Photodecomposition of the Carbamate Pesticide Carbofuran: Kinetics and the Influence of Dissolved Organic Matter

Abstract

This study examined the photodecomposition of carbofuran, a carbamate pesticide with high oral toxicity. Rate constants are measured for the pesticide in aqueous solution and in the presence of various samples of dissolved organic matter (DOM). Kinetic experiments are monitored with HPLC, while reaction products are determined using HPLC, GC−MS, and 1H NMR: mechanisms are proposed for the first three steps of the reaction. It was found that the photodecomposition proceeds via first-order reaction kinetics and that the presence of various DOM samples inhibits the photolysis reaction of carbofuran. This phenomenon can be correlated to the magnitude of the binding interaction between carbofuran and DOM. Finally, techniques such as GC−MS and 1H NMR are used to identify the photodecomposition products. The first three steps of the reaction are defined. In the first step of the reaction, the carbamate group is cleaved from the molecule. The furan moiety is opened in the second step producing a substituted catechol with a tert-butyl alcohol group as the substituent at the number three carbon. This molecule then undergoes a dehydration reaction to form an alkene side group from the tert-butyl alcohol side group.