Bioavailability has been estimated in the past using equilibrium partitioning-based biota-sediment accumulation factors. These values are not always reliable using field-collected sediments, however, likely due to varying amounts of different organic carbons, particularly black carbon, in sediments. Therefore, improving approaches to better evaluate contaminant bioavailability in sediment are needed. In the present study, a literature-based model was constructed that relied on both laboratory-exposed and field-collected oligochaete bioaccumulation data. The model system used 24-h Tenax extraction data paired with bioaccumulation tests using oligochaetes to establish the ability and utility of the biomimetic extraction. The model was then tested to confirm its utility and reliability to estimate bioavailability of oligochaetes exposed to polychlorinated biphenyl (PCB) contaminated sediments from the Ottawa River in Ohio, USA. The model correctly identified the bioaccumulation of PCBs for 94.9% of the data and 97% of the dioxin-like congeners. The mono- and di-substituted chlorinated biphenyls were the least well described, but the estimates were conservative, for example, the model overpredicted bioaccumulation. Thus, the Tenax model was robust and reliable across a wide range of sediment characteristics for estimating PCB bioaccumulation in oligochaetes.

Recent literature has shown that bioavailability-based techniques, such as Tenax extraction, can estimate sediment exposure to benthos. In a previous study by the authors, Tenax extraction was used to create and validate a literature-based Tenax model to predict oligochaete bioaccumulation of polychlorinated biphenyls (PCBs) from sediment; however, its ability to assess sediment remediation was unknown. The present study further tested the Tenax model by examining the impacts of remediation on surface sediment concentrations, Tenax extractable concentrations, and tissue concentrations of laboratory-exposed Lumbriculus variegatus. Tenax extractable concentration was an effective exposure metric to evaluate changes in Lumbriculus exposure preremediation and postremediation, with 75% of the postremediation data corresponding to the Tenax model. At nondredged sites, bioaccumulation was better predicted by the Tenax model, with 86% of the data falling within the 95% confidence intervals, than at dredged sites, for which only 64% of the data fit the Tenax model. In both pre- and postdredge conditions, when the model failed, it was conservative, predicting higher PCB concentrations than observed in the oligochaetes, particularly for the postdredge data. The present study advances understanding of the applicability of the Tenax model for use when examining systems that may have undergone significant disturbances. The Tenax model provides a unique tool for quickly quantifying potential exposure to benthic organisms.