US Army Corps of Engineers

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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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Introduction Ashtabula 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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Background PCBs 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

TOCCs

LipidCtBSAF

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 2.43

Lower BSAFs►Outer Harbor and Lower River Channel

Higher 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 deposition

BSAFs 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

1 2 3 4 5 6 7 8 90.00

0.50

1.00

1.50

2.00

2.50

3.00

0.00%

5.00%

10.00%

15.00%

20.00%

25.00%

30.00%

35.00%

40.00%

45.00%

50.00%

BSAF Black Carbon (%TOC)

Moving Upstream from Outer Harbor

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Potential Factors Influencing BSAF Variability Throughout the Harbor

BSAF

Variability

Organic Matter

Characteristics

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 data SQG predicts bioaccumulation from harbor

sediment similar to that expected in the open-lake

BSAF

LipidCtTOCCs

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

Outer Harbor Lower River Upper River

300

200

70

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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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Conclusions PCB contamination in harbors can be

assessed based on bioavailability Bioavailability 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

US Army Corps of Engineers

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Questions?. . .