Labex CAPPA/IReSPE

Séminaire du Professeur Duy Quang Dao de l'Université de Danang, au Vietnam

Environmental Degradation of Pesticides – A case study of Metazachlor Oxidation by HO•, SO4•- and O3

Résumé :
Pesticides contain numerous groups of insecticides, fungicides, herbicides, garden chemicals, household disinfectants, and rodenticides operated to destroy and protect from pests. The rapidly widening utilization of pesticides gave rise to contamination and pollution of different environments, e.g. soils, air, and aquatic systems. The excess amount of pesticide residues in agricultural land may harm terrestrial and aquatic ecosystems and cause adverse environmental and human health issues.
Pesticide residues have become a growing concern in many countries, including France and Vietnam. In France, Froger et al. recently monitored 111 pesticide residues (48 fungicides, 36 herbicides, 25 insecticides and/or acaricides, and two safeners) in 47 soil samples across the country under various land uses (arable lands, vineyards, orchards, forests, grasslands, and brownfields) [1]. In Vietnam, Pham et al. investigated an analytical study on pesticide pollution in agricultural areas of Northern Vietnam at Hoang Liet and Minh Dai communes [2]. Various pesticides, such as cypermethrin, trichlorfon, fenobucarb, cyfluthrin, cartap, and imidachlorprid were detected in water, soil and vegetables samples. These compounds can be existed in the atmosphere from hours to many years, and they may be decomposed to more stable and toxic products. Based on the common concern and research interest, over the last three years, two computational chemistry groups from PC2A (University of Lille, France) and DTC2 (Duy Tan University, Viet Nam) have initiated the first collaborative works on the thermochemistry and kinetics of the pesticides oxidation in the environmental conditions. The first exciting results from this fruitful collaboration on the metazachlor [3] and quinmerac [4] herbicides were successfully communicated to the scientific community. Furthermore, detailed studies on the oxidation of other representative pesticides (e.g. chlorpyrifos, endosulfan, fenpyrazamine, thiram, phosmet) have been carried out.
In this talk, a brief story of the environmental oxidation of metazachlor herbicide initiated by different oxidative species (HO•, SO4•-, and O3) in the aqueous phase employing Density functional theory (DFT) approaches will be presented. The toxicological effects on the aquatic species as well as on human cholinergic nervous system using Molecular docking/ Molecular dynamics (MD) are also resumed. It hopefully contributes to better understanding of degradation and fate of pesticides and its influences on the environmental and human health.