Biogeochemistry of Capped Sediments
Biogeochemical Controls on Contaminant Mobility in Contaminated Sediments Following In Situ Capping Dr. David Himmelheber Geosyntec
David W. Himmelheber, Ph.D.
Biogeochemical Controls on Contaminant Mobility in Contaminated Sediments Following In Situ Capping
Environmental Business Council of New England 21 October 2011
Introduction Sediment contaminants
threaten health of aquatic organisms, wildlife, and humans 4,600 EPA Fish Advisories
restricting fish consumption from surface waters in 2010 44% of total lake acreage 41% of total river miles
Photograph by Skip Brown, www.nationalgeographic.com
USEPA. Fact Sheet: 2010 National Listing of Fish Advisories
Remedial options for sediments have been limited MNR EMNR 3
Removal In Situ Treatment
In Situ Capping
In Situ Capping
In Situ Capping: Clean material at the sediment-water interface Overlying Water
In Situ Cap
Bioturbation
Contaminated Aquatic Sediment 4
Resuspension
Diffusion Advection
Biogeochemistry of Capped Sediments Presence of cap can perturb redox cycling Implications for contaminant fate and transport Overlying Water
O2
In Situ Cap Aerobic mineralization of HOCs Oxyhydroxide binding of metals Reduction of nitroaromatics, chlorinated organics Reductive dechlorination Metal sequestration with S(s) Hg methylation
Contaminated Aquatic Sediment 5
Oxygen Reduction Nitrate Reduction Manganese Reduction
Aerobic
? Redox Transition Zone
cm
Anaerobic
m
Iron Reduction Sulfate Reduction Methanogenesis
Biogeochemistry of Capped Sediments Materials and Methods Surficial sediment obtained from Anacostia River, Washington, D.C. Elevated levels of PAHs, PCBs, metals
Homogenized and stored at 4 °C
Images from MSN Virtual Earth
6
6
Biogeochemistry of Capped Sediments Experimental Method
Capped Sediment Column • Packed with wet sediment
Freshwater
4 cm
ASTM C-33 Sand
7 cm
from the Anacostia River, Washington DC • Capped with ASTM C-33
concrete sand • 13 weeks of static incubation;
16 weeks upflow incubation simulated groundwater Q = 2.0 cm3 hr-1 v = 4.4 cm day-1; q = 2.4 cm day-1
7
7 cm Anacostia Sediment
5 cm
Biogeochemistry of Capped Sediment Analytical Method 19.05 mm
Redox conditions measured via Voltammetric Microelectrodes Microelectrodes Gold wire with Hg plated onto tip Housed within glass tubing filled with epoxy
Advantages: Measure multiple analytes with virtually nonconsuming process Minimizing sediment disturbance Multiple profiles with time High vertical resolution
8
Brendel, P.J. and G.W. Luther, 1995. Development of a gold amalgam voltammetric microelectrode for the determination of dissolved Fe, Mn, O2, and S(-II) in porewaters of marine and fresh-water sediments. Environmental Science & Technology. 29, 3, 751-761. 8
Biogeochemistry of Capped Sediments Results – Controls
200
300
400
0
40
40
20
20
0
0
-20
-20
-40
-40
-60
-60
-80
-80
-100
-100
-120
-120
-140
-140
-160
-160
-180
-180 100
200
300
400
500
O2, Mn2+, Fe2+, H2S ( M)
600
Depth (mm)
Depth (mm)
Water Anacostia sediment
100
Ferric-organic and FexSy complexes Curent Intensity (nA) (nA) – Current Intensity 100
200
300
400
40
40
20
20
0
0
-20
-20
-40
-40
-60
-60
0
100
200
O2, Mn O2, Mn2+, Fe2+, ΣH2S (μM)
2+
300
400
500
600
, Fe2+, H2S ( M)
Cap-water interface O2
Cap-water interface Sediment-cap interface O2
Uncapped sediment maintained redox stratification for duration of experiment 2+
Mn Sand control maintained oxic conditions for duration of experiment 2+ 9
Fe H2S
Mn2+ Fe2+
9
Water
Curent IntensityIII (nA) Organic-Fe (aq) and FexSy(aq) complexes
0
0
Sand Control
x
C-33 Sand
(aq)
Depth (mm)
Uncapped Control Organic-FeIII Sediment and Fe Sy(aq) complexes
Cap-water interfa Sediment-water in Sediment-water in O22 O 2+ Mn2+ 2+ Fe2+ H22S S ΣH organic-FeIIIIII(aq) Organic-Fe (aq) FexxS Syy(aq) Fe (aq)
Biogeochemistry of Capped Sediment III III Organic-Fe and FexSxy(aq) Organic-Fe(aq) Sy(aq)complexes complexes (aq) and Fe
and(nA) Fe Curent CurentIntensity Intensity (nA) (aq) xSy(aq)
0 0
400
100 100
200 200
4040
Water
300
Organic-FeIII
300 300
Organic-Fe (aq) and FexSy(aq) complexes complexes – Curent Current Intensity Intensity (nA) (nA) 400 400 0
100
200
300
40
16 weeks upflow
13 weeks static
2020
400
20
500
600
( M)
0
-20-20
-20
-40-40
-40
-60-60
-60
-80-80
-80
-100 -100
-100
-120 -120
-120
-140 -140
-140
Depth (mm) Depth (mm)
Anacostia sediment
Sand Cap
0 0
0 0
100 200 200 300 300 400 400 500 500 600 600 100
0
100
200
300
400
500
2+, Fe2+, ΣH S (μM) 2+ OH , SMn , Mn, Fe , Fe, , H ( M) O2, Mn , Fe2+, H2S ( M) O2O, 2Mn 2 22S2 ( M) 2+ 2+
2+2+
600
Cap-water interface Sediment-water interface Sediment-water interface O22 O 2+ Mn2+ 2+ Fe2+ H22S S ΣH
Oxygen penetration limited to the upper few centimeters Upward, vertical shift of biogeochemical processes into cap 10
Depth (mm)
complexes A)
)
ResultsIII – Static vs. Upflow
10
organic-FeIIIIII(aq) Organic-Fe (aq) FexxS Syy(aq) Fe (aq)
Biogeochemistry of Capped Sediment Microbial Colonization Goal: Quantify microbes in capped sediment column to assess degree of colonization and diversity of microbes present Bacteria present in all regions; Archaea present in most
200
300
40
20
20
0 1 2 3 4 5 6 7
-20 -40 -60
8
-80
9
-100
0 -20 -40 -60 -80 -100
10 -120
11
-140
1
2
0
3 100 4
200
5
300 6 4007
5008
Dissection number
O2, Mn2+, Fe2+, H2S ( M) 11
9 600
10
9
10
8
10
7
106 10
6
105 10
5
109
40
0
Depth (mm)
400
1010
108 107
4 104 10
103 103 102 102
-120
101 101
-140
100 100
10 Sand
10
Bacteria Archaea
1
10
10
10
10
10
10
Archaea N/D
100
Depth (mm) Gene copies / mL porewater
0
10
10
Gene copies/ aqueous mL sample
Bacteria and Archaea
Organic-FeIII(aq) and FexSy(aq) complexes Curent Intensity (nA)
2
3
4
10
10
10 5
6
7
8
9
10 Sand
Dissection number Sand Cap
Sediment
10
Biogeochemistry of Capped Sediment Microbial Colonization Bacteria with metal-reducing capabilities present in all regions 1010
% FeRB of Total Bacteria 0.4 4.0 2.7 4.1 6.3 8.7
7
1.2
8
3.8
9 10
6.9 0.2
109 Gene copies / mL porewater
Dissection Zone 1 2 3 4 5 6
108 107 106 105 104 103 102 101 100
1
2
3
4
5
6
7
8
9
10 Sand
Dissection number Sand Cap 12
Sediment
Biogeochemistry of Capped Sediment Microbial Colonization
• Increases in sulfate reducers in sediment • Methanogens comprised larger portion of
reflected geochemical data
Archaea in strongly anaerobic locations
Methanogens (and methane oxidizers) 10910
10
107 106 105 104 103 102 101
108
1077 10
10 1066 105
105 104
4 10 103 2
103 10 101 2
1
2
3
4
5
6
7
8
9
10 100
10 Sand
Dissection number
1
Dissection 1 2 Zone % dsrA of Total 0.0 0.3 Bacteria
2
3
4
5
6
7
8
9
10
Dissection number 3
4
5
6
0.5
0.7
2.1
2.9
7
8
9
10
1.6 22.2 22.3 6.7
Sand
109 108 107 106 105 104 103 102
1
2
3
4
101
100
Dissection 1 2 Zone % mcrA of Total 23.4 12.5 Archaea
5
6
7
8
9
10
Sand
100
Dissection number
101 Sediment
Sand Cap
Archaea mcrA
N/D N/D N/D
Gene copies / mL porewater
Gene copies / mL porewater
108
Gene copies/ aqueous mL sample
1089 10
109
100
1010
10
10
Sediment
Sand Cap
3 0
4
5
6
7
8
9
10
NA >100 92.5 57.9 75.9 >100 52.2
Biogeochemistry of Capped Sediment Knowledge Gained
Capping induced a vertical, upward shift of biogeochemical processes Bacteria and Archaea indigenous to sediment colonize cap
Implications for contaminant fate and transport Metal mobility Reducing zone elongated – more opportunities for reducing processes
Overlying Water In situ Cap
Active cap development
Aerobic
Microbially-Active Cap
Anaerobic
Indigenous Microorganisms + Redox Zones
Reducing processes favorable versus oxidative processes Contaminated Aquatic Sediment 14
O2
Anaerobic
Anaerobic
Application of Knowledge Onondaga Lake, NY
SMU 5
Partial dredging and isolation cap remedy Uncertainty regarding contaminant breakthrough of cap BTEX, chlorobenzenes (DCB + MCB), naphthalene + other PAHs, phenol Potential for contaminant biodegradation within cap? 15
Remediation SMU 4 Area A
SMU 8 SMU 3
Remediation Area B
Remediation Area C
SMU 2
Remediation Area E
SMU 6
SMU 1 Remediation Area D
SMU 7
Case Study Schematic of Cap Design
Overlying water column – zero concentration
Sediment Water Interface
Onondaga Lake high foc1
Model predicted contaminant concentration and flux
Habitat Layer (12” minimum)
low foc
Chemical Isolation Layer (12” minimum)
Sediment
Note: 1) foc – fraction organic carbon 2) Biological decay explicitly modeled for phenol, considered qualitatively for other compounds
16
Bioturbation & Bioirrigation Adsorption Advection Diffusion Dispersion Biological Decay2
Case Study Basis for Biotreatability Testing
Initial design incorporated concurrent anaerobic biodegradation of chlorobenzenes, BTEX and naphthalene in sediment cap
Literature suggests: Dechlorination of chlorinated benzenes can occur under anaerobic conditions
Degradation of BTEX & naphthalene under aerobic conditions Slower degradation of BTEX & naphthalene under anaerobic conditions
17
Case Study Treatability Testing for Biodegradation Constructed microcosms with sediment from different locations Spiked with target COPCs Total of 70 treatments, each in triplicate No amendments (anaerobic)
Sterile controls
Sulfate amendment
Temperature (12C vs 20C)
Nitrate amendment
pH
Aerobic (air amendment)
Subsamples within areas
Electron donor amendment
Amendment with other sediment
Monitored for over 400 days
18
Case Study Treatability Testing for Biodegradation
19
Case Study Results - Sediment Location A
Anaerobic Sterile Control benzene 1,2-DCB
MCB
20
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location A
Anaerobic Sterile Control
naphthalene
BTEX
21 21
Case Study Results - Sediment Location A
Anaerobic with No Amendment MCB
benzene
1,2-DCB
22
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location A
Anaerobic with No Amendment naphthalene
benzene
toluene
23
ethylbenzene
xylenes
Case Study Results - Sediment Location A
Aerobic Amended with Oxygen
1,2-DCB
MCB
1,3-DCB
1,4-DCB
benzene 24
24
Case Study Results - Sediment Location A
Aerobic Amended with Oxygen toluene
ethylbenzene benzene xylenes
naphthalene 25
25
Case Study Results - Sediment Location B
Anaerobic with No Amendment MCB
benzene
1,2-DCB
26
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 3 MCB benzene
1,4-DCB 1,2-DCB
27
1,3-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 2 MCB benzene
1,3-DCB 1,2-DCB
28
1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 1
MCB benzene
1,3-DCB 1,2-DCB
29 29
1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment naphthalene
toluene
30
ethylbenzene
benzene
xylenes
Case Study Results - Sediment Location C
Anaerobic with No Amendment
benzene
31
Case Study Major Conclusions
Microcosms show rapid dechlorination of DCB and biodegradation of toluene and phenol under unamended anaerobic conditions Longer-term sampling shows dechlorination of MCB in some microcosms and degradation of ethylbenzene and xylenes Also indication of benzene degradation in tests without DCB or MCB Amendment with nitrate or sulfate promotes degradation of BTEX and naphthalene Aerobic tests showed rapid biodegradation of BTEX, naphthalene and CB
32
Some biodegradation of DCB but slower than under anaerobic 32 conditions
Case Study Major Conclusions
Anaerobic biodegradation of contaminants will contribute significantly to cap longevity Challenging to develop explicit biotransformation rates for modeling Relatively rapid biodegradation in aerobic zone can reduce exposure to sediment biota Degradation will occur at different depth intervals and sampling in exposure zone relevant to assess risks 33 33
Overall Implications Better understanding of contaminant fate/transport within sediment caps Reduced uncertainty regarding contaminant breakthrough
Contaminant biotransformation can be a key component of a remedy (EMNR, MNR, capping) Treatability tests and contaminant fate/transport models can help predict cap/remedy performance
34 34
Questions? Colleagues Georgia Tech – Joe Hughes, Kurt Pennell, Martial Taillefert, Frank Löffler Geosyntec – Tom Krug, Jeff Roberts
Further Information Himmelheber et al., 2007. Natural Attenuation Processes During In Situ Capping. ES&T, 41: 5306-5313. Himmelheber et al., 2008. Spatial and Temporal Evolution of Biogeochemical Processes Following In Situ Capping of Contaminated Sediments. ES&T, 42: 4113-4120. Himmelheber et al., 2009. Microbial Colonization of an In Situ Sediment Cap and Correlation to Stratified Redox Zones, ES&T, 43: 66-74. Himmelheber et al., 2011. Evaluation of a Laboratory-Scale Bioreactive In Situ Sediment Cap for the Treatment of Organic Contaminants. Water Research, 45: 5365-5374. 35
David W. Himmelheber, Ph.D.
Biogeochemical Controls on Contaminant Mobility in Contaminated Sediments Following In Situ Capping
Environmental Business Council of New England 21 October 2011
Introduction Sediment contaminants
threaten health of aquatic organisms, wildlife, and humans 4,600 EPA Fish Advisories
restricting fish consumption from surface waters in 2010 44% of total lake acreage 41% of total river miles
Photograph by Skip Brown, www.nationalgeographic.com
USEPA. Fact Sheet: 2010 National Listing of Fish Advisories
Remedial options for sediments have been limited MNR EMNR 3
Removal In Situ Treatment
In Situ Capping
In Situ Capping
In Situ Capping: Clean material at the sediment-water interface Overlying Water
In Situ Cap
Bioturbation
Contaminated Aquatic Sediment 4
Resuspension
Diffusion Advection
Biogeochemistry of Capped Sediments Presence of cap can perturb redox cycling Implications for contaminant fate and transport Overlying Water
O2
In Situ Cap Aerobic mineralization of HOCs Oxyhydroxide binding of metals Reduction of nitroaromatics, chlorinated organics Reductive dechlorination Metal sequestration with S(s) Hg methylation
Contaminated Aquatic Sediment 5
Oxygen Reduction Nitrate Reduction Manganese Reduction
Aerobic
? Redox Transition Zone
cm
Anaerobic
m
Iron Reduction Sulfate Reduction Methanogenesis
Biogeochemistry of Capped Sediments Materials and Methods Surficial sediment obtained from Anacostia River, Washington, D.C. Elevated levels of PAHs, PCBs, metals
Homogenized and stored at 4 °C
Images from MSN Virtual Earth
6
6
Biogeochemistry of Capped Sediments Experimental Method
Capped Sediment Column • Packed with wet sediment
Freshwater
4 cm
ASTM C-33 Sand
7 cm
from the Anacostia River, Washington DC • Capped with ASTM C-33
concrete sand • 13 weeks of static incubation;
16 weeks upflow incubation simulated groundwater Q = 2.0 cm3 hr-1 v = 4.4 cm day-1; q = 2.4 cm day-1
7
7 cm Anacostia Sediment
5 cm
Biogeochemistry of Capped Sediment Analytical Method 19.05 mm
Redox conditions measured via Voltammetric Microelectrodes Microelectrodes Gold wire with Hg plated onto tip Housed within glass tubing filled with epoxy
Advantages: Measure multiple analytes with virtually nonconsuming process Minimizing sediment disturbance Multiple profiles with time High vertical resolution
8
Brendel, P.J. and G.W. Luther, 1995. Development of a gold amalgam voltammetric microelectrode for the determination of dissolved Fe, Mn, O2, and S(-II) in porewaters of marine and fresh-water sediments. Environmental Science & Technology. 29, 3, 751-761. 8
Biogeochemistry of Capped Sediments Results – Controls
200
300
400
0
40
40
20
20
0
0
-20
-20
-40
-40
-60
-60
-80
-80
-100
-100
-120
-120
-140
-140
-160
-160
-180
-180 100
200
300
400
500
O2, Mn2+, Fe2+, H2S ( M)
600
Depth (mm)
Depth (mm)
Water Anacostia sediment
100
Ferric-organic and FexSy complexes Curent Intensity (nA) (nA) – Current Intensity 100
200
300
400
40
40
20
20
0
0
-20
-20
-40
-40
-60
-60
0
100
200
O2, Mn O2, Mn2+, Fe2+, ΣH2S (μM)
2+
300
400
500
600
, Fe2+, H2S ( M)
Cap-water interface O2
Cap-water interface Sediment-cap interface O2
Uncapped sediment maintained redox stratification for duration of experiment 2+
Mn Sand control maintained oxic conditions for duration of experiment 2+ 9
Fe H2S
Mn2+ Fe2+
9
Water
Curent IntensityIII (nA) Organic-Fe (aq) and FexSy(aq) complexes
0
0
Sand Control
x
C-33 Sand
(aq)
Depth (mm)
Uncapped Control Organic-FeIII Sediment and Fe Sy(aq) complexes
Cap-water interfa Sediment-water in Sediment-water in O22 O 2+ Mn2+ 2+ Fe2+ H22S S ΣH organic-FeIIIIII(aq) Organic-Fe (aq) FexxS Syy(aq) Fe (aq)
Biogeochemistry of Capped Sediment III III Organic-Fe and FexSxy(aq) Organic-Fe(aq) Sy(aq)complexes complexes (aq) and Fe
and(nA) Fe Curent CurentIntensity Intensity (nA) (aq) xSy(aq)
0 0
400
100 100
200 200
4040
Water
300
Organic-FeIII
300 300
Organic-Fe (aq) and FexSy(aq) complexes complexes – Curent Current Intensity Intensity (nA) (nA) 400 400 0
100
200
300
40
16 weeks upflow
13 weeks static
2020
400
20
500
600
( M)
0
-20-20
-20
-40-40
-40
-60-60
-60
-80-80
-80
-100 -100
-100
-120 -120
-120
-140 -140
-140
Depth (mm) Depth (mm)
Anacostia sediment
Sand Cap
0 0
0 0
100 200 200 300 300 400 400 500 500 600 600 100
0
100
200
300
400
500
2+, Fe2+, ΣH S (μM) 2+ OH , SMn , Mn, Fe , Fe, , H ( M) O2, Mn , Fe2+, H2S ( M) O2O, 2Mn 2 22S2 ( M) 2+ 2+
2+2+
600
Cap-water interface Sediment-water interface Sediment-water interface O22 O 2+ Mn2+ 2+ Fe2+ H22S S ΣH
Oxygen penetration limited to the upper few centimeters Upward, vertical shift of biogeochemical processes into cap 10
Depth (mm)
complexes A)
)
ResultsIII – Static vs. Upflow
10
organic-FeIIIIII(aq) Organic-Fe (aq) FexxS Syy(aq) Fe (aq)
Biogeochemistry of Capped Sediment Microbial Colonization Goal: Quantify microbes in capped sediment column to assess degree of colonization and diversity of microbes present Bacteria present in all regions; Archaea present in most
200
300
40
20
20
0 1 2 3 4 5 6 7
-20 -40 -60
8
-80
9
-100
0 -20 -40 -60 -80 -100
10 -120
11
-140
1
2
0
3 100 4
200
5
300 6 4007
5008
Dissection number
O2, Mn2+, Fe2+, H2S ( M) 11
9 600
10
9
10
8
10
7
106 10
6
105 10
5
109
40
0
Depth (mm)
400
1010
108 107
4 104 10
103 103 102 102
-120
101 101
-140
100 100
10 Sand
10
Bacteria Archaea
1
10
10
10
10
10
10
Archaea N/D
100
Depth (mm) Gene copies / mL porewater
0
10
10
Gene copies/ aqueous mL sample
Bacteria and Archaea
Organic-FeIII(aq) and FexSy(aq) complexes Curent Intensity (nA)
2
3
4
10
10
10 5
6
7
8
9
10 Sand
Dissection number Sand Cap
Sediment
10
Biogeochemistry of Capped Sediment Microbial Colonization Bacteria with metal-reducing capabilities present in all regions 1010
% FeRB of Total Bacteria 0.4 4.0 2.7 4.1 6.3 8.7
7
1.2
8
3.8
9 10
6.9 0.2
109 Gene copies / mL porewater
Dissection Zone 1 2 3 4 5 6
108 107 106 105 104 103 102 101 100
1
2
3
4
5
6
7
8
9
10 Sand
Dissection number Sand Cap 12
Sediment
Biogeochemistry of Capped Sediment Microbial Colonization
• Increases in sulfate reducers in sediment • Methanogens comprised larger portion of
reflected geochemical data
Archaea in strongly anaerobic locations
Methanogens (and methane oxidizers) 10910
10
107 106 105 104 103 102 101
108
1077 10
10 1066 105
105 104
4 10 103 2
103 10 101 2
1
2
3
4
5
6
7
8
9
10 100
10 Sand
Dissection number
1
Dissection 1 2 Zone % dsrA of Total 0.0 0.3 Bacteria
2
3
4
5
6
7
8
9
10
Dissection number 3
4
5
6
0.5
0.7
2.1
2.9
7
8
9
10
1.6 22.2 22.3 6.7
Sand
109 108 107 106 105 104 103 102
1
2
3
4
101
100
Dissection 1 2 Zone % mcrA of Total 23.4 12.5 Archaea
5
6
7
8
9
10
Sand
100
Dissection number
101 Sediment
Sand Cap
Archaea mcrA
N/D N/D N/D
Gene copies / mL porewater
Gene copies / mL porewater
108
Gene copies/ aqueous mL sample
1089 10
109
100
1010
10
10
Sediment
Sand Cap
3 0
4
5
6
7
8
9
10
NA >100 92.5 57.9 75.9 >100 52.2
Biogeochemistry of Capped Sediment Knowledge Gained
Capping induced a vertical, upward shift of biogeochemical processes Bacteria and Archaea indigenous to sediment colonize cap
Implications for contaminant fate and transport Metal mobility Reducing zone elongated – more opportunities for reducing processes
Overlying Water In situ Cap
Active cap development
Aerobic
Microbially-Active Cap
Anaerobic
Indigenous Microorganisms + Redox Zones
Reducing processes favorable versus oxidative processes Contaminated Aquatic Sediment 14
O2
Anaerobic
Anaerobic
Application of Knowledge Onondaga Lake, NY
SMU 5
Partial dredging and isolation cap remedy Uncertainty regarding contaminant breakthrough of cap BTEX, chlorobenzenes (DCB + MCB), naphthalene + other PAHs, phenol Potential for contaminant biodegradation within cap? 15
Remediation SMU 4 Area A
SMU 8 SMU 3
Remediation Area B
Remediation Area C
SMU 2
Remediation Area E
SMU 6
SMU 1 Remediation Area D
SMU 7
Case Study Schematic of Cap Design
Overlying water column – zero concentration
Sediment Water Interface
Onondaga Lake high foc1
Model predicted contaminant concentration and flux
Habitat Layer (12” minimum)
low foc
Chemical Isolation Layer (12” minimum)
Sediment
Note: 1) foc – fraction organic carbon 2) Biological decay explicitly modeled for phenol, considered qualitatively for other compounds
16
Bioturbation & Bioirrigation Adsorption Advection Diffusion Dispersion Biological Decay2
Case Study Basis for Biotreatability Testing
Initial design incorporated concurrent anaerobic biodegradation of chlorobenzenes, BTEX and naphthalene in sediment cap
Literature suggests: Dechlorination of chlorinated benzenes can occur under anaerobic conditions
Degradation of BTEX & naphthalene under aerobic conditions Slower degradation of BTEX & naphthalene under anaerobic conditions
17
Case Study Treatability Testing for Biodegradation Constructed microcosms with sediment from different locations Spiked with target COPCs Total of 70 treatments, each in triplicate No amendments (anaerobic)
Sterile controls
Sulfate amendment
Temperature (12C vs 20C)
Nitrate amendment
pH
Aerobic (air amendment)
Subsamples within areas
Electron donor amendment
Amendment with other sediment
Monitored for over 400 days
18
Case Study Treatability Testing for Biodegradation
19
Case Study Results - Sediment Location A
Anaerobic Sterile Control benzene 1,2-DCB
MCB
20
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location A
Anaerobic Sterile Control
naphthalene
BTEX
21 21
Case Study Results - Sediment Location A
Anaerobic with No Amendment MCB
benzene
1,2-DCB
22
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location A
Anaerobic with No Amendment naphthalene
benzene
toluene
23
ethylbenzene
xylenes
Case Study Results - Sediment Location A
Aerobic Amended with Oxygen
1,2-DCB
MCB
1,3-DCB
1,4-DCB
benzene 24
24
Case Study Results - Sediment Location A
Aerobic Amended with Oxygen toluene
ethylbenzene benzene xylenes
naphthalene 25
25
Case Study Results - Sediment Location B
Anaerobic with No Amendment MCB
benzene
1,2-DCB
26
1,3-DCB
1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 3 MCB benzene
1,4-DCB 1,2-DCB
27
1,3-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 2 MCB benzene
1,3-DCB 1,2-DCB
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1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment Rep 1
MCB benzene
1,3-DCB 1,2-DCB
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1,4-DCB
Case Study Results - Sediment Location B
Anaerobic with No Amendment naphthalene
toluene
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ethylbenzene
benzene
xylenes
Case Study Results - Sediment Location C
Anaerobic with No Amendment
benzene
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Case Study Major Conclusions
Microcosms show rapid dechlorination of DCB and biodegradation of toluene and phenol under unamended anaerobic conditions Longer-term sampling shows dechlorination of MCB in some microcosms and degradation of ethylbenzene and xylenes Also indication of benzene degradation in tests without DCB or MCB Amendment with nitrate or sulfate promotes degradation of BTEX and naphthalene Aerobic tests showed rapid biodegradation of BTEX, naphthalene and CB
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Some biodegradation of DCB but slower than under anaerobic 32 conditions
Case Study Major Conclusions
Anaerobic biodegradation of contaminants will contribute significantly to cap longevity Challenging to develop explicit biotransformation rates for modeling Relatively rapid biodegradation in aerobic zone can reduce exposure to sediment biota Degradation will occur at different depth intervals and sampling in exposure zone relevant to assess risks 33 33
Overall Implications Better understanding of contaminant fate/transport within sediment caps Reduced uncertainty regarding contaminant breakthrough
Contaminant biotransformation can be a key component of a remedy (EMNR, MNR, capping) Treatability tests and contaminant fate/transport models can help predict cap/remedy performance
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Questions? Colleagues Georgia Tech – Joe Hughes, Kurt Pennell, Martial Taillefert, Frank Löffler Geosyntec – Tom Krug, Jeff Roberts
Further Information Himmelheber et al., 2007. Natural Attenuation Processes During In Situ Capping. ES&T, 41: 5306-5313. Himmelheber et al., 2008. Spatial and Temporal Evolution of Biogeochemical Processes Following In Situ Capping of Contaminated Sediments. ES&T, 42: 4113-4120. Himmelheber et al., 2009. Microbial Colonization of an In Situ Sediment Cap and Correlation to Stratified Redox Zones, ES&T, 43: 66-74. Himmelheber et al., 2011. Evaluation of a Laboratory-Scale Bioreactive In Situ Sediment Cap for the Treatment of Organic Contaminants. Water Research, 45: 5365-5374. 35
