Hydrolysis and photolysis of two organophosphorus pesticides in dilute aqueous solutions: kinetics and by products

Hydrolyse et photolyse de deux pesticides organophosphorés en solution aqueuse diluée : cinétique et sous-produits

Laboratoire de Chimie de l'Eau et de l'Environnement UMR CNRS N° 6008 - Université de Poitiers ESIP - 40, Avenue du Recteur Pineau - 86022 Poitiers Cedex - France

Abstract

The transformation of two selected organophophorus pesticides (OPs) by hydrolysis and photolysis processes has been studied in aqueous solution. Because of their extensive use profenofos and isazofos were chosen for this study. Hydrolysis and photolysis experiments were performed in purified water at pH = 8.0 and ionic strength equal to 2.5 mM. The irradiation was obtained with a polychromatic light starting at 285 nm. Kinetic investigations coupled with analytical studies (identification of degradation products) were performed. Apparent first order rate constants were determined for hydrolysis and photolysis processes. For each organophosphorus pesticide, experiments have been performed to identify the photodegradation products. The proposed structures will be discussed.

Résumé

La transformation par hydrolyse et photolyse de deux pesticides organophosphorés en solution aqueuse diluée a été étudiée. Les cinétiques de dégradation de l'isazofos et du profenofos, ainsi que les sous-produits de transformation sont présentés dans ce travail.