Uptake of polychlorinated biphenyls (PCBs) by fish is controlled by the bioavailability of ingested PCBs in the gut and the freely dissolved concentration in the water moving across the gills. Prediction of bioaccumulation in fish relies on models that account for these exposure routes, however, these models typically do not account for incidental ingestion of sediment by fish, which is not well studied. The literature values for the PCB assimilation efficiency (AE) in the gut have been reported for compounds in food matrices and not associated with sediment particles. It is also unclear how mitigation strategies that alter PCB bioavailability in sediments affect predictions made by the bioaccumulation models when sediment ingestion is involved. To test the bioavailability of PCBs from treated and untreated sediments, dietary AEs were measured for 16 polychlorinated biphenyl (PCB) congeners in mummichogs (Fundulus heteroclitius) that were fed four experimental diets. Diets consisted of PCB-spiked earthworms, spiked untreated sediment mixed with earthworms, spiked activated carbon (AC)-treated sediment mixed with earthworms, and spiked AC mixed with earthworms. AEs were determined by calculating the ratio of PCB mass in the fish tissue to the PCB mass in the food after a pulse feeding experiment. AEs of PCBs associated with earthworm diet were similar to the values reported in the literature. Fish that were fed the PCB-spiked untreated sediment and AC particles exhibited the highest and lowest AEs respectively over a wide KOW range, respectively. AEs of sediment-bound PCBs were significantly reduced (31 to 93% reduction for different congeners) upon amendment with AC. The present study indicates that assimilation of PCBs can be reduced by sorption to black carbon.
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