Polychlorinated biphenyl (PCB) contaminated sediments pose a risk to human health and ecological integrity. These bioaccumulate in organisms that inhabit contaminated waters.  Sediments often continue to receive ongoing contaminant inputs after remedies are put in place due to incomplete source identification or poor source control.  Studies have found correlation between porewater concentration and bioavailability. In this study, bioaccumulation was examined in 3 organisms with different associations with the sediment in laboratory mesocosms. Three replicate mesocosms received clean input sediment and three replicate mesocosms received contaminated input sediment (spiked with PCB 13, 54 and 173). This design allowed comprehensive testing of remediation efficacy of sand capping, mixed sand and activated carbon (AC) capping, and the combination of mixed capping and AC addition to surface. Organisms were analysed for lipid-normalized concentrations of PCBs and polyethylene passive samplers were deployed to determine sediment porewater concentrations. Percent reduction in sediment porewater and organism tissue concentration between uncapped and sand capped sediment was examined.  Sand Capping showed efficacy in reducing total PCB porewater concentration and tissue concentration relative to control conditions. Total porewater concentration was reduced 69% and 80% in clean and spiked input mesocosms respectively. This was lower than in AC amended experiments which showed 100% reduction in porewater concentration in clean and spiked mesocosms.  Fish tissue was reduced by 65% and 80% and in AC amendment 96% and 76% in clean and spiked mesocosms respectively.   Sand capping, with the exception of congener 54 in worm tissue, showed decreased concentration of all input congeners in all organsims and in porewater relative to control conditions.  AC amendement showed increases in tissue concentrations of input congeners across all three organisms in both spiked and clean input mesocosms relative to control.   The parameters of these experiments, including relatively short duration (90 d) and lack of turbulence, present some limitaiton in extrapolation of results to field applications. AC reduces thermodynamic exposure to organisms and sand capping creates a physical barrier. Over time, AC will continue to sorb.  This is not likely the case with the sand cap which may degrade overtime.  Presentation will also include data from mixed cap and mixed cap+ AC experiments.

Thermodynamic exposure reduction by amendment techniques to limit bioaccumulation during ongoing depositional input – a sediment mesocosm study with three organisms

256th National Meeting (2018)

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