Predicting bioaccumulation of PCBs in benthic organisms in field and laboratory exposures

Developing reliable estimates of contaminant concentrations in aquatic organisms is crucial for setting cleanup benchmarks, guiding sediment remediation strategies, and designing long-term monitoring at contaminated sediment sites. Passive sampling has been used in recent years to estimate contaminant availability for bioaccumulation predictions. This study compares tissue concentrations predicted by passive samplers with concentrations in measured tissues for both in situ and ex situ exposures. Paired deployments of polydimethylsiloxane (PDMS)-coated solid-phase microextraction fibers and test organisms were conducted at two U.S. Environmental Protection Agency-listed Superfund sites: Wetland 64 (estuarine) and Penniman Lake (freshwater). The polychlorinated biphenyl (PCB) congener concentrations were measured in sediment, porewater, and biota, including estuarine clams and polychaetes; fingernail clams and oligochaetes under both field (in situ) and laboratory (ex situ) conditions. In situ and ex situ exposures gave similar results for both tissue bioaccumulation and measured porewater concentrations. Measured tissue bioaccumulation (∑PCBs) correlated with PDMS uptake corrected for disequilibrium. The relationship varied by up to a log unit between sites due to differences in congener distribution between sites. The freely dissolved porewater concentrations estimated from PDMS correlated with in situ and ex situ tissue uptake on an individual congener basis in both clams and both sites according to log bioconcentration factor (±0.38) = 1.06 (±0.001)* log Kow (R2 = 0.997). The results suggest that polymeric uptake can predict total PCB bioaccumulation on a site-specific basis, whereas porewater concentrations provide a mechanistically consistent predictor of individual congener uptake across sites with differing sediment characteristics and organism types.