Year 4 Research

Fate of CCA-Treated Wood

Evaluate Fate of Wood Treated With Preservative Chemicals Evaluate CCA- and alternative-chemical- treated

wood through TCLP and SPLP (Phase I) Evaluate arsenic species in leachates collected from

landfills(Phase II)

Objectives

Note: Complimentary Study on Chromium Speciation

Phase I: Leaching of Alternative-Chemical Treated-Wood Products

Samples Include ACQ-Treated Wood CBA “ “ CC “ “ *** CDDC “ “ CCA “ “ Treated Through Facility A CCA “ “ Treated Through Facility B Untreated Wood Unknown Treated Wood (?)

Sample Processing

8, 2”x4”x16 ft were purchased

AC

Q

AC

Q

AC

QC

BA

CBA

CBA

CC

A,1

CC

CC

CC

CD

DC

CD

DC

CD

DC

CC

A,1

CC

A,1 C

CA,

2

CC

A,2

CC

A,2

U

U

U

X

X

X

16ft

1 2 3 .....8

2 ft

Analytical Methods for Alternative Chemicals

Description of Leaching Test Plan Review of existing methods for analysis

of alternative chemicals(AWPA, EPA, and others)

Proposed methods of analysis Questions for TAG

Plan for Leaching

Primary Leaching Tests TCLP SPLP

Additional Leaching Tests Deionized/Distilled Water Synthetic Seawater

Leaching Tests

Wood Sample

Size reducedfollowing standardleaching protocols

Leaching Test

18 hour contact, 20:1 Liquid to Solid ratio, Rotary extraction

Leachate Analysis

Leachate analyzedusing standardizedmethods

Methods of Analysis

Sources of methods: AWPA Standards EPA Methods Instrument Manufacturer Methods Other

Methods are often matrix specific The matrix of interest in the this study is

aqueous leaching fluid

Chemicals to be Analyzed

CC

CCA

ACQ

CBA

CDDC

As, Cr, Cu

Cu

Cu, B

Cu

Cu

--

DDAC

Tebuconazole

Dimethyldithio-carbamate

Citrate

PreservativeInorganicChemical(s)

OrganicChemical(s)

Inorganic Methods

ICP-AES

FLAA

GFAA

6010B

7211

7210

A21-93

A11-93

A11-93

AnalyticalMethod

EPAMethod

AWPAStandard

Note: Methods may require extraction or digestiondepending on the matrix or method

Organic Chemical Analysis

Citrate

DDAC

CDDC

Tebuconazole HPLC, GC

Colorimetric

HPLC,Titration

UV Spec

A16-A/17-97

A25-94 *

A23-94/A24-94

A2-98

OrganicChemical

AnalyticalTechnique

AWPA Method(liquids)

Other Analytical Methods

Citrate by Ion Chromatography Dionex methods manual

Alternative Titration for DDAC Manufacturer suggestion

Proposed Methods

Methods selected based on resources available, time constraints, and analytical objectives

Analysis of Inorganic Chemicals

Copper and Boron will be analyzed using ICP, FLAA, or GFAA following US EPA methods (including acid digestion).

ICP

Perkin-Elmer 5100 FLAA/GFAA

Analysis of Tebuconazole

A GC/MS will be used for analysis. Based on a modified version of AWPA

method A24-94 Detection limit is approximately 100 g/L

Trace 2000 GC/MS

Analysis of DDAC (ACQ)

A two-phase titration analysis will be performed following method A17-97.

Titration Setup

Analysis of CDDC

Analysis will be performed using a colorimetric method specified in A25-94 and instrument methods manual.

Hach DR/4000U Spectrophotometer

Analysis of Citrate

Analysis will be performed using Ion Chromatography

Dionex DX-500 Ion Chromatograph

Chromatogram

Other Possibilities

Toxicity Tests MET-plate Microtox Algal assay Yeast assay

Questions for TAG

Are we missing any analytes of concern?

Suggestions on methods? Comments on leaching tests?

Bernine KhanUniversity of Miami

Arsenic:Arsenic: Toxicity, Mobility & Analytical

Methods for Speciation

Part I - Characteristics Arsenic Species Arsenic Toxicity Arsenic Mobility

Part II - Arsenic Speciation Study Purpose of Study Goals for Year 4 Hydride Generation Method - SDDC

OutlineOutline

Definition

Various species of an element which make up the total concentration of that element

- different oxidation states (e.g. arsenic +3, +5, -3)

inorganic - contains sulfur

organic - contains carbon/hydrogen groups

SpeciationSpeciation

Why are we interested in speciation? Not all species are toxic Total concentration - over-/under-estimate toxicity Standards EPA’s MCL for DW- 50 g/L (5 g/L) As TCLP limit - 5000 g/L

SpeciationSpeciation

Arsenic SpeciesArsenic Species

AsH3 - arsine (gas)

As(III) - inorganic arsenite

As(V) - inorganic arsenate

MMAA - monomethylarsonic acid

DMAA - dimethylarsinic acid

TMAO - trimethylarsine oxide

AsB - arsenobetaine (marine) *

AsC - arsenocholine (marine) *

Decreasing Toxicity

Arsenic SpeciesArsenic Species

AsH3 - arsine (gas)

As(III) - inorganic arsenite

As(V) - inorganic arsenate - CCA

MMAA - monomethylarsonic acid

DMAA - dimethylarsinic acid

TMAO - trimethylarsine oxide

AsB - arsenobetaine (marine) *

AsC - arsenocholine(marine) *

Decreasing Toxicity

Arsenic SpeciesArsenic Species

AsH3 - arsine (gas)

As(III) - inorganic arsenite

As(V) - inorganic arsenate

MMAA - monomethylarsonic acid

DMAA - dimethylarsinic acid

TMAO - trimethylarsine oxide

AsB - arsenobetaine (marine)*

AsC - arsenocholine (marine)*

Decreasing Toxicity

Arsenic SpeciesArsenic Species

AsH3 - arsine (gas)

As(III) - inorganic arsenite

As(V) - inorganic arsenate

MMAA - monomethylarsonic acid

DMAA - dimethylarsinic acid

TMAO - trimethylarsine oxide

AsB - arsenobetaine (marine)*

AsC - arsenocholine (marine)*

Decreasing Toxicity

Toxicity DataToxicity Data

Arsenic Compound

Inorganic arsenite [As(III)]

Inorganic arsenate [As(V)]

MMAA - monomethylarsonic

DMAA - dimethylarsinic acid

TMAO - trimethylarsine oxide

AsB - arsenobetaine (marine)

AsC - arsenocholine (marine)

LD50

(mg/kg)

4.5

14-18

1,800

1,200

10,600

10,000

6,000

Animal

rat

rat

mouse

mouse

mouse

mouse

mouse

LD50 - concentration at which 50% of a population dies.Low LD50 - more toxic High LD50 - less toxic

Arsenic MobilityArsenic MobilityReducing O2 & Eh

As(V)+5

As(III)+3

As(III)+3

AsH3 (aq)

AsS+3

As

Most surface waters

Most ground waters

0 2 4 6 8 10 12 14

pH

Eh (

volt

s)0.75

0.50

0.25

0

-0.25

-0.50

-0.75

Eh-pH diagram

measure of system state (aerobic/ anaerobic)

As(III) - OxidizedAs(V) - ReducedMethylation

Hyphenated techniques

Separation + detection methods

Separate As(III) and As(V) from interfering ions

Detection methods - detect & quantify

Part IIPart IIArsenic Speciation StudyArsenic Speciation Study

Purpose of StudyPurpose of Study

• CCA treated wood disposed of in unlined C&D landfills

• Leaching studies show significant amounts of CCA leaching from wood under varying pH solutions

• Determine the total arsenic & individual concentration of As(III) & As(V) species

• Chemical Hydride Generation method

Leaching StudyLeaching Study(Warner et al. 1990)

Arsenic leaching increases linearly with decreasing pH

Buffer pH %

As

citric acid/NaOH 2.5 -

citric acid/NaOH 3.5 68citric acid/NaOH 4.5

52citric acid/NaOH 5.5

32distilled water 7.0

17borax/HCl 8.5

9

Buffer pH %

As

H2SO4 2.5 40H2SO4 3.5 23H2SO4 4.5 17

Arsenic after 40 days - retention of 1.99 kg/m3 in new wood

Goals for Year 4Goals for Year 4Current Study:

• Analysis of As(III) & As(V) by Chemical Hydride Generation (CHG) method

• SDDC - CHG method chosen - NaBH4

to reduce arsenic to its gaseous form (arsine) so as to be detected

• SDDC method - Test reproducibility using standard solutions

Silver Diethyldithiocarbamate (SDDC) Method

Current StudyCurrent Study

20 10 5 2 1 0 ug

Results of SDDC MethodsResults of SDDC Methods

Absorbance

0.185

0.082

0.038

0.03

0.018

0.009

Conc. (g)

20

10

5

2

1

0

Absorbance

0.17

0.072

0.05

0.02

0.018

0.009

Conc. (g)

20

10

5

2

1

0

Arsenite [As(III)]

y = 0.0086x + 0.0057

R2 = 0.9846

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0.2

0 5 10 15 20 25

Concentration (ug)

Ab

so

rba

nc

eAs(III) Calibration CurveAs(III) Calibration Curve

Results of SDDC MethodsResults of SDDC Methods

Absorbance

0.24

0.15

0.078

0.04

0.02

0.009

Conc. (g)

20

10

5

2

1

0

Absorbance

0.24

0.142

0.08

0.037

0.03

0.015

Conc. (g)

20

10

5

2

1

0

Arsenate [(As(V)]

y = 0.0113x + 0.0189R2 = 0.9951

0

0.05

0.1

0.15

0.2

0.25

0.3

0 5 10 15 20 25

Concentration (ug)

Ab

so

rba

nc

eAs(V) Calibration CurveAs(V) Calibration Curve

Goals for Year 4Goals for Year 4

Next Steps:

• Determine how best to preserve sample

• Analyse GW samples near C&D landfills

• Analyse leachate from MSW and C&D(?) landfills

Speciation of Chromium

Chromium Speciation

Background

Methods of Analysis

Proposed Methodology

Chromium Exists as Several Chemical Species

Most common oxidation states: 0, +3, +6

0: Elemental Chromium (Cr)+3: Trivalent Chromium

Species: Cr+3, Cr2O3

+6: Hexavalent ChromiumSpecies: CrO4

2-, Cr2O7-

Chromium Speciation Important!

The characteristics and properties of trivalent chromium and hexavalent chromium are greatly different.

Cr(VI) is much more toxic and mobile than Cr(III)

Difference between Cr(VI) and Cr(III) Factored into Regulations

RCRA Regulations40 CFR 261.4(b)(6)(i)

A solid waste that is a characteristic or listed hazardous waste solely because of chromium is not hazardous if…..

A solid waste that is a characteristic or listed hazardous waste solely because of chromium is not hazardous if…..

– (A) The chromium in the waste is exclusively (or nearly exclusively) trivalent chromium; and

– (B) The waste is generated from an industrial process which uses trivalent chromium exclusively (or nearly exclusively) and the process does not generate hexavalent chromium; and

– (C) The waste is typically and frequently man-aged in non-oxidizing environments.

Ingestion: Cr(III): 78,000 mg/kg Cr(VI): 390 mg/kg

Cr(III) versus Cr(VI)

Hexavalent chromium exists in alkaline, strongly oxidizing environments

Trivalent chromium exists in moderately oxidizing and reduced environments

pH

Eh (V)

10 12 144 6 820

0.0

-0.2-0.4

-0.6

1.0

0.2

0.8

0.4

0.6

1.2

Cr2O3

CrO4 2-

Cr2O7 -

Cr 3+

pH

Eh (V)

10 12 144 6 820

0.0

-0.2-0.4

-0.6

1.0

0.2

0.8

0.4

0.6

1.2

Cr2O3

CrO4 2-

Cr2O7 -

Cr 3+

Chromium in Wood Preservation

The chromium in CCA preservative solution is hexavalent chromium.

Upon fixation in the wood, Cr(VI) becomes converted to Cr(III)

When Might Cr(VI) Be Encountered?

If wood is improperly fixed (as a result, for example, of inadequate fixation time at low temperatures)

When in contact with oxidizing chemicals such as deck brighteners

Oxidation of Chromium in the Environment

In the natural environment, chromium tends to exist as Cr(III)

Oxidation of Cr(III) to Cr(VI) as a result of manganese (hydr)oxides

Methods of Cr(VI) Analysis

Typical chromium measurements are total chromium (Cr(III) + Cr(VI) + other)

Methods have been developed for Cr(VI) analysis

Sample holding time is minimal

Methods of Cr(VI) Analysis

Solvent extraction followed by total chromium analysis

Colorimetric Determinations Chromatographic Determinations

Selected Method

Ion Chromatography

Research Project:Assessing the Impact of Chromium in the Environment

Funding provided by Florida Department of Environmental Protection

Tasks

1. Literature Review2. Assessment of pH and ORP as

indicators or Cr speciation3. Evaluate kinetics of conversion of

Cr(VI) to Cr(III) in natural soils4. Develop guidance document

Additional Tasks

5. Examine Cr(VI) in ash from combustion of wood containing CCA-treated wood

6. Examination of Cr(VI) formation potential in C&D debris disposal environments

Previous Research

In year 2, wood ash containing CCA-treated wood was found to leach chromium in an unpredictable manner (relative to arsenic)

Arsenic Leaching from Wood Ash

0.01

0.1

1

10

100

1000

Ars

en

ic L

ea

ch

ate

Co

nc

en

tra

tio

n (

mg

/l)

TCLPSPLP

TC (5)

GWCTL(0.05)

Chromium Leaching from Wood Ash

0.1

1

10

100C

hro

miu

m L

each

ate

Co

nce

ntr

atio

n (

mg

/l)

TCLPSPLP

TC (5)

GWCTL(0.10)

Questions