Bioavailability of Hydrophobic Pesticides in Sediment

A significant number of current use pesticides are hydrophobic compounds, such as synthetic pyrethroid insecticides that are heavily used in both urban and agricultural environments. In the environment, residues of these compounds tend to be found in sediment. Evaluation of the impact of these chemicals in surface aquatic systems, however, is complicated by the presence of multiple phases, phase distribution of these compounds, and the implied bioavailability. We have completed a series of experiments to understand the bioavailability of pyrethroid residues in sediment as a function of sediment type and aging. Results from these studies suggest that with K_OCs in the 10⁶ range, the bioavailability and toxic effect of pyrethroid compounds depend closely on the sediment properties as well as factors such as aging. The availability of pyrethroids in these systems can be well predicted with non-biological methods including the use of polymer-coated fibers as biomimetic samplers and extraction by Tenax beads. These observations further suggest that the use of selective sampling and analytical methods over whole-sample methods will improve the assessment of ecotoxicological effects of these pesticides in surface aquatic systems.