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Organophosphorus (OP) Pesticide Degradation in the Presence of Chlorinated Oxidants: Kinetics, Modeling, and Structure-Activity Relationships
Citation:
DUIRK, S. E., L. M. Desetto, AND G. M. Davis. Organophosphorus (OP) Pesticide Degradation in the Presence of Chlorinated Oxidants: Kinetics, Modeling, and Structure-Activity Relationships. Presented at Gordon Research Conference, Environmental Sciences: Water, Holderness, NH, June 22 - 27, 2008.
Impact/Purpose:
The emphasis of this research is to assess exposure to pesticides, toxics, and their transformation products from consuming potable water that has undergone either chemical disinfection and/or lime softening.
Description:
The rates and pathways for pesticide transformation during drinking water treatment are known for only a few pesticides and under limited conditions. The resulting oxons are more toxic than the parent pesticides. The transformation rates and pathways for chlorpyrifos, an OP pesticide, have been established in buffered deionized water and in the presence of naturally occurring aquatic constituents. However, it has not been established how the OP pesticides react in the presence of chlorinated oxidants as a class of pesticides. The objective of this work is to investigate OP pesticide transformation pathways as a class in the presence of aqueous chlorine and chloramines. Eight priority OP pesticides from two subgroups will be examined for their reactivity with chlorinated oxidants: phosphorothioate subgroup (chlorethoxyfos, chlorpyrifos, parathion, diazinon, tebupirimfos) and phosphorodithioate subgroup (malathion, methidathion, and phosmet). These OP pesticides were selected for their use patterns as well as their diverse structures and chemical properties. Experimental results will be used to determine intrinsic rate coefficients and model the reaction between chlorine/chloramine and OP pesticides. Molecular descriptors will be used to correlate reactivity with chlorinated oxidants to OP structural characteristics. Structure-activity relationships and models will aid regulators in determining the risk associated with drinking potable water contaminated with a mixture of pesticides that elicit a common mode of toxicity.