Degradation of eleven pyrethoids was measured over approximately 100 days in three sediment/water systems under aerobic and anaerobic conditions at 25�C in the dark. The three California sediments represented a range of textures and organic matter. Test compounds were bifenthrin, cypermethrin, zeta-cypermethrin, cyfluthrin, beta-cyfluthrin, deltamethrin, esfenvalerate, fenpropathrin, gamma-cyhalothrin, lambda-cyhalothrin, and permethrin. The test compounds were applied as two test mixtures (six active ingredients per mixture, with bifenthrin common to both) at approximately 50 �g of test compound per kg of sediment (dry weight). Extracts of sediment/water were cleaned up by SPE, concentrated, and analyzed by GC/MS (except deltamethrin) against matrix-matched standards with cyfluthrin-d6 as internal standard. Deltamethrin was analyzed by LC/MS/MS using deltamethrin-phenoxy-13C6 as internal standard. The study was fully replicated and, for the same sediments, results from the two test mixtures indicate general agreement between degradation rates measured for bifenthrin in both mixtures and for related isomeric products (e.g., cyfluthrin and beta-cyfluthrin). Degradation was generally faster under aerobic conditions compared to anaerobic.

Laboratory degradation rates of eleven pyrethroids under aerobic and anaerobic conditions

244th National Meeting (2012)

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