Transcript Arsenic speciation in Soil and Sediment

Arsenic speciation in
Soil and Sediment
Myron Georgiadis
Florida International University
TAG Meeting January 10, 2003
Backgrounds
Leaching occurs from CCA-Treated Wood
into soil and sediments
Traditional methods for arsenic analysis in
soil - Digestion
Develop an extraction method for Arsenic
in soils and sediments while preserving
the species.
Method Development
Reference Soil PACS2
PACS2 – Marine Sediment Reference Material
from National Research Council Canada
Extraction Solution: pH, Buffer Capacity,
Chemical Interactions
PACS2 was extracted with a phosphate
buffer.
Analyzed by HPLC-HG-AFS.
Arsenic Concentration vs Time
9
8
As(III)
As(V)
Conc. ( m g/g)
7
6
5
4
3
2
1
0
1
3
5
Time Extracted (hours)
- Conversion of As(III) to As(V).
- Reabsorption back into soil.
12
24
Approaches
Potential Effect of Fe and Mn
Extract with EDTA to remove metals from
solution which may aid in the
interconversion
Provide a reducing environment using
hydroxylamine
Use of Complexing Reagent NaDDC and
APDC
Potential Effect of Fe and Mn
2.50
As(III)
As(V)
Conc (m g/g)
2.00
1.50
1.00
0.50
0.00
1
3
5
12
Extraction Time (Hours)
24
Extraction with EDTA
Conc (m g/g)
PACS2 Extraction with PO4 + EDTA
9.0
8.0
7.0
6.0
5.0
As(III)
As(V)
4.0
3.0
2.0
1.0
0.0
1
3
5
12
Time Extracted (Hours)
24
Use of Hydroxylamine
5.E+06
As(III)
4.E+06
As(V)
Peak Area
4.E+06
3.E+06
3.E+06
2.E+06
2.E+06
1.E+06
5.E+05
0.E+00
24
0
Time (Hours)
Use of Hydroxylamine
Arsenite stability over a period of 24 hours with
and without 1% Hydroxyl Amine
As(III)
50ppb Spiked Arsenite
PO4 NH2OH
70.0
Conc (ppb)
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0
24
Time (Hours)
Complexing Reagents
Sodium diethyldithiocarbamate
trihydrate (NaDDC)
Ammonium pyrrolidine
dithiocarbamate (APDC)
Arsenic Concentrations in
Marine Organisms Attached to
CCA-treated Wood
Organisms analyzed: soft coral, hydroids,
crabs, barnacles, orange sponge, yellow
sponge, black sponge, oyster, tube worm,
amphipods, starfish, unknown invertebrate
(black outer layer, soft inner)
Hydroids and amphipods showed elevated
arsenic concentration for those collected from
on CCA-wood
As Speciation: standards
[ 2
5
0
0
]
T
I C
: 4
5
5
5
8
. D
[ C
o
u
n
t ]
0
10 ppb standards
1
2
5
0
5
0
4
3
2
s
e
c
- >
0
2
0
0
4
0
0
6
0
0
8
0
0
1
0
0
0 1
2
0
0 1
4
0
0 1
6
0
1. AsB; 2. As(III); 3. DMA; 4. MMA; 5. As(V)
0 1
8
0
0 2
0
0
0
As speciation: Hydriods on Concrete
Pilings
[ 2
2
0
0
]
T
I C
0
0
5
5
8
4
. D
[ C
o
u
n
t ]
0
Unknown 1
AsB
1
: 4
0
Unknown 3 or MMA
Unknown 2
AsC
As(V)
As(III)
DMA
s
e
c
- >
0
2
0
0
4
0
0
6
0
0
8
0
0
1
0
0
0 1
2
0
0 1
4
0
0 1
6
0
0 1
8
0
0 2
0
0
0
As speciation: Barnacle on OLD RSMAS
Pier
[ 2
5
0
0
]
T
I C
: 4
5
5
7
0
. D
[ C
o
u
n
t ]
0
AsB
Unknown 1
2
5
0
0
Unknown 3 or MMA
Unknown
Unknown
22
As(III)
Unknown 4
As(III)
AsC
AsC
As(V)
As(V)
DMA
s
e
c
- >
0
2
0
0
4
0
0
6
0
0
8
0
0
1
0
0
0 1
2
0
0 1
4
0
0 1
6
0
0 1
8
0
0 2
0
0
0
Acknowledgements
Dr. Helena Solo-Gabriele
Dr. Pat Walsh
Dr. Greg Mayer
Dr. John Barimo
Ms. Zhangrong Chen
Mr. Myron Georgiadis