T9 PM Pyrethroid Insecticides in Urban and Agricultural Environments
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 339-340

(HUN-1117-822276) Bioavailability of pyrethroids in sediment: Estimated with.

Hunter, W¹, Yang, W¹, Gan, J¹, ¹ University of California Riverside, Riverside, CA, USA

ABSTRACT- Synthetic pyrethroid insecticides (SPs) are being increasingly used in agriculture and urban environments as a replacement for the organophosphate insecticides. Recent studies show presence of SPs in sediments from various locations in California. Pyrethroids have high acute toxicity to a broad spectrum of aquatic organisms, and thus, it is imperative to understand the ecotoxicological implications of SPs in water-sediment environments. Because SPs have high affinity for sediment and DOM, their bioavailable concentrations in sediment environments are expected to be significantly lower than the total chemical concentration. Measurement of bioavailable concentrations of SPs will likely allow better prediction of toxicity from chemical concentrations, and improve our understanding of factors affecting sediment toxicity. In this study, the bioavailability of permethrin and cyfluthrin to Chironomus tentans larvae in water-sediment systems was investigated. During the bioassays, polydimethylsiloxane (PDMS) fibers were used as a "biomimetic" tool and simultaneously exposed to the same samples as the organisms. The freely dissolved concentration (C_w) in the sediment porewater was estimated from pesticide accumulation in the PDMS fiber. The C_w estimated by the PDMS fiber was only a small fraction of the total pore water concentration. Uptake of SPs by C. tentans generally followed the same trend as pesticide accumulation in the PDMS fiber, and both decreased with increasing organic matter content in the bulk sediment or in the porewater. Also, LC50 values increased with increasing OM content, and was conversely correlated with PDMS-measured concentrations. These results suggest that only the dissolved fraction of SPs in the sediment was bioavailable to C. tentans, and the bioavailability was likely dependent on sediment properties, especially the OM content.

Key words: bioavailability, chironomus tentans, spme, pdms