Arsenic Speciation of CCA-Treated Wood

Bernine KhanUniversity of Miami

May 6th, 2002

Purpose:Speciation analysis - to identify & quantify the arsenic species leaching from CCA-treated wood

Interest of individual arsenic species?Arsenic toxicity varies with each species

Species of interests to this study: Inorganic - As(III) & As(V)Organic – MMAA & DMAA

Purpose of Study

Speciation

Arsenic

As(III) As(V) MMAA DMAA

Various forms of an element that make up the total concentration of that element

Inorganic Organic

-3 0 +1 +3 +5Valence

InorganicArsine (g)

Speciation

Arsenic

As(III) As(V) MMAA DMAA

Various forms of an element that make up the total concentration of that element

Inorganic Organic

-3 0 +1 +3 +5Valence

InorganicArsine (g)

Toxicity of Arsenic Species Dependent on chemical form

• AsH3 - arsine (gas) – most toxic (formed under reduced conditions eg. landfills)

• As(III) - arsenite

• As(V) - arsenate

• MMAA - monomethylarsonic acid

• DMAA - dimethylarsinic acid

• TMAO - trimethylarsine oxide

• AsB - arsenobetaine (marine) *

• AsC - arsenocholine (marine) *

Toxicity of Arsenic Species Dependent on chemical form

• AsH3 - arsine (gas)

• As(III) - arsenite – inorganic (more toxic)

• As(V) - arsenate – inorganic - CCA

• MMAA - monomethylarsonic acid

• DMAA - dimethylarsinic acid

• TMAO - trimethylarsine oxide

• AsB - arsenobetaine (marine) *

• AsC - arsenocholine (marine) *

Toxicity of Arsenic Species Dependent on chemical form

• AsH3 - arsine (gas)

• As(III) - arsenite – inorganic

• As(V) - arsenate – inorganic

• MMAA - monomethylarsonic acid

• DMAA - dimethylarsinic acid

• TMAO - trimethylarsine oxide

• AsB - arsenobetaine (marine) *

• AsC - arsenocholine (marine) *

bacteria

Toxicity of Arsenic Species Dependent on chemical form

• AsH3 - arsine (gas)

• As(III) - arsenite – inorganic

• As(V) - arsenate – inorganic

• MMAA - monomethylarsonic acid

• DMAA - dimethylarsinic acid

• TMAO - trimethylarsine oxide

• AsB - arsenobetaine (marine) *

• AsC - arsenocholine (marine) *

To Study Arsenic Leaching From CCA-Treated Wood

Group 1 - Controlled Laboratory Batch Experiments

Group 2 - Controlled Field-Scale Experiments

Group 3 - Uncontrolled Field-Scale Experiments

Study Setup:

Group 1 - Controlled Laboratory Batch

Experiments• pH Stat – Leaching of As species under

different pH conditions (similar to TCLP)

• TCLP – Should treated wood waste be considered hazardous

• SPLP – Should treated wood waste be land applied

• Solvent-Extraction – Leaching characteristics from Deionized Water, Rainwater, & Seawater

Group 2 - Controlled Field-Scale Experiments

•Lysimeter Study – Leaching of As species under simulated MSW and C&D landfill conditions using field columns

•Deck Study – Leaching of As species from a field built treated deck

Group 3 - Uncontrolled Field-Scale Experiments

•Testing of Groundwater & Landfill Leachate – Identify & quantify As species found at MSW and C&D landfills

Group 1 - Controlled Laboratory Batch Experiments

pH Stat

• Unburned CCA-treated wood subjected to leaching solvent (HNO3 or NaOH – to obtain desired pH)

New (0.4 pcf) CCA-treated woodmeasured at 0.214 pcf

pH 123456789

101112

Used (0.4 pcf) CCA-treated wood

measured at 0.386 pcf

Results of pH StatNew Wood

0.00

10.00

20.00

30.00

40.00

50.00

1 2 3 4 5 6 7 8 9 10 11 12 13

pH

Con

cen

trati

on

(mg/L

)

• As(V) was the only specie detected• Highest concentration at extreme pH • Environmental pH range – As(V) ~ 5mg/L

TCLP 5 mg/L

Environmental pH

Results of pH StatUsed Wood

• Both As(III) & As(V) detected • As(III) up to pH 8.5• Environmental pH range – Total As increase• Total As > 5 mg/L

TCLP 5 mg/L0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

1 2 3 4 5 6 7 8 9 10 11 12

pH

Con

cen

trati

on

(mg/L

) As(III)As(V)TotalEnvironmental

pH

Results of pH Stat Total Arsenic

• More As from new wood – pH 1 - 3 (40 – 9 mg/L)• More As from used wood – pH 3 - 12 (9 – 27

mg/L)

05

1015202530354045

1 2 3 4 5 6 7 8 9 10 11 12 13pH

Tota

l ars

en

ic c

on

c.(m

g/L

)New (0.214 pcf)Used (0.386 pcf) – 14

yrs

TCLP 5 mg/L

Environmental pH

Summary of Results pH Stat• Species - New – As(V), Used - As(V) & As(III)

• pH significant in As leaching

• As(III) due to biological factors

• More As leaching from new wood at pH 1 to 3 – more As on new wood surface

– easily released under acidic conditions

• More As from used wood at pH 3 to 12 - Higher retention - Age of wood – weakening release more As

- As(III) - more mobile specie & may not bind

as strongly as As(V) to the wood

Group 1 - Controlled Laboratory Batch Experiments

TCLP & SPLP

• Unburned CCA-treated wood & CCA-treated wood ash subjected to leaching solvent & rotated for 18 2 hrs.

Unburned CCA-treated wood

CCA-treated wood ash

TCLP

SPLP

TCLP

SPLP

Untreated0.25 pcf0.6 pcfWeathered (0.6 pcf)2.5 pcfC&D 1C&D 3

Results of TCLP Unburned Wood

TCLP 5 mg/L

0

1

2

3

4

5

6

7

8

9

10Conce

ntr

ati

on (m

g/L)

As(III)As(V)Total

untreated

0.25 pcf0.6 pcf

weathered2.5 pcf C&D 1 C&D 3

- As(III) highest - weathered wood- As(V) highest - 2.5 pcf- Total As increased with increasing retention- As from 0.6 pcf weathered > 0.6 pcf new wood

0

50

100

150

200

250

300

350

400Conce

ntr

ati

on (m

g/L)

Results of TCLP Wood Ash

TCLP 5 mg/L

As(III)As(V)Total

untreated

0.25 pcf0.6 pcf

weathered2.5 pcf C&D 1 C&D 3

- As(III) highest – 2.5 pcf- As(V) highest - 2.5 pcf- Total As increased with increasing retention- As from 0.6 pcf weathered > 0.6 pcf new wood

Results of SPLP Unburned Wood

SPLP0.05 mg/L

As(III)As(V)Total

untreated

0.25 pcf0.6 pcf

weathered2.5 pcf C&D 1 C&D 3

- As(III) highest - weathered wood- As(V) highest – 0.6 pcf- Total As increased to 0.6 pcf & decline at 2.5 pcf- As from 0.6 pcf weathered > 0.6 pcf new wood

0

2

4

6

8

10

12

Co

nce

ntr

ati

on

(mg/

L)

Results of SPLP Wood Ash

SPLP0.05 mg/L

As(III)As(V)Total

untreated

0.25 pcf0.6 pcf

weathered2.5 pcf C&D 1 C&D 3

- As(III) highest – 2.5 pcf- As(V) highest - 2.5 pcf- Total As increased with increasing retention- As from 0.6 pcf weathered < 0.6 pcf new wood

0

50

100

150

200

250

300

350C

on

cen

tra

tio

n (m

g/L)

Results of TCLP & SPLP

Sample

Untreated

0.25 pcf

0.6 pcf

Weathered

2.5 pcf

C&D 1

C&D 3

TCLP (U)

0.02

3.9

5.4

8.3

9.0

1.3

0.2

TCLP (A)

0.08

126

217

224

386

9.2

11.2

SPLP U)

0.03

3.7

6.7

10

5.7

0.5

0.03

SPLP (A)

0.02

56.2

179

128

325

0.5

2.5

Total As – mg/L Fail TCLP – 5mg/LU – unburned wood Fail SPLP – 0.05 mg/LA - ash

Summary of Results TCLP & SPLP

• Ash samples leached considerably more As- Ash (new) ~118 to 245 mg/L (TCLP)

~ 53 to 330 mg/L (SPLP)- Unburned (new) ~3 to 10 mg/L (TCLP)

~ 3 to 6 mg/L (SPLP)

• As(III) predominant in weathered than new

• Overall As leaching for SPLP < TCLP- SPLP (pH ~4.22) & TCLP (pH ~4.93) - As release sensitive to small pH changes

• All failed TCLP & SPLP regulatory limit set forth for other arsenic-containing wastes

Group 1 - Controlled Laboratory Batch Experiments

Solvent-Extraction – Deionized Water

• Unburned CCA-treated wood subjected to deionized water & rotated for 18 2 hrs.

Unburned CCA-treated wood

Untreated0.25 pcf0.6 pcfWeathered (0.6 pcf)2.5 pcfC&D 1C&D 2

Results of Deionized Water(Hypothetical Scenario)

As(III)As(V)Total

untreated

0.25 pcf0.6 pcf

weathered2.5 pcf C&D 1 C&D 3

0

1

2

3

4

5

6C

once

ntr

atio

n (m

g/L)

- As(III) highest - weathered wood- As(V) highest – 0.6 pcf- Total As increased to 0.6 pcf & decline at 2.5 pcf- As from 0.6 pcf weathered > 0.6 pcf new wood

Summary of Results of Deionized Water

• Unburned (new) ~2.5 to 4.5 mg/L

• Unburned (weathered) ~ 5 mg/L

• As(III) predominant in weathered

• pH of deionized water ~ 6.27 - pH of new wood sample ~4.3- pH of weathered sample ~5.2 - DI water -no buffering capacity- CCA chemical caused acidic leachate- One factor that drives As leaching - pH

Group 2 - Controlled Field-Scale Experiments

Lysimeter Study - to be discussed by Jenna Jambeck (University of

Florida)

Deck Study – to be discussed by Dr. Helena Solo-Gabriele

(University of Miami)

Tasks to be Completed

Group 1- Controlled Lab Batch Expt- Rainwater & Seawater Extraction

Group 2 - Controlled Field-Scale Expt- Lysimeter study – awaiting rainfall- Deck study – deck completion

(end of May)

Group 3 - Uncontrolled Field-Scale Expt- Re-collect & re-analyze groundwater & landfill leachate in Florida

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