Science Inventory

Comparing Equilibrium Concentrations of Polychlorinated Biphenyls Based on Passive Sampling and Bioaccumulation in Water Column Deployments

Citation:

Burgess, Robert M., Mark G. Cantwell, Z. Dong, James S. Grundy, AND A. Joyce. Comparing Equilibrium Concentrations of Polychlorinated Biphenyls Based on Passive Sampling and Bioaccumulation in Water Column Deployments. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY. Society of Environmental Toxicology and Chemistry, Pensacola, FL, 42(2):317-332, (2023). https://doi.org/10.1002/etc.5536

Impact/Purpose:

Recent advances in passive sampling methods can result in improved risk-based decision making at contaminated sediment sites (like Superfund sites). This is because passive sampling allows the bioavailability of sediment contaminants to be directly measured. This is important as biomonitoring at contaminated sites is expensive, not always logistically practical, and uses living organisms. Finding scientifically robust alternatives for biomonitoring, like passive sampling, is of interest to the U.S. EPA. For this investigation, concentrations of several sediment contaminants (specifically PCB congeners) bioaccumulated by the blue mussel (Mytilus edulis) were compared to concentrations taken-up by a polyethylene passive samplers (i.e., an inexpensive plastic film) during five deployments over a three-year time-period at the U.S. EPA Superfund site in New Bedford Harbor (MA, USA). For one deployment, the metal passive sampling system called "Gellyfish" was also deployed and the concentrations of several metals bioaccumulated by the mussels were compared to the concentrations accumulated by the passive sampler. Results of this investigation will provide environmental scientists and managers with useful information for using passive sampling data for making informed decisions about contaminated sites. Specifically, these results will assist in deciding how to interpret passive sampling data compared to traditional biomonitoring data. Ultimately, this investigation will contribute to the successful clean-up and restoration of contaminated sites around the United States.

Description:

Biomonitoring at contaminated sites undergoing cleanup, including Superfund sites, often uses bioaccumulation of anthropogenic contaminants by field-deployed organisms as a metric of remedial effectiveness. Bioaccumulation studies are unable to assess the equilibrium status of the organisms relative to the contaminants to which they are exposed. Establishing equilibrium provides a reproducible benchmark on which scientific and management decisions can be based (e.g., comparison with human dietary consumption criteria). Unlike bioaccumulating organisms, passive samplers can be assessed for their equilibrium status. In our study, over a 3-year period, we compared the bioaccumulation of selected polychlorinated biphenyls (PCBs) by mussels in water column deployments at the New Bedford Harbor Superfund site (New Bedford, MA, USA) to codeployed passive samplers. Based on comparisons to the calculated passive sampler equilibrium concentrations, the mussels were not at equilibrium, and the subsequent analysis focused on evaluating approaches for estimating equilibrium bioaccumulation. In addition, a limited evaluation of metal bioaccumulation by the exposed mussels and a metal passive sampler was performed. In general, mussel and passive sampler accumulation of PCBs was significantly correlated; however, surprisingly, agreement on the magnitude of accumulation was optimal when bioaccumulation and passive sampler uptake were not corrected for nonequilibrium conditions. A subsequent comparison of four approaches for estimating equilibrium mussel bioaccumulation using octanol–water partition coefficients (KOW), triolein–water partition coefficients (KTW), and two types of polymer–lipid partition coefficients demonstrated that field-deployed mussels were not at equilibrium with many PCBs. A range of estimated equilibrium mussel bioaccumulation concentrations were calculated, with the magnitude of the KOW-based values being the smallest and the polymer–lipid partition coefficient-based values being the largest. These analyses are intended to assist environmental scientists and managers to interpret field deployment data when transitioning from biomonitoring to passive sampling.