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• 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
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