial pressure treated wood market to other copper-containing formulations. But, what will happen in other parts of the world? Knowledgeable people in many countries were canvassed about the present and future role of CCA in their market areas. Their opinions are reported anonymously and in a non-statistical way. A continued important role for CCA is indicated for many places at least over the next 10 years, although market share will be lost. Forecasters also predict the types of formulation likely to be used in different situations and name the main factors behind changes they foresee.


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Human and Ecological Risk Assessment of Borate-based Wood Preservatives

Christian E. Schlekat, Susan A. Hubbard, Mark E. Stelljes

Abstract Borates are naturally occurring substances consisting of boron and oxygen. These compounds, which include borax and boric acid and disodium octaborate tetrahydrate (DOT), are used in a wide range of industrial and consumer applications. Since boron is an essential element for plants, borates are used as fertilizers worldwide. Borates are known biostats and have been used as wood preservatives for decades, due to their efficacy against termite attack and fungal growth. Originally used to treat framing lumber used in house construction, borates are now used in conjunction with other preservatives to treat engineered wood composites and lumber used for outdoor structures, e.g., decks. The safety of borates used in various treated wood products was evaluated by conducting a screening level risk assessment. The assessment addressed the following preservative/end-use combinations: 1) disodium octoborate tetrahydrate (DOT) in pressure treated lumber; 2) zinc borate (ZB) in oriented strand board; 3) ZB in engineered wood siding; and 4) copper-boron-azole (CBA) and ammonium copper quaternary (ACQ) in pressure treated lumber. DOT and ZB are used in house construction, whereas CBA and ACQ are used in outdoor structures. Exposures to human and ecological receptors associated with in-service use were assessed. Human exposure pathways included direct dermal contact with treated wood, and dermal contact and ingestion of borate-enriched soil that occurs from the leaching of borates from treated wood. Exposure to soil was the most relevant pathway for ecological receptors, which included small mammals, birds, and plants. All modeled human exposures were at least 60 times below the reference dose for borates, which is 0.2 mg B/kg body weight/day when expressed in terms of boron (B) equivalents. The reference dose is the highest acceptable daily intake of boron that is not considered to pose a risk to humans. Borate wood preservatives are therefore acceptable from a human health perspective, especially considering that worst-case assumptions were used for borate loss rates from wood and for assessing frequency of exposure. In the ecological assessment, the use of worst-case fate and transport models yielded very high estimated soil boron concentrations. However, even if these soil concentrations were achieved, the use of borates can be considered acceptable from an ecological perspective, because the hazard quotients for ecological exposures were <5, and because worst-case assumptions were consistently used regarding the frequency with which receptors were exposed to soils. Additionally, ecological soil screening levels currently available for boron are of uncertain reliability. Next steps in the assessment process will include field validation studies to measure actual boron soil concentrations that result via leaching of borates from treated structures, and reevaluation of ecological soil screening levels for boron.


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Impact of restrictions on the use of CCA-treated wood in Sweden

Jöran Jermer

SP Swedish National Testing and Research Institute Wood Materials and Structures

Box 857, SE-501 15 Borås, Sweden Abstract

In Sweden severe restrictions against arsenic and chromium containing preservatives were introduced already during the period 1992-1993. With the aim of reducing the use and distribution of potentially environmentally dangerous substances, the Swedish Chemicals Inspectorate (KemI) in 1992 introduced restrictions for the use of wood treated with arsenic and chromium containing wood preservatives. In the KemI Code of Statutes KIFS 1990:10 it was stated that such treated wood was restricted for use accordingly:

• When the wood is buried in, or otherwise in permanent contact with damp soil or water;

• When the wood is used for the construction of jetties or other marine applications;

• When the wood is permanently installed as safety devices to protect against accidents;

• When the wood is used for the interior of constructions where it is difficult to replace and where there is a risk of accidental wetting, e.g. ground plates on plinths and concrete slabs, ground-floor joists, etc

• All other use of such treated wood is prohibited.

During a transition period 1992-1993 wood treated with chromium-based preservatives was allowed also for other end-uses than the ones mentioned above. The KemI restrictions had a dramatic impact on the use of CCA-treated sawn timber on the domestic market for preservative-treated wood. It decreased from approximately 85 % in 1991 to below 40 % in 1994, whereas the arsenic and chromium free preservatives increased their market share from about 10 % to nearly 60 % during the same period. Since 1994 the percentage of CCA-treated sawn timber on the domestic market has been fairly constant around or just below 40 %. During the transition period 1992-1993 the use of CCPpreservatives, i.e. those containing copper, chromium and phosphorous compounds, had a remarkable peak. It is


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assumed that the coming restrictions against CCA in the European Union will further reduce the use of CCA-treated wood in Sweden.

Percentage production of preservative-treated sawn timber with different waterborne preservative types in Sweden 1991-1997 for the domestic market.


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Influence of weathering conditions on leaching of CCA, ACQ and Cu-azole components and their reaction with soil

Silvija Stefanovic, Paul Cooper Faculty of Forestry, University of Toronto

There is little information available about the leaching of preservative components, especially from alternative preservatives, by rainfall. Because all of those preservatives are based on Cu-oxide, high concentration of Cu in leachate could be expected. Coating treatments potentially should decrease leaching of preservative components. Also, amounts of preservative components in water after filtration through a soil and potential contamination of ground water are not known. Treated wood samples (89”X140X300mm) were mounted in perforated plastic containers and exposed to natural weathering in Toronto, Ontario for 9 months. Some containers were connected to soil lysimeters containing one of three selected soils with different soil characteristics (clay, sandy loam and organic soil). The leachates were able to pass through the soil column and any preservative components that were not adsorbed by the soil were measured in the water collected below. Other containers (without the perforations) with treated wood samples were used to collect leachates after rain events for chemical analysis and volume measurement (soil input). Influence of two types of coatings on leaching of preservative components was examined. Leached amount of preservative components decreased with time. Concentration of Cu in ACQ leachate was higher than in CCA and Cu-azole due to the high Cu concentration in ACQ. Extremely high concentration was detected in leachate from ACQ treated jack pine. Coated samples leached significantly lower amounts of all chemicals. But the development of cracks in the coatings due to weathering conditions increased leaching of preservative components. Examined soils reached adsorption maxima after certain period of time and showed different capacity for adsorption of chemicals.


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Leaching of copper containing preservatives according to OECD guideline XXX and YYY

Ali Temiz*, Fred G. Evans

In Norway restrictions against CCA was approved October 2002. All Norwegian preservation plants have turned to copper containing preservative. This study will look at the leaching from these preservatives compared with CCA according to the new proposal from CEN and OECD XXX and YYY.


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Leaching of Copper, Chromium and Arsenic from CCA Treated Wood in Sanitary Landfill Leachate

Brajesh Dubey1, Timothy Townsend1 and Helena Solo-Gabriele2. 1 Department of Environmental Engineering Sciences, University of Florida, Gainesville,

FL. 32611-6450 2 Department of Civil, Architectural and Environmental Engineering,

University of Miami, Coral Gables, FL 33124-0630

ABSTRACT Scrap treated wood from construction activities and demolished treated wood structures are typically disposed in landfills. To examine the potential mobility of metals from pressure treated wood disposed in landfills, wood samples preserved with chromated copper arsenate (CCA) were subjected to a solvent extraction experiment using leachate from lined landfills. The concentrations of arsenic, chromium and copper were measured in the leachates after extraction. Two types of wood samples were used in the experiment: weathered and non-weathered. The two non-weathered samples were southern yellow pine dimensional lumber purchased from a retail outlet and sent to two different treatment facilities for preservation. Eight weathered samples of CCA- treated wood were collected from a variety of demolition sites and waste disposal facilities. Each of the eight weathered CCA-treated wood samples used in this study represented a composite of seven individual CCA treated boards. Landfill leachate was collected and characterized from six lined municipal solid waste landfills in Florida. The solvent extraction study was conducted using each of these six leachates as the leaching fluid. The extraction was performed following methods outlined for the toxicity characteristic leaching procedure (TCLP). All samples were processed to meet the regulatory requirement of having a particle size no larger than 0.95 cm at its narrowest dimension. The leachates were filtered and digested prior to analysis on ICP-AES (inductively coupled plasma – atomic emission spectroscopy). The results were compared to those obtained using the toxicity characteristic leaching procedure (TCLP) and the synthetic precipitation leaching procedure (SPLP). The mean arsenic concentration in the non-weathered CCA treated wood leachate was 7.41 mg/L for TCLP and 7.17 mg/L for SPLP. The weathered wood leachates had As concentrations in the range of 3.0 to 6.6 mg/L for TCLP and 3.2 to 7.6 mg/L for SPLP. The arsenic concentrations in the extract using the landfill leachate was in the range of 1.49 to 5.91 mg/L for non-weathered samples and 1.97 to 6.57 mg/L for weathered treated wood samples. In general the arsenic and chromium concentrations leached using the landfill leachate samples varied somewhat among the sites, but tended to be similar or somewhat lower than the TCLP and SPLP concentrations. Copper leaching was greatest when extracted with the landfill leachate.


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Life Cycle Management of Treated Wood - The Canadian Approach

Curtis Englot

In July 1999, following a stakeholder consultation process, a report titled "Strategic Options for the Management of CEPA-Toxic Substances from the Wood Preservation Sector was published. The report contained 52 recommendations designed to minimize the impact of releases of toxic substances throughout the complete life-cycle of treated wood. Since 1999, Environment Canada and Health Canada have been working with stakeholders on the implementation of those recommendations. Significant progress has been made in areas such as the implementation of best management practices (BMPs) by wood treatment facilities and consumer information. In other areas such as industrial use of treated wood and the development of a national waste management strategy, work is ongoing. This poster will provide a summary of the actions being pursued by the Government of Canada.


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Quantification and Speciation of Arsenic Leaching From an In-Service CCA-Treated Wood Deck and Disposed CCA-Treated Wood to

Lysimeters Simulating Different Landfill Conditions

Bernine I. Khan1, Helena Solo-Gabriele1, Timothy Townsend2, Yong Cai3

1University of Miami, Department of Civil, Architectural, and Environmental Engineering,

Coral Gables, Florida 33124-0630. 2University of Florida, Department of Environmental Engineering Sciences, Gainesville, FL 32611-6450

3Florida International University, Department of Chemistry & Biochemistry and Southeast Environmental Research Center (SERC), Miami, Florida 33199

ABSTRACT Most studies report soil and leachate arsenic concentrations in terms of the total arsenic concentration. While arsenic toxicity is a function of speciation the total concentration may not accurately reflect true exposure risks. Predominant forms of arsenic detected in environmental samples are inorganic As(V) and As(III) and organoarsenic, MMAA and DMAA; with trivalent species being more toxic than pentavalent species and inorganic forms more toxic than organic forms. To provide insight into arsenic speciation and transformation in new and weathered CCA-treated wood, leachate from a constructed in-service CCA-treated wood deck and lysimeters containing disposed CCA-treated wood designed to simulate different landfill conditions were collected and speciated for arsenic using HPLC-ICP-MS. The landfill conditions tested were wood monofill, construction and demolition (C&D), and municipal solid waste (MSW). Results showed that the average arsenic concentration in the rainwater runoff impacting the new CCA-treated deck after 1 year was 0.73 mg/L and that both inorganic As(III) and As(V) were detected; although the form of arsenic in the chemical CCA is inorganic As(V). Arsenic concentration in the rainwater infiltrating soil 2 ft below the ground surface beneath the CCA-treated deck rose from 2 to 18 µg/L in one year. The ratio of inorganic As(III) to As(V) in the infiltrated rainwater was much higher than that observed in the rainwater runoff, suggesting biological/chemical transformation of inorganic As(V) to the more toxic inorganic As(III) or preferential sorption of inorganic As(V) by the soil. When weathered CCA-treated wood was disposed to wood monofill and C&D lysimeters, the predominant arsenic species observed in the leachate was inorganic As(V), whereas, for the MSW lysimeter it was inorganic As(III). Unlike the C&D and MSW lysimeters, there was no organoarsenic species detected in the wood monofill lysimeter suggesting that inorganic arsenic concentrations were too toxic for microorganism survival; which is necessary for the conversion of inorganic arsenic to organoarsenic species (a detoxification mechanism). The total mass of arsenic leached from the wood monofill, C&D, and MSW lysimeters after one


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year was 1,400, 120, and 85 mg, respectively. DMAA was the predominant arsenic species detected in the leachate from the three control lysimeters. After 1 year, the overall rate of arsenic leaching was greater from in-service CCA-treated wood deck (7%) than CCA-treated wood disposal to the wood monofill (0.8%), C&D (0.7%), and MSW (1.8%) lysimeters and both leached enough arsenic to qualify CCA-treated wood as a hazardous waste.


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Recycling of CCA Treated Timber

Leo Lindroos Abstract There are many reasons that speak for the incineration of CCA waste wood with the recovery of arsenic and copper based on recycling combined with it. The incineration of wood generates energy. After incineration only 0.5-3 % of the mass (weight) of the wood remains. After arsenic and copper have been recovered, there is hardly any waste left that needs to be stabilized. When the waste to be stabilized does not contain any water-soluble arsenic in the form of As2O3, stabilizing becomes considerably easier. The selection of the incineration method is of great significance. Incineration with fluidized bed provides a good incineration result, but the sand used as an additive makes the recovery of copper slightly more difficult. Fire grate incineration does not make big demands on the wood to be incinerated, but another incineration stage is required in order to achieve a perfect incineration result. Fixed bed combustion is a less common technological solution. However, full-scale trial runs have been conducted using this technology, too. The recovery of arsenic and copper is efficient when this technology is used. There has been rapid development in the purification technology of combustion gases. The separation of arsenic from the gases is of critical importance. When gas is cooled using a dry or wet method and finally filtered using textile filters, the purity of combustion gases is sufficiently high. I feel the best alternative would be to separate arsenic in the form of As203 at the gas purification stage. When this is done, only a small part of the flue dust contains water-soluble arsenic or the arsenic is in a water-soluble form. Using this method, arsenic can be utilized in the form of copper arsenic in the manufacture of CCA. Occupational hygiene is a primary concern in the purification of gases. Using mainly the wet method to separate arsenic is a much better alternative as far as occupational hygiene is concerned. Arsenic-free flue dust and bottom ashes could be used as raw material for copper in copper works. If arsenic was recovered in the incineration of CCA waste wood, the production of arsenic could be reduced in the mining industry. This would be a substantial environmental advantage. Additionally, it would also be useful to utilize other arsenious waste materials in the production of CCA, which would also promote environmental protection.


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Unregulated Use of Toxic Wood Preserving Chemicals in Kenya: Health and Environmental Issues

Ramakrishna Venkatasamy Health, safety, and environmental contamination related to wood preservation and preservatives are issues in Kenya, as well as in other eastern and central African countries, that need to be addressed urgently. Substantial amounts of toxic chemicals used for wood preservation find their way into the environment in an unregulated manner. Wood treaters, consumers, the relevant authorities responsible for forest products or environmental health and safety, and the public, appear to be unaware of the risks that these chemicals represent due to the absence of information and regulations. Lack of appropriate training for plant operators and managers in matters relating to health, safety or the environment, and inadequate legislations to ensure protection of operatives and minimise environmental contamination, increase risks at treatment plants. Failure to properly inform timber users and the public on the risks that treated timbers represent further accentuates such risks. Appropriate techniques of conditioning and fixation are neither practiced nor enforced, resulting in reduced permanency and high leaching. The bulk of treated timbers are used in ground contact and risks of leaching into soils, watercourses and ground water are high. There are no policies or regulations to ensure that, when removed from service, treated timbers are properly and safely disposed of. Existing regulations are either too old or silent on wood treating chemicals. That situation has been allowed to persist for the past 50 years and there is an urgent need for immediate action. The four chemicals used in the country, CCA, Creosote, PCP and BFCA are known to be toxic, dangerous to human health and the environment, and need to be regulated more rigorously through appropriate policies, codes of good practices and legislations. Key Words Kenya, Africa, health, safety, environment, contamination, CCA, Creosote, PCP, BFCA, policies, legislations.


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Water-Borne Copper Naphthenate: An Arsenic and Chromium Free Preservative for Wood

Mike Freeman1, Pascal Kamdem2, and Jim Brient3

1- Wood Scientist, 7421 Hunters Tree Cove, Memphis, TN, 38125 2-Professor - Michigan State University, Dept. of Forestry, East Lansing, MI, 38824 3-Naphthenic Technology Manager- Merichem Company, Inc., Houston, TX 77012

ABSTRACT Coppers Naphthenate is a well known commercially used wood preservative used for the preservative treatment of wood poles, fence posts, lumber, glulam beams, timbers, and wooden shakes/shingles. Recently, researchers have begun to investigate alternative formulations of the typically oil-borne preservative into new, environmentally friendly waterborne formulations. This preservative system offers many environmental advantages over other chromium and arsenic-containing formulations that will soon be banned for certain uses. Included in this research to be reported is six-year stake test efficacy data comparing waterborne Copper Naphthenate with oil borne copper naphthenate, ACQ and CCA-C at four exposure sites in the USA. In addition to studying the performance of Copper Naphthenate in Southern Pine (Pinus spp.), this study also briefly reviews the efficacy in lesser-studied softwood species such as Red Pines and Ponderosa Pine and the performance in Maple, Oak, Beech, and Y. Poplar. Additional work presented here also indicates that waterborne Copper Naphthenate may be a good biocide for the protection of wood composites. At retentions of 0.7-1.0 kgm/m3(as copper), this new preservative system is giving excellent performance results in all softwood species and most hardwood species. This emerging new preservation technology offers a potential new lumber treatment offering benefits to treaters and consumers over that of conventional arsenical wood preservatives. Keywords: Copper Naphthenate, Hardwoods, southern pine, Softwoods, efficacy, composites, and performance


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Wood Preservative 101: Frequently Asked Question (FAQ)

1Yuki Sotome and Alysia M. Muniz, 2Tomoyuki Shibata and Helena M. Solo-Gabriele

1Academy of Leisure Medicine and Health Science, Coral Reef Senior High School, Miami, FL

., 2Department. of Civil, Arch., and Environmental Engineering, University of Miami, Coral Gables, FL

Abstract This poster presents basic information on treated wood particularly CCA (Chromated Copper Arsenate)-treated wood. The primary objective of this presentation is to provide beneficial information to those who are not familiar with treated wood. Preservatives are used to protect wood from organisms, such as fungi and insects that attack untreated wood, and natural weather conditions, for example, rainfall, sunlight, and seawater that may increase the vulnerability of the wood subject to biological attack. Thus, the life of the wood expands by the addiction of preservative chemicals. There are various wood preservatives available in the commercial market and the CCA-preservative is one of them. Dr. Sonti Kamasan, of India, was the first person to develop a CCA product in the 1930s. Because of the effectiveness of the CCA-preservative, the use has grown worldwide. Commercialization of CCA-treated wood began in the 1960s and by 1980s, the CCA-preservative became the most popular product in the U.S. While the CCA-preservative effectively protects the wood from degradation, some issues have been raised recently, in particular with respect to health concerns. Since arsenic in CCA-treated wood is highly toxic, it leaves chance to affect those who come in contact with the CCA-treated wood. Most of the recent concerns focus on possible children’s exposure to arsenic when playing on CCA-treated playgrounds. Other possible exposure routes may include contamination of food placed on CCA-treated picnic tables and possible ingestion due to hand-to-mouth activity after contact with CCA-treated wood. Though the dosages might be too small to cause acute health effects, it could possibly result in health effects in the long term. Many countries have placed restrictions on the usage of CCA, such Japan and some European countries. In some countries CCA has been banned. In Germany, Switzerland and Vietnam, CCA has either never been used or has not been used in significant quantities. Although there are many countries that are trying to place restrictions on the use of CCA, it is still the commonly used preservative world wide. In the United States, beginning January 1, 2004 CCA will not be treated for residential use.


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Because of health concerns, it is useful to identify if a wood is treated with CCA or not. However, identification of CCA-treated wood for the general public is not commonly known. Visual identification is difficult. The green color of treated wood could show that wood may have been treated with copper but such identification is not always obvious. Identification can be done by using chemicals such as PAN indicator stain, ascorbic acid stain, and an arsenic test kit. These require relatively simple procedures. The most advanced technologies are those that utilize x-ray fluorescence. X-ray fluorescence analyzers are easy to use and provide the concentration of 12 different metals in a target wood in about 1 second but the cost of the instrument is high ($30,000 U.S.). [1] Clausen C.A., Smith R.L., 1998. Removal of CCA from treated wood by oxalic acid extraction, steam

explosion, and bacterial fermentation. Journal of Industrial Microbiology and Biotechnology 20, 251-257.

[2] Stephan, I., Peek, R.D., Nimz, H., 1996. Detoxification of Salt impregnated wood by organic acids in a pulping process. Holzforschung 50, 183-187.

[3] Stephan, I., Peek, R.D., 1992. Biological detoxification of wood treated with salt preservatives, The International Research Group for Wood Preservation, IRG/WP 92-3717, 12.

[4] Honda, A., Kanjo, Y., Kimoto, A., Koshii, K., Kashiwazaki, S., 1991. Recovery of Copper, Chromium and Arsenic compounds from the waste preservative treated wood. The International Research Group for Wood Preservation. IRG/WP91-3651, 8.

[5] Ribeiro, A.B., Mateus, E.P., Ottosen, L.M., Bech-Nielsen, G., 2000. Electrodialytic removal of Cu, Cr, and As from chromated copper arsenate treated timber waste. Environmental Science and Technology 34, 784-788.

[6] Skoog, D.A., West, D.M., Holler, F.J., 1992. Fundamentals of Analytical Chemistry, Saunders College Publishing, Fort Worth USA, 118-143.

[7] Green III, F., Larsen, M.J., Winandy, J.E., Highley, T.L., 1991. Role of oxalic acid in incipient brown-rot decay. Material und Organismen 26, 191-213.

[8] Humar, M., Petrič, M., Pohleven, F., 2001. Changes of pH of impregnated wood during exposure to wood-rotting fungi. Holz als Roh- und Werkstoff 59, 288-293.

[9] Humar, M., Petrič ,M., Pohleven, F., Šentjurc, M., Kalan, P., 2002a. Changes of copper EPR spectra during exposure to wood rotting fungi. Holzforschung 56, 229-238.

[10] Jellison, J., Connolly, J., Goodell, B., Doyle, B., Illman, B., Fekete, F., Ostrfsky, A., 1997. The role of cations in the biodegradation of wood by the brown rot fungi. International Biodeterioration & Biodegradation 39, 165-179.

[11] Tsunoda, K., Nagashima, K., Takahashi, M., 1997, High tolerance of wood-destroying brown-rot fungi to copper-based fungicides. Material und Organismen, 31: 31-44.

[12] Takao, S., 1965. Organic acid production by basidiomycetes, I. Screning of acid-producing strains. Applied Microbiology 13, 732-737.

[13] European Committee for Standardization, 1989. Wood preservatives; Determination of the toxic values against wood destroying basidiomycetes cultured an agar medium, EN 113, Brussels, 14.

[14] European Committee for Standardization, 1994. Wood preservatives – Methods for measuring losses of active ingredients and otherpreservative ingredients from treated timber – Part 2: Laboratory method for obtaining samples for analysis to measure losses by leaching into water or synthetic sea water. EN 1250, Brussels, 16.


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[15] Kleist, G., Morris, I., Murphy, R., 2002, Invasion and colonisation of bamboo culm material by stain and

decay fungi. IRG/WP 02-10453, 10.

[16] Raspor, P., Smole-Možina, S., Podjavoršek, J., Pohleven, F., Gogala, N., Nekrep, F.V., Rogelj, I., Hacin, J., 1995. ZIM: zbirka industrijskih mikroorganizmov. Katalog biokultur; Biotehniška fakulteta, Katedra za biotehnologijo, Ljubljana: 98.

[17] Pohleven, F., Humar, M., Amartey, S., Benedik, J., 2002, Tolerance of Wood Decay Fungi to Commercial Copper Based Wood Preservatives. IRG/WP 02-30291, 12.

[18] Tavzes, C., Pohleven, J., Pohleven, F., Koestler, R.J., 2002. Anoxic eradication of fungi in wooden objects. Art, biology, and conservation: biodeterioration of works of art: New York, The Metropolitan museum of art, 116-117.

[19] Green III, F., Highley, T.L., 1997. Mechanism of brown rot decay: Paradigm or paradox. International Biodeterioration & Biodegradation 39, 113-124.

[20] Srivastava, P.C., Banerjee, S., Banerjee, B.K., 1980. Magnetic & spectroscopic behaviour of some copper oxalate complexes. Indian Journal of Chemistry, 19 A, 77-79.

[21] Humar, M., Pohleven, F., Šentjurc, M., Effect of oxalic, acetic acid and ammonia on leaching of Cr and Cu from preserved wood. Wood Science and Technology. In press

[22] Hughes, A.S., Murphy, R.J., Gibson, J.F., Cornfield, J.A., 1994. Electron paramagnetic resonance (EPR) spectroscopic analysis of copper based preservatives in Pinus sylvestris. Holzforschung 48, 91-98.

[23] Lahiry, S., Kakkar, R., 1982. Single-crystal magnetism of sodium magnesium chromium(II) oxalate, NaMgCr(C2O4)3×9H2O. Chemical Physics Letters 88, 499-502.

[24] Hartford, W.H., 1972. Chemical and physical properties of wood preservatives and wood preservative systems. In Wood deterioration and its prevention by preservative treatments. Vol. 2, Preservative and preservative systems, Syracuse University Press, Syracuse, 154.


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RESEARCH PRIORITIES WORKSHOP

Environmental Impacts of Preservative-Treated Wood February 8-11, 2004, FL, USA

Helena M. Solo-Gabriele, Timothy G. Townsend, and John D. Schert

Helena M. Solo-Gabriele, Ph.D., P.E., Department of Civil, Architectural and Environmental Engineering, University of Miami, PO Box 248294,Coral Gables, FL

33124-0630, [email protected] Timothy G. Townsend, Ph.D., P.E., Environmental Engineering Sciences, University of

Florida, PO Box 116450, Gainesville, FL 32611-6450, [email protected] John D. Schert, Florida Center for Environmental Solutions, University of Florida, 2207D

NW 13 Street, Gainesville, FL 32609, USA, [email protected]


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Abstract

This manuscript documents the feedback received from conference participants concerning research needs for evaluating the environmental impacts of preservative treated wood. The purpose of this effort was to develop a list of research priorities, which can be potentially used by funding agencies as they develop their research agenda and identify key areas for future funding. The documents included in this manuscript were developed through a conference sponsored by the Florida Center for Environmental Solutions (FCES), located in Gainesville, Florida. The conference was held in Orlando, Florida, February 8 – 11, 2004 and the title of the conference was, “Environmental Impacts of Preservative-Treated Wood.” Approximately 150 people from 12 countries attended the conference. Research priorities were solicited from conference participants in three phases including: 1) an email solicitation prior to the conference, 2) a two hour workshop held at the conclusion of the conference, and 3) an email solicitation, including a ballot, sent to participants after the conference. The draft ballot was developed from information received during the first two phases. The ballot was separated into 3 sections, each section corresponding to a different topic area. Five or six research priorities were to be ranked within each topic area. A total of 28 conference participants returned the ballot. The following research priorities received the highest ranking among those who voted: 1) evaluate the exposure and risk to people from preservative chemical releases, 2) develop new more environmentally friendly alternative chemicals, and 3) evaluate the impact of treated wood during disposal within landfills. Additional results from the vote along with more details are provided within the following pages of this document.

Organization of Manuscript

The research priorities were established in three phases. Phase I included an email solicitation prior to the conference. The responses from this email solicitation were compiled and provided to conference participants during the conference (Section I). The conference concluded with a two hour workshop which consisted of a set of three panel sessions during which panelists and conference participants provided their opinions concerning research needs (Section II). The information documented in Sections I and II was used to develop a voting ballot which was distributed via email after the conference. Those who returned the ballot also had the opportunity to provide additional feedback at this time. The post-conference feedback is summarized within Section III. The voting ballot is provided in Section IV and the results from the vote are provided in Section V.


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SECTION I: SUMMARY OF RESEARCH NEEDS RECEIVED PRIOR TO THE

FCES CONFERENCE The suggestions for research needs received prior to the conference were placed within one of three

groupings: “release of preservatives to the environment (sub-section I.1),” “exposure/risk assessment (sub-section I.2),” and “disposal, reuse, and recycling of treated wood (sub-section I.3).” These groupings were chosen in an effort to organize and consolidate the suggestions into related topic areas. The last name of the person submitting that suggestion is provided in parentheses within the following sections. I.1 Release of Preservatives to the Environment Mechanisms of Releases

• Some of the areas of research that we consider to be priorities are: Fate/attenuation of leached preservative components in soil, nature of chemical preservative reactions in wood and effects on leaching and dislodging, methods of promoting optimum fixation or stabilization to minimize leaching, and long term prediction of leaching and application of leaching models to risk assessment (Cooper).

• Standardizing methodology for quantifying the emission of wood preservative

components from full-dimension timber in service. Having such methodology could facilitate the development of low-emission wood preservative formulations and impregnation processes, or supplementary emission-reduction treatments (Kennedy).

Soil Transformations

• Arsenic, Cu and Cr transformations in soil systems (biotic processes of interest to Florida ecosystems). I feel there is a dearth of knowledge in this area. It could be used to paint a complete picture of As, Cr and Cu dynamics in Florida soils (Chirenje).

• Pedogenic processes governing As, Cu and Cr kinetics in solid and aqueous media. Will these

three chemicals end up in groundwater or will they be sequestered in soils for good (we have characterized sorption and desorption, but do we know the processes that will lead to future releases? (Chirenje).

• Arsenic movement in soil- Data developed by researchers in Florida shows some

movement of arsenic downward in the vadose (unsaturated) zone. Does arsenic move downward thru the vadose zone? How much do natural soils act to bind up and attenuate arsenic that is leaching downward thru the vadose zone? If arsenic reaches the groundwater, is it attenuated or does it move with the groundwater? (Schert)

• Bioremediation and extraction methods – How to remediate soils contaminated with As.

(Stilwell) Aquatic Impacts

• Effects of decks on the intercoastal waterways; subdivisions in Ft Lauderdale? (Chirenje).


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• More research is needed to evaluate freshwater impacts of preservative treated wood (Weis).

Release of Arsenic in Gaseous Form

• As outgassing in houses. Is there any way that outgassing of CCA could occur at toxic levels in the home? Microorganisms are known that convert As to volatile forms, but are they on wood in houses? Has anyone done air sampling in houses with CCA wood in the interior and with significant water/mold damage? (Stilwell)

• Arsenic in landfill gas. Is As reduced to arsine gas in landfills? Are the reducing

conditions present in a landfill powerful enough to force the conversion of arsenic to arsine gas? (Stilwell)

• Can gaseous As be released from a landfill in volatile forms other than arsine gas?

(Solo-Gabriele) I.2 Exposure/Risk Assessment Exposure

• I believe there is legitimate concern about the extent to which arsenic may be tracked into households from CCA deck surfaces and nearby soils. This tracked-in As may pose a significant exposure threat especially to young children playing on indoor floors and carpets. A couple of good well-designed track-in exposure studies would serve an important unmet need by enabling us to assess this potential route of exposure compared to the outdoor exposure routes where we have focused our efforts up until now (Maas).

• There are many studies that estimate the risk of developing cancer after long-term

exposure to CCA in preserved wood. However, the critical question is whether the known exposures to CCA over the last 30 years have resulted in an increased incidence of arsenic related cancer. The critical next step is to conduct a study that directly measures past exposure to CCA treated wood and then determines whether that exposure is associated with an increased rate of arsenic-related cancer. Other important questions include determining the bioavailability of ingested CCA and the efficiency of transfer from hands and fingers to the mouth. Development of an animal model for arsenic induced cancer would also be extremely helpful in determining whether a cancer threshold level exists for arsenic ingestion (West).

• At a recent EPA SAP meeting (Dec 3-5, 2003) some gaps in our understanding of arsenic in

wood as it pertains to human risk assessment were identified. Among them were: A) the nature of the dislodgeable residue on wood (1. Cr/As ratio in residues is greater than in leachate. To explain this discrepancy there may be chemical reactions on the wood surface which result in preferential release of As and 2. Sequential extraction techniques would be one way to determine the various forms of arsenic on the surface, particularly the soluble


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and insoluble fractions.) B) As leaching and dislodgeable residues – (How are they tied in to each other with rainfall? After a significant leach event is the surface depleted in As. What are the major effects which cause surface increases in As (the observed rejuvenation). C) Bioavailability of As in wood in soil from CCA wood leachate (Development of sequential extraction methods might be a way to predict bioavailability), and D) Skin Absorption. (Any suggestions in this area?) (Stilwell)

• There also seems to be a dearth of information when it comes to specific risk assessment and

characterization for As, Cu and Cr (not just from the toxicological point of view; but environmental risk assessment [especially risk charactyerization]!!). (Chirenje)

Methods for Exposure and Risk Assessment

• Testing Methods – How would the available methods need to be revised to carry out these studies? For example the sequential extraction methods were developed for soil not for wood residues. Can leaching protocols be used in coating studies. What improvements can be made in using animal models for bioavailability and skin absorption studies?

• Developing methodology for evaluating the environmental effects of wood preservative

emissions. While it may be relatively simple to develop appropriate bioassays for primary aquatic organisms, practicable bioassays for soil-dwelling organisms, and other organisms up the food chain from both types, will require a lot of work to perfect. Until we have such bioassays, any work done to reduce emissions from preservative-treated wood will lack a valid frame of reference (Kennedy).

Remediation

• Research is needed on the short term and long term effects of coatings, stains and water repellents on preservative leaching. (Cooper)

• Coatings and encapsulates- According to the EPA’s risk assessment model, application of

coatings significantly reduces risk, to the extent that they reduce dislodgeable As on the wood surface. Coatings also reduce leaching and could even have application for use in aquatic environments. Work needs to be done on the following: A) Survey of coatings, B) Methods – field and simulated, C) Formulations – what material forms As barrier, D) Iron – what would be the effects of adding iron oxides (or hydroxides) in the formulation, and E) Surface preparation. (Stilwell)

• However, the fact remains that it would be best if we could instead focus our research efforts on finding or developing an effective and economically-viable treatment system to seal in this arsenic for a period at least equal to the usual expected service life of the lumber. If, as the leading scientists in this field, we could accomplish this, it would be an achievement we could truly be proud of, and would transend disagreements about the exact dynamics and extent of public risk. (Maas)


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Plant Uptake

• Rice - A significant amount of As was reported in rice. How much As is in different varieties of rice? Is the amount geographically dependent? How much uptake of As in plants grown near CCA wood is there compared to rice. (Stilwell)

• Phytoremediation – How to remediate soils contaminated with As? (Stilwell)

• Are there plant indicators of As, Cu or Cr problems? IS Cu a problem in Florida? While it

is not as harmful as the other two components of CCA, little has been done on its distribution and effects on other environmental compartments. (Chirenje)

• Do these chemicals (As, Cu and Cr) have any impact on other components of the Florida ecosystem (e.g. wildlife associated with stormwater retention wetlands?). How about plant uptake in wetland systems? (Chirenje)

• Arsenic in Vegetables- Is CCA leaching out of wood timbers (used in gardens to make

raised beds) being taken up by vegetables grown by home gardeners? Data developed by Stillwell and others indicates that certain vegetables (turnip greens, salad greens, carrots, etc) can accumulate arsenic in the edible portion of the plant if the vegetables are grown in soils that contain arsenic from CCA. Data developed in Texas several years ago indicates that this did not occur in those experiments. Is it advisable to grow vegetables in gardens framed with CCA wood? Which vegetables are accumlators of arsenic? Under what conditions does this occur? (Schert)

I.3 Disposal, Reuse, and Recycling of Treated Wood Sorting

• Prior sorting needed? Additional cost! (Helsen)

• Disposal – Identification of CCA. How do we identify and remove CCA from the recovered wood stream?, Is it wise to try to extract the CCA from the wood prior to disposal? (Stilwell)

Thermochemical Processes

• Research is needed in the identification of the best available thermochemical technology

including possibly pyrolysis, gasification, incineration, and co-incineration. (Helsen) • Is combustion or pyrolysis of CCA a viable method of disposing/treating CCA? (Stilwell)

Landfills

• Final Resting Place for Arsenic- What should the final resting place be for the arsenic in CCA wood? Background- The treating industry has used about 30,000 tons of arsenic to


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treat the wood that has been sold in Florida since 1970. Most of the arsenic that has been used is still in the wood that is in service. Leachate data from Class I landfills indicates that some Florida landfills have elevated concentrations of arsenic that are above the pre-treatment standards for some waste water treatment plants (also called Publicly Owned Treatment Works, POTW). Groundwater data that has been collected at groundwater monitoring wells near Constrution and Demolition Debris Landfills suggests that some of these wells have elevated concentrations of arsenic. Research is underway to determine how much arsenic will leach out of CCA treated wood after it has been placed in a Class 1 Landfill. Similar research is underway to determine how CCA behaves when it is placed in a Construction and Demolition Debris Landfill. The DEP has proposed that all CCA taken out of service be placed in lined landfills. (Schert)

Mulch

• Arsenic Contamination of Mulch- Does arsenic contamination in commercial mulch present a hazard to homeowners and workers who operate chippers and bagging equipment? Data developed by Solo-Gabriele and Townsend shows that some of the CCA that has been taken out of service in Florida has made its way into the commercial chipped wood market. Wood recovered by the Construction and Demolition Debris recycling industry is chipped and sold as fuel or as mulch. In a case reported in the press, a homeowner who handled relatively high amounts of bagged chipped wood had highly elevated levels of arsenic in his urine. Does CCA contamination in commercially sold mulch present a threat to human health? If so, what are the pathways for exposure? (Schert)

Bioremediation

• What is the Cost/effect ratio of such processes? Issues to be addressed include two-step process of bioremediation, use of fungi, scale up, sorting of various treated wood, use of remediated wood, phytoremediation, and what to do afterwards with organic material. (Humar)

• Influence of Cu, Cr and Ac from CCA wood leachate on soil micro flora, soil organisms and plant uptake. It is known, that fungal colonization of CCA treated wood influence fixation of the biocides in wood. These elements can be afterwards leached out of wood, this is used already in bioremediation techniques. But, what happens if colonization of CCA treated wood appears in the nature. How this influence leaching, and particularly how toxic is this leachate. What is the pattern of decay succession afterwards? Spread of copper tolerant fungal strains. Local micro-conditions, micro-clima, soil type, where these organisms are more frequent. (Humar)

Hydrolysis • Development of new ideas what to do with waste impregnated wood. Hydrolysis (Liquefied wood),

production of resins from wood, and removal of toxic biocides from using electrolysis. Extraction of biocides within pulp and paper processes. (Humar)


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Wood Cement Composites

• Potential to recycle treated wood in wood cement composites (how to overcome oxidation of chromium). (Cooper)

Other Important Comments

• Can the same technology be used for preservatives of the future? (Helsen)

• I think more emphasis should be diverted towards finding a method for removing these CCA from waste wood before disposal. In my view CCA is like money, spread around in small quantities has its benefits and is useful but, too much of it piled up in one place is dangerous and can cause problems. CCA while in use does not create major problems (except in direct contact situations) but when it is piles up on an unprotected soil or put in an unlined landfill in huge quantities, can create major problems. (Oskoui)

• How is CCA-treated wood handled upon disposal within countries around the world?

(Solo-Gabriele)


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SECTION II: ORGANIZATION AND TRANSCRIPTS FROM CONSENSUS WORKSHOP

The overall organization of the 2-hour conference workshop is described in sub-section II.1 and the transcripts from the workshop are provided in sub-section II.2.

II.1 Organization of the Consensus Workshop The consensus workshop was held Wednesday, February 11, 2004 from 8 to 10 am. The purpose of the workshop was to identify research needs for possible future funding opportunities. Three 40-minute panel sessions were held that focused on the topics outlined in table 1. The themes for each of the three panels were: 1) disposal, reuse, and recycling of treated wood, 2) release of preservatives to the environment, and 3) exposure/risk assessment. During each panel session, panelists and participants were asked for their input concerning research gaps and needs. Each panelist was given about 2 minutes to speak. After the panelists provided their feedback, input was requested from the audience at large. The last 5 minutes of the panel session were devoted to summarizing the information that was presented during the panel. The moderator of the workshop was Helena Solo-Gabriele.

Panelist and Affiliation

Panel 1 Disposal, Reuse and

Recycling of Treated Wood

Lieve Helsen, Catholic University in Leuven, Belgium Bill Hinkley, Florida Dept. Of Environ. Protection, Tallahassee, FL, USA Joran Jermer, SP Swedish National Testing and Research Inst, Sweden Pascal Kamdem, Michigan State University, USA Jeff Morrell, Oregon State University, USA Lisbeth Ottosen, Technical University, Denmark

Panel 2

Release of Preservatives to the Environment

Tait Chirenje, Richard Stockton College of New Jersey, USA Paul Cooper, University of Toronto, Canada Michael Kennedy, Queensland Agency for Food & Fibre Science, Australia Daniel Mourant, Laval University, Canada Tim Townsend, University of Florida, Gainesville, FL, USA

Panel 3 Exposure / Risk Assessment

Rolf Dieter-Peek Federal Research Centre for Forestry & Forest P., Germany Curtis Englot, Environment Canada, Canada Tim Leighton, U.S. Environmental Protection Agency, Washington D.C., USA John Schert, Florida Center for Environmental Solutions, Gainesville, FL, USA David Stilwell, Connecticut Agricultural Experiment Station, CT, USA

Table 1: Topics and Panelists who Participated in the Research Needs Consensus Workshop


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II.2 Transcript from the Consensus Workshop The transcripts were written from a tape recording of the conference. These transripts are provided below. Introduction Helena Solo-Gabriele: It’s a few minutes after 8 oclock and we’ve got a tight agenda. The purpose of this morning’s meeting is to develop a research agenda. Assuming that we have research funding available where should those funds be spent. We would like to get feed back from the panelists and participants at the conference. The way we have organized this is into three panel sessions. Panel one focuses on disposal, reuse, and recycling of treated wood. Panelists are : Lieve Helson, Joran Jermer, Pascal Kamdem, Jeff Morrell, Lisbeth Ottosen, Bill Hinkley. This panel will be held for 40 minutes. Each panelist will be asked to provide a 2 minute informal summary of where they believe research should go in the future. Then we will open it up for public comments and input from the rest of the audience. The last 15 minutes of the session will focus on summarizing what we have heard and to come up with consensus on what we have heard. Following panel one we will have another 40 minute session. I am switching the order of the sessions because flight schedules of our panelists and participants. Panel three will be second; it focuses on exposure and risk assessment, followed by panel two which will focuses on leachating preservatives in the environment. I also want to mention that we will be taping this, this way we can keep track of everything that is said. I will be keeping notes, but it may be a little bit too fast for me to catch everything so to get all the information the session will be taped. At this point I would like to begin with our panel session, also before I get started we have green inserts within your conference packets. These green inserts are feedback obtained concerning research needs obtained prior to conference. We have complied these into the same categories corresponding to our various panels. The comments that we received before the conference is on the third to the last page on disposal, reuse and recycling. At this point in time I would like to begin with our panelist and Lieve if you have a two minute summary. Panel #1: Disposal, Reuse, and Recycling of Treated Wood Panelists: Lieve Helsen, Bill Hinkley, Joran Jermer, Pascal Kamdem, Jeff Morrell, Lisbeth Ottosen Lieve Helsen: Well I remember from yesterday that there is a great difference between the United States and Europe. In the States there are a lot of landfill waste. There is a big point about lining or not lining the landfills. I think it is very important from what we have heard yesterday that we remember that there is leaching from these kinds of wood waste so lining


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is very important so I think there should more studies on that: leaching. And regarding Europe it is totally different because we don’t have space for landfills so we have to look for alternative methods. Therefore we have seen a lot of different opportunities. We have seen biological methods, thermal method, electrochemical methods, chemical extraction. I think the solution will become a mission of this so maybe we have to start with a thermal process but then we still have to separate the metals out of residue. This can be done in several ways. I think more research is needed to determine which alternative method is the best technology taking into account all economic considerations. I think we have to focus on lining the landfills, and focus on looking for the best thermal/alternative technology and there I think it is important to know if research is needed or not because there is a big additional cost and I think if a solution can be found research is not needed. Also this is the age that disposal peaked now and in the near future of revising. When this peak is going down again we don’t have much to do with CCA treated wood waste anymore. If these technologies exist, then it would be good because they could be used for other waste streams. So I think we have to look a little more boarder beyond not only CCA treated wood waste. That is all I have to say. Joran Jermer: I will talk about the Swedish experience. We have been using waste as a fuel for couple of years, large amounts in some plants. The problems that we are most concerned with are the operational problems including: slagging, fowling, and corrosion in the boilers. The reason for these problems is that the fuel is contaminated. The most important contaminant is painted wood, lead, and chlorine to some extent. In order to reduce these problems measures need to be taken and one of course is to improve the fuel quality, we have discussed yesterday that sorting is a realistic thing. Personally I don’t believe that we can spend time and money on sorting the waste wood because that would be costly. However it should be considered. Also we have carried out trials with sieving the material, if you analyze the different fractions of waste wood, you will find that a lot of the metals are found in the finer fractions. If you sieve the materials however you will have a problem with a sieve fraction, what to do with that. We need to however discuss the fuel quality still and also there are possibilities. If you incinerate waste wood without any sorting you will have to modify the combustion process to avoid reducing conditions at the heat exchange surfaces and that will help to minimize slagging, fowling, corrosion in the boilers. We don’t know everything about this yet so I think more research is needed on this. There is also a possibility to add certain additives like sulfur to avoid troublesome metals like metal chlorides in the process. I think all these measures that are necessary. I agree with Lieve about the ash, if you don’t have any sorting you will get all the stuff in the ash and more research is needed to know what to do with this. Another thing we have discussed in Sweden is whether regulations imposed by the European Commission and the national authorities if they would make it more difficult to handle waste wood that could influence the market for this because in the end everything is about money and you have to have a market that is working. If there are too many restrictions, for example on the transportation of the wood, it could be a problem to take care of all the waste. That should also be considered when we talk about waste wood in the future. That is all.


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Jeff Morrell: I think one of the first things that you want to do when you have a problem is figure out how big it is. I think Florida did a good job of that . I think you guys have figured out how big the issue is within recycling facilities. One of the big gaps is that we think that Florida represents the rest of the U.S. So one of the first things that we want to do is figure out what the impacts is on C & D and landfills around the country so that you can get a grasp of the magnitude. My suspicion is that that it might be a localized affect. You might be able to target those facilites to then separate materials. One of the first things would be a national assessment. At the same time I think there is some room for looking at a practical approach. Florida has the lowest remediation levels of any State in the nation and if we let the level drive our decision making we will be making a mistake because in many parts of the country the arsenic background levels are much higher and the impacts are much lower due from this issue. And so I think it is important to look at that and look across the country and see what the risk is because there is no sense in cleaning up to a level that is essentially below background or to trying to meet a level that is below background. Once we do that then we can start looking at the sorting and the education, etc on a more national scale. I totally understand the level of the problem across the country. You are really wasting a lot time and money. Pascal Kamdem: I think one of the main problems is how to collect and handle all the wood preservatives or how to handle all the wood contaminated with lead, mercury and other contaminants, how to store them if you want to collect them. And another problem is to characterize, to get a picture of what is in the wood. If you don’t know what is in the wood, it will be difficult to address the issue because we won’t know the amplitude of the problem. So to characterize the wood itself, and then I would say the final solution would be incineration. But if we know the level of contamination we may be able to come up with some intermediate solution like some wood composites or some other medium solution to delay incineration to take advantage of the wood fiber that we still have there. But we need to know what is in the wood first. And if we go with incineration a lot of studies need to be carried out to understand exactly how we can incinerate to have a very low level of toxic gas release. How do we control the air emission during incineration or combustion? Also I would like to address the problem of ashes. How do we remove all the heavy metals that are concentrated in ashes. I believe those are the major issues that we need to address. Lisbeth Ottosen: My starting point is that I am from a very small country with only 5 million inhabitants and it not very big so all the problems that a huge country experiences are the same but Denmark has fewer inhabitants. But in Denmark we already must collect all the treated wood from demolition and private households and it will be just pilled up and landfilled. We can not incinerate it because it is not allowed so we must landfill it until a new method is developed where we can recover the energy from the wood and remove the residue from the incineration or combustion process. And since I don’t think that landfilling, even though we have lined all of our landfills, is the best solution to this and we can definitely use the energy in Denmark so that is why I think it is very urgent that we find a


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message that will meet the requirements from the EPA so that we can get off landfilling of this wood. Because right now we are just landfilling all these we can not burn, so that is not really a good solution. I agree with the others here that we need to find other methods, I think it is important to sort it and treat the residues and we have to find to do this and also avoid arsenic emissions from the thermal processes and to treat the ashes afterwards. And I think in a small country like ours it should actually be possible. We should not have more than 100 tons a year. Bill Hinkley: Thank you. First I just can’t resist the opportunity to respond to Jeff’s point on the soil numbers that I have been batting around here. I think they are wrong on a couple of points. First of all Florida is not the lowest in the country, secondly it will be in the range of half a dozen other states when it is raised, thirdly this is most important, if you look at the average soil concentration in the data that Helena and Tim collected under decks that were treated with CCA, the average concentration if I recall is 27 mg/kg. That is way above almost all other states clean up numbers. I actually went to the association for environmental health of soils website and got all the numbers for arsenic cleanup and plotted them. And found maybe 2 states. So lets not get too carried away with all these arsenic numbers. CCA leaches virtually well above all states numbers so I don’t think we should spend too much time worrying about whether it 0.8 , 2.1 or 5 or whatever. But on that point I would like to add that the national arsenic natural background standard is only 5 mg/kg. So again this is a bigger problem than just a risk based number that is quite theoretically derived. Here are my items that I think are the priorities and this is based on my role as a garbage guy. I work in solid and hazardous waste like Tim that is where I focus my energy and my interest. First off we are in rule making in Florida to require all this CCA treated wood to go lined landfills, though it sounds like a good idea, and it is a good idea but once you do that your problems have just began. Arsenic is here to forever, its on the periodic chart, it is not treated it is not going anywhere. What happens, the wood goes into the landfill it leaches arsenic, arsenic goes into leachate collection system, where does it go? Well it is commonly tanked or hard piped to a waste water treatment plant where they knock down the BOD and so forth but they do not do nothing to the arsenic. Well where does the arsenic go, it ends up in sludge and sludge is land applied. That is the standard practice nation wide. So we need to think about that, what I think we will have to is manage these leachates at these sites. What does that mean. You can’t use activated carbon, which is the cheap way. You will have to go the hard way which is reverse osmosis which is expensive. Management will have to re-circulate the leachate to keep the arsenic in the fill, we have to figure out a way to do that without poisoning the biological process because you get build up of ammonia for example. There is a lot we need to learn I think about recirculation of leachate, not for the purpose of not having to haul the water out which it is currently used for to cut costs, but to sequester and ultimately put the arsenic in some kind of geological state. I don’t know if that means it will combine with the sulfides in the landfill, I don’t understand the chemistry well enough, though I think it is fascinating. For number two, for C&D landfills in Florida, why don’t you just line your C& D landfills and be done with it, that will solve your problem right there. And then your problems have


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just begun. When you look at the C&D waste trend its not that bad: its wood, rocks, concrete, dry wall, wood, most of it is innocuous inert waste, its largely an aesthetic problem getting rid of C& D waste, its not an pollution problem like putrescible and solid waste with a few notable exception most prominately CCA. I was talking with Lena Ma about this yesterday, to me the ideal solution is go ahead and keep in the C&D stream and put it in unlined C&D landfills if you don’t want to line landfills if you can help it. We launched strategy of waste management in this county decades ago when we decided to build all these closed dry tombs to manage waste, but we are not really managing it we are just storing in big piles and putting something on the bottom and on top and walking and we are doing that all over the country; its called subtitle D- RCRA. This is how waste is managed. It is stupid. We would be better served in my opinion to have leaky C&D landfills. We don‘t want to collect leachate, it is expensive it is needless in most case, could we in the lifts that we put in the cover of the landfills bring in certain types of soil , Lena mentioned iron filings I though that was interesting. I was at a fluidized bed coal plant the other day in Jacksonville, where they had huge mountains of their treatment sludge which is all virtually all calcium oxides. Could that could be used, in other words the C & D sites would be a treatment facility where the arsenic is binding up while letting everything else go through. That would be slick. The third area is the waste energy plant emissions. That looks like a great opportunity for us but I am leaving this conference completely confused about this issue. I don’t understand it. I don’t understand if it is good or bad and that is because I am stupid I am sure. I don’t know enough about air. That would be a slick solution to burn. I am in favor of waste energy. It is good technology under the new max standards these plants all have scrubbers, bag houses, activated carbon injection, continuous emission monitoring. They are very sophisticated. They are a great way to get rid of it. We have actually had some preliminary discussions with Wheelabrator and Covana (?) Energy on this topic but we have to set up a test burn. This would be a real applied area where we could greatly us the help of the Center. Quickly , I have learned from this process that the arsenic free alternatives that we have been talking about, ACQ, copper azole, aren’t quite arsenic free. They will have arsenic as a trapped contaminant in the copper that was used to make those materials. We have been involved with discussion with the treaters on closure of old CCA treatment sites and we have been talking about how clean is clean. How clean do I have to make it? Well you have to wash the system out, shot glass the drip pad, whatever. But how clean do we have to have it. We said we wanted them to get parts per billion. The correct MCL and they said we can’t get there from here and I said why? All you have to do is just keep washing, take the rinse water and use it in your CCA line, most of these guys are keeping CCA as an option, they can’t get there because there is enough arsenic in the copper that is in the ACQ that you will still get a 150 parts per billion in the wash water. Why do we care? What is happening in the mulch market is, the big corporate guys the big box stores are testing their own mulch now because they have been burned, they have law suits against them. This issue is being regulated by the market in a really nice way I would have to say. Home Depot is canceling contracts with mulch makers when they detect arsenic. The problem is though that they are going to be detecting arsenic even if that wood is made from ACQ. This is an issue we need to think about as we move forward


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because if we don’t we are going to end up killing us the recycled wood mulch market. If these big box guys say if we detect arsenic then we are not going to buy mulch from you, so what are these guys (mulch makers) going to say, they are going to use all virgin chips. Anyway that’s me as a side issue. Lastly I was intrigued, this might take away from the whole thing from the air people, is slow pyrolysis gasification or something like that is probably the optimum way to deal with this if I understood everything correctly. I like that, but I have seen every pyrolysis scheme in the book in my 15 years in this business: tires, medical waste you name it. There has never been a commercially successful pyrolysis unit in the United States and I dare say that we have seen 20 facilities globally there are a few in Italy that are burning waste and making a go of it. But in this country because of low disposal costs its very tough. I think that that could work. But I think that the disposal cost is going to have to be keep in the 100-150 dollar per ton range that Kazem talked about yesterday. There are wastes out there right now that we charge 100 bucks a ton to get rid of them: waste tires, asbestos, medical waste, so that is not out of range. If you go above 150 it is spent in the water. Comments from Audience: Comment: Hi, Bill’s idea with removing arsenic selectively with ferric hydroxide or maybe some of those schemes that they use in India to remove arsenic from water. Gerard Deroubaix: I think the recollection issue is also very important and I would like to give you some direction to look for, we have certain kind of waste in France where it is the responsibility of the marketer. We are exploring the idea that the people putting on the market the treated timber can be involved in managing the system for recollection and recycling of this timber because as it been said yestereday it is wide spread across the country and there are difference kinds of sources for this waste and it would be, I agree with you and your merits that it would be very difficult to collect this thing specifically if there is a special way of recycling these materials. Mary Stewart: I am just concerned about doing too much research in isolation, especially looking at the waste to energy processes. You can’t look at those without looking at what happens to your ash when investigating the combustion processes. Combustion determines what your ash will be and you can’t just say that that is a problem you can solve by another technology later. You need to start intergrating work and need to start understanding how those two things interact. Just to say also, that the minerals industry has a lot of expertise in looking at the environmental stability of these materials and we heard yesterday from the coal people about the combustion of coal and what metals do in combustion and the same way the minerals industry has a lot to say about the stability of metals and to start looking at their research. I don’t know if this comment belongs in this session or, but relative to the release of preservatives in the environment to recognize that a geologically stable form of arsenic has not yet been found. The longest time it has been possible to deposit arsenic stably is 30 years. After that it will move. Further chromium also ages you get a move from


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chromium 3 to chromium 6 switch and depending on what other metals are present in that waste the chromium will start leaching over time. So we need to integrate the research, you need to integrate technology and waste management and you need to start looking at other regions of interest especially around the metals. Paul Cooper: One of the thermal methods that really hasn’t been mentioned, and there is some interest in Canada for CCA that’s as fuel start for cement kilns. Cement kilns have, the clinker has quite a bit of capacity to hold arsenic and quite high allowance for arsenic and copper. The indication is chromium because of the conversion to hexavalent chrome in the high pH environment. We calculate in Canada that roughly 20% of the total CCA wood being produced could be accommodated in the cement counts in Canada. The big problem is the collection and grinding of the material. But I think that’s one were you would not have to sort wood to put it into use. Curtis Englot: I would just like to speak on Dr. Cooper’s point there. In Canada we have done test burns to look at incineration. And one of the big one’s I am quite disappointed that we haven’t been able to move along is the burning of creosote treated wood. That is easy to accomplish yet we don’t do it done in Canada, instead we send our creosote treated ties down to the US. And the big issue there is gaining acceptability by the general public that this can be done safely. That is why I think that sessions like this are important. There is a lot of experience in other areas in the world where they have been doing this for a long time. And we really need to pull the science together to show that different processes can be done effectively and gain acceptance by the public and that is one of the biggest problems we face in Canada and that sharing of the knowledge is very important here. Comment: Just a comment about thermal treament, ball park numbers on the resource and what that means in terms of energy. Some ballpark numbers, if you took the entire CCA resource that is expected to be available you can fuel about 200 one MegaWatt power plants and that is about 1 MW of electricity. So the point is that this is a widely distributed resource that would have to go into some kind of distributed heat and power facility. I think cement kilns is an interesting idea, I know that cement kilns are using alternative fuels. They are burning tires and other things like that. Just so everyone understands, getting this resource into a large heat source or power generating facilities is more difficult than pushing a market of smaller distributed opportunities. But then the challenge with the smaller distributed opportunities is that pollution control is less on the back end. What I am trying to say is that from a market stand point, you have to fit the resource where it can be used. Research on all thermal treatment methods and how you create that process to handle those materials, and then recycling of copper and chromium back into the market place maybe the best final fate for those materials. Bill Hinkley: A quick comment on that and to Mary’s comment, I do not favor the recycling of CCA or arsenic. I think it is time for arsenic to be retired from the biosphere. We are doing the same with mercury, mercury is been withdrawn from all products,


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conditions have dropped dramatically, the amount of mercury in the waste stream is going down down down, thermometers are being dutifully replaced , etc, etc. Now the problem is what do we do with all this mercury? There is honest research is to turn it all into cinanabar and put it back into the ground. And I think we need to start thinking that way with arsenic. It has served it purpose, it’s a a powerful chemical, but we have got to move on. We need to figure out a way to sequester it permanently either in landfills or in ash or in old salt mines. We have 31 thousand metric tons of arsenic to manage in this state according to Tim and Helena’s data. That is a lot of metal. For something that has a standard for 10 parts per billion. Talk about scaling. Rolf Dieter-Peek: I am working for a resource center which belongs to the ministries of consumer protection for agriculture. Sometimes I have to sit on their side, on the ministry side. The decisions there are so far away from what we are as scientists are thinking. We make our experiments about ashes and we make our experiments and thinking about thermal processes, landfilling and all these things but politicians decide on a different basis, much more pragmatic than we are sometimes. So we have discussions about landfills in Germany and I am making a strong point that they are forbidden. We can not bring any timber in the landfills in Germany. The reason why is that there is potential hazard at risk that this wood would break down and that we would have to cope with the leachates. That was one reason to say. We don’t want to have this any more. On the other hand we have so much more other demolition materials other than wood which go into landfills and don’t do any harm to the landfills so why not take all the wood out of landfills except this little part which has been burned and the ashes which are not contaminated go to public landfills. This is the only option we have at the moment. If there are ashes as I said from incinerators they have to go to special dumps and salt mines and wait there for a second generation of recovery which has not been developed as somebody said at the moment. So our way was to incinerator plants very special, only for wood nothing else, not municipal waste incinerators, but only for wood. The technology, I have been in a number of sessions where people from the burning industry were sitting together, where people who have knowledge of filters and all these things, this kind of technology is so sophisticated today that the emission rates really which I showed in my paper can be met even when they are under these limits values. So the only way, the political decision in Germany is to get rid of the treated material by incineration in special incinerators. I think what we have to do is like Bill said go around the world, or John would come to Germany, and have a look at these incinerators and see what technology is used there and start to think again. We are in many cases not enough informed and not enough skilled to know all the details which are available all over the world, we do research in many fields without knowing that the results, the solutions are already on the table. Helena Solo-Gabriele, Summary: At this point I would like to close this particular session, the plan is to put everything on paper. I am going to re-listen to the tapes and I will try to assimulate all the information that has been provided here and then send to all the participants via email at this workshop for one final set of input. What I have heard in this


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particular panel, I have heard some general themes, there are some issues of US versus Europe, with respect to the US there is characteristizing of what is happening in the US as a whole vs the state of Florida. Also there is a theme of issues of regulation both throughout the Europe, as mentioned in Sweden and also in the US. And most importantly the issue of landfill vs. thermal chemical processing. These are the two processes that have appeared to be the most economical at this time. There may be some opportunities for some wood cement composites or other recycling options, perhaps if recycling should be encouraged. As far as the landfill, I thought it was interesting with respect to Europe it seems that thermal chemical processing are encouraged there except with the exception of Denmark and in the US it appears of the low landfills cost, landfills may be preferred. But it seems that there maybe some issue or areas where thermal-chemical processes would be highly desirable. With respect to the landfills there is an issue of liners vs no liners that need to be evaluated also issues of clean up of the landfill leachate. With respect to the thermo chemical processes a lot of the discussions focused on issues of fuel quality and whether or not sorting is necessary. It seems as though if we could get around not having to sort it would be better by lowering cost. But that might have an impact with respect to ultimate disposal of the metals within the ash and also quality of the emissions. Also with respect to sorting the issues brought up as far as the responsibilities of the marketer and the people who produce the waste. The importance of integrating thermo-chemcial studies with ash quality. We need to learn from other industries such as the mining industry as far as what they are doing. I thought it was interesting as far as going out and visiting other incineration facilities, pyrolysis facilities to gather information to see what is being done world wide in some coherent fashion to come up with the best possible solution. Issue of slow pyrolysis, cement kilns were a possibility, large versus small facilities, and air pollution control facilities on the small facilities versus large facilities. Also the issue of creosote, and encouraging the burning creosote within thermo-chemical plants. That is what I have taken away from this. There are certain themes that are consistent throughout many of the discussions. What I will try to do is put a summary of these themes together and provide a summary statement of what was said here and sent it out via email. At this point in time, given the lack of time, I would like to proceed with our next panel. The next panel which will be rearranging due to airport schedules. We will be discussing exposure risk assessment in the next session. Our panelists include Rolf Dieter-Peek, John Schert, Tim Leighton, Curtis Englot, and David Stillwell. At this point I would like to turn over the floor. Panel #3: Exposure/Risk Assessment Panelists: Rolf Dieter-Peek, Curtis Englot, Tim Leighton, John Schert, David Stilwell Rolf Dieter-Peek: I am coming from a small country like Florida, but with more inhabitants, 70 -80 million people. So we have different opportunities, different challenges, and different chances. Some of you might be informed about that wood preservatives will be


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approved according to the European Biosolid Product Directive. This Biosolid Product Directive was taken into place last year, and all the new wood preservative have to be approved according to this regulation. That means that they have to go through an efficacy test as we had in the past and we have to be careful about our environment and environmental risks from the wood preservatives and people look for it and we have a new panel on board that is their place exposure. There we are on the risk side of exposure, risk assessment. Risk assessment and exposure are two different topics in my opinion. One is of course the exposure to the environment, so what is coming out of the timber and how can we measure the possible risk to the environment and of course workplace exposure and the exposure to the consumer, secondary exposure or indirect exposure. The first work place exposure is direct exposure to the wood preservative and to the treated wood as such. The indirect exposure is to the consumer. And to my knowledge there are great programs going on especially in the UK, HSE is looking for the exposure to work place and to people on the work place. And in Germany we will do the same. So at the end of the day every new wood preservative will have to go through four different functions: is it efficient, is it harmful to the environment, what is the risk to consumer, and what is the work place situation. All the new formulations and actives will go this way. So what I would propose is having more risk assessment especially concerning the workplace exposure. If we don’t have figures there we at least in Europe run into the possibility that special wood preservatives will not get approval anymore. And since we are a little bit advanced in Europe this might also come to the US and other countries. So be careful about exposure, and measurements, and invest some money in this field. John Schert: I am from the Florida Center for Environmental Solutions. It is really great to see the exchange of ideas, and to see other folks from other countries coming to share their ideas. Over the years that we have been working with this, I have really been struck by how little is known about the exposure issue and what sort of a murky area that is. A lot of people have called me over the years finding us on the web believing that they might have had some exposure. My answer is usually well I am a garbage guy I am not a toxicologist and I am not a health and safety person. So I have always been really uncomfortable with that issue. But I think we need to get a better handle on how people are going to maintain structures and work with existing structures. Are they getting exposure problems from that, from sanding or sawing or those kind of things from the existing stalk that is out there. My big task is what to do with all of this C& D wood. To sort or not to sort, how do we use it as an energy source. Joran mentioned the metals in the fines when we start handling this stuff and chipping it up what kind of exposure problems are we creating for the people who are doing that, the people handling it. We have had some cases of people who looked like they had been pretty heavily contaminated by handling mulch here in Florida because of the arsenic in the mulch. There have been some legitimate concerns raised about that. I personally noticed a lot of burning of waste wood by people who aren’t clear at all that they are burning treated wood. We have so much wood in Florida that is heavily weathered, I am just not sure, that whoever is in charge of doing this, is not doing a good job of letting people know that they shouldn’t be burning this stuff especially with construction workers.


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I routinely see it happening. A lot of little burn sites I have pulled out pieces of CCA 2 by 4’s and things. So anyway I think we need to look at are we doing a good job at managing this as a waste. I think we need to find easy ways of distinguishing CCA from non CCA wood. We don’t have any easy means of doing that. I mean you can go and buy a 40 thousand dollar X-ray device. The stains that we have been working with here in Florida do not distinguish CCA from non CCA. They just detect metals. I think the ideas that Rick Maas and Dr. West have on the green sheet are some really good ideas too. Tim Leighton: Thank you John, I am here from the US EPA. I work for the Office of Pesticides where we register and reregister the wood preservatives. Generally when I come to a conference and I get an opportunity to speak with researchers I go more along the line of we need some basic research and some more information on the efficiency on the sampling methods. But today I am going to be a little bit more focused and the research needs that I am going to push for are more towards the reregistration and registration of wood preservatives, especially because this group is more tending toward that. We look at both worker exposure and non-worker exposure for the non-occupational, specifically we are looking at children on treated decks, children on treated play sets or whatever areas that are there. I think the best way to start looking at where our research needs are is to looking at exactly what kind of data that we have now. For the exposure portion of the data right now we do have residue data that we have been using for registration, really the registration of CCA, creosote and pentachlorophenol. The residue data that we are looking are hand versus cloth wipes from actual wood on decks. We are also looking at soil residue concentrations. One of the things we are looking at for CCA is the incidental ingestion of soil and for the chromium portion we were looking at assumptions on how to get from total chromium to hexavalent chromium. And right there, there is some needs because nobody has speciated that in the soil as far as I can see. There’s other exposure type information that we need and that includes, mostly assumptions, such as hand to mouth assumptions. When I saw one of the slides earlier yesterday that children are not miniature adults there are other exposure activities that are involved. We need to get to areas of replenishment for hand-to-mouth. We also need to look at saliva extraction efficiency. We do have some data there. And you could probably go to some of our website at EPA and find out the values that we are using. For the toxicity side, this is where I usually capture the bioavailability issues and that was also brought up. The exposure that people are getting or children getting from decks are not necessarily liquid forms of arsenic. The arsenic is bound with the wood and the chromium. So we have some data and you can see this from our science advisory panel on the data that we have used and our CCA probabilistic assessment. And from that information you can look to see the ranges and assumptions or if we have used specific data. And from there you can go on to see what further needs to be done for those issues. For more concrete steps, if you really want to get down to what the further research needs are the SAP is going to release its comments on our probabilistic assessment and I believe that release might even be as early as this week. There will be some specific comments in there on the data that we have used and from the data where we should start looking for additional information. So as far as a concrete step that is one spot that I suggest everybody


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go to. Now for some specific data needs we always talk about residue data and exposure data, but there is also survey data that we need. There are measurements, but besides the measurements we need to know how long children are out there and contacting, and what kind of frequency are people are on treated structures. One of my pet peeves that I usually have in exposure data, I want to make sure that everybody gets this across, this goes to my (preference) of being able to use data, is that environmental concentrations that are collected are not necessarily equal to human exposure. So when you do look at collecting residue type data do look at it as what is existing. If you are going to look at carpet residue for instance, I think that was brought up in the green paper here, if you are going to look at carpet residues we want to look up residues that are transferable and not necessarily deep into the plush where it is not going to be available for exposure. There has been …. (end of Tape 1, Side 1)……So when you are thinking of designing look at some of our guidelines like series 875 and look and see what kind of transfer coefficients exist and use similar sampling methodologies so that we can link those data directly to human exposures. And then the final thing that I would like to say, if you are going start large scale type exposure monitoring due come to us in the antimicrobial division and we will review protocols to help you decide if we have the information where we can link environmental concentrations to human exposure. Curtis Englot: I am going to take a little bit of a different angle on this one and I hope no one throws me out of the room. I deal with risk management not assessment and so I have a little bit different take on this issue. I think if we look at the information that we have learned here throughout this workshop but also in the past. We know that leaching occurs of the chromium and the arsenic. It is getting into a variety of different forms into the aquatic environment and into the soil. There is a lot of debate about what are the numbers, are they high numbers, and are they low numbers. We have talked about under decks and all the different potential areas where we could be exposed to the leachate and contaminants. But the bottom line is the exposure to that. Even if you do have a high number, I know that most decks that I see that I don’t crawl under them. And they are usually the place where things get dropped and never get recovered until the deck’s torn out. You really have to examine that situation and I think part of that comes down to information. My boss when he brought me into this whole wood preservative issue, his bottom line was look you have a piece of wood with a pesticide in it and I think that is what has happened here is that the general public doesn’t know that and once they become aware of that and they know that, then they can address it more effectively. There was a comment made yesterday about the workers and getting the workers to separate the waste stream out at the source. So that you would have a treated wood waste source and untreated. And there was a comment that well trying to educate these people about what they were using and the need to separate them was difficult because of the turn over and that sort of thing. I have worked with the big boxes as well to trying to inform their staff so that they could properly answer questions and pass this information along to the public and they gave the same compliant or the same excuse is that there is a high turn over. Well the bottom line is that we need to up the education level of everyone so that they really understand what they are using. And I think


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if we look at certain issues as the public becomes more aware of them they can deal with the exposures more appropriately and we can manage the risk. They know that they are dealing with a piece of wood with pesticide in it and they treat it a little more different respect than just a piece of wood when it comes to issues like burning it and that sort of thing. And they understand that they can’t do that sort of thing. So I think that is a really important point here and my concern number one is the education and not necessarily the research aspect of it. If we do look at the research perspective, I think we need to bring in a lot of other disciplines here. I am actually quite glad to see quite a few engineers in the room here. A lot of the wood preservation meetings that I have gone to are full of all of forestry guys. We had one doctor come here and present yesterday. I think we need to bring in a lot more of these other disciplines. Statisticians, I mean the variability that you can find in treated wood: how much will be leaching, the different treating rates. There is huge variabilities here; the exposures to the public. Two years ago I spent 3 weeks in Virginia where I basically looked after my daughter. We went around from playground to playground in June/July and there was very seldom children at the playground. We were virtually the only ones playing on these structures a lot of times. So when you are doing the calculations and trying to figure the exposures look at what is a reasonable number and what is the variability in those numbers. It can be huge. We have been working on a study in Edmonton right now and we went out and we did some sampling in the summer as well and it was surprising when you figure out how many kids are geographically served by one structure and how many kids are there. It is a really low percentage. So trying to figure out the variability in the exposure to kids. You can have some kids who would play a lot and some that never go there. So you need to bring in these other disciplines to provide more science and better answers to these questions. Looking at the waste we were talking about how to deal with that yesterday. One of the things that came to mind was essentially we are trying to mine a resource was what about looking at some of the mining processes that they use for removing the copper and the arsenic from the ores and that sort of thing. And maybe they would have some sort of take on how to get that stuff out easier because they deal with that in a different scenario. But again they are trying to do the same thing, they are trying to pull something out and I think the comment that was made about bringing the metallurgists and sort of thing it supports that kind of approach. One of the other things that we need to do is to decide when we have enough information. I don’t think I have ever read a paper where were there wasn’t an end section that said we need to do more research on this, this and this and a lot of times, we keep trying to look for the ultimate answer and we can’t do that we need to move forward. I think my conclusion to this is that perhaps we don’t need a lot more effort on this when it comes to the exposure and risk assessment. If we look at the future I am speaking specifically for CCA here, it is out of the residential market. I think that is the primary exposure and it is not going to be happening much longer. And as such we should probably move the bulk of the work away from the assessment and the exposure there. Aside from the fact that there is still exposure associated with the product that is still installed. So you know if there is going to be research on the exposure and the assessment, lets concentrate it on minimizing the risk, the risk management so things like the coating and those sort of thing. But other than that educate the public so that when they are tearing


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their decks out as they need replacement that they know how to do it properly and things should be probably covered. Thank you. Dave Stilwell: After a deck gets removed though now you have the arsenic polluted soil now exposed and other people might not know that there was a deck there. Tim covered a lot of the stuff so I think a specific experiment would be sequential extraction to determine the forms of arsenic on the surface. Also the coatings, survey of coating, methods, formulations, iron and those sorts of things would be a way to reduce the exposure. Somebody mentioned yesterday smoke, for the firemen, and the EPA report that’s really going to cover a lot of topics: biomonitoring, skin absorption, bioavailability, arsenic leaching and dislodgeable residues and how they relate to each other and the nature of the residue. There was proposed that there was a chromium dimer associated with one arsenic atom. However the leaching data show quite the opposite and to explain this discrepancy there may be chemical reactions on the wood surface which result in preferential release of arsenic. This would be another reason to design a sequential extraction experiment. That would be one way to determine the various forms of arsenic on the surface, particularly the soluble and insoluble fraction. That would also be tied in to the bioavailability, biomonitoring is also a lot more complicated than I would ever imagine. I wouldn’t suggest that anybody take that up just by themselves. There is also plant uptake around the raised bed gardens. Most people would agree that the tomatoes plant will not pick up arsenic but there are plenty of leafy green vegetables, lettuce, mustard greens, arugula, Swiss chard and to a lesser degree those sorts of things like herbs basil, chives, some may take them up, to a variety of degrees. Actually, when I monitored playgrounds, I did a little study, and I had to wait for a cold rainy day because there were like tons of kids on the playground in Connecticut. Thank you. Helena Solo-Gabriele: Thank you panel. We would like to open it up for comments from participants. Comments from Audience: Comment: Well I am pleased to see the emphasis by the panel on the workers who will be handling CCA waste and handling CCA solutions. That is a very important factor compared to the public. We would like to suggest there be a definition of proper medical tests and procedures to indicate exposure to arsenic. It is very important to the sector who is working with the arsenic products. I will give you my example, in Canada wood preservation plants are to have health monitoring programs on a yearly basis. The question is what do we monitor for and how? We have had a number of plants that have monitored yearly for arsenic concentrations. One plant I know the office staff had the highest arsenic concentrations compared to people who were actually handling the solutions. So was it that the test wasn’t conducted properly or were we are looking for the wrong parameters, maybe we shouldn’t have been looking for arsenic in urine we should be looking for some other test. The other aspect deals with annual physicals that people are required, particularly


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those who are exposed to arsenic. In Canada workers who were exposed to arsenic are to have such annual tests. They go to their physician and say ok I work in a wood preservation plant. I am suppose to have this test. The physician says I don’t know what I am supposed to be looking for. We might have some general idea, but there has to be some kind of reference point for indication that there is exposure to arsenic that may be of potential concern. The other point that I would like to make has to do with exposure limits for the new chemicals. Right now we have ACQ, if you have a monitoring program in a facility that is using ACQ what are the proper parameters to be monitoring and secondly what would be the limit for those parameters. Raj Sharma: One of the things that also needs another look is the NRC analysis of our arsenic potency in the first place. Recent studies have shown that arsenic isn’t quite as potent as we thought from the NRC analysis. There has been further analysis of the Taiwan data set which really falls into two populations: a very high exposure in the hundreds of micrograms per liter of arsenic where the cancer developed and the second population where really there was a very low exposure and no cancer development. There have also been recent studies in the US published very recently by Bates and also by Smith. One of which was up on Dr. West’s slide the yesterday, which again does not show any association at lower doses for arsenic and cancer. Another study just came out last week, which is in the Argentinean population, which again says the same thing. There are also recent ecological studies by Lam and Frost, which is saying the same thing in the US. There is a Takoma Smelter study, which has just come out by Frost, which had very high levels of arsenic in the environment, which really looked at the exposure to people through a lifetime and didn’t show an increase. And really there are now new studies which really require that the NRC analysis be looked at again and these have been all submitted to EPA and I know that they will be looked at. And it really is very important for us to realize that we are targeting arsenic as a culprit and there is no doubt that arsenic is a carcinogen but the dose makes the poison, we shouldn’t forget that. Helena Solo-Gabriele, Summary: As far as the over arching themes that I can summarize from what has been said so far is that there are various areas of risk assessment, these include evaluating the risk of associated with the efficacy making sure that the wood holds up structurally and also the risk to the general environment. Most of the discussions focused on exposure to workers at the treatment plant and exposure to individuals within the solid waste sector, and in particular those who handle mulch and process mulch and also issue of secondary exposures through fire fighters and possibly smoke. A lot of the comments focused on exposure to consumers, specifically evaluating the exposure to people who may be sanding and working with the wood. Secondary exposure through children playing on play sets and also secondary exposure through uptake through plants to people who consume plants that may have been impacted by CCA. As far as the children and playgrounds there was a long list of areas or data that would be useful these included information on the soil residue concentration, chromium 6 in soils, hand-to-mouth, saliva extraction, also the need for surveys, I heard from a couple of the panelists with respect


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with how often a child plays on a playground, transfer coefficients, skin absorption and also the issue of bioavailability was discussed amongst a couple of the panelists, the need for sequential extraction studies to determine the soluble versus insoluble fractions of residues from the wood. Also there is the issue of low versus high doses and the impacts and health affects associated with low versus high does of chemicals from the treated wood products. And also there was a need to minimize or remediate the exposures through the use of sealants on existing structures. As far as follow up concerns or follow up issues that include issues of risk management and the need to educate consumers also the need to recognize possible exposure by improving our medical tests, developing new ways to recognize exposure among the general population. Another over arching theme that I heard in the last panel and also in this panel is the need to bring individuals from all different disciplines to address this problem including the forestry groups, engineering, medical doctors, statisticians, and individuals from the mining industry. Also there is a need to evaluate exposure to other chemicals. So, I would like to thank everyone and if you have comments we will be emailing everyone a summary statement. I would like to thank the panelist. At this point I would like to invite the panelist for panel two who will provide feedback on the release of preservatives to environment. Our panelist includes Tait Chirenje, Paul Cooper, John Ruddick, Michael Kennedy, Daniel Mourant and Tim Townsend. Panel #2: Release of Preservatives to the Environment Panelists: Tait Chirenje, Paul Cooper, Michael Kennedy, Daniel Mourant, John Ruddick, Tim Townsend Tait Chirenje: A lot of what I wanted to say has already been covered especially by members in panel two. But from doing research over several years here in Florida especially soil characterization and sorption there are a few things that we feel that we don’t quite understand about the dynamics of arsenic especially arsenic in soils. A lot of research by Dr. Solo-Gabriele and Townsend shows that arsenic is leaching from these structures and yet we have gone to a lot of sites, especially there is a site outside Gainesville where they have had test plots for over 60 years and when you look for arsenic in those soils it is gone. We know the concentration in existing decks is probably 20 to 30 ppm. So something is releasing this arsenic from soils after certain period of time. And one of the things that we feel we should do is to understand what are the conditions that lead to the release of these chemicals from soil. Especially soil properties, pedogenic processes that are involved in these. Another issue that I feel needs to be looked at is the environmental impact apart of from human health assessment. I consider myself an environmentalist and when I look at the environment I don’t just look at the impact on people but also on plants, and other parts of the environment flora and fauna. Especially here in Florida where there are a lot of wetlands, if you look at it from a point of view from a watershed approach you


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want to see if any of the arsenic which is leaching is going in anyway to affect parts of the same ecosystem. So that is one of the things that I would like to see done. Paul Cooper: I would like to focus on some of the issues that were identified in Canada during a process called the Strategic Options Process which was a multi-stake holder group that mandated by Environment Canada to look at ways that of minimizing the impact of the toxic components of all the wood preservatives. One of the issues of course is release at the treatment plants and this was addressed through mandating that the industry would accept the technical recommendation documents that recommended that practices at the wood treatment plants. And so for example there was a requirement that complete hexavalent chromium be reduced in CCA treated wood before material was moved off and this is a requirement of the industry. These TRDs have now been extended to the new preservatives ACQ, copper azole, and borates. There are either available now or will be available soon. They are living documents, we really don’t have the data that we need yet on the new preservatives and John Ruddick mentioned yesterday that there are a lot things that could be done to reduce the releases of copper from ACQ. But we haven’t pin pointed those completely yet and so more work needs to be done to understand the mechanism of stabilization or fixation of these preservatives and what can be done at the process level to reduce the amounts released. Two other things that were identified as being data gaps were when we tried to do the inventory of how much preservative was in product that would go to disposal and how much of that had already entered the environment in some way. It was really hard to come up with the numbers and we identified that there was not enough information on the fate and emissions and fate of creosote from railway ties and CCA from treated products and we have now extended that of course to, say we obviously don’t have the information we need on the new preservatives. So we need to generate that information and I believe find a way that we can predict the performance of new preservatives as part of the evaluation process so that we know how a new preservative is going to do not just in terms of efficacy but in terms of impacts on the environment. So those are sort of broad things and there a few specific things like the coatings that I am hoping that the EPA study will give a fairly definitive indication of how effective coatings are short term and long term on leaching and dislodgeability. But otherwise we more work on that as well. John Ruddick: Thank you, yes a couple of things, first of all phasing out of arsenic or retire arsenic as I think I heard someone say earlier reminded me of Alice in Wonderland and the walls and the carpenter sweeping the ocean. To me there is a large amount of arsenic so that this really is not a realistic target. A more realistic target is to try and manage the material that we have and I think that should be our goal rather than trying to think that we are going to get rid the world of arsenic. So really our focus should really be management and management of these risks in a reasonable and responsible way. I am going to deal with the topic in a general way but I will focus on CCA to some extent. Modeling I think is a really critical aspect of what we do and there we can learn again from Europe with the Biocide Directive and the OECD and various groups that have looked at the modeling impact of the use of treated wood and the various situations and the modeling of releases and the


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modeling of things like impact of fixation and the size of product and density load of wood in the particular environmental exposure. These are things that have been looked at in Europe and I think we can learn a lot from Europe in understanding the environmental impacts, differences say between a deck and a dock structure and an isolated pole. These are different environmental considerations and I think we can learn a lot by sharing information. There are data caps like Paul mentioned and these need to be recognized and filled. What is the long-term impact for instance, if you have already impacted and released arsenic from decks well you’re a bit late, because most of them are in. And we need to understand what is the situation now. The situation is most of the decks have already lost most of the arsenic that they are going to lose anyway. That means arsenic is not in the decks anymore, it mobile, and it’s mostly in the soil, underneath. So what are you managing, are you managing the soil that is underneath or are you managing the deck that is still there. So you need to consider what exactly what is the target that you are aiming for. Looking at some of the other topics Paul mentioned and really is an expert in this area which is modeling loses of chemical from wooden structures and as we both know things like species, things like coatings, things like retention, things like type of treatment and things like fixation, all these things impact on what is going to be lost from that wood in service and we need to conduct and to continue to conduct research to better understand how these systems work when they are put into wood. And that is an on going area. That will be driven not by government though, that will be driven by industry and by others who are interested, curiosity driven to understand how these things work. But I don’t think it is going to be driven by government, it hasn’t been in the past. I already mentioned modeling and Paul Cooper done tremendous work in that area. I would make sure that kind of work continues to be done, it is really critical. This is also a moving target, so speaking to the new preservatives, you know you’ve already got ACQ type B,C, D, copper azole types A,B and I mean it goes on so you have to understand that this is a moving target. The industry itself is improving and enhancing these preservatives sometimes it is driven by environmental considerations, sometimes it is corrosion, sometimes its color, sometimes it is wood quality. But the target itself will move, the CCA wasn’t always all CCA. It was CCA and sometime it was with water repellant. So the target itself is not always the same and you need to understand that, that the quality of the preservative and the type of the preservative and the formulation of the preservative, even here now, this week you actually went to a plant last night and you may not realized it but that actually is a latest version of ACQ. It actually is not just the quat, but it actually contains a quart carbonate as opposed to a quart chloride which has most widely been used and that is actually just been introduced. You may understand or appreciate the impact of carbonate on the leachability of copper. So there are many variations going on and those are being driven by industry not by government. That’s why I don’t think that research will be driven by the government. I think that research is going to be driven by the industry. But those involved and interested in environmental impact and releases need to understand the formulations themselves change. The other thing we need to look at is the impact of losses in real time, not just in little beakers or in big basins. You need to look at real time. And many of these preservatives have been used for a significant periods of time. Particularly in Europe, ACQ


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for example has been around in Europe for a decade or longer, not necessarily in the amine form. So we need to take a look at material that is already has been out in service for several years to see what the impact of that product in that particular environment has been; what are the losses in real time? I think there is information out there. Finally I would like to say also in context, it is very easy to take a look at a small industry that has a relatively small impact and small use of chemical, we are in an area in the southeast states where we talk about arsenic but I mean there are huge usages of arsenic in the southeast states that has nothing to do with wood preservatives all. So if you want to take a look at the removal of a particular element from industrial use it is a very interesting and useful thing to do in terms of human health and environmental impact. But I think it should be industry wide and not just wood preservation wide. It should be across the board of interest in getting rid of copper for example, you better talk to the computing industry who have a very great reliance upon this element and what are you going to do with the waste materials that that industry produces. So I think it is an important idea, how you are going to deal with and manage materials that should be on an industrial wide basis and not just on a specific industry basis. That is enough. Michael Kennedy: I am Michael Kennedy. I would like to address a few more remarks to the specific subject of release of wood preservatives components to the environment from wood in service. I would like to point out two real requirements before the process of wood preservative improvement and development can proceed. I would like to take an urge, a proactive approach in this. John has already mentioned that industry is really driving the improvement and the development of wood preservative formulations. But they do that in response to a whole range of different factors, just one of which is the environmental performance. Now when CCA was developed all of the thoughts of leaching and fixation were driven towards efficacy rather than towards environmental performance and the industry obviously recognized the learning problems with chromium and arsenic many years ago and they have been developing chromium and arsenic free alternatives. These alternatives take a long time to develop, maybe 10 or 15 years to go through the whole product development cycle. So if we are going to take a whole proactive approach, we need to be looking forward and setting ourselves some targets for environmental release for the new actives. So it might be, it is already easy and simple now to say well the arsenic release we have been measuring is not acceptable. But are we yet in the position of being able say what level of copper release is acceptable. Because until we do that it is very difficult for wood preservative developer to adjust his formulation and develop his product to meet that target if that target hasn’t been set. So I think that we need to be looking into the future and working out in which environments copper release is important and trying to set some figures for that so that can be factored into the development cycle. And not just with copper but with the new biocides that are coming along, perhaps some metal free wood preservatives. Well once we have a target, then we need to have a methodology in order to assess that in a rapid way. It is all very well to go back to a deck that has been in service for 15 years and measure what has come out. It is all very well to take some decking boards and put them into some kind of a test deck and measure them over a year. But neither of


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them is rapid enough to provide the feedback necessary for wood preservative development program by a commercial wood preservative developer. And we really do not have accelerated emission measurement systems that, for which the correlation between them and losses in service is well understood. So I think we need to do some work on defining targets which the future formulations and the improvements of the current formulations need to meet and we need to do some work on the methodology that can be used in the development cycle to assess whether or not the preservatives are meeting those targets. Daniel Mourant: Maybe to continue a little on that vain of coatings, to be able to better assess what will be the needs in the future. I think the life cycle of the product should be elaborated first using timber then possibly using wood panels or other engineered materials, then ending up in possibly concrete or other thermal conversion systems. We optimize our resource because the release of preservatives is one thing but there is also the management of the resource to take into account. Another thing that I would like to say is we need the metals also. For now most preservatives have been copper based or arsenic based. There is a lot of research that has been done especially in Asia and in Europe concerning wood extractives and tannins. Those products have limited applications but could they be increased or incorporated more into formulations lowering the need for such metals. Also resins could be a possibility even though it is not naturally economically viable. We need to look into these things. We need to look at renewable resources or organics to include into those compounds, these resins that could be used to lower the demand on petroleum industry based phenol. So we must aim at renewable energy or renewable resources into that area as well. That is my input for now. Tim Townsend: With regard to the release of preservatives a couple of immediate research needs that jump to me based on some of our experiences here. One relates to the copper in the newer preservatives. I heard different folks in the meeting the last couple of days express different opinions about copper. Of course there were some folks who said copper is a biocide. It’s very toxic. It just shouldn’t be used at all and then based on some of the literature and some other things you get the impression that copper is something that is relatively bound up in these aquatic environments and gets in the sediment and is not readily available. And copper is known to complex with humic and tannic substances in the water and is not necessarily bioavailable to these organisms so right now as some folks discussed in Florida a lot of these people who are going to be building these structures in aquatic systems are not going to have the option of using CCA any more because the only thing available to them is going to be ACQ or copper azole. So I think a real question that needs to be addressed is whether or not the copper and its release, whether that is a real aquatic impact or not. And then are there tools that you could use in assessing what type of water bodies is it ok for. Ken Brooks who some of the people industry know who has done a lot of modeling to determine worst case releases in estuarine systems and things like that and using fairly complex assumptions finds that in most cases you shouldn’t see a build up in water quality standards or sediment quality standards. But at the same time again you see


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others who say well no, because of the aquatic toxicity associated with that is something that shouldn’t be there at all. So I think that is something that is a realistic need in the relatively near future that folks are going to want to see. Another release research need, we talked about the mulch and of course the direct exposure of the mulch, which was, folks touching and working with it have certainly been addressed. One of the things that we do in Florida is that we will do a leaching test for example on the mulch and find that it leaches and therefore can conclude it is not something that should be land applied but the question about what the ultimate fate of a preservative is going to be. Is that really something that is ever going to have an impact on ground water quality if you put down an inch or two of mulch in a landscape bed or if you do that year after year, is that something in terms of release, because it were to just use the direct exposure standards or even the leaching standards on these mulch tests it basically means that you can’t use recycled construction demolition debris wood for mulch in Florida right now and so you would think that there is some deminimus amount that should be acceptable that would encourage that other positive environmental aspect of recycling that wood, so that is something. The thing that is a little concerning that I think needs a little bit more thought is the whole organic side everybody is talking about arsenic and copper and chromium but at the same time I am hearing in the future what we will be seeing is organic preservatives and that the writing is on the wall and that is what is going to be there. As an engineer one of the things that I rely on are tables of data and standards that toxicologists and risk assessors have put together and I can go and I can find what values of toxicity limit are for things like copper, chromium and arsenic, but when it comes to some of these newer organic chemicals that are out there, the question is are they going to be introduced and the data that was collected to prove that it was safe for use is that the same data that someone in a regulatory agency is going to need to evaluate what its impact on soil is going to be or its impact on disposal. And I think a good research area is going to be for experts like in this room to get together and say here are all the data that is needed when you are developing a new wood preservative that are going to need to be addressed to evaluate all these issues in the life cycle not necessarily just the ones that are normally used in terms of efficacy and then direct use in the environment, like the long term impacts on disposal. And another kind of release issue which goes back to disposal a little bit which is a big picture question which I don’t know, I am just wrestling with it in my mind right now, but what is the better idea, is the better idea to concentrate all the arsenic as an example or to dilute it all. It goes into that lined vs. non-lined landfill. If you have a non lined landfill you are concentrating whatever arsenic is to leach down there at the one particular spot so a few areas around in Florida, or anywhere, or if you are talking about lining the landfills what are you doing? Well its going to a waste water treatment plant, and Bill mentioned before some of it is going to get into the biosolids but a lot of it is not. And those biosolids might be spread out everywhere and so while there is a goal to concentrate it and keep it. On the other hand there are some folks, ecologists, who have suggested that best ways is to just distribute that all back to the lower levels in the environment that are below any kind of risk threshold. I don‘t necessarily come down one side or the other, but I think that is a good interesting debate that should occur. Thanks.


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Comments from Audience: Lisbeth Ottosen: I just wanted to follow up on your comments on the new organic preservatives because I think it is really scary that they can be moved from A to B and it is not nice when they go to B most often. But when we move to the organics so we don’t know what they will be transformed into so we so not know what we are looking for. So I think there must be a huge work to be done there to see if it is getting worse actually when it leaves wood or what are we looking for there. I think there must be so much work to be done there. Rolf Dieter-Peek: If I may, I would like to support John in what he said on the OECD work that is going on and about losses in real time to the environment. There is really an option, at the moment OECD goes the way that they test a given wood preservative in a block in a laboratory and try to model flux rates out of it to see how much comes out during a life time. That is one way, and I would say that it is a wrong and a right way. The other way that I would propose, what John is obviously thinking of is the large experiment we have out in the field. We know that there are poles outside for more than 20, 25, 30 years. In Europe we made an experiment, we made a survey, on these old poles many years ago, really many years ago before we started all these discussions and we found out that the CCB poles when it fails that has about half of it still remaining so we know about the releases during the service time. We know about the releases of CCA during the service time of 25 years. If we start with a retention of 6 kilogram in the ground lines after 25 years or 30 years we can calculate we have a daily of release below surface line of about 3 to 5 ppm per day. That is the release rate. If we don’t take into consideration that we have losses at the beginning that are much higher and which fades out so that is one. The other approach is what we did in Sweden with a project on creosote. We know that there are fields outside, test fields for more than 40 years and even longer and we know the releases to the environment of creosote during this time. A creosote pole will fail about when you test 40 kg so we calculate the amount of loses by real time, by looking at these poles in real time and this would be an experiment now for all the old wood preservatives which are out in the field to look for the real remaining (metals) in the timber and calculate back how much the release was. And for the new preservatives we have to bring the samples out into a field tests for 5 years, look for the samples, how much is remaining in the samples, we have some studies on that at the moment, but not enough. Look at that and then we see how large the releases are. That would be a good way to do it and the last point I would like to make is fate and behavior studies, which have not been done sufficiently. We should start to do that. What is the bioavailability of the new wood preservatives in the soil. Comment: Good morning. Let me start off thanking the officials in Florida for their effort here. I think they are certainly leading the states in environmental concerns in certainly the issues of arsenic control, chromium and copper. Let me first address this to one of the panel’s comments that a lot of this research is driven by industry. I think the question is why? It maybe for self-defense and it may be for a genuine effort to improve the product.


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There are a lot of legal issues at play, a lot of the decisions being made are based on legal advice from lawyers and it may not be in the publics' interest. A lot of this research may be done by the public, paid by the taxpayers, used as self defense mechanisms and some of the research, which should be done, may be avoided by support from the industry. No one has addressed other options that have been freely discussed with the industry and that is high penetrating polymers that will seal arsenic and will lock in copper and will lock in chromium. There is absolutely no mention about them after discussion for over a year about the availability of this process, its been proven a lot of the testing has been anecdotal some of it being done by a few of the people that have given programs and it is a little bit in the early stage to meet the scientific criteria. But the possibilities of this working is highly beneficial and highly objective and it will meet all the basic needs that I have heard here about the concerns about economic issues, about the control of copper, chromium, and arsenic for existing decks as well as for new lumber. The product is available, it reduces the cost, it has superior characteristics in that if provides a totally hydrophobic condition; it’s cathodic, the weight is much less, there is no leaching and I would support or ask you to support whatever research you think is necessary to make this a viable option in the quest to provide health and safety for….(end of Tape 1 Side 2)

Paul Cooper: … and back to the hexavalant state but as part of our study we did a pressure (test) with water and compared to the others and you will get slightly elevated levels in pressure washing if you are going to remove material. But I think this is material that would normally come off eventually through the rainfall and so it is not having a large additive effect. But the chemicals that you might use in conjunction with this are more of a concern. Kazem Oskoui: I would like to make a comment on actually the true cost of different disposal systems. For example I hear a lot about the cost of landfills being very cheap and very economical and that’s what is driving the whole thing, but especially on unlined landfill. I think there is a need for doing some research to find out what is the cost of cleaning up an aquifer which that land fill may actually contaminate and we have cleaned some aquifers and I can tell you it is not very cheap and if any of these C&D landfills found that the arsenic level in those aquifers around that area are above a certain level, the cost will be astronomical and it is not going to be very cheap to do. So when we are actually considering the cost of a particular treatment, Bill mentioned about 100-150 dollars a ton, it may sound like a lot of money but when you are actually looking at the implications of not doing that in the future, especially, now we all know how much it costs to go and take out asbestos from a house and take it into proper treatment. We do that all the time and we charge a lot of money for that. And what worries me is that we may end up coming into a landfill and being forced to empty that landfill completely take away everything, I mean go into the garbage there and you know identify arsenic contamination and remove that because we are contaminating the aquifer. Another aspect of it is the leaching collection, now some of the publicly owned treatment plants are refusing to accept this leachate because there are in mid-western areas where the arsenic levels are already high. There are already struggling with that and to add to that their compost, not their compost, their sludge,


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is not going to meet the requirements for disposal so they have to go and dispose it in a hazardous waste place and it is going to add a cost so there are actually refusing that. The other area is that in the state of Minnesota in most of the landfills who volunteer, they are refusing to accept CCA wood. And that is automatically limiting the number of options for people who dispose it to one or two landfills and that will gradually raise the cost. So it might be, if you are looking at the alternatives, a few dollars more cost now for an alternative, we shouldn’t put it away and say it is really not a good solution because it is costing so much. Lets look at the overall cost and the true cost of this and I think there is need to do some research on this area to do the real economics of different disposal methods, not just how much it costs us today. Thank you. Comment: I would like to make a comment. Dr. Tim had made earlier about dilution being the solution to the pollution. 28 years ago when I began my career as an environmental engineer I was told that was absolutely not the truth at all. Looking back over the last 28 years I realize that much of the pollution today results from the concentration naturally occurring elements in the environment. So I think we need to take another look at the practical side of waste management. There is a lot of CCA treated wood out there that is going to come to our waste disposal facilities and I think we need to take a much better look at what percentage of this material is in the total waste stream. What practical affects do we get from dilution. Do we really have the environmental impact from our waste disposal facilities that at least hypothetically we are concerned about. There is a lot of research being done in Florida right now to address that. One of the important research activities on going right now is the leaching test at the University of Florida that we heard about yesterday. We need to know is this stuff really going to come out of C & D landfills. Is it going to come out in MSW landfills to the point where we have moved the arsenic problem from one place to another but we have not solved it. The second thing is that the Florida DEP has a technical advisory group that is looking at existing C & D landfills to see what impacts these landfills have had on the environment with regard to arsenic and other metal releases. We may not have a real problem here that we need to solve that it is already being taken care of for us or there may be some modification to a C& D landfill that we can make with a particular metals filter or something like for a liner or mixing the CCA treated wood with other materials to bind that arsenic up in the landfill. I am more concerned now about source separating or separating at a processing facility of CCA treated wood. When I hear about risk and exposure to the very workers that will be now concentrating this material yet again. And can we mitigate that exposure. We can have guys in respirators and white suits out there handling this material. There is a lot of good research going on and I encourage you all to continue to support it and get that information to us. That is the science. The engineers are the applied scientists and right now I don’t know which part of this science to apply so I applaud all the research that is being done and encourage you to continue. Comment: I would like to come back to the releases and the needs that we have, that has already been stressed a few times, a need to predict the emissions from treated timber in


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service. We have a draft OECD guideline on the topic to measure that in the lab for the new preservatives. It has to be updated and it has to be refined. It also has to be linked to the real life situations and I support very strongly the idea that there is a lot of data out there in the field tests and probably we can make good used of the data. We also may have probably have to do such large scale experiments also to monitor the new preservatives in use in treated wood. Thank you. Helena Solo-Gabriele, Summary: I would like to go ahead and provide some sort of summary statement. What I have heard towards the beginning is the identification of our targets. We need to determine what it is we are going to evaluate releases from; what type wood, CCA vs other formulations and what kind of environment these releases are going to be impacting. With respect to the other formulations there were a lot comments on the other formulations, in particular the need for the concept of going to non metallic formulations, resins where mentioned, purely organic formulations, polymers were mentioned. There was concern about the release of the organics and the lack of guidelines concerning the release of the organics and that these organics may be causing other problems. Another topic that was discussed was the need, what is our goal as far as going back to our target: are we trying to dilute the waste or concentrate it back. As far as releases are concerned there was interest in the mechanisms of releases. These include releases from the wood, from the soil, and also the impact of the releases on the water. As far as the soil: what are the losses from soil, what is the bioavailability of the metal releases into the soil. Once in the soil what are the impacts to the ecosystem. Once in the water, what are the dynamics of the metals in the water? Are they bound up or are they complexed in some fashion that makes them less bioavailable with lower toxicity to the environment. As far as the wood itself, there is a need to understand the mechanism of fixation not only for CCA, a lot of work has been done on CCA, but especially the new alternatives. We need to model the releases from the wood itself. This would help in assessing the long term impacts. Also in assessing the long term impacts we need new measurements systems by which we can evaluate the accelerated or rather we need accelerated measurement systems by which we can better assess the long term impacts. To assses the long term impacts we should use available information. There was a mention of the OECD method of block testing that may not be good enough. We should look at available large scale field test such as the results that we get from poles, test plots, and information that we can get from real life uses of treated wood products. We also need to evaluate the mechanism of the releases upon disposal and during their in service use. There was a mention of during in service of the affects of the brighteners and pressure washing and also during disposal to evaluate releases from mulches. There was a discussion on C&D landfills and binding within C&D landfills. And also the issue was brought back as far as concentrating once we start disposing the material and trying to concentrate it back; is that a good idea? There needs to be an overall assessment of the products. These products need to be evaluated on a life cycle analysis. We need to look at it from the point of view that treated wood is a renewable resource. Should we recycle the wood or the metals in the wood. Also when the wood is first proposed we need to develop guidelines that include not only guidelines in the production


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but also guidelines in the disposal of the material. We also need to integrate information from other possible industries: arsenic, copper, is not only from pressure treated wood but maybe coming from other sources as well and we need to look at these other possible sources. The issue of funding also came up. The industry vs the tax payer, economical solutions were discussed. The need to evaluate or balance off the need for clean up vs that for proper disposal. In summary that is where I have gone. I will summarize it and put it in written form and send it out. At this point I would again like to thank our panelist and again I would like to thank everyone who participated in the conference


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SECTION III: POST CONFERENCE FEEDBACK As part of the voting ballot, feedback was solicited from respondents. Specifically, respondents were asked to provide research suggestions or comments that were not included within the ballot. A summary of the post-conference feedback is provided below. The post-conference feedback was split into 4 sub-sections: the three topic areas utilized earlier plus a section on general comments. III.1 General Comments

• The results from the ballot will be a dependent upon those who attended. Many at the conference were engineers and therefore engineering issues will likely be prioritized. Representation by biologists/ecologists/ecotoxicologists was very low. The lack of ecologists at the meeting indicates that the needs for research in this area are the most pressing, because the amount of research is so small. (Weis)

• Research should focus on the investigation of alternative material types to

replace chemically treated wood. A lot of time, effort and expense is devoted to identifying additional chemical coatings for wood, but not for seeking an alternative material for use in certain applications. (Thomason)

III.2 Disposal, Reuse and Recycling of Treated Wood

• Research should focus on alternative disposal strategies including chemical, biological, electrochemical. Research should focus on determining the appropriate concentrations of metals in the wood after extraction in order for the wood to be used in other applications. (Helsen)

• There is a need for a hands-on (non-academic) review of whether some of the

research is going in a practical and useful direction, e.g., a good review of research related to thermo-chemical processes and its potential for real world applications is required. Research should be put in the context of real world logistics. (Konasewich)

III.3 Exposure/Risk Assessment Exposure

• Research is needed to evaluate the potential exposure of workers at wood preservation sites since the exposure of these individuals is significantly greater


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than exposure that users may experience. A concern arises in that little is known about the toxicity and environmental impacts of A and the Q in ACQ. (Konasewich)

• Reasearch should focus on evaluating exposure and risks to the environment and

people during the disposal of CCA-treated wood. Risks should also be evaluated when CCA-treated wood is inadvertently burned, by people who are unfamiliar with the composition of the wood, and during house fires. The risks to firemen should be evaluated when they work to extinguish fires on structures containing CCA-treated wood. (Godson)

Managing Risks

• Research is needed to development of coatings to minimize releases. (Konasewich)

• Efforts should focus on educating and informing those who recommend the use of wood preservatives and preservative treated wood (retailers, wood treaters, Architects, Engineers, Builders etc.). (Venkatasamy)

• Options that specifically address production issues including "best management

practices" should be evaluated. (Robinson) III.4 Release of Preservatives to the Environment

• Less hazardous alternatives should be evaluated. (Robinson)

• Not only the amount (or concentration) of metals released is important, but also the oxidation state of the released metals, since both mobility and toxicity highly depend on the oxidation state (As(III) versus As(V) and Cr(III) versus Cr(VI)). Therefore, speciation studies are also important. (Helsen)

• An extensive amount of laboratory research has already been conducted. The focus

should be on real world applications. Evaluation of soil/water releases must be site-specific. There is a need to utilize real-world data in evaluating releases (e.g. from EPRI). Compilation and interpretation of such real world data might be of more value than continued studies on a micro-level. (Konasewich)

Gaseous Releases


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• Emissions from the combustion of treated wood be evaluated further. Specifically

there is concern about the "increased PCDD/F (polychlorinated dibenzo-p-dioxins and dibenzofurans formation) in the bottom ash from fires of CCA-treated wood " which was the title of the study conducted by Tame et al., 2003 (Chemosphere Volume 50, Issue 9 March 2003, Pages 1261-1263). (Godson)

• Research should focus on evaluating the effects of large “brush fires” on the

outdoor environment containing large quantities of CCA treated timber (e.g. such as the bushfires which devastated Canberra Australia January 2003, Waste Management & Environment Vl14#10 November 2003, “Need an Environmental Solution?”, pages 52- 53). (Godson)


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SECTION IV: VOTING BALLOT FOR RESEARCH PRIORITIES

Below is the voting ballot that was distributed to conference participants after the conference. This voting ballot was developed from the information presented in Sections I and II and from comments received from the Technical Advisory Committee (TAC) established for the FCES conference. Please note that the ballot was separated into three different topic areas, with separate rankings within each topic area.

******** beginning of voting ballot***************

“Environmental Impacts of Preservative Treated Wood” Conference

Research Priorities

VOTING BALLOT (Distributed via email April 14, 2004)

Name: _______________________________________ Affiliation: ____________________________________ Purpose: The conference organizers intend to use this voting ballot to develop a ranking of the research priorities. This ranking will be provided to the National Science Foundation, the agency that funded the conference, and to other funding agencies. This ranking will be useful to such funding agencies as they prioritize their research funding programs. The ranking will be based upon a majority vote among those who return this ballot by April 26, 2004. Only ballots from those individuals who registered for the “Environmental Impacts of Preservative Treated Wood” conference will be included within the vote. Instructions: Below are three tables of research priorities that were summarized from: a) the research suggestions submitted via email prior to the conference, and b) from the discussions held during the conference workshop held February 11, 2004. The first table corresponds to research topics associated with the disposal of treated wood products. Please rank these topics from 1 to 6 where 1 corresponds to the item that should receive the highest priority and 6 the lowest. Similarly please rank the research topics in the “exposure/risk assessment” table from 1 to 5 and the research topics in the “leaching of preservatives to the environment” table from 1 to 6. If you have additional research suggestions or comments that have not been included within these tables, please list these at the end of this ballot. These comments will be added to a POST conference list of research topics that were suggested by the conference participants. The results of this ranking, along with the PRE-CONFERENCE, WORKSHOP, and POST-CONFERENCE list of research agenda items will be included within the POST conference proceedings.


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Over-arching theme that will contribute to the success of a research project: During the workshop clear statements were made concerning the need to include experts from different disciplines to address the areas of research needs. Some of these experts include statisticians, forestry professionals including experts in wood preservation, engineers, experts in medicine and public health, biologists/ecologists/ecotoxicologists, and experts from the mining and metallurgical industries. It is understood that a successful research project will require an interdisciplinary approach which draws upon experts from different fields.

Disposal, Reuse, and Recycling of Treated Wood Please Rank from 1 to 6 with 1 receiving the highest priority Rank Research Item Research should focus on the role of regulations (national and European Commission)

in influencing disposal markets. Acceptable remediation levels (e.g. acceptable soil concentrations) should be evaluated. Re-evaluate role of U.S. regulations (RCRA subtitle D) which encourage particular disposal methods. Research also needs to be included on the effects of public perception in accepting available disposal strategies. Research should also evaluate the impacts of making those that distribute the material responsible for its collection and management upon disposal (e.g. currently under evaluation in France).

The economics of all available disposal options should be evaluated. An economic evaluation should include costs plus a term that accounts for environmental protection in terms of long-term future releases that may occur as a result of the disposal option evaluated. If the disposal alternative is to compete with landfill disposal which is currently allowed in the U.S., the costs should not exceed 150 U.S. dollars per ton. Costs can be higher in countries that do not allow landfill disposal.

Alternative disposal strategies should be evaluated. These alternative strategies should include wood composites, recycling of wood fiber, liquefaction, chemical extraction, electrodialytic processes, bioremediation and cement kilns. In Canada, it has been estimated that cement kilns have the capacity to dispose of up to 20% of the CCA-treated wood produced. The conversion of Cr from Cr(III) to Cr(VI) within the alkaline environment within cement kilns should be evaluated further. A considerable amount of work has been conducted on bioremediation technologies at the laboratory and bench scale. Future work should focus on scale-up of these processes. Electrodialytic and chemical extraction processes are also very promising and should be evaluated further.


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Research is needed on thermo-chemical processes (pyrolysis, gasification, and

incineration) that are capable of disposing CCA treated wood, mixtures of CCA-treated wood with other wood types, and mixtures of wood with other waste materials. Work in this area should include evaluation of optimum temperature, air, and possibly pressure conditions. The ability to recover energy from this process should be also included. Research should also focus on practical issues such as slagging, fowling, and corrosion within boilers. Research in this area should focus on the separation of the metals from the residue for possible reuse or ultimate disposal and on controlling air emissions. Additives, such as sulfur, should be evaluated to determine their possible role in controlling air emissions and minimizing leaching from the ash. Efforts should focus on cataloguing thermo-chemical conversion processes implemented throughout the world that process treated wood. Efforts should focus on drawing information from different disciplines (e.g. including the minerals and metals industries) when evaluating thermo-chemical processes and stabilization of the metals from treated wood.

Research should focus on controlling the quality of the incoming waste stream used for fuel or incineration processes. Sorting processes may be useful for this purpose. The incoming waste stream should be characterized, including the amount of metals within various size fractions of waste. Efforts should focus on quantifying the amount of CCA to be disposed (e.g. Florida versus other States, amounts in various countries). Logistical issues associated with collecting, transporting, grinding, and disposing contaminated wood waste should be evaluated. The practicality of identifying and removing CCA from the waste stream should be evaluated. Quick methods of identifying CCA-treated are needed.

Research is needed to evaluate the impacts of disposing treated wood within landfills including municipal solid waste landfills and construction and demolition landfills. Studies should focus on leaching rates and on possible additives (such as iron filings, iron hydroxide, or calcium oxides) which may minimize leaching. Once leached, the metals are found in the landfill leachate. The ultimate fate of the metals within these leachates need to be evaluated, which may include disposal at wastewater treatment plants and ultimately within the sludge at these plants . New strategies need to be implemented to manage these metals at wastewater treatment plants. Possible management schemes to be evaluated include reverse osmosis or recirculation of the landfill leachate to keep the metals within the landfill. Technologies for remediating arsenic should be evaluated from throughout the world (e.g India/Bangladesh). Methods are needed to sequester the metals that are leached. The possibility of intentionally constructing “leaky” landfills which promote the biodegradation of waste materials should be evaluated. The impacts of these “leaky” landfills on CCA leaching rates should be evaluated.


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Exposure/Risk Assessment

Please Rank from 1 to 5 with 1 receiving the highest priority Rank Research Item Evaluate exposure and risks to workers at wood treatment plants. Research should

focus on standardizing medical tests used to evaluate exposures in workers. Exposure limits should be identified for those industry workers who will be exposed to the new chemicals.

Evaluate risks to the environment during in-service use of the wood. Methodologies or assays should be developed to evaluate the environmental impacts of wood preservative chemicals among aquatic and terrestrial organisms. Toxicity assays should be developed for both aquatic and terrestrial organisms. Work should focus on identifying plant indicators of possible As, Cu, and Cr problems. Does the As, Cu, and Cr impact other components of the ecosystem? Work should also focus on the copper releases from CCA-treated wood and the copper based alternatives to CCA-treated wood within freshwater environments, since the copper in these wood preservatives is more toxic to aquatic organisms than the arsenic.

Evaluate exposure and risks to people during in-service use. This includes consumers who use the wood as a building material and their exposures to sawdust through sanding and sawing the wood. Risks and exposures should be evaluated for children who play on CCA-treated structures. Specific data needs for children’s exposure assessments include better estimates of hand-to-mouth behavior, speciation of chromium in CCA contaminated soil, saliva extraction efficiencies, transfer coefficients, survey data for time children play on CCA-treated structures, skin absorption rates, amount of dislodgeable metals and leachable metals from CCA, and bioavailability. Bioavailability studies should include a series of sequential extractions to determine the soluble and insoluble fractions of the metals in the residues on the treated wood surfaces. The dose-response data set evaluated by the National Research Council should be re-evaluated along with data available from more recent studies to determine cancer risks associated with arsenic exposures. An animal model for arsenic induced cancer is needed. Animal models are needed for bioavailability and skin absorption studies. A study is needed that directly measures past exposure to CCA-treated wood and then determines whether that exposure resulted in an increased risk for cancer. Research should also focus on secondary human exposures. These secondary exposures include uptake of metals by plants from CCA contaminated soils. Plant types evaluated should include rice, green leafy vegetables and herbs. Also “track-in” exposures should be evaluated from arsenic that may be tracked into households from CCA deck surfaces and nearby soils.


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Evaluate exposure and risks to the environment and people during the disposal of

CCA-treated wood. Risks to people who work within the disposal sector should be evaluated. This includes workers at construction and demolition processing facilities. Exposures should be evaluated among mulch workers and homeowners who spread the mulch on their yards. Risks should also be evaluated when CCA-treated wood is inadvertently burned, by people who are unfamiliar with the composition of the wood, and during house fires. The risks to firemen should be evaluated when they work to extinguish fires on structures containing CCA-treated wood.

Research and funds are needed to develop and implement risk management strategies that are based upon best management practices. Stronger efforts are needed in educating retail store staff and consumers concerning the proper handling and disposal of the wood. Methods are needed to remediate soil after CCA treated structures are removed. Research is needed on coatings as a means to minimize exposures and leaching during in-service use. Coating work should also focus on the effects of iron oxides within the coating formulation and the impacts of surface preparations prior to addition of the coatings.


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Release of Preservatives to the Environment

Please Rank from 1 to 6 with 1 receiving the highest priority Rank Research Item Research should focus on identifying critical targets and goals for wood preservative

chemical releases and disposal. The allowable concentration or mass of the release from treated wood products needs to be defined. Research should be very specific concerning the particular type of preservative treated wood and research should clearly identify the system to be impacted (freshwater, soil, etc…). For disposal, research is needed to determine if the appropriate disposal technology should focus on concentrating the wood preservative metals and removing them from the environment or diluting the metal to below a threshold level. Research should be initiated to determine the appropriate threshold level for various disposal scenarios. Releases from preservative treated wood should be evaluated in the context of other industries. Is the arsenic, chromium, and copper released from CCA large or small in terms of releases from other products?

Research is needed to identify new more environmentally-friendly alternative chemicals including purely organic chemical wood preservatives (e.g. resins, polymers, wood extractives, and others). These alternatives should be evaluated through a life-cycle analysis to estimate the true costs and environmental benefits associated with these non-metallic alternatives as opposed to the copper-based preservatives. Toxicological studies should be conducted for the new organic-based wood preservatives. The impacts of the primary chemical plus its breakdown products should be evaluated for the purely organic chemical wood preservatives of the future.


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The mechanisms of chemical releases from preservative treated wood should be

evaluated further. Fixation of CCA versus that of the arsenic-free alternatives should be investigated. For the existing arsenic-free alternatives, research should focus on the copper and on the organic co-biocides and possible break-down products of the organic co-biocides. Guidelines are needed to assess impacts from the organic co-biocides. Standardized methods should be developed that minimize the releases from the arsenic-free alternatives. Coatings should be evaluated further as a means of minimizing leachability and dislodgeability. Chemical releases from the wood should be modeled in an effort to assess long term impacts. Research should include an evaluation of OECD criteria (Organization for Economic Co-operation and Development). Accelerated testing methodologies should be developed to evaluate releases over the long term. Existing structures and test plots, which have already been in the environment for long periods of time, should be evaluated to estimate leaching rates. Work is needed to evaluate the impacts of pressure washing and the addition of brighteners on the release of chemicals. Speciation of the metals should be examined given that metal toxicity is largely a function of species. Research should also focus on the release of chemicals from preservative treated wood after the wood has been disposed, including the releases during landfill disposal (C&D and MSW) and when incorporated inadvertently into mulch. Efforts should focus on quantifying the acceptable levels of releases of the new organic co-biocides associated with the alternatives to CCA.

The mechanisms of chemical releases from soils impacted by preservative treated wood should be evaluated further. Research should focus on evaluating the fate and behavior of the chemicals in soil including, loss rates, bioavailability, and transformation of As, Cr, and Cu. Releases as a function of different soil properties should be evaluated. Research should focus on the movement of the chemicals through the vadose zone to determine whether or not these chemicals can impacts groundwater. The impacts of soil contamination on the flora and fauna of ecosystems should be evaluated further. Soil remediation technologies including phytoremediation should be also evaluated.

The dynamics of metals releases in water should be evaluated, in particular with respect to the copper releases. What is the aquatic impact of copper releases? Are these impacts significant within waterways lined with docks? Under what conditions will the copper be complexed and bound to sediments thereby reducing the bioavailability of this metal? An emphasis of this research should be placed on evaluating freshwater impacts since this is where the impacts of the new copper based alternatives would be greatest.

Research should focus on possible gaseous releases. Microbes are known to convert arsenic to volatile forms. Can such microbes transform the arsenic from the wood preservative to the gaseous form? Can arsenic be converted to arsine gas in landfill environments? Can gaseous arsenic be released from a landfill in volatile forms other than arsine gas?

*********end of ballot**********


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SECTION V: RESULTS FROM THE VOTE

The ballot was sent to conference participants via email on April 14, 2004. The due date for return of the ballot was April 26, 2004. A total of 28 ballots were returned, which corresponds to a 19% response rate. The results from the vote are provided below. Please refer to the voting ballot (Section IV) for details concerning the specific verbage used to describe each research priority. Research priorities with lower numbers (closer to 1) are considered to represent a higher priority by those who voted. Results of the ballot indicate that evaluating the behavior of treated wood within landfills is the highest research priority within the “disposal, reuse, and recycling” topic area. This research priority was closely followed by evaluating alternative disposal strategies. Within the “exposure and risk assessment” topic area evaluating the exposures to people during in-service use represented the highest priority, followed by evaluating risks to the the environment during in-service use. The highest priority within the “release of preservatives to the environment” topic area was identification of new more environmentally friendly alternative chemicals. This was closely followed by evaluating the releases from the wood.


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Table 2: Results from the “Research Priorities” Vote held as part of the “Environmental

Impacts of Preservative Treated Wood” Conference

environmental impacts of preservative-treated wood conference... · environmental impacts of...

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