Comparing Equilibrium Concentrations of PCBs based on Passive Sampling and Bioaccumulation in Water Column Deployments.
Citation:
Burgess, R., M. Cantwell, Z. Dong, J. Grundy, AND A. Joyce. Comparing Equilibrium Concentrations of PCBs based on Passive Sampling and Bioaccumulation in Water Column Deployments. SETAC North America, 43rd Annual Meeting, Pittsburgh, PA, November 13 - 17, 2022.
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 clean-up, including Superfund sites, often use bioaccumulation of anthropogenic contaminants by field-deployed organisms as a metric of remedial effectiveness. Such 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 upon which scientific and management decisions can be based (e.g., comparison to dietary consumption criteria). Unlike bioaccumulating organisms, passive samplers can be assessed for their equilibrium status and are being considered as a surrogate for bioaccumulation at some sites. In this investigation, over a three-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 co-deployed passive samplers. Analysis of the data focused on which approaches for estimating equilibrium bioaccumulation best agreed with calculated passive sampler equilibrium concentrations. In addition, a limited evaluation of metal bioaccumulation by the exposed mussels and a metal passive sampler (i.e., Gellyfish) 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 non-equilibrium conditions. A subsequent comparison of four approaches for estimating equilibrium mussel bioaccumulation using octanol- and triolein-water partition coefficients (i.e., KOW and KTR), and two types of polymer-lipid partition coefficients demonstrated field deployed mussels were not at equilibrium with many PCBs. Interestingly, when combined with equilibrium passive sampler results, the simplest approach using KOW was the best predictor of equilibrium mussel bioaccumulation. This finding suggests this relatively simple approach, along with passive sampling, could be used to estimate equilibrium bioaccumulation during remedial operations at contaminated sites. Bioaccumulation of metals was better correlated with the dissolved metals and not the free metal ions alone. These analyses are intended to assist environmental scientists and managers to interpret their field deployment data when transitioning from biomonitoring to passive sampling.
