Assessing the Influence of Organic Carbon, Aging Time and Temperature on Bioaccessibility of Bifenthrin

Tenax extraction, a measure of chemical desorption rates from sediments, was used to evaluate the bioaccessibility of bifenthrin in two different sediments exposed to three temperatures aged over a 56-d holding period. A 24-h single-point Tenax extraction was used and parent 14 C-bifenthrin and polar metabolites were quantified in the sediment and Tenax. Bioaccessibility of bifenthrin was inversely related to the organic carbon (OC) content in the sediment, holding time, and temperature. Sequestration of the bifenthrin into slowly desorbing fractions within the sediment appears to have decreased degradation of the parent compound into metabolites and decreased the amount of parent compound bioaccessible for uptake by the Tenax. These results suggest that the environmental risk of bifenthrin to aquatic species is greatest immediately after the pesticide enters a waterbody after runoff, for low-OC content sediments, and in areas or seasons where water temperatures are colder.