chlorinated organic pollutants in soil and groundwater at ...145308/fulltext01.pdf · 5.1...

Chlorinated Organic Pollutants in Soil and Groundwater at Chlorophenol-Contaminated

Sawmill Sites

Ylva Persson

Akademisk avhandling

som med vederbörligt tillstånd av rektorsämbetet vid Umeå Universitet för avläggande av filosofie doktorsexamen i kemi med inriktning mot miljökemi vid Teknisk-Naturvetenskapliga fakulteten, framlägges till

offentligt försvar vid Kemiska Institutionen, hörsal KB3B1, KBC-huset, fredagen den 23 februari, 2007, klockan 10.00. Avhandlingen kommer

att försvaras på engelska.

Fakultetsopponent: Docent Jaana Koistinen, Department of Environmental Health, National Public Health Institute, Kuopio,

Finland

Department of Chemistry, Environmental Chemistry Umeå University

Umeå 2007

UMEÅ UNIVERSITY DOCTORAL DISSERTATION Department of Chemistry SE-901 87 Umeå University February 2007 Ylva Persson

Chlorinated Organic Pollutants in Soil and Groundwater at Chlorophenol-Contaminated Sawmill Sites

Abstract Mixtures of chlorinated organic pollutants can be found in the soils at chlorophenol-contaminated sawmill, including (inter alia) polychlorinated phenols (CPs), phenoxyphenols (PCPPs), diphenyl ethers (PCDEs), dibenzofurans (PCDFs) and dioxins (PCDDs). These hydrophobic compounds have low water solubility and hence low mobility as truly dissolved compounds. However, they may migrate through the soil at significant rates via co-transport with dissolved organic matter (DOM) and colloids of fine, waterborne particulate matter. In the work underlying this thesis the distribution of chlorinated hydrophobic pollutants between these two mobile fractions in soil samples from five sawmill sites was studied Soils at five sites at which CPs were formerly used were characterized, and found to have complex profiles of chlorinated hydrophobic pollutants. CPs, PCPPs, PCDEs and PCDD/Fs were present at up to ppm-levels. Furthermore, the relative proportions of the pollutants differed from their relative proportions in the preservatives used at the sites, indicating that they have been transported from, and/or degraded in, the soil at different rates. These organic pollutants have low water solubility and strong affinity for soil organic matter (SOM). The importance of SOM for the fate of CPs, PCPPs, PCDEs, PCDFs and PCDDs in soil was investigated by examining the distribution of compounds between the mobile DOM and the immobile particulate organic matter (POM). The partitioning of CPs between DOM and POM was found to be approximately equal. However, the relative strength of association with POM of groups of chlorinated organic pollutants was positively correlated with their hydrophobicity, and thus increased in the order CP < PCPP < PCDE < PCDF < PCDD. Despite the weak association of PCDD/Fs with DOM our investigations found that considerable concentrations of these pollutants were bound to mobile fractions (DOM and colloids, >0.2 µm) in both a groundwater analysis and a leaching test. CPs and PCPP were present at up to ppm- and ppb-levels, respectively, and PCDEs and PCDD/Fs at up to ppt-levels. The importance of transport in association with the mobile fraction (DOM and colloids) increased with increasing hydrophobicity e.g. PCDDs were almost entirely associated with fine particulate matter, while CPs were largely found in the water phase and only minor proportions were associated with colloids. Key words: Contaminated soil, hydrophobic organic contaminant, preservation, mobility, colloid, dissolved organic matter, particulate organic matter, groundwater, equilibrium column test, chlorophenol, chlorinated phenoxyphenol, chlorinated diphenyl ether, chlorinated dibenzofuran, chlorinated dibenzo-p-dioxin Language: English ISBN: 978-91-7264-251-5 Number of pages: 50 + 5 Papers

Chlorinated Organic Pollutants in Soil and Groundwater at Chlorophenol-Contaminated

Sawmill Sites

Ylva Persson

UMEÅ UNIVERSITY Department of Chemistry, Environmental Chemistry

Umeå 2007

Department of Chemistry, Environmental Chemistry Umeå University SE-901 87 Umeå, Sweden

Copyright © 2007 by Ylva Persson

ISBN 978-91-7264-251-5 Printed in Sweden by VMC, KBC, Umeå University, Umeå 2007

i

TABLE OF CONTENTS List of papers........................................................................................................................... ii List of abbreviations ............................................................................................................... iii

1. INTRODUCTION...................................................................................................1 2. CHLORINATED SAWMILL POLLUTANTS ....................................................4

2.1 CHLOROPHENOLS .................................................................................................6 2.2 CHLORINATED PHENOXYPHENOLS ......................................................................7 2.3 CHLORINATED DIPHENYL ETHERS .....................................................................10 2.4 CHLORINATED DIBENZOFURANS AND DIBENZO-P-DIOXINS ..............................12

3. SAMPLING, EXPERIMENTAL SETUP AND CHEMICAL ANALYSIS ....16 3.1 SOIL SAMPLING ...................................................................................................16 3.2 FRACTIONATION OF DISSOLVED AND PARTICULATE ORGANIC MATTER ............17 3.3 EQUILIBRIUM LEACHING TEST ............................................................................18 3.4 GROUNDWATER SAMPLING.................................................................................19 3.5 CHARACTERIZATION OF SOIL ORGANIC MATTER AND COLLOIDAL PARTICLES...19 3.6 LABORATORY PROCEDURE AND INSTRUMENTAL ANALYSIS ................................21

3.6.1 Clean-up of phenolic compounds and neutral compounds ............................................... 22 3.6.2 Instrumental analyses ................................................................................................... 23

4. PARTITIONING OF POLLUTANTS TO SOIL ORGANIC MATTER.......26 5. WATERBORNE TRANSPORT OF SAWMILL POLLUTANTS FROM CONTAMINATED SOILS.......................................................................................31

5.1 DISTRIBUTION OF CHLORINATED COMPOUNDS IN GROUNDWATER...................32 5.2 ESTIMATION OF MOBILITY FROM LEACHING TESTS ............................................35

6. CONCLUSIONS AND FUTURE PERSPECTIVES ........................................38 SUMMARY IN SWEDISH........................................................................................39 ACKNOWLEDGMENT ...........................................................................................40 7. REFERENCES ......................................................................................................42

ii

List of papers This thesis is based on the following papers, which are referred to in the text by the respective Roman numerals. I. Ylva Persson, Staffan Lundstedt, Lars Öberg, Mats Tysklind. 2007.

Levels of chlorinated compounds (CPs, PCPPs, PCDEs, PCDFs and PCDDs) in soils at contaminated sawmill sites in Sweden. Chemosphere 66 (2), 234-242

II Sofia Frankki, Ylva Persson, Mats Tysklind, Ulf Skyllberg. 2006. Partitioning of CPs, PCDEs and PCDD/Fs between dissolved and particulate natural organic matter, in a contaminated soil. Environmental Science and Technology 40, 6668-6673.

III Sofia Frankki, Ylva Persson, Andrei Shchukarev, Mats Tysklind, Ulf Skyllberg. 2006. Partitioning of chloroaromatic compounds between the aqueous phase and dissolved and particulate soil organic matter at chlorophenol contaminated sites. Environmental Pollution, in press,

IV Ylva Persson, Andrei Shchukarev, Lars Öberg, Mats Tysklind. Dioxins, chlorophenols and other chlorinated organic pollutants in colloidal and water fractions of groundwater from a contaminated sawmill site. Submitted for publication

V Ylva Persson, Kristian Hemström, Lars Öberg, Mats Tysklind and Anja Enell. Use of a column leaching test to study the mobility of chlorinated HOCs from a contaminated soil and the distribution of compounds between soluble and colloid phases. Manuscript

Published papers are reproduced with kind permission from Elsevier Science (Papers I and III) and the American Chemical Society (Paper II).

iii

List of abbreviations ATP Adenosine triphosphate BC Black carbon CP Chlorinated phenol DCXX Decachlorinated compound DOM Dissolved organic matter d.w. Dry weight FNU Formazin nephelometric unit, turbidity measured at a

wavelength of 860 nm GC Gas chromatography HOC Hydrophobic organic contaminant HpCXX Heptachlorinated compound HxCXX Hexachlorinated compound IS Internal standard KDOC Partitioning coefficient to dissolved organic carbon KOC Partitioning coefficient to organic carbon KOW Octanol-water partitioning coefficient KPOC Partitioning coefficient to particulate organic carbon LOI Loss on ignition L/S Liquid to solid ratio l.w. Lipid weight MS Mass spectrometry NoCXX Nonachlorinated compound OCXX Octachlorinated compound OM Organic matter PAH Polycyclic aromatic hydrocarbon PCB Polychlorinated biphenyl ether PCDD Polychlorinated dibenzo-p-dioxin PCDE Polychlorinated diphenyl ether PCDF Polychlorinated dibenzofuran PCPP Polychlorinated phenoxyphenol PeCXX Pentachlorinated compound POM Particulate organic matter RS Recovery standard SIR Selected ion recording SOM Soil organic matter TeCXX Tetrachlorinated compound TEF Toxic equivalence factor TrCXX Trichlorinated compound TSS Total suspended solid

iv

WHO-TEQ Toxic equivalence according to the World Health Organization

XPS X-ray photoelectron spectroscopy

1. Introduction

1

1. Introduction Rapid industrialization, starting at the end of the 19th century, combined with a lack of environmental awareness and/or legislation, resulted in the release of increasing amounts of potentially harmful industrial products and by-products into the Swedish environment until the latter half of the 20th century. Growing environmental awareness and legislation in the 1960´s to 1980´s in Sweden and elsewhere led to a decrease in the dispersion of pollutants. However, many areas at or near industrial sites have contaminated soils and sediments as a consequence of the industrial processes. These contaminated soils are potential secondary sources of harmful compounds that could be released into the surrounding local environment if, for example, they migrate into groundwater supplies1, of people living in the vicinity of a contaminated site2 or regional sinks, e.g. Lake Baikal3. Contaminated soils are often associated with high concentrations and complex mixtures of environmental pollutants. In Sweden, and other countries, contaminated sites are prioritized for remediation to reduce the exposure of humans and the environment to hazardous compounds. As part of official efforts to create and maintain a “Non-toxic environment” the Swedish Environmental Protection Agency (S-EPA) has inventoried 80 000 polluted sites in Sweden 4. Figure 1 shows numbers of contaminated sites (estimated and identified) according to the Swedish risk assessment program MIFO (methodology for inventory of contaminated sites)4, which is used to categorise contaminated sites into four classes according to the risk they pose to humans and the environment. As shown in Figure 1, approximately 20%, or 16 000 of the identified contaminated sites in Sweden are in the highest risk classes (1 and 2). In Sweden the highest priority sites (class 1) are often sites that were formerly associated with activities of the metallurgical, pulp, paper and chloralkali industries, while many sites in the second highest priority class (class 2) are at sites such as gas works, tanneries and sawmills.5.

1. Introduction

2

0

30000

60000

90000

Estimated Identified Classified inMIFO

num

ber o

f site

s Class 1Class 2Class 3Class 4Other

Figure 1. Estimated and identified numbers of contaminated sites in Sweden4. Sites posing the highest potential risks are given the highest priority for remediation classification (Class 1). Class 4 sites pose the lowest risk. This thesis focuses on sawmill sites contaminated by chlorinated organic compounds. Chlorinated hydrocarbons have been widely used in many industrial processes, and they include some of the highest priority pollutants, e.g. dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). PCDD/Fs are formed in various processes, often those where temperatures are high and chlorine is present, e.g. in combustion in municipal solid waste incinerators, metallurgic processes, bleaching of pulp using chlorine gas and industrial chemical systems6-8. In the chemical industry the production of chlorophenols (CP) and chlorinated phenoxyacetic acids (2,4-D and 2,4,5-T) has been shown to result in the production of PCDD/Fs9 as by-products. Apart from PCDD/Fs the production of CPs gives rise to a number of other chlorinated by-products such as polychlorinated phenoxyphenols (PCPPs), polychlorinated dihydroxybiphenyls, polychlorinated diphenylethers (PCDEs) and polychlorinated phenoxyanisoles10,11. Thus, sites where chlorophenols have been used may have complex contamination profiles, with diverse chlorinated aromatic compounds. Chlorophenols have been widely used as fungicides in the sawmill and textile industries, and rice paddies6,12,13. The S-EPA has estimated that chlorophenols have been used at 400-500 sawmill sites in Sweden14. In Sweden, chlorophenols, for example Ky-5, Dowicide G, Santobrite, BP Hylosan, were used as a preservatives to protect sawn timber against blue stain fungus until they were banned in 1978. They were often applied by dipping sawn timber into a water-based 1-5% chlorophenol solution10. Alternatively, the timber was sometimes applied with a solution of

1. Introduction

3

chlorophenols in an organic solvent. In the studies underlying this thesis five former sawmill sites with a historic use of chlorophenols were examined, at: Byske, Hillringsberg, Luleå, Sikeå and Umeå (referred to in Papers I and III as Öbacka). The location of the sites is shown on the map in Figure 2. Between the 1940s to the 1970s chlorophenols were used as to treat wood either by dipping or spraying at all of these sites.

Sikeå

Luleå

Byske

UmeåHillringsberg

Sikeå

Luleå

Byske

UmeåHillringsberg

Sweden

Figure 2. Locations of the investigated sawmill sites. Figure 3 summarises the work involved in the five studies this thesis is based upon, all of which were concerned with chloroaromatic compounds and their distribution in soil and groundwater. The compounds were: CPs, PCPPs, PCDEs, PCDFs and PCDDs (molecular structures shown in Figure 4, Chapter 2). The studies had three main objectives. The first was to characterize the composition and distributions of chlorinated compounds at sawmill sites by analysing soil samples from the five sites shown in Figure 2 (Paper I). The second was to study the partitioning of chlorinated compounds in soil organic matter, which can strongly affect the fate of hydrophobic contaminants (HOCs) (Papers II and III). In these studies soil samples from Hillringsberg, Sikeå and Umeå were used. The third was to evaluate the transport of chlorinated compounds by analysing groundwater from the Umeå site (Paper IV) and by leaching tests of contaminated soil samples from the Luleå site (Paper V). The chlorinated compounds of most interest in these two studies were those associated with fine particulate matter, colloids.

Paper I. Composition of chloroaromatic compounds

Paper V. Vertical distribution and leachability of chlorinated compounds in soil

Paper II and III. Partitioning of chlorinated compounds to DOM and POM

Groundwater surfacePaper IV. Partitioning between particulate and dissolved fractions of groundwater









Figure 3. Overview of the studies the thesis is based upon.

2. Chlorinated sawmill pollutants

4

2. Chlorinated sawmill pollutants The structures and properties of CPs, PCPPs, PCDEs, PCDFs and PCDDs are shown in Figure 4 and Table 1. The relative proportions of chlorinated compounds, and groups of compounds, varied between different chlorophenol preservatives depending on the production processes applied, which can be essentially divided into chlorination of phenols (to produce lower chlorinated phenols) or hydroxylation of hexachlorobenzene (e.g. to produce PCP)15.

OHCl x

a)

OCl x

Cl y

c)O

Cl Clx y

Cl yO

OH

Cl x

b)

Cl x Cl yO

Oe)d)

Figure 4. Molecular structures of (a) CPs, (b) PCPPs, (c) PCDEs, (d) PCDFs and (e) PCDDs. Five, nine, ten, and eight carbon atoms that can be chlorinated (x, y) in the CPs, PCPPs, PCDEs, PCDFs and PCDDs, respectively. Table 1 summarizes ranges of selected properties (of congeners with one chlorine atom to the maximum number possible) for each of five groups of chlorinated compounds. With increasing molecular weight and degree of chlorination their hydrophobicity increases. The CPs are a relatively water soluble class, and even the least soluble of the chlorophenols, pentachlorophenol, has a water solubility of 5 mg/L16. PCDDs constitute compounds with a very low solubility in water, OCDD having a water solubility of 7 pg/L16. Their large ranges of physico-chemical properties make the compounds especially interesting to study from a mobility perspective. The hydroxyl group of PCPPs can be located at ortho-, meta- or para-positions, so theoretically up to 837 congeners could be present. However, the numbers of the congeners present in the preservatives and the environment are probably much lower.


5

Table 1. Overview of properties of congeners with one chlorine atom to the maximum possible for each considered group of chlorinated aromatic compounds (CP=5, PCPP=9, PCDE=10, PCDF=8, PCDD=8) 16,17. Compound Molecular

weight (g/mol) Number of congeners

Water solubility (mg/L)

Log Kow

CP 128 – 266 19 2.9×104 - 5 0.8-5.2PCPP 220 – 496 837 5.6 - 1×10-4 4.7-8.5PCDE 204 – 514 209 59 - 5×10-8 4.1-8.2PCDF 202 – 443 135 2.1×10-1 – 1.4×10-7 5.8-13.9PCDD 218 – 459 75 3.2×10-2 –7.4×10-8 5.4-13.1 The chemical properties of compounds affect their distribution in the environment. The preservatives applied at the examined sites consisted of CPs and the order of abundance of by-products in them was (approximately) PCPPs>> PCDEs ≈ PCDDs ≈ PCDFs10. In the evaluations described in Paper I two commonly used preservatives were analysed as well as the soil samples for comparative purposes. The preservatives were Ky-5 (in which 2,3,4,6-TeCP was the main congener) and Dowicide G, representing TeCP and PeCP preservatives, respectively. Both of these technical products consisted of sodium chlorophenates. However, during the course of time the relative proportions of chloroaromatic compounds in the contaminated soil have changed due to the differences in their properties (and hence interactions with the soil), as shown in Paper I and Figure 5. Most notably, hydrophobicity-related changes in the proportions of the compounds in the soil samples relative to their proportion in the preservatives have occurred. For example, PCDFs constituted 0.003% of Ky-5 and 0.02% of Dowicide G, but between 1% and 6% of the chloroaromatic compounds in soil samples from the Hillringsberg, Luleå, Sikeå and Umeå sites.

0

25

50

75

100

Byske Luleå Hillringsberg Sikeå Umeå CP-Preservative

%

CPPCPPPCDEPCDFPCDD

Figure 5. Relative proportions of chloroaromatic compounds in soil samples and a CP preservative, Dowicide G.


6

The following chapter provides an introduction to the studied compounds, including a brief introduction to the toxicity of the compounds and their distribution in biota for example fish and birds, as well as human exposure to them. However, main foci of the chapter are the distribution and composition of CPs, PCPPs, PCDEs and PCDD/Fs in soils and sediments.

2.1 Chlorophenols Chlorophenols were widely used since 1936 when pentachlorophenol (PeCP) was introduced as a commercial product18. The structure and selected properties of chlorophenols are shown in figure 4a and Table 1. CPs had useful properties, and were widely used, as fungicides and herbicides in both agricultural and industrial processes notably as preservatives of textile, wood and leather products, and as herbicides in rice paddies in Asia18. The most widely used CP congener was PeCP, but TrCPs and TeCPs were also used in various applications. 2,4,5-TrCP was mostly used as a herbicide, while congeners of TeCP and PeCP were used as fungicides to preserve wood. Furthermore, lower chlorinated CPs were also used in the production of phenoxy acids such as 2,4-D and 2,4,5-T18. These two compounds were included in a technical product, Agent Orange, which was used as a herbicide and defoliant during the 1960s in the Vietnam War, leading to large areas being contaminated with PCDD/Fs19. The toxic effect of CPs is related to interference with the lipid cell membranes of organisms. Association of chlorophenols with the mitochondrial membrane disrupts cells’ energy metabolism18. The widespread use of CPs has led to continuous exposure of humans to CPs. PeCP is one of the most common phenolic compounds found in human blood, and plasma from fish20,21. However, PeCP in blood and tissues may also originate from hexachlorobenzene, since PeCP is a metabolite of hexachlorobenzene22. CPs have been found in many environmental matrixes including soil, sediments, groundwater, surface water and air23. Paper I reports the distribution of CPs in samples of soils from five different sawmill sites in Sweden. As expected, many of the samples investigated contained low concentrations of CPs due to their comparatively high water solubility (Table 1). Some of these sites were “hot spots” with high concentrations of the contaminants, e.g. those at Byske, Luleå and Öbacka. The concentrations of CPs at the sites ranged from 0.3 to 4 800 mg/kg dry


7

weight (d.w.). The dominating congeners in the soil samples were 2,3,4,6-TeCP and PCP. The wood preservatives usually used at the sites consisted of either mixtures of 2,4,6-TrCP, 2,3,4,6-TeCP and PeCP or pure PeCP10,18. Paper I also reports contents of preservatives dominated by 2,3,4,6-TeCP (Ky-5) and PCP (Dowicide G). The use of mixtures with TeCP were common in Sweden and Finland10,24. In contrast, PeCP accounted for the largest amount of chlorophenols produced worldwide for both wood preservation and other applications18. Figure 6 presents differences in CP composition in soil samples between two sawmill sites where a 2,3,4,6-TeCP preservative (Luleå) and a PeCP preservative (Byske) were used. The relative proportions of organochlorines at Byske clearly correspond with use of PCP, while those at Luleå have similarities to the 2,3,4,6-TeCP preservative used; 2,3,4,6-TeCP accounted for 73% of the CPs, and PCP 20%.

0

25

50

75

100

Luleå Ky-5 Byske Dowicide G

%

2,4,6-TrCP2,3,4,6-TeCP2,3,4,5-TeCPPeCP

Figure 6. Relative proportions of CPs in soil samples contaminated from a 2,3,4,6-TeCP preservative and a PeCP preservative. Only the main congeners are shown. Several minor congeners of CPs were also present.

Apart from the samples from Byske and one sample from Luleå, which were highly contaminated with CPs (2 200 to 4 800 mg/kg d.w.), the CP contents of the other soil samples (0.1 to 66 mg/kg d.w.) indicated that they had been largely washed out from the soil. The site at Byske had been covered with a roof and, hence, much of the contaminant had remained, while the high-level sample from Luleå was collected close to an old barrel of preservative that was found during remediation. Both these samples had a composition of chloroaromatic compounds (CPs, PCPPs, PCDEs, PCDFs and PCDDs) similar to the preservatives.

2.2 Chlorinated phenoxyphenols Figure 4b and Table 1 show the structure and selected properties of PCPPs. PCPPs are found with the hydroxyl group positioned in ortho-, meta- or para-position and those with ortho hydroxyl group can be transformed to PCDDs by ring closure25. Due to this possible ring closure the ortho-PCPPs are also called predioxins. Ezerskis and Jusys26


8

studied the metabolites formed from chlorophenols using electro polymerization in an alkaline solution, and found that PCPPs were formed, as well as trimeric structures. Similar results were obtained by Onodera et al.27 in experiments in which water containing phenol and chlorophenols was treated with hypochlorite, and the number of chorines in the resulting PCPPs depended on the chlorophenols used: TrCPs, TeCPs and PCPs gave rise to PCPPs with five to nine chlorines. The homologues with six to eight chlorines were the most common in the soil samples and two preservatives described in Paper I. Little information on PCPPs is available in the literature, and our knowledge of the distribution and toxicity of PCPPs is limited. However, one PCPP, 5-chloro-2-(2,4-dichlorophenoxy)phenol (Triclosan), is used as a bactericide. The immune toxicities of different fractions of technical grade pentachlorophenol have been studied by Isaacson Kerkvliet et al.28. Unfractionated technical grade PeCP caused a reduction in the immune responses of mice. However, neither a fraction containing PCPPs and PCDEs, nor purified PCPP extracts, at concentrations comparable to the tested preservative concentrations (dose levels, 10 mg/kg body weight,) caused any suppression of the immune response. The decreases in immune response induced by chlorophenol preservatives were solely related to the fraction containing PCDD/Fs. On the other hand, purified PCPPs with concentrations higher than relevant for chlorophenol preservatives caused reductions in immune responses at dose exceeding 50 mg PCPPs/kg body weight. A study by Koistinen29 examined the distribution of PCPPs in samples of mussels (Anodonta piscinalis) from a contaminated river and pike (Esocidae lucius) from a polluted lake in Finland. PCPPs were found in the mussels with relative proportions resembling those in the chlorophenol preservative Ky-5, but with larger contributions of TeCPPs and PeCPPs than in Ky-5 (25% compared to 0.4% for TeCPPs and 40% compared to 30% for PeCPPs). In the pike only residual amounts of OCPPs were found. In contrast, PCPPs (mainly OCPPs and NoCPPs) were found in plasma from salmon (Salmo salar) caught in River Dalälven, Sweden, in work related to a master’s thesis published by Stockholm University30. In the Finnish samples analysed by Koistinen29 the preservative Ky-5 was concluded to be the source, but in the Swedish samples the source was unknown. The samples from both Sweden and Finland contained detectable levels of a number of congeners of each homologue; the salmon plasma contained one HxCPP, two HpCPPs, five OCPPs and


9

two NoCPPs30, whereas the mussels contained one TeCPP, five PeCPPs, four HxCPPs and two HpCPPs29. The presence of higher chlorinated PCPPs in the Swedish sample indicates that the source could be PeCP. However, our knowledge of the uptake and metabolism of PCPPs in organisms is limited, and mussels are known to largely reflect the composition of contaminants in the water phase, with only minor metabolic changes. Conclusions regarding the source of PCPPs in fish based on the relative proportions of PCPPs in mussels are therefore somewhat uncertain. PCPPs are the most abundant by-products in CP preservatives15, as shown in Paper I and today, more than 30 years after the use of chlorophenol preservatives was banned in Sweden, PCPPs in soil samples constitute a large fraction (up to 90%) of the chlorinated compounds. The soil samples contained concentrations between 0.5 and 940 mg/kg d.w. Figure 7 shows the distribution of PCPPs in two soil samples reported in Paper I. The Byske sample contained large amounts of HpCPPs, OCPPs and NoCPPs, while the PCPP profiles in the other soil samples were dominated by HpCPPs (as shown in Figure 7 for a soil sample from Luleå). Soil samples analysed in a study by Kitunen et al.24 had approximately equal amounts of HxCPPs and HpCPPs and a small amount of OCPPs. In contrast, the soil samples contaminated by the use of TeCPs analysed in the studies underlying this thesis contained a larger proportion of HpCPPs, as shown in Figure 7 (Luleå). Similarly, more HpCPPs than HxCPPs were found in a sediment sample collected near a sawmill site in Finland29. The probable sources of the contaminants in both the sediment samples and the soil samples from Luleå are TeCP preservatives. The conclusion is that the composition of PCPPs in TeCP may have varied, but HxCPPs and HpCPPs were the dominant homologues. In a study by Gaus et al.31 PCDD/Fs and PCPPs were found in the two contaminated soil samples from Queensland, Australia. The main PCPP were found to be NoCPPs. The profiles included detectable levels of two NoCPPs, three OCPPs and HpCPPs with concentrations up to 0.04 mg/kg d.w. of each NoCPPs and OCPPs31. The source of the PCPPs was believed to be PeCP from a pineapple farm. Comparison of these PCPP profiles with the profiles from Dowicide G and the sites where PeCP was used described in Paper I indicate that PeCP was the probable source of PCPPs.


10

0

30

60

90

Byske Dowicide G Luleå Ky-5

%

PeCPP

HxCPP

HpCPP

OCPP

NoCPP

Figure 7. Relative proportions of homologue groups of penta- to nona PCPPs in soil samples from Byske and Luelå, and preservatives. In conclusion, the use of TeCP and PCP preservatives gave rise to distinct profiles, with the presence of OCPPs and NoCPPs typifying profiles where PCP were used, while HxCPPs and HpCPPs are typically present where TeCPs have been used. Both of these types of profiles were seen in samples analysed in the studies described in Paper I, and similar profiles have been observed in soil and sediment samples analysed by Gaus et al.31, Kitunen et al.24 and Koistinen et al.29.

2.3 Chlorinated diphenyl ethers Figure 4c and Table 1 show the structure and properties of PCDEs, which have one to ten chlorine atoms and a nomenclature following the numbering system of PCBs32. There has been limited industrial use of PCDEs although higher chlorinated PCDEs have been used in the electrical industry as heat exchange and hydraulic fluids since they have high thermostability and useful dielectric properties33. PCDEs have largely reached the environment through their presence as by-products in chlorophenol preservatives34,35. The toxicity of PCDEs has been investigated due to their structural similarities with PCDD/Fs and PCBs. However, unlike PCDD/Fs, the PCDEs do not adopt planar conformations as shown by Lyytikainen et al.36 and thus their properties are distinct in a number of ways. Several studies have concluded that PCDEs have low dioxin-like toxicity, such as limited capacity to induce the aryl hydrocarbon-receptor (AhR) and ethoxyresorufin-O-deethylase (EROD) activity 34,37. The non-planar structure of PCDEs may be the reason for their weak dioxin-like activity, as discussed in a PCDE review by Koistinen33. On the other hand, PCDEs have been reported to affect in the production of thyroid hormone and may be potential oestrogen inducers due to their structural resemblance to ortho-PCBs33.


11

Recently Bocio et al.38 assessed human exposure to PCDEs in Spain via various foodstuffs, including meat, fish, dairy products and vegetables. PCDEs were only detected in fish and shellfish, which contained mainly HxCDEs, and no congeners with less than four chlorine atoms were found. The estimated dietary intake was highest for men 51-65 year old, who were found to have a mean intake of 0.040 µg/day38. The corresponding human daily intake of PCBs (both dioxin-like and non-dioxin-like PCBs) was estimated to be 0.26 µg/day by Turci et al.39 in an Italian study. In conclusion, the human exposure of PCDEs is generally minor compared to exposure to PCBs, but due to our limited knowledge of the toxic effects of PCDEs their toxicity needs to be further investigated. Koistinen et al.40 found that pike (Esox lucius) from the river Kymijoki, contained significant levels of PCDEs; 706 µg/kg lipid weight (l.w.) and 677 µg/kg l.w. Furthermore, the PCDE profile in the fish had similarities to the sediments in the contaminated river, the major congeners being 2,2´,3,4´,5,6 / 2,2´,4,4´,5,5´ HxCDE (#147/153), 2,2´,4,4´,5,6´ HxCDE (#154), 2,2´,3,4,4´,6,6´ HpCDE (#184) and 2,2´,3,3´,4,4´,6,6´OCDE (#197). PCDEs have also been determined in fish from the Great Lakes, Canada, and the congener patterns found in them showed similarities with the patterns found in Finland, including relatively large proportions of HxCDE #153 and #15440,41. The concentrations ranged between 35-300 µg/kg in fish from Lake Ontario and Lake Erie, these two lakes containing the highest concentrations of the Great Lakes 41. The presence of PCDEs in fish strongly indicates that PCDEs bioaccumulate. In additional studies by Koistinen et al.42,43 the levels of PCDEs were determined in breast muscle of white-tailed sea eagles (Haliaeetus albicilla), ringed seals (Phoca hispida botnica) and grey seals (Halichoerus grypus) from the Baltic Sea. Levels of detected PCDEs ranged from 7 to 13 000 µg/kg l.w. in the eagles and 40-370 µg/kg l.w. in the seals. The presence of PCDEs in organisms at the upper part of a food chains, i.e. seals and eagles, indicate that PCDEs are biomagnified. In the soil samples discussed in Paper I the concentrations of PCDEs ranged from <38 to 6 800 µg/kg d.w. Figure 8 shows the relative proportions of PCDE homologues in two of the soils and the preservatives Ky-5 and Dowicide G. Previous studies have shown the main PCDEs present in chlorophenol preservatives to be the higher chlorinated HpCDEs, OCDEs and NoCDEs44. Results presented in Paper I showed reasonable agreement with these literature data. The


12

relative proportions of PCDEs in the PeCP preservatives and the soil samples contaminated by PeCP preservatives correlated well, with a large amount of OCDE followed by HpCDE and NoCDE (Byske). Soil samples contaminated by use of TeCP (from Luelå) showed a weaker correlation with the Ky-5 preservative, having larger proportions of OCDE and NoCDE than the preservative. The main congeners in all samples were the 22´33´44´56´OCDE (#196) and 22´33´44´66´OCDE (#197). For comparison, Koistinen et al.40 found the main PCDEs in sediments from the Kymijoki River to be #197 (octa), #184 (hepta) and #154 (hexa), with concentrations ranging from 130 to 550 µg/kg dw. The profiles in these sediment samples show similarities to those of soil samples analysed in the studies described in Paper I.

0

20

40

60

80


%

PeCDEHxCDEHpCDEOCDENoCDE

Figure 8. Relative proportions of homologue groups of penta- to nona PCDEs in soil samples and corresponding preservatives. The differences between sites contaminated by the TeCP and PeCP preservative were not as distinctive as for PCPPs and PCDD/Fs (Chapter 2.4), but higher relative abundances of HpCDE and OCDE were found at TeCP-contaminated sites and higher relative abundances of OCDEs and NoCDEs at PeCP-contaminated sites.

2.4 Chlorinated dibenzofurans and dibenzo-p-dioxins The structures of PCDFs and PCDDs are shown in Figures 4d and 4e, respectively, and Table 1 summarizes (inter alia) the range of water solubilities of tetra- to octa-chlorinated PCDD/Fs. Their persistence and hydrophobicity increases with increases in their number of chlorine atoms. PCDD/Fs were detected in chlorinated chemical products the beginning of the 1970s45. PCDD/Fs, unlike many pollutants, have never been produced intentionally. However, they are created in many processes, as mentioned in Chapter 1. Thus, the presence of PCDD/Fs in chlorinated chemicals, e.g. chlorophenol preservatives, have been suggested to be major sources (together with municipal solid waste incineration) of PCDD/Fs in the environment6,7.


13

PCDD/Fs have been shown to have a wide spectrum of toxic effects. In humans an acute effect of exposure to PCDD/Fs is chloracne46,47. However, most effects are not acute but chronic or long-term, such as teratogenicity, carcinogenicity, reproductive problems and lymphoid disturbances46. PCDD/Fs with chlorine atoms in the 2,3,7 and 8 positions have the most pronounced toxic properties, and the vast majority of toxicity data reported for PCDD/Fs relates to the effects of the 17 congeners with chlorines at these positions. 2,3,7,8-TCDD is the most toxic congener. To relate the toxicity of different congeners a system of Toxic Equivalence Factors (TEF) has been introduced. Each of the congeners with a 2,3,7,8 substitution pattern has been given a TEF value relating its toxicity to that of 2,3,7,8-TCDD48. The TEF concept of the World Health Organization (WHO-TEQ) was originally intended for assessments of risks posed by oral consumption of the compounds 48, but it is has also been extensively used in other contexts, e.g. risk assessments of contaminated soils. As discussed in van den Berg et al.48 calculations of WHO-TEQs in contaminated soils have little toxicological relevance due to the limited bioavailability of contaminants sorbed in soil. However, the wide use of WHO-TEQs when presenting concentrations of PCDD/Fs in soil and sediment samples enables the results of different studies to be readily compared; hence the WHO-TEQ concept was used in Paper I and in the discussions within this thesis. Sawmill workers were exposed to both the chlorophenols and the by-products included in the preservatives. A study by Hertzman et al.49 found a positive correlation between handling chlorophenate and the incidence of cancer (non-Hodgkins´s lymphoma) amongst sawmilll workers. However, there are inconsistent results in other studies, with indications of both correlations and a lack of correlation between cancer incidence and the use of chlorophenol in the sawmill industry49. Moreover, in an exposure assessment of residents living near a sawmill site where chlorophenols (and creosote) had been used Dahlgren et al.2 found that blood samples from the residents had elevated levels of PCDD/Fs, especially OCDD, which were present at levels ranging from 0.28 to 2.12 µg/kg (mean, 0.86 µg/kg, n=10), in comparison with a mean OCDD level of 0.33 µg/kg (n=200) in the general population2. One of the exposure routes was believed to be PCDD/Fs-containing dust in the houses, since PCDD/Fs were found in 20 of the 33 dust wipe samples collected from houses situated on the sawmill area2. The cited study showed that the risk of human exposure to PCDD/Fs was elevated near contaminated sawmill sites, and highlighted the importance of reducing the dust from such sites. However, the residents lived on or very close to


14

the contaminated site, and it is probably unusual for humans to be so highly exposed to contaminants from such sites. At Kuusankoski, situated by the River Kymijoki, Ky-5 was manufactured between 1940 and 1984. Soil, sediments and fish from the surrounding area, and areas near various sawmills in Finland, have been studied by several authors40,43,50. The cited studies have shown that PCDD/F concentrations are higher in these areas than in unaffected areas. In the sediment samples the concentrations ranged between 3-877 µg/kg d.w, and in a soil sample from Finland, contaminated by the use of Ky-5, in which only the PCDF were analysed, the PCDF concentration was 3 780 µg/kg d.w. The PCDD/F concentrations in the soil samples described in Paper I ranged between 20-53 000 µg/kg d.w. In comparison, soil samples from southern Vietnam contaminated by the use of Agent Orange showed concentrations from 11 to 1 800 µg/kg d.w19. Figure 9 displays differences found in two soil samples, from Byske and Luleå, arising from the use of PeCP- and TeCPs preservatives, respectively. In contrast to soil samples from Luleå and Sikeå the soil samples from Byske, Hillringsberg and Umeå showed a dominance of OCDD indicating use of PeCP, but at some sites the relative proportions of HpCDD/Fs and OCDD suggests use of both PeCP and TeCP preservatives.

0

30

60

90


%

TeCDFPeCDFHxCDFHpCDFOCDFTeCDDPeCDDHxCDDHpCDDOCDD

Figure 9. Relative proportions of PCDD/Fs in soil samples and preservatives. The soil samples from Luleå and Sikeå analysed in the studies reported in Paper I, which were probably contaminated by a TeCP preservative, showed a different PCDD/F profiles compared to those in the Ky-5 profile reported in Paper I and in previous Finnish studies of Ky-5 and sediments40,51. The profiles of the Finnish samples and Ky-5 (Figure 9) displayed a clear dominance of HpCDFs. In the soil samples, however, the HpCDDs were more abundant than HpCDFs. No explanation for


15

the differences in these patterns has been found to date. Despite the deviations, the preservative that was probably used was a 2,3,4,6-TeCP, as discussed in Paper I. Soil samples from Byske and Hillringsberg showed “typical” PeCP patterns dominated by OCDD, as shown in Figure 9, in accordance with literature data2,9. Paper I presented results from five chlorophenol-contaminated sawmill sites. The relative proportions and concentrations of PCDD/Fs at these sites are probable applicable to many of the estimated 500 such sites in Sweden since the soil samples included both soils with low soil organic matter (SOM) contents (Luleå, Byske) and soils with high SOM contents (Sikeå, Hillringsberg and Umeå). At Umeå the soil contained large amounts of sawmill residues and wood fibres, which is probably a common feature at sawmill sites. At Byske the CPs had been applied in an organic solvent, while at the other sites they were applied in an aqueous solution. PCDD/Fs are a high priority class of compound and there are vast numbers of potentially contaminated sawmill sites. This (in combination with the high concentrations of PCDD/Fs at such sites and the risk of their dispersal and consequent exposure of nearby residents) makes remediation of chlorophenol-contaminated sites, or limitation of the dispersal of the contaminants in them, important in order to minimise potential human exposure.

3. Sampling, experimental setup and chemical analysis

16


3.1 Soil sampling Some historical data and information about the studied sawmill sites are shown in Table 2. Soil from the contaminated sites was sampled in two ways: surface sampling and core drilling. The soil samples from Byske, Hillringsberg, Sikeå and Umeå analysed in the studies described in Papers I-III were surface samples. Each site addressed in Paper I was represented by three samples (except Sikeå). On each sampling occasions approximately 1 kg of soil was sampled and mechanically homogenised in a bucket. The soil samples from Hillringsberg, Sikeå and Umeå were sieved through a 2 mm sieve. The soils from Byske and Luleå which were sandy and homogenous in texture, were not sieved. The samples from Luleå described in Papers I and V were sampled by core drilling. Chlorinated compounds were extracted from 1-20 g subsamples of the soils. Despite the homogenization substantial heterogeneity was found in the profiles obtained from triplicate subsamples of soil samples from Hillringsberg, Luleå, Sikeå and Umeå. One way to avoid these problems would be to extract an even larger amount of soil, then make clean-up and fractionate small amounts of the resulting extracts. Table 2. Background information regarding the sawmill sites from which soil was sampled in the studies this thesis is based upon.

Sawmill site Byske Hillringsberg Luleå Sikeå Umeå Location 64°56’N,

21°12’E 59°32’N, 12°37’E

65°35’N, 22°03’E

64°9’N, 20°58’E

63°83’N, 20°27’E

CP usage 1970´s 1945-? 1961-1975 1964-1975 1960’s-1975 Type of preservative

PeCP solvent based)

PeCP (water based)

2,3,4,6-TeCP (water based)

2,3,4,6-TeCP (water based)

PeCP and/or 2,3,4,6-TeCP (water based)

Soil description

Sand, low in organic matter

Organic rich mineral soil

Sand, low in organic matter



LOIa (%) 1.4-2.7 5.3-9.7 0.4-2.6 14 4.6-52 Included in Paper

I I and III I and V I to III I to IV

a Loss on ignition The soil samples from Luleå were sandy, with soil organic matter (SOM) contents ranging from 0.4% to 3%, determined by loss on ignition (LOI).


17

The soils at the Byske site consisted of rather coarse sand with LOIs between 1.4% and 2.7%. At Hillringsberg and Sikeå the soils contained more silt and clay than those at Luleå and Byske, and their LOI were 5.3%-9.7% and 14%, respectively. The Umeå samples had the largest LOI values, 4.6% to 52%, of which a substantial amount was attributable to sawmill residues. At Byske, in contrast to the other four sites, the CPs had been applied in organic solvents.

3.2 Fractionation of dissolved and particulate organic matter In Papers II and III the distribution of chlorinated compounds between dissolved soil organic matter (DOM) and particulate soil organic matter (POM) was assessed. The studies were based on the assumption that most of the non-polar compounds in soil will be partitioned to SOM52. In support of this assumption, Schwarzenbach and Westall53 found a correlation between the sorption of non-polar compounds and SOM in soils with soil organic carbon contents exceeding 0.1%. Regarding the distribution of HOCs in soil, two pools can be recognised; the stationary POM fraction and the potentially mobile DOM fraction. The DOM fraction is defined as the organic matter that is soluble in water while the POM comprises organic matter that will negligibly dissolve in a water solution. In the studies described in Papers II and III the DOM was separated from POM by a glass fibre filter with a pore size of 0.7 µm. Thus, the POM was implicitly regarded as the SOM that did not pass through the 0.7 µm filter, while the DOM was regarded as the SOM that was in solution at pH 6.8 to 9.1 and passed through the filter. The POM and DOM fractions contain not only organic matter but also inorganic soil constituents, e.g. minerals and oxides so the results presented in Papers II and III were normalized against the amount of organic carbon present in the samples. Three of the soil samples (Sikeå, Hillringsberg and Umeå) analysed in the studies described in Paper I were also assessed in Papers II and III. These soils were chosen because they had high organic carbon contents (LOI values 14%, 10% and 42%, respectively). The DOM was extracted from the soil samples by raising the pH using sodium hydroxide, since increases in pH increase the water solubility of DOM and, thus, the amount of DOM in water solution. However, the amount of DOM in solution will then be greater than in the undisturbed soil-water solution. The distribution of the chlorinated compounds between DOM and POM was assumed to be unaffected by the enhanced DOM extraction.


18

3.3 Equilibrium leaching test As discussed in Chapter 3.2, HOCs are assumed to be mainly associated with organic matter in soil. In Paper V the contaminants released from soil in leaching tests was evaluated, since leaching of DOM and colloids of organic material from soil may facilitate the transport of HOCs. This colloid-associated transport of HOCs was studied using the leaching test illustrated in Figure 10. The leaching test was an equilibrium recirculation column test developed for determining equilibrium solute concentrations in soil and wastes contaminated with non-volatile organic contaminants54. The re-circulation increases the possibility that HOCs sorbed in the soil and HOCs dissolved in the water will fully equilibrate. The re-circulation of solutes also filters fine particulate matter mobilised by the flow of solute in a natural way, and results from the test have been suggested to include contributions from the naturally mobile colloids55. Increases in the amounts of particles and colloids in leaching tests arising from changes in variables such as increasing the flow rate could lead to an overestimation of potential transport rates of contaminants from the soil. In the leaching tests, soil from Luleå was used. This sandy soil contains a low amount of SOM (LOI 0.4%). The leaching tests were performed on two occasions, on each of which two parallel columns were used. On the first occasion the recommended flow velocities (approximately 20 ml/hour) recommended by Hansen et al.55 was applied. On the second occasion the effects of increasing the flow velocity to approximately 30 ml/hour were assessed. To obtain estimates of the amounts of particle that were mobilised during the leaching tests the leachates were filtered through 2.7 µm, 0.7 µm and 0.2 µm filters.

Ø = 160

EluateQuartz sand

Contaminated soil

Quartz sand

Eluate

Ø = 60

Ø = 160

EluateQuartz sand

Contaminated soil

Quartz sand

Eluate

Ø = 60

Figure 10. Setup of the equilibrium leaching test (Paper V).


19

The amount of particles in the leachates was measured as turbidity and ranged between 0.9 to 2.3 formazin nephelometric units (FNU) indicating that there was a low amount of total suspended solids (TSS) in the leachates, and the dissolved organic carbon (DOC) contents was 55-89 mg/L. One conclusion from Paper V was that the column test was not affected by the 50% increase in flow rate, and the four column tests were treated as replicates. This conclusion was based on the similarity in turbidity, DOC, pH and concentrations of compounds found in the leachates in all tests (regardless of pore water velocity).

3.4 Groundwater sampling The objective of the groundwater sampling was to study the particulate/colloidal distribution of chlorinated compounds. When sampling groundwater the amount of particles can easily be overestimated if the sampling procedure is too vigorous. A fast pump rate or sampling by conventional bailing has been showed to increase the amount of particles in groundwater56,57. Therefore, to ensure that representative groundwater samples were collected several precautions were taken, as described in Paper IV. Firstly, the groundwater was pumped slowly, at rates between 100 to 250 ml/min. Secondly, the pH, temperature and redox potential of the groundwater were measured prior to and during the sampling to ensure that the samples were truly representative. The groundwater samples analysed in these studies were all amber coloured but transparent and no sedimentation was observed, indicating that they were representative and that the risk of overestimating the abundance of particles in the groundwater had been minimised. The amount of particles varied between sampling occasions; the concentrations of the >0.7 µm, 0.7-0.4 µm and 0.4-0.2 µm fractions ranging from 2 to 90 mg/L, from 53 to 155 mg/L and from 52 to 131 mg/L, respectively.

3.5 Characterization of soil organic matter and colloidal particles The soil organic matter (SOM) and particulates analysed in Papers II-IV were characterized using X-ray photoelectron spectroscopy (XPS)58, which provides information on the atomic composition (to within ca 2 atomic percent, at.%) structure and oxidation states of molecules in the outer 10 nm of analysed surfaces. In the studies described in Papers II and III XPS was used to distinguish between different carbon-containing


20

groups, e.g. carboxylic acids, hydroxyl groups and carbon-carbon bonds. In Paper IV, XPS data were used to determine the chemical composition of particles captured in the filtration of groundwater. The groundwater particles (Figure 11) predominately consisted of carbon-containing molecules (45-67 at.%) and the second most abundant constituents were iron hydroxides (19-42 at.%). Minor constituents of the particles included calcium carbonates and silica. No major differences were found in the composition of organic matter between the samples or between fractions. Of the carbon-containing structures approximately 50% were aliphatic carbon (Figure 11 C-(C,H)) and 50% carbon-oxygen containing groups (Figure 11; COOH, C-O). The aliphatic carbon contributes to the hydrophobicity of SOM while the oxygen-containing groups strongly contribute to their hydrophilic domains.

0

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# 1

# 2

# 3

# 3

<0.7

μm

# 3

<0.4

μm

# 3

<0.2

μm # 4

# 5

at.%

SiFe CaCO3COOHC-OC-(C,H)

Figure 11. The chemical composition of particles in the groundwater samples (Paper IV). The labelling #1 to #5 denotes the sampling occasion and 0.7-0.2 µm the filter cut-off used to separate the particles in the groundwater. DOM and POM fractions from samples collected from Hillringsberg, Sikeå and Umeå were analysed in the studies described in Papers II and III. In the Hillringsberg samples the DOM and POM fractions were similar, both consisting of approximately 40% carbon-to-carbon groups and 60% carbon-oxygen containing groups. In the Sikeå samples similar proportions of carbon-carbon and oxygen-carbon groups were found in the DOM and POM, but the relative proportions of carbon-carbon and oxygen-carbon groups in the DOM and POM from the Umeå samples differed; being approximately 50:50 (similar to the proportions in the Sikeå samples) and 70:30, respectively. The deviant composition of the POM in the Umeå samples was attributed to the large amount of wood fibres at the site, due to similarities in the spectra of Umeå POM with spectra obtained from pure wood fibres from the site (for details see Paper III). The carbon composition of DOM of Umeå and the colloidal


21

(<0.7 µm) fraction in the groundwater samples, characterized by XPS, showed a strong correlation. In Papers II and III DOM was defined using the same filter cut-off as used for defining the colloidal fraction in the groundwater samples: 0.7 µm. Thus, the fraction defined as colloidal in Paper IV corresponded to the DOM fractions described in Papers II and III. The hydrophobic properties of HOCs and the strong association between SOM and HOCs in comparison with inorganic constituents makes it likely that the chlorinated compounds in the colloidal fractions of the groundwater were associated with DOM of similar origin and content as in the DOM-POM studies of Paper II and III. However, the colloidal fraction of the groundwater might also, besides DOM, contain POM-particles that have colloidal (<0.7 µm) properties.

3.6 Laboratory procedure and instrumental analysis A summary of the laboratory work is shown in Figure 12. The solid samples (soil, POM, DOM, groundwater particulates) were extracted using Soxhlet-Dean-Stark equipment with toluene as solvent. After extraction the extracts were divided into three parts; one used for cleaning up and analysing neutral compounds, one for phenolic compounds, while the third was saved as a precaution.


22

Derivatization Acetic anhydrid

Hexane extractionNa2SO4

CP, PCPPRS 13C PCB

HRGC-LRMS

½ extract PCDE, PCDF, PCDD

IS 13C PCB, PCDF, PCDF

¼ extract for storage

Multilayer silica(acid/neutral/alkaline)

Extraction 0,5 M KOH

50 % EtOH

Organic phase discarded Alkaline phase

Extraction Soxhlet Dean-StarkWater samples: liquid/liquid

Soil, acidified

Ax21 Carbon/Celite

Fr. 1 DCM:hexane

Fr. 2Toluene

PCDERS 13C PCB

GC-LRMS/ HRGC-HRMS

Alumina oxide

Fr. 1 discard

Fr. 2 DCM:hexane

PCDD/FRS 13C

PCDD/F

HRGC-HRMS

¼ extract CP, PCPP

IS 13C CP, OH-PCB

Figure 12. Summary of the laboratory procedures59,60 (see Papers I-V for detailed descriptions). The alumina oxide columns ( ) were used as fractionation in Paper I and II. HRGC-LRMS were used in the PCDE analyses in Paper I and II and in Paper III to V HRGC-HRMS were used.

3.6.1 Clean-up of phenolic compounds and neutral compounds A detailed description of the analytical procedures can be found in Papers I and II. After the extractions appropriate internal standards (IS) were added and the chloroaromatic compounds were corrected for losses of IS during clean up. The phenolic compounds (CPs and PCPPs) were isolated from the neutral compounds by liquid-liquid partitioning of the toluene extract with potassium or lithium hydroxide in 50% ethanol60. The compounds were derivatized using acetic anhydride59, after derivatization the compounds were transferred to hexane. Prior to GC-MS analyses the samples were evaporated into toluene and spiked with recovery standard (RS), see figure 12.


23

The clean-up and fractionation of the neutral compounds was based on methods presented by Liljelind et al.59. The clean-up procedures included passage through a multilayered silica column containing silica treated with concentrated sulphuric acid, neutral silica and potassium hydroxide-spiked silica to reduce levels of interfering substances. The purified extracts were fractionated using AX21-carbon mixed with Celite. PCDEs were eluted with hexane:dichloromethane in a first fraction and the PCDD/Fs in a second fraction with toluene. In the studies reported in Papers I and II the extracts containing PCDD/Fs were further fractionated using an alkaline alumina oxide column, from which the PCDD/Fs were eluted with hexane:dichloromethane in a second fraction59. This fractionation were found to be of minor importance and ignored in the analyses reported in Papers III to V.

3.6.2 Instrumental analyses The instrumental analyses of all samples were performed by gas chromatography-mass spectrometry (GC-MS) in which samples are injected into the GC and transported through a capillary chromatographic column by the flow of an inert gas e.g. helium or nitrogen. In the GC the compounds are separated by a temperature program according to the strength of their retention on the capillary column, which is determined by the physico-chemical properties of the compounds, and as they elute they are transferred from the GC into the MS61. In the MS the compounds are fragmented and ionized (by electron impact in our studies), and ions with certain mass-to-charge ratios, determined by the type and settings of the MS used, pass into the detector where the signals they generate are recorded61. In addition, the fragmentation patterns allow the molecular structure of the analytes to be determined. This is especially important in the evaluation of unknown compounds classes of compounds for which few, if any, reference standards are available, as in the cases of PCPPs and PCDEs. Full-scan analyses of samples can also provide quality assurance measures of the identified compound. In the following quantifying analyses selected ion recording (SIR) is used and the signals from the unknown compounds are compared to those obtained from reference compounds in known concentrations. In the studies this thesis is based upon, the PCPPs were identified and reported as sums of homologues due to the lack of reference compounds and spectral information. They were identified by full scan analyses using a high resolution gas chromatograph in combination with a low resolution mass spectrometer (HRGC-LRMS) with the settings reported


24

in Paper I. Analytes were quantified in selected ion recording (SIR) mode, using six different 12C PCPPs: 2-OH 2´,4,4´-trichloro phenoxyphenol and penta- to nona-chlorinated PCPP 2-OH 2´,3,4,4´,5-pentachloro phenoxyphenol, 2-OH 2´,3´,4,5,5´,6´-hexachloro phenoxyphenol, 2-OH 2´,3´,4,4´,5,5´,6´-heptachloro phenoxyphenol, 2-OH 2´,3´,4,4´,5,5´,6,6´-octachloro phenoxyphenol, and 2-OH 2´,3,3´,4,4´,5,5´,6,6´-nonachloro phenoxyphenol 62. The PCPPs were present at high concentrations, compared to PCDEs and PCDD/Fs, and there were no sensitivity problems when using HRGC-LRMS to evaluate PCPPs in the soil samples. However, interfering substances complicated the analysis of some highly contaminated samples and use of a HRMS system instead of LRMS could have facilitated their evaluation. The PCPP chromatograms contained a number of individual PCPPs. However, identifying the structures of these unknown PCPPs was beyond the scope of these studies. Figure 13 shows example of chromatograms covering penta- to octa- PCPPs in a soil sample from Umeå. The relative proportions of PCPP congeners found in the soil samples were generally similar, but there were differences in the ratios between some of the congeners. In the samples analysed in Paper I the main PCPP congeners were one TeCPP, eight PeCPPs, six HxCPPs, eleven HpCPPs and two OCPPs reflecting the use of TeCP and Ky-5 use. Fewer PCPPs were detected in samples from sites where Dowicide G had been used: one HpCPP, four OCPPs and two NoCPPs.

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Figure 13. Chromatograms of PCPPs from a “typical” soil sample, collected from the Umeå site. Congeners of penta to octa PCPPs are shown, the TePCPP and lower substituted PCPPs were few. Two different NoPCPP were detected at low or marginal concentrations in some soils.


25

PCDEs were identified using reference compounds, full scan spectral data and retention indices as listed in Paper I. Approximately half of the congeners present in the samples were identified by reference compounds, the other half by retention index and mass spectral data reported by Nevalainen et al.63 and Kurz and Ballschmiter64. In the studies described in Papers I and II the PCDEs were evaluated with LRMS, however, to increase the sensitivity HRMS was used in the subsequent studies (Papers III to V). Figure 14 shows an example of chromatograms of PCDEs in one of the soil samples (Hillringsberg)

.

STD 1 HIBERG 1 POM Cal3:KAL_3

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Figure 14. The composition of PCDEs in samples of the soil from the Hillringsberg site. Lower chlorinated PCDEs were minor constituents of the total PCDE pool and are thus not shown with chromatograms. Congeners listed within parenthesis was identified by retention order63,64. In chlorophenol preservatives the PCDD/Fs profiles were largely dominated by non-2,3,7,8-substituted PCDD/Fs, 2,3,7,8-TCDD were rarely detected in any samples. Papers II, III and V reported the amounts (and relative proportions) of non-2,3,7,8-substituted PCDD/Fs detected. These PCDD/Fs were not identified by using reference compounds but from their known retention order on the GC-column used (DB-5, J&W Scientific, California, USA) in comparison with a fly ash sample analysed at the same time under the same conditions as the soil samples. Dominating non-2,3,7,8-congeners were 1,2,4,6,7,9/1,2,4,6,8,9-HxCDD, 1,2,3,4,6,8-HxCDD, 1,2,3,6,7,9/1,2,3,6,8,9-HxCDD, 1,2,3,4,6,7,9-HpCDD, 1,2,3,4,6,8,9-HpCDF and OCDD. The 17 2,3,7,8-substituted PCDD/Fs were identified and quantified against 2,3,7,8-substituted PCDD/Fs in a reference standard.

4. Partitioning of pollutants to soil organic matter

26

4. Partitioning of pollutants to soil organic matter The characterization of contaminated sawmill sites showed that complex mixtures of pollutants, with differing chemical properties, are present at the investigated sites. At contaminated sites, it is important to understand, and eventually control, the mobility of pollutants. The nature and abundance of the SOM in the soil has been shown to strongly affect the retention of hydrophobic organic contaminants. For instance, Karickhoff et al.52 showed that these parameters influence the sorption of HOCs in soils and sediments more strongly than the amount of clay. In addition, Swarzenbach and Westall 53 reported that the majority of HOCs can be considered to sorb to SOM in soils with SOM contents exceeding 0.1%. Furthermore, as the hydrophobicity of compounds increases, the strength of their association with SOM increases, and the association of pollutants with dissolved organic matter, i.e. the mobile fraction of SOM, may facilitate the compounds’ mobility. Since the strength of the interaction between organic pollutants and SOM depends on the hydrophobicity of the compounds it is possible to estimate the relative amounts of HOCs that are sorbed to SOM from their log KOW as suggested (inter alia) by Seth et al.65, Burkhard66 and Gawlik et al.67. Such estimates provide theoretical partitioning coefficients, KOC, between soil organic carbon and water. KOC values can also be calculated from the measurements of the distributions of compounds between the sorbate (soil, DOM or POM) and water, which should be normalized to the amount of organic carbon to enable comparisons between different samples. Soil organic matter is formed from decaying organic matter and consists of a hydrophobic carbon skeleton, with aromatic and aliphatic structures. It also contains functional groups that add polarity to the substance. The most important functional groups are carboxyl groups (acids), hydroxyl groups, amino groups (bases), sulphur and phosphorus containing groups. The affinity and adsorption strength of a given HOC to SOM will depend on the composition of the SOM. Grathwohl68 reported that the adsorption of HOCs decreases with increasing amounts of oxygen-containing functional groups. This conclusion was supported by Kile et al.69 in a study of the sorption of carbon tetrachloride to soils and sediments. A second conclusion by Kile et al.69 was that the amount of aliphatic or aromatic carbon strongly affects the sorption parameters, which is supported by evidence that HOCs sorb most strongly to


27

materials such as coal and kerogen68 that contain low amounts of polar functional groups. SOM, as defined in this thesis, includes substances ranging from poorly degraded plant residues to highly degraded humic acids and black carbon. Particulate organic matter (POM), including humins and other insoluble organic matter, is distinguished in this context from dissolved organic matter (DOM), which includes humic and fulvic acids as well as other soluble organic matter (Chapter 3.2). An important part of SOM is its content of black carbon (BC), which originates from both natural and anthropogenic combustion processes. When present, BC has been shown to enhance the sorption of HOCs and their partitioning to SOM-BC more than would be predicted from their log KOW values. In an extensive study of 90 soil samples and 300 sediment samples BC was shown to constitute 9% and 4% (median values) of the SOM in sediments and soils, respectively70. Pollutants with planar configurations, e.g. polyaromatic hydrocarbons (PAHs) were also shown to sorb more strongly to BC than non-planar compounds70. Thus, the compounds considered in this thesis that are likely to most affected by BC are planar PCDD/Fs. To evaluate the influence of BC on the distribution of chloroaromatic pollutants the BC content was determined in three of the soils analysed in Papers I-III. However, BC constituted minor proportions of the SOM in these soils (1.2% in Hillringsberg, 0.7% in Sikeå and 0.1% in Umeå). Thus, the calculated significance of BC for the sorption of chlorinated compounds in the three soils thus was minor (Paper III) and correcting the log KPOC to account for adsorption to BC caused changes of less than 0.1 units. As expected, the distribution of the investigated chloroaromatic compounds between DOM and POM was shown to depend on their chemical properties. The relative proportions of CPs associated with DOM and POM in the analysed samples ranged approximately equal proportions to slightly more partitioning to POM (Figure 15). With increasing hydrophobicity the proportions associated with POM increased. Hence, PCDDs sorbed most strongly to POM (Figure 16). Previous studies have shown that the affinity between hydrophobic compounds and SOM tends to decrease as the polarity of the SOM increases69,71. For instance, Tanaka et al.71 found that the partitioning (log KOC) of 1,2,3,4,6,7,8-HpCDD to 23 different humic substances declined as the polarity of the SOM increased. However, in the soil samples analysed in the studies underlying this thesis no difference in polarity was


28

found between DOM and POM. The differing affinity of the chlorinated pollutants to DOM and POM i.e. partitioning of CPs versus PCDDs, may be due to POM particles being larger and having more hydrophobic compartments than DOM72. With increasing hydrophobicity of the compounds the importance of the hydrophobic sections of the sorbate increases.

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Figure 15. Distributions of CPs between DOM and POM in soil samples from Hillringsberg, Sikeå and Umeå (Paper III). Error bars represent standard deviation obtained from analyses of three (Hillringsberg and Umeå) or five (Sikeå) samples.

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Figure 16. Distributions of PCDDs between DOM and POM in soil samples from Hillringsberg, Sikeå and Umeå (Paper III). Error bars represent standard deviations obtained from analyses of three (Hillringsberg and Umeå) or five (Sikeå) samples.


29

As discussed above, the properties of SOM can influence the sorption of HOCs. Figure 17 shows the adsorption capacity for PCDFs and PCDDs of three soils from sawmill sites at Hillringsberg, Sikeå and Umeå, expressed as partitioning coefficients to dissolved organic carbon, KDOC, and particulate organic carbon, KPOC. A high KPOC or KDOC indicates strong sorption of the compound to the organic matter, and differences between KPOC and KDOC values indicate differences in adsorption capacity between DOM and POM. The adsorption to DOM and POM of the investigated compounds increased in the order CPs< PCPPs ∼ PCDEs ∼ PCDFs < PCDDs. Of the three soils included in the DOM-POM studies, the Umeå soil deviated in that the partitioning of the PCDEs, PCDFs and PCDDs to POM was slightly weaker than in the Sikeå and Hillringsberg soils (Figure 17 and Paper III). This deviation was attributed to the larger amounts of wood fibres in the Umeå POM, since wood fibres are known to have a relatively low adsorption capacity (see chapter 3.2 for further discussion of SOM characteristics).

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Figure 17. Distribution of partitioning coefficients of PCDD/Fs to dissolved (log KDOC) and particulate (log KPOC) organic matter in Hillringsberg (H), Sikeå (S) and Umeå (U) soils. The hatched and dotted lines represent calculated log KOC values based on relationships suggested by Burkhard66 and Seth et al.65. In a study by Tanaka et al.71 the log KOC of 1,2,3,4,6,7,8-HpCDD was shown to range between 6.3 and 7.6 depending on the properties of the humic substances. Our studies of the distribution between DOM and POM presented in this thesis support these results and emphasise the importance of investigating the organic carbon at contaminated sites. Reductions in the sorption capacity of HOCs to POM may lead to increases in the mobility of pollutants in the presence of large amounts of a mobile DOM fraction, and large amounts of organic carbon are not


30

necessarily synonymous with strong retention in the soil. Consequently, when modelling compound mobility in a soil, site-specific log KOC values should be determined.

5. Waterborne transport of sawmill pollutants from contaminated soils

31

5. Waterborne transport of sawmill pollutants from contaminated soils The assessments of the distribution of HOCs between DOM and POM prompted further studies to investigate the environmental fate of pollutants at sawmill sites. Of great interest in this respect was the downward transport of pollutants from the soil surface to the groundwater. Figure 18 shows the vertical distribution of CPs, PCPPs, PCDEs, PCDFs and PCDDs at the Luleå site. Despite the low water solubility of PCDEs, PCDFs and PCDDs they were found at depths lower than 2.5 m. At this site the groundwater surface was at depths of approximately 2.5 to 3 m. The SOM content was low at Luleå and consequently organic pollutants were weakly retained in the soil. The CPs and PCDDs were present in similar concentrations, and the maximum total concentrations of PCDD/Fs and CPs were 470 µg/kg d.w. and 450 µg/kg d.w., respectively. These findings indicate that CPs were less strongly retained in the soil than PCDDs.

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Figure 18. Vertical distributions of CPs, PCPPs, PCDEs, PCDFs and PCDDs in a soil profile obtained by core drilling at the Luleå site. The profiles were obtained from seven samples from the surface to 3.5 m below the surface; the interval between the samples is approximately 0.5 m. The observed vertical distribution and the partitioning of the investigated compounds between DOM and POM presented in Chapter 4 (Papers II and III) indicate the potential for waterborne transport of CPs, PCPPs, PCDEs, PCDFs and PCDDs from the contaminated sawmill sites. Thus,


32

estimates of waterborne transport rates were obtained by investigating the distribution of the compounds in groundwater at the Umeå site (Paper IV) and by a leaching test of the soil from the Luleå site (Paper V). The low water solubility and high affinity of chlorinated compounds to organic matter result in low transport of compounds as truly dissolved in water. On the other hand, transport rates of the compounds associated with mobile particles in soil and groundwater, e.g. DOM and organic colloids, may be considerably higher (Figure 19). Due to their small size, <1 µm particles, may be suspended in water, and do not precipitate and thus they are considered to be colloids73.

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Figure 19. Schematic diagram of the dissolved and colloidal transport of contaminants in soil, adapted from Buffle and Leppard73. The groundwater study (Paper IV) and leaching tests (Paper V) focused on the distribution of compounds between the water phase and the fine particulate, colloidal fractions. Especially interesting in this context was the importance of colloids for the mobility of the different groups of chlorinated aromatic compounds.

5.1 Distribution of chlorinated compounds in groundwater Several studies have provided evidence of increased transport rates and/or association of HOCs with dissolved organic matter and colloidal matter in groundwater74-76. For instance, Mackay and Geschwend76 found that transport rates of PAHs and the importance of colloids in this respect increased with increasing hydrophobicity of the PAHs. Paper IV presents a sampling and fractionation of colloids in groundwater from a contaminated sawmill site in order to investigate the chlorinated compounds associated with fine particulate matter, colloids. The groundwater was sampled and fractionated by filtration into three particulate fractions: >0.7 µm, 0.7-0.4 µm and 0.4-0.2 µm. Compounds in


33

the <0.2 µm filtrates were defined as being truly dissolved in the water phase. In accordance with previous studies on PAHs76,77 and PCBs78, the distribution of PCPPs, PCDEs, PCDFs and PCDDs at the Umeå sawmill site was found to be influenced by colloids, and the compounds were distributed according to their chemical properties. The most water-soluble compounds, CPs, were mainly found in the water phase, i.e. associated with the <0.2 µm fraction (Figure 20). The pH of the groundwater varied between 5.9 and 6.8 and both TeCP and PeCP were, thus, mainly present as phenolates. Studies by Fingler et al.79, Lafrance et al.80 and Amiri et al.81 have reported that sorption of CPs decreases when pH>pKa. The distribution of CPs in the groundwater we analysed is consistent with these findings.

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Figure 20. Distribution of CPs in the particulate fractions (>0.7 µm, 0.7-0.4 µm and 0.4-0.2 µm) and water phase (<0.2 µm) of the investigated groundwater. The increasing association to particles with increasing hydrophobicity is shown by the differences in the distributions of CPs and PCDD/Fs shown in Figures 20 and 21. Our results support the findings regarding the distribution of PAHs in groundwater presented by Mackay and Gschwend 76 that the concentrations of indeno[1,2,3-cd]pyrene were up to 50 times higher than would be expected if they had been solely dependent on the equilibrium between water and creosote76. Similarly, Burgess et al.78 found that the amounts of PCBs associated with colloids increases with increasing chlorination and that levels of colloid-associated PCBs increases with increasing concentrations of PCBs in a stationary sediment.


34

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Figure 21. Distribution of PCDD/Fs in the particulate fractions (>0.7 µm, 0.7-0.4 µm and 0.4-0.2 µm) and water phase (<0.2 µm) of the investigated groundwater. In paper IV the compounds in the water phase (<0.2 µm) were defined as truly dissolved. However, some congeners of PCDD/Fs were present at higher concentrations in the water phase than would be predicted from their water solubility16. Hence, the water phase probably contained PCDD/Fs associated with DOM or colloids < 0.2 µm. PCDFs and PCDDs distributions differed, although their chemico-physical properties are quite similar. Figure 21 shows the differences between the particulate fractions and the dissolved phase. In the particulate samples HxCDDs, HpCDDs and OCDD dominated, but in the water phase a shift towards PCDFs occurred. The PCDFs are more water soluble than PCDDs which to some extent explains the differences found in the groundwater samples. Difference were also seen in the partitioning of PCDFs and PCDDs between DOM and POM (Papers II and III), the differences between log KDOC and log KPOC being smaller for PCDFs than for PCDDs (Figure 17, Chapter 4). The yearly groundwater outflow from the Umeå site to the Umeå River was estimated to be 3000 m3. This is estimated from the area of the site and the yearly infiltration of precipitation. Based on calculations of groundwater outflow and concentrations of CPs and PCDD/Fs in groundwater (Paper IV), the estimated amounts of CPs and PCDD/Fs (WHO-TEQ) that were transported from the Umeå site each year were 720 g and 2.1 mg, respectively. These estimates were based on data from only one site, but still suggests that contaminated sawmill sites should be


35

investigated in order to determine the contribution of these pollutants to the environment. In Sweden up to 500 sites may have similar contamination, and our results suggest that chlorophenol-contaminated sites could be significant secondary sources of PCDD/Fs in the Baltic Sea. However, the soil at Umeå contained large amounts of SOM, up to 50% and Laegdsmand et al.82 showed, using column leaching tests, that the amounts of colloids increase with increasing amounts of SOM. Thus, the groundwater at Umeå may contain relatively large amounts of colloids and the release rates of contaminants may be higher here than at sites with low SOM content.

5.2 Estimation of mobility from leaching tests To verify the results from the groundwater sampling leaching tests were performed using the set-up described in section 3.3 and soil from the Luleå site. The distributions of compounds between the particulate fraction (> 0.2 µm) and water phase (< 0.2 µm) found in the four column tests are shown in Figure 22. Most of the CPs were found in the solute fraction, while PCDEs, PCDFs and PCDDs were found in the particulate fractions, correlating well with the results from the groundwater study (Paper IV). The PeCP concentrations were close to their water solubility and, hence, some PeCP was likely DOM/colloid associated.

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Figure 22. Distributions of CPs, PCDEs and PCDFs and PCDDs between the particulate fraction (> 0.2 µm) and water phase (< 0.2 µm) found in four replicates (1a, 1b, 2a and 2b) of the column tests.


36

The sorption capacities for the investigated compounds, i.e. log KOC values were determined from the results of the leaching tests and shown in Figure 23. For comparison, corresponding linear plots of theoretical KOC values based on Seth et al.65, are also shown in the figure. Log KOC aqua values apply to compounds found in the water phase and log K leachate values to compounds associated with both colloids and in the water phase. The log K leachate values were lower than the log KOC aqua values indicating the transport potential of HOCs is higher if HOCs associated with fine particulate matter are included in estimates of transport rates of these groups of compounds.

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Figure 23. Correlation between log KOW values17,83,84 and partitioning coefficients of CPs, PCDEs, PCDFs and PCDDs determined from the leaching tests. The error bars represent standard deviation obtained from analyses of four samples. The inserted lines are plots of theoretical log KOC values based on Seth et al. 65. Log KOC aqua values represent coefficients derived for the water phase (<0.2 µm) and log K leachate values represent coefficients derived for both the particulate fractions and the water phase. In addition, Figure 23 shows a deviation from a linear relationship between log KOC and log KOW values at log KOW values >7; the higher the log KOW the larger the deviation. A similar deviation was found by Mitra and Dickhut85 in a study of the distribution of PAHs in sediments. Modelling the contribution of DOC-associated PAHs explained the deviation to a certain extent, but not entirely. Further, Burgess et al.78 found a similar deviation when studying the distribution of PCBs between stationary sediment, colloid fractions and the water phase. One explanation of this phenomenon suggested by Burgess et al.78 was that there was insufficient time for higher chlorinated PCBs to equilibrate in the sediment-colloid-water system. Other explanations included (inter alia) steric hindrance of PCBs and colloid instability. A third explanation, applicable to the data in Paper V, is the presence of colloids in the water


37

phase. The dissolved phase in the groundwater samples and leaching test is defined as all particles and molecules with diameters < 0.2 µm. However, the water phase is likely to contain colloids smaller than 0.2 µm, which may contribute to divergences from calculated log KOC values. Similarly, section 5.1 described concentrations of PCDD/Fs in the dissolved phase exceeding the water solubility of PCDD/Fs that were caused by the presence of colloids. The results indicate that the column test is suitable for determining distributions of HOCs with log KOW values < 6-7. However, for HOCs with log KOW values > 7 the influence of colloids is important and the reproducibility of the test is reduced. The standard deviations of the data for these compounds were high and the results of each leaching test were influenced by the mobilised colloids. Similar results, with increasing standard deviation with hydrophobicity of PAHs, were found by Hansen et al.55. Further, the heterogeneity of the Luleå soil sample caused considerable variability in the distribution of compounds with log KOW values > 7. For compounds with higher water solubility, i.e. CPs the differences in reproducibility were consistent with the results of a previous study of leaching of PAHs in soil and wastes by Hansen et al.55, supporting the conclusion that the column test is suitable for analysing the distribution of HOCs with log KOW values < 6-7. In conclusion, the results of the studies described in Papers IV and V support the importance of investigating the fine particulate fractions when studying the mobility of hydrophobic pollutants from contaminated sites. However, the colloid fraction was the cause of large variations in mobility parameters and it should be kept in mind that increases in the amounts of colloids in a groundwater sampling or a leaching test may lead to overestimates of the mobility of HOCs, but ignoring colloids may lead to underestimates of the mobility of HOCs such as PCDD/Fs.

6. Conclusions and future perspective

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6. Conclusions and future perspectives In summary, the chlorophenol-contaminated sawmill sites contained considerable amounts of CPs, PCPPs, PCDEs, PCDFs and PCDDs. Investigations of the distributions of the pollutants between immobile and mobile fractions of soil were biased towards the immobile fraction i.e. particulate organic matter (POM). This affinity for the stationary POM fraction increased with increases in the pollutants’ hydrophobicity. Although the pollutants were mainly associated to POM, substantial proportions of the chloroaromatic contaminants were found to be associated as waterborne contaminants via fine particulate matter, colloids, and dissolved organic matter (DOM) in the groundwater samples and the leaching test. The results suggest that pollutants are continuously transported and that chlorophenol-contaminated sites may act as secondary sources of toxic compounds in the environment. To summarise, mobile fractions of soil, i.e. DOM and colloids should be considered in groundwater analyses and leaching tests. If these compartments are not considered there is a risk that the transport potential of HOCs will be underestimated. However, the sampling should resemble processes in natural conditions, in order to avoid overestimating their abundance in the colloid fraction. The author would like to suggest the following future studies:

• Investigation of the transport of chlorinated aromatic contaminants from soils via groundwater at different sawmill sites with differing conditions with respect, for instance, to the origins of the SOM and groundwater flow rates. The influence of variations in factors such as the outflow of contaminants during the snow melting season should also be investigated, in order to determine if contaminated sawmill sites are secondary sources of chlorinated organic pollutants for their surrounding areas.

• Detailed characterizations of the differences between DOM and POM in contaminated soils. Of special interest in this respect would be quantitative and qualitative assessments of the hydrophobicity of POM in comparison to DOM.

• The importance of co-transport with DOM and colloids found here highlights the importance of investigating the bioavailability of colloid-associated CPs, PCPPs, PCDEs, PCDFs and PCDDs.

39

Summary in Swedish Svensk sammanfattning Sågverkstomter där man impregnerat virke med klorfenolpreparat kan vara förorenade med ett antal giftiga klororganiska föreningar, t.ex. klorfenoler, fenoxyfenoler, difenyletrar, dibensofuraner och dioxiner. Dessa föreningar har låg vattenlöslighet vilket gör att de i stor utsträckning binds till organiskt material i jorden. Organiskt material kan delas upp i en stationär organisk del, POM, och en potentiellt rörlig del, DOM. Föroreningars bindning till DOM eller till kolloider kan leda till en ökad transport av föroreningen. Denna avhandling baseras på studier av klororganiska föroreningar i jord och deras fördelning till POM samt DOM och kolloider. Studier har skett vid fem sågverk där man fram till 1978 använde klorfenolpreparat för att skydda virke mot svampangrepp. Resultaten visade på betydande koncentrationer av alla de undersökta föroreningarna i jordprov från sågverken. Sammansättningen av de klororganiska föroreningar i jorden skiljde sig från sammansättningen i klorfenolpreparat vilket antyder att det har skett en transport och/eller en nedbrytning av föroreningar. De fortsatta studierna undersökte i vilken utsträckning de klororganiska föroreningarna band till DOM respektive POM. Klorfenoler hittades i lika stora delar i den mobila fraktionen som i den orörliga fraktionen. Med minskad vattenlöslighet hos föreningarna (fenoxyfenoler, difenyletrar och dioxiner) ökade bindningen till POM. Trots att en liten andel dioxiner återfanns bundet till det lösta organiska materialet, DOM, jämfört med bindning till POM, så visade fortsatta studier att DOM och kolloidfraktionen var viktig för spridning av dioxiner. Dessa slutsatser kunde dras genom undersökningar av hur mycket av föroreningarna som fanns lösta i grundvatten respektive hur mycket som var bundna till kolloider. De flesta klorfenolerna fanns lösta i vattnet medan dioxinerna var bundna till kolloider. Slutsatsen är att en hög hydrofobicitet hos en förorening kan ge en ökad spridning av föroreningen genom dess association till rörliga fraktioner i jorden.

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Acknowledgment De första och mycket välförtjänta tacken är till Mats och Lars. Jag har varit ”bortskämd” med två aktiva handledare som delat med sig av kunskap och gett respons på mitt arbete. Extra kul var att få våra samtal betygsatta som ”Det perfekta handledarsamtalet”. Mats, tack för att du har lyckats se höjdpunkter bland spretande resultat. Nästa tack är till Staffan som såg till att även en icke-kemisk geoekolog kan få fram resultat. En mycket viktig person har varit Sofia. Med POM-pedi-DOMPOMDOM fick projektet den där roliga geo-touchen, en massa trevligt sällskap och intensiva forskningsdiskussioner (ibland blir det andra diskussioner också). Men Sofia, viktigast är du som vän! Tack till Anja och Kristian vid SGI i Malmö som gjorde att laknings-projektet blev proffsigt utfört och ställde upp på det tajta schemat. Jag hoppas att ni inte överger lakning av dioxiner helt efter detta… Tack till Andrei för hjälp med XPS analyser och tolkningar. Jag har fått mycket hjälp av Länsstyrelsen i Västerbotten och Norrbotten, kommunerna i Luleå, Skellefteå, Umeå och Arvika samt Tyréns, WSP och Sweco Viak i Umeå med jordprov och bakgrundsinformation om sågverkstomter, tack! Mitt projekt har ingått i Marksaneringscentrum Norr, finansierat via EU:s strukturfond, Mål 1, i samarbete med kommuner, länsstyrelser och företag. För mig har MCN-möten varit höjdpunkter varje år, med aktuell forskning men främst för alla trevliga människor. Bra ordnat, Thomas! Tack till Knut och Alice Wallenbergs Stiftelse, vars bidrag gav mig möjlighet att resa på Dioxin-konferenser! Miljökemi består av många generösa, hjälpsamma och fikasugna personer! Jag hoppas att alla arbetsplatser har en så go´ samanhållning. Tack alla doktorander som ser till att det händer något! Och tack till Barbro som hjälper oss doktorander att ”få ordning på torpet”. Malin, tack för att du är så omtänksam! Sofia J, du förgyller Miljökemi (även när du verkar från ”styret”). Conny, tack för sällskap i avhandlingsfunderingar. Richard, tack för att du gjorde mig snygg(are). Per, Anna och Maria, er lab- och masshjälp har varit behövlig. Lena, du är ovärderlig som administratör och arbetskamrat. Ulrika O, tack för otaliga pratstunder på rummet och för fantasieggande pasta.

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Att jobba är roligt men att vara ledig med vänner är roligare! Tack alla vänner, både från Miljökemi och utanför, som ser till att mitt sociala liv är fyllt. Ida och Gunnar, tack för matpratstunder (med eller utan mat), Elin och Håkan för många roliga stunder, Sofia, Jenny, Linda, Eva, Johanna, fjällbruttorna, keramiktjejerna och telefonterror med Mareé och inte minst Ulrika! Tack till Evy och Dan för att vi får hjälp med allt möjligt. Edvin, du har öppnat en helt ny värld för mig, WoW. Mamma Märta och Pappa Per och systrarna Ulrika och Helen är det bästa som finns, att veta att ni finns nära (men för långt bort geografiskt) betyder mycket för mig! Och med svågrar som Martin och Nisse finns alltid något att diskutera… Syskonbarn (i kronologisk ordning: Emil, Ida, Erik och Måns) är härliga, fler sådana pärlor tack! Pär, du är mitt allt, hmm, vad var det du ville att jag skulle skriva sen…? Puss, min älskade!

Umeå, januari 2007

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