Selective bioaccumulation, biomagnification, and dissipation of hexachlorocyclohexane isomers in a freshwater food chain.

Hexachlorocyclohexane isomers (HCHs) are persistent organic pollutants (POPs), having potential risks to humans and ecosystem. This work evaluated the propensity of organisms to accumulate, eliminate, and transfer HCHs along the food chain (Tubifex tubifex and common carp (Cyprinus carpio)). The accumulation of HCHs from water by worms and carp was observed, and the concentrations increased with exposure time. After 8 days, the HCH concentrations in organisms remained stable. The accumulation factor (AF) values of HCHs in T. tubifex were higher than those in carp, indicating that the bioaccumulation abilities of HCHs in T. tubifex were higher than those in carp. The contaminated worms as a dietary source in the food chain led to significantly higher bioaccumulation in carp. The biomagnification factor (BMF) values of HCH isomers were all greater than 1. In the dissipation experiments, the elimination was fast and the half-lives were shorter than 2.5 days. The enantioselective accumulation and dissipation of α-HCH enantiomers were observed in worms and carp (food chain), and the enantiomeric differences should be taken into consideration in the study of contaminants risk assessment. The results on trophic transfer of HCHs in a freshwater food chain should be helpful for better understanding the fate, transport, and transfer of HCHs in freshwater environments.