Uptake, Efflux, and Sequestration of Hg in the Asian Clam, Corbicula fluminea, at Environmentally Relevant Concentrations, and the Implications for Hg Remediation

Abstract Mercury is a persistent, ubiquitous contaminant that readily biomagnifies into higher trophic level species in aquatic environments across the globe. To better understand the bioaccumulation kinetics of aqueous Hg exposure in the invasive Asian Clam, Corbicula fluminea , a tank study was conducted at 3 treatment levels (20, 100, and 200 ng/L). These concentrations are lower than previous Hg uptake studies in clams, but more relevant to actual stream conditions. They represent the range of values commonly measured on several streams with legacy Hg contamination from past industrial operations, having undergone some remediation efforts to reduce Hg discharges. A biokinetic model, the first parameterized for Hg uptake in freshwater clams, was developed to describe uptake and efflux parameter and compared to previous parameter values estimated for other mollusk species. A decay model was used to account for rapid changes in concentration in the tanks due to Hg sorption to the container sides, a common issue in Hg empirical, lab-based studies. Results demonstrated that even at low Hg concentrations, Corbicula record signals of contamination through bioaccumulation, and both direct measurement and biokinetic models demonstrate large Hg bioaccumulation factors (as high as 1.34x10 5 mL/g dry tissue), similar to partitioning coefficients seen in engineered Hg sorbents.