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Dynamic PCB Partitioning in Ashtabula Harbor, Ohio Sediments

Andrew Lenox

Environmental Engineer

US Army Corps of Engineers, Buffalo District

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IntroductionAshtabula Harbor, Ohio►Federally (USACE) maintained deep-draft

harbor►USEPA Great Lakes Area of Concern (AOC)

• Restriction on dredging beneficial use impairment (BUI)

• Contaminants of Concern (COC) listed as mercury, chromium, lead, zinc, chlorinated organic compounds, polychlorinated biphenyls (PCBs), and low level radionuclides

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Buffalo

Cleveland

Ashtabula

Lake Erie

Erie

N

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Lake Erie

Ashtabula Harbor

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BackgroundPCBs are main COC with respect to dredged material management►Evaluation based on tiered assessment of

bioaccumulation in benthic organisms (Great Lakes Dredged Material Testing and Evaluation Manual )

• Use sediment chemistry data to model bioaccumulation

• Measure uptake into tissue in lab

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Theoretical Bioaccumulation Potential (TBP) Model

►Equilibrium partitioning theory-based algorithm for bioaccumulation of sediment associated non-polar organic contaminants in benthic organisms

►BSAF – Biota-Sediment Accumulation Factor, a measure of bioavailability that relates TOC normalized contaminant concentration in sediment to lipid-normalized contaminant concentration in organisms

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Biota-Sediment Accumulation Factor

TOCCsLipidCtBSAF =

Site-specific BSAF values encompass unique bioavailability influencing parameters including contaminant and sediment sorption properties, resulting in variability

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BSAF Variability Within Ashtabula Harbor

Bioaccumulation testing show BSAFs within the harbor differ significantly -ranging from 0.25 to 2.43Lower BSAFs►Outer Harbor and Lower River ChannelHigher BSAFs►Upper limits of Federal Channel

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Outer HarborBSAFs range from 0.25 to 0.51

Lower RiverBSAFs range from 0.54 to 0.91

Upper RiverBSAFs range from 1.20 to 2.43

Lake Erie

N

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Factors Affecting Bioavailability

Physical►Contaminant resuspension►Concentration gradient

Chemical►Contaminant sorption/desorption

Biological►Organism lipid content, size, growth rate,

gender, diet, metabolism

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Coal Dock and Stockpiles

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Black Carbon

Coal dock and stockpiles are located at the head of the Ashtabula River►Condensed, aromatic carbonaceous material

show strong and nonlinear sorption, leading to lower bioaccumulation than assumed for natural organic matter

►PCBs partition onto black carbon over time

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Strong BC Influence

Outer Harbor provides an accumulation area for black carbon affected sediments, leading to increased contact time between PCBs and sediment

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Moderate BC Influence

Lower River sediments reflect differing degrees of contact time between PCBs and sediment ►Riverine and lacustrine current-based coal

soot deposition►More stable sediments at depth show

bioavailability similar to the Outer Harbor

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Negligible BC Influence

Upper River sediments receive less lacustrine current-based coal soot depositionBSAFs of 1.2 to 2.43 are more reflective of PCB bioavailability associated with a predominance of natural TOC in sediments

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BSAF Compared to BC Content

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

0.00

0.50

1.00

1.50

2.00

2.50

3.00

1 2 3 4 5 6 7 8 9

BSAF Black Carbon (%TOC)

Moving Upstream from Outer Harbor

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Potential Factors Influencing BSAF Variability Throughout the Harbor

BSAFVariability

Organic MatterCharacteristics

Equilibrium Time with Sediment

Sediment Resuspension/

Mixing

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PCB Sediment Quality Criterion (SQC) needed to model future dredging restrictions►Should emphasize a bioaccumulation

endpoint►Should be spatially variable (due to spatial

changes in PCB bioavailability)

Incorporating Variability into Dredged Material Management

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Incorporating Variability into Dredged Material Management

Develop SQG based on TBP model and site-specific BSAFs Use Lake reference area tissue dataSQG predicts bioaccumulation from harbor sediment similar to that expected in the open-lake

BSAFLipidCtTOCCs =

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Ashtabula Harbor Total PCB Sediment Quality Guidelines (ug/kg)

300

200

70

Outer Harbor Lower River Upper River

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Dredged Material Management Considerations

PCB bioavailability is key driver in the characterization and management of Ashtabula Harbor dredged material ►Variability results in different conclusions

throughout the harbor►Bioavailability rather than bulk sediment

concentrations dictates suitability determinations

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ConclusionsPCB contamination in harbors can be assessed based on bioavailabilityBioavailability can be variable; use of default BSAFs may be overly conservative or inaccurate in estimating bioavailability TBP model with site specific, empirical BSAFs can be utilized in dredged material testing and evaluation

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Questions?. . .