Uptake and Bioconcentration of 2,2′,4,4′,5,5′-Hexachlorobiphenyl by Lotic Periphyton

Abstract

Abstract Laboratory experiments were conducted to examine the uptake and bioconcentration of 2,2′,4,4′,5,5′-hexachlorobiphenyl (HCBP), a model hydrophobic organic compound, in lotic periphyton. The instantaneous rate of uptake and bioconcentration factor (BCF) were determined by following the time course of uptake of 14C-HCBP in periphytic communities established on glass slides. The rate of accumulation was highest in the first 3 hours, and steady state was reached within 8 days. The bioconcentration factor on a dry weight basis (BCFd) averaged 21,000. The results of a depuration experiment indicated that HCBP desorbed from periphyton, but at a much slower rate than its adsorption. The results support the hypothesis that the mechanism of uptake of HCBP in periphyton is a rapid surface sorption followed by a much slower transfer into lipids, and that sorption is largely dependent on the surface area available. The results of this study suggest that lotic periphyton provide a large surface area for adsorption and uptake of persistent hydrophobic compounds such as HCBP and, depending on the extent of grazing pressure, could greatly influence the fate and transport of these compounds in lotic systems.