Transformation of Organophosphorus Pesticides in the Presence of Aqueous Chlorine: Kinetics, Pathway

时间：2009-04-18  阅读：    我要评论:

Stephen E. Duirk*, Lisa M. Desetto^† and Gary M. Davis^†U.S. Environmental Protection Agency, Office of Research and Development, National Exposure Research Laboratory, 960 College Station Rd., Athens, Georgia 30605Environ. Sci. Technol., 2009, 43 (7), pp 2335–2340DOI: 10.1021/es802868yPublication Date (Web): March 9, 2009Copyright This article not subject to U.S. Copyright. Published 2009 by the American Chemical Society * Corresponding author phone: (706) 355-8206; fax: (706) 355-8202; e-mail: duirk.stephen@epa.gov., †

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Abstract

The fate of organophosphorus (OP) pesticides in the presence of aqueous chlorine was investigated under simulated drinking water treatment conditions. Intrinsic rate coefficients were found for the reaction of hypochlorous acid (k_HOCl,OP) and hypochlorite ion (k_OCl,OP) for several OP pesticides. The reaction of hypochlorous acid (HOCl) with each OP pesticide was relatively rapid near neutral pH, k_HOCl,OP = 0.86 − 3.56 × 10⁶ M⁻¹h⁻¹. HOCl reacts at the thiophosphate (P = S) moiety of the OP pesticide resulting in the formation of the corresponding oxon (P = O), which is more toxic than the parent pesticide. Hypochlorite ion (OCl⁻) was found not to oxidize OP pesticides but act like a nucleophile accelerating hydrolysis, k_OCl,OP = 37.3−15910 M⁻¹h⁻¹. Both the k_HOCl,OP and the k_OCl,OP were found to correlate well with molecular descriptors within each subgroup of the OP pesticide class. A model was developed to predict the transformation of OP pesticides in the presence of aqueous chlorine. With hydrolysis rate coefficients, the transformation of OP pesticides under drinking water treatment conditions was found to be adequately predicted. The structure−activity relationships and model developed here could be used by risk assessors to determine exposure to OP pesticides and their transformation products in potable water.

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