Comparing Polychaete and Polyethylene Uptake to Assess Sediment Resuspension Effects on PCB Bioavailability

Polyethylene sampler uptake was compared to polychaete uptake to assess bioavailability of polychlorinated biphenyls (PCBs) from resuspended sediments. New Bedford Harbor (MA, U.S.) sediment contaminated with PCBs, was resuspended under four different water column oxidation conditions: resuspension alone, resuspension under aeration, resuspension under helium, and no resuspension (control). Residuals were tested for differences in PCB availability to the marine polychaete Nereis virens and to polyethylene (PE) passive samplers. Few significant differences between the four resuspension treatments were observed: under aeration, three of 23 PCBs analyzed showed significant increases in polychaete accumulation, while resuspension alone showed increased concentrations in PE samplers for nine of 23 PCBs. Otherwise, no differences were observed and overall we concluded that resuspension had no effect on residual PCB availability. The relationship between disequilibrium-corrected PE and lipid-normalized polychaete PCB concentrations was nearly 1:1 with a strong linear correlation (r2 = 0.877), demonstrating PCBs are taken up similarly into PE and lipid. On average, PE samplers suggested dissolved PCB concentrations 3.6 times greater than those calculated with lipid-water partitioning, though on a congener-specific basis this was only observed for lower chlorinated PCBs; for higher chlorinated PCBs, PE-water partitioning suggested lower dissolved concentrations than those based on lipid. Organic carbon (OC)-water and OC and black carbon combined (OC+BC)-water partitioning suggested average dissolved concentrations 29 and 10 times greater, respectively, than those estimated with lipid-water partitioning. This demonstrates that PE-measured porewater concentrations can provide a more reliable estimate of bioavailability than sediment geochemistry.