Dynamic PCB Partitioning in Ashtabula Harbor, Ohio Sediments

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1 Dynamic PCB Partitioning in Ashtabula Harbor, Ohio Sediments Andrew Lenox Environmental Engineer US Army Corps of Engineers, Buffalo District US Army Corps of Engineers

2 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

3 N Buffalo Lake Erie Ashtabula Erie Cleveland

4 Lake Erie Ashtabula Harbor

5 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

6 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

7 Biota-Sediment Accumulation Factor BSAF = Ct Cs Lipid TOC Site-specific BSAF values encompass unique bioavailability influencing parameters including contaminant and sediment sorption properties, resulting in variability

8 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

9 N Outer Harbor BSAFs range from 0.25 to 0.51 Lake Erie Lower River BSAFs range from 0.54 to 0.91 Upper River BSAFs range from 1.20 to 2.43

10 Factors Affecting Bioavailability Physical Contaminant resuspension Concentration gradient Chemical Contaminant sorption/desorption Biological Organism lipid content, size, growth rate, gender, diet, metabolism

11 Coal Dock and Stockpiles

12 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

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

14 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

15 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

16 BSAF Compared to BC Content % 45.00% % % 30.00% % 20.00% % % 5.00% BSAF Black Carbon (%TOC) 0.00% Moving Upstream from Outer Harbor

17 Potential Factors Influencing BSAF Variability Throughout the Harbor Equilibrium Time with Sediment Organic Matter Characteristics Sediment Resuspension/ Mixing BSAF Variability

18 Incorporating Variability into Dredged Material Management 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)

19 Incorporating Variability into Dredged Material Management Cs TOC = Ct Lipid BSAF 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

20 Ashtabula Harbor Total PCB Sediment Quality Guidelines (ug/kg) Outer Harbor Lower River Upper River

21 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

22 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

23 Questions?... US Army Corps of Engineers