Determination of in situ polychlorinated biphenyl elimination rate coefficients in the freshwater mussel biomonitor Elliptio complanata deployed in the Huron-Erie corridor, southeast Michigan, USA, and southwest Ontario, Canada

Abstract

Quantitative mussel biomonitoring studies often use laboratory-measured whole-body elimination rate coefficients (k(tot) in conjunction with concentration data from field-deployed mussels to estimate bioavailable steady-state contaminant concentrations (C(m(ss)) in aquatic systems. However, the validity of applying laboratory k(tot) values to field-deployed mussels has not been verified. The present study quantified in situ k(tot) values by the common mussel biomonitor species Elliptio complanata for a group of performance reference compound polychlorinated biphenyl (PCB) congeners (International Union of Pure and Applied Chemistry 23, 61, 109, and 173) at 11 sites along the Lake Huron-Lake Erie corridor (southeast MI, USA, and southwest ON, Canada). Predictive site-specific k(tot) versus log K(ow) relationships were derived to estimate in situ k(tot) values for the bioaccumulated environmental PCB congeners, and the resultant steady-state concentration estimates were compared against values estimated using laboratory-derived k(tot) values. In situ k(tot) values were almost always faster (1.3-10-fold) than rate coefficients determined by laboratory studies, with a mean difference +/- standard error of 3.89 +/- 0.28-fold. Consequently, control adjusted steady-state concentrations of sum PCBs in the mussels were overestimated by factors ranging from 1.30 to 3.45 across sites when using laboratory-derived k(tot) values in place of in situ k(tot) values and a field deployment period of 90 d. This error was shown to increase with increasing congener hydrophobicity, as represented by their log K(ow) values, and when shorter field deployment times are performed. To more accurately predict the steady-state concentrations of environmentally accumulated PCBs in mussels, it is recommended that future quantitative biomonitoring studies employ the reference compound approach for measuring site-specific in situ k(tot) values.