As and Cr Speciation of New & Weathered CCA-Treated Wood

• Purpose

• Basic As and Cr Chemistry

• Solvent-Extraction Leaching Experiments

(Cr & As)

• As Analysis of GW at Florida C&D Landfills

• As Leaching from Lysimeters

Outline

• Quantify As & Cr species in leachates from CCA-treated wood

• As & Cr toxicity varies with each specie

• As & Cr mobility varies with each specie

• Estimate the impact of As & Cr leaching from in-service & disposed CCA-treated wood on groundwater

Purpose & Motivation of Study

As Speciation

Arsenic

As(III) As(V) MMAA DMAA

Inorganic Organic

-3 0 +1 +3 +5Valence

InorganicArsine (g)

Arsenic

As(III) As(V) MMAA DMAA

Inorganic Organic

-3 0 +1 +3 +5Valence

InorganicArsine (g)

As Speciation

Toxicity & Mobility

Arsenic

As(III) As(V) MMAA DMAA

Inorganic Organic

-3 0 +1 +3 +5Valence

InorganicArsine (g)

As Speciation

Toxicity & Mobility Toxicity & Mobility

Cr Speciation

Chromium

Cr(VI) Cr(III)

Inorganic

0+3+6Valence

Inorganic

Cr Speciation

Toxicity & Mobility

Analytical Methods for Speciation

• As: HPLC-ICP-MS or HPLC-HG-AFS

• Cr: IC for Cr(VI) Total Cr by ICP-AES Cr(III) by difference

Solvent Extraction Study

CCA-treated wood subjected to leaching solvent, rotated for 18 2 hrs & filtered. Filtrate analyzed for As & Cr species

New CCA-treated

wood

TCLP

SPLP

DI Water

Rainwater

Untreated0.25 pcf0.6 pcf2.5 pcf

WeatheredCCA-treated

wood

PlaygroundUtility pole

FenceC&D waste

Solvent-Extraction of CCA-Treated Wood

pH 1,2,3. etc..

pH Experiment - New Wood (0.32 pcf)

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

Total As (As(V)) – HPLC-HG-AFSTotal As – ICP-AES

0

5

10

15

20

25

30

35

40

1.00

2.00

3.00

4.00

5.00

6.00

6.28

6.93

7.52

7.96

9.13

10.9

0

12.6

5

pH

Ars

en

ic C

on

ce

ntr

ati

on

(m

g/L

)

Environmental pH

pH Experiment - Weathered Wood (0.41 pcf)

• As(III) & As(V) detected, As(III) up to pH 9.5• Environmental pH range – Total As increase Total As > 5 mg/L

05

1015202530354045

1.27

2.56

3.72

4.15

5.16

5.41

6.54

8.04

9.43

10.1

9

10.6

8

11.9

1

12.7

6

pH

Ars

enic

Co

nce

ntr

atio

n (

mg

/L)

Environmental pH

As(III)As(V)Total As - HPLC-HG-AFSTotal As – ICP-AES

0

2

4

6

8

10

12

J (4

6.01

)

L (

27.

54)

H (

24.

57)

K (

20.

37)

G (

13.0

3)

I (9

.12)

D (

5.9

0)

C (

5.6

3)

B (

4.0

6)

E (

3.86

)

F (

3.6

2)

A (

1.4

9)

M (

24.

05)

N (

6.2

6)

Q (

5.79

)

O (

5.28

)

R (

5.4

7)

S (

3.16

)

P (

1.96

)

V (

1.86

)

T (

1.4

1)

SPLP

Ars

enic

Co

nce

ntr

atio

n (

mg

/L)

As(III)

As(V)

Total As

Retention (kg/m3)

New Weathered

SPLP New & Weathered Wood(Simulated Rain Water)

Leachate As Conc. vs CCA Retention

0123456789

10

0 5 10 15 20 25 30 35 40 45 50

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14 16 18 20 22 24 26 kg/m3

kg/m3

New

Weathered

Total As Conc. (mg/L)

Total As Conc. (mg/L)

SPLPRainwaterTCLPDI WaterSeawater

0

5

10

15

20

25

30

1.0

2.1

3.2

4.2

5.1

5.6

6.3

6.9

7.5

8.0

9.1

10.9

12.7

pH

Con

c. o

f C

r (m

g/l)

Cr(VI)

Cr(III)

Total Cr

Environmental pH

pH Experiment - New Wood (0.32 pcf)

• Cr(III) predominates• Cr(VI) observed at high pH values

0

1

2

3

4

Untreated 0.25 pcf 0.6 pcf Pole 2.5 pcf C&D 1 C&D 3

Cr

Con

cen

trat

ion

(m

g/L

)

Total Cr = CrIII, SPLP

BDL

No Cr Data TCLP

• Unburned wood Cr as Cr(III)• No Cr(VI) observed

SPLP New & Weathered Wood

(Simulated Rain Water)

0

10

20

30

40

50

Untreated-ash 0.25 pcf-ash 0.6 pcf-ash Pole-ash 2.5 pcf-ash C&D 1-ash C&D 3-ash

Cr

Con

cen

trat

ion

(m

g/L

)

Total Cr = CrVI, TCLP

Total Cr = CrVI, SPLP

BDL

Note: TCLP Leachates for C&D 1-ash, C&D 3-ash, and Pole-ash Samples Were Not Analyzed.

BDLBDL

pH = 6.2

pHTCLP = 5.5

pHSPLP = 6.5

pH = 7.8

pH = 10.7

pH = 10.4

pH= 7.5pHTCLP = 5.1

pHSPLP = 4.7

• Ashing results in converstion of Cr(III) to Cr(VI)• Cr in ash leachate exists as Cr(VI)

Ash – SPLP and TCLP

R2 = 0.68

0

10

20

30

40

50

0 5 10 15

pH

Cr C

once

ntrat

ion (m

g/L

)C&D 3-ash

Pole-ash

0.25 pcf-ash

C&D 1-ash

2.5 pcf-ash 0.6 pcf-ash

Ash Results for Chromium

Low RetentionLevel WoodLeaches More Cr

• As & Cr species leaching pH dependent

• At environmental pH range (6-10)

- As ~ 5mg/L

- Cr ~ 1 mg/L

• More As leaching from weathered wood than new wood As(III)

• As Leaching in rainwater, TCLP, SPLP comparable. Seawater less.

• Incineration results in the conversion of some Cr(III) to Cr(VI). Greater conversion for lower retention levels.

Summary

??Questions?