Effect of PCB Bioavailability Changes in Sediments on Bioaccumulation in Fish

In situ sediment amendment with sorbents such as activated carbon (AC) can effectively reduce the bioavailability of hydrophobic organic chemicals such as polychlorinated biphenyls (PCBs). However, there is limited experimental or modeling assessment of how bioavailability changes in sediments impact bioaccumulation in fish - the primary risk driver for exposure to humans and top predators in the aquatic ecosystem. In the present study we performed laboratory aquarium experiments and modeling to explore how PCB sorption in sediments impacted exposure pathways and bioaccumulation in fish. Results showed that freely dissolved PCBs in porewater and overlying water measured by passive sampling were reduced by more than 95% upon amendment with 4.5% fine granular AC. The amendment also reduced the PCB uptake in fish by 87% after 90 days of exposure. Measured freely dissolved concentrations were incorporated in equilibrium and kinetic models for predicting uptake by fish. Predicted uptake using the kinetic model was generally within a factor of 2 for total PCBs measured in fish. The kinetic model output was most sensitive to overlying water PCBs, lipid fraction, and dissolved oxygen concentration (regulating gill ventilation). Our results indicate that by incorporating changes in freely dissolved PCB concentrations in bioaccumulation models it is possible to predict effectiveness of sediment remediation in reducing PCB uptake in fish.