PH06 Agrochemicals, Pesticides, Pharmaceuticals
Exhibit Hall
8:00 AM - Thursday
(PH043) Bioavailability of Permethrin in Surface Water.
Yang, WC1, Gan, J1, Liu, WP1, 1 University of California, Riverside, CA, usa
ABSTRACT- Permethrin is the most widely used insecticide from the synthetic pyrethroid family. Permethrin has a broad spectrum of insect activity and very low mammalian toxicity. As the use of certain organophosphate insecticides (e.g., diazinon and chlorpyrifos) is being restricted, the use of synthetic pyrethroids may further increase. Like most other synthetic pyrethroids, permethrin has high acute toxicity to fish and aquatic invertebrates. On the other hand, it is well known that synthetic pyrethroids tend to be strongly adsorbed to soil, organic matter, and sediment. Therefore, in a surface water system, it may be expected that adsorption to suspended solids and dissolved organic matter (DOM) may result in removal of permethrin from the dissolved phase and hence a reduced bioavailability of permethrin to aquatic organisms. To provide scientific basis for evaluating the risk of permethrin in runoff and surface streams, it is essential to understand the effect of suspended solids and DOM on the bioavailability and toxicity of permethrin. In this study, we used solid phase microextraction (SPME) to characterize the partition of permethrin between suspended solids/DOM and the dissolved phase. The effect of the type and level of suspended solids/DOM on the dissolved permethrin concentration was quantitatively determined. We further correlated the phase distribution behavior of permethrin with the concurrently measured LC50 for indicator organisms (Ceriodaphnia dubia and Daphnia magna) using simulated surface water systems. Concentrations measured by SPME were significantly smaller than those measured by solvent extraction, and acute toxicity decreased proportionally as the amount of suspended solids/DOM in the test system increased. These results suggest that suspended solids and DOM in surface water can significantly reduce the toxicity of pyrethroids to water column invertebrates. Therefore, the role of suspended solids and DOM should be considered when assessing the ecological risk and establishing water quality standards for pyrethroids.
Key words: bioavailability, permethrin, surface water, SPME