Comparative Bioavailability of Sediment-Sorbed Hexachlorobiphenyl

The bioavailability of sediment-sorbed hexachlorobiphenyl (HCB) to bacteria, midge larvae (Chironomus tentans), and mosquitofish (Gambusia affinis) was examined in order to elucidate the influence of abiotic and biotic factors on the bioaccumulation process. Factors examined included sediment type, sediment organic matter, HCB concentration, temperature, and biological viability. Additional experiments were conducted to evaluate the relative role of sediment and dietary HCB sources to the accumulation of HCB in mosquitofish.

In general, the bioavailability of sediment-sorbed HCB was inversely related to the surface area and the organic content of the sediment. The organic content of the sediment was deemed important due to its large surface area and its hydrophobic intermatrix, which accounts for the affinity of organic matter for hydrophobic organic compounds. The bioaccumulation of HCB was proportional to the sediment HCB concentration. Changes in temperature did not alter the steady-state HCB concentrations in midge. HCB accumulation was similar in live and dead bacteria; however, live midge had greater HCB accumulation than dead midge. Mosquitofish HCB accumulation from dietary and sediment sources was additive and approximately equal.

This investigation indicates that the physical process of equilibrium partitioning is responsible for the bioaccumulation of sediment-sorbed HCB. However, the process of equilibrium partitioning can be facilitated by physiological activity.