Persistence of 12 insecticides in water

Abstract The relative importance of chemical and biological processes in the degradation of 12 insecticides in water was studied by comparing their persistence in four types of water: natural, distilled, sterilized natural and sterilized distilled. DDT, lindane and parathion dissappeared fairly quickly in the natural water, but were very persistent in the other types indicating the importance of microbial action in their degradation. There was little indication of chemical degradation of any of the organochlorine (OC) insecticides. The four compounds most stable in water were dieldrin, endrin (OCs) ethion and leptophos [organo-phosphorus (OP) insecticides]. Generally the other OP insecticides and both carbamates disappeared from all four types of water, demonstrating that chemical processes played a major role in their degradation, with biological processes having a secondary role for chlorpyrifos, diazinon and carbaryl. The observed order of persistence after 8 weeks in natural water was dieldrin > endrin > ethion > leptophos > lindane > chlorpyrifos > diazinon > mevinphos > carbofuran > p , p ′-DDT > carbaryl > parathion. The random occurrence of the chemical types in this list demonstrates that generalization on persistence in the environment cannot be made on the basis of chemical structure.