arsenic speciation of cca-treated wood bernine khan university of miami may 6th, 2002
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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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