Evaluation of azamethiphos and dimethoate degradation using chlorine dioxide during water treatment

Abstract

Chlorine dioxide (ClO 2) degradation of the organophosphorus pesticides azamethiphos (AZA) and dimethoate (DM) (10 mg/L) in deionized water and in Sava River water was investigated for the first time. Pesticide degradation was studied in terms of ClO 2 level (5 and 10 mg/L), degradation duration (0.5, 1, 2, 3, 6, and 24 h), pH (3.00, 7.00, and 9.00), and under light/dark conditions in deionized water. Degradation was monitored using high-performance liquid chromatography. Gas chromatography coupled with triple quadrupole mass detector was used to identify degradation products of pesticides. Total organic carbon was measured to determine the extent of mineralization after pesticide degradation. Real river water was used under recommended conditions to study the influence of organic matter on pesticide degradation. High degradation efficiency (88-100% for AZA and 85-98% for DM) was achieved in deionized water under various conditions, proving the flexibility of ClO 2 degradation for the examined organophosphorus pesticides. In Sava River water, however, extended treatment duration achieved lower degradation efficiency, so ClO 2 oxidized both the pesticides and dissolved organic matter in parallel. After degradation, AZA produced four identified products (6chlorooxazolo[4,5-b]pyridin-2(3H)-one; O,O,S-trimethyl phosphorothioate; 6-chloro-3-(hydroxymethyl)oxazolo[4,5b]pyridin-2(3H)-one; O,O-dimethyl S-hydrogen phosphorothioate) and DM produced three (O,O-dimethyl S-(2-(methylamino)-2-oxoethyl) phosphorothioate; e.g., omethoate; S-(2-(methylamino)-2-oxoethyl) O,O-dihydrogen phosphorothioate; O,O,S-trimethyl phosphorodithioate). Simple pesticide degradation mechanisms were deduced. Daphnia magna toxicity tests showed degradation products were less toxic than parent compounds. These results contribute to our understanding of the multiple influences that organophosphorus pesticides and their degradation products have on environmental ecosystems and to improving pesticide removal processes from water.

Direct and Activated Chlorine Dioxide Oxidation for Micropollutant Abatement: A Review on Kinetics, Reactive Sites, and Degradation Pathway

“…The main reactive site of ametryn herbicide and methiocarb pesticide during ClO 2 oxidation was the sulfur center in their molecules [47,49]. ClO 2 oxidation of two organophosphorus pesticides started with an attack on the amide group of azamethiphos and the phosphinothioyl group of dimethoate [16].…”

“…Similarly, during the ClO 2 oxidation of the carbamate pesticide of methiocarb (MC), methiocarb sulfoxide and methiocarb sulfone were generated by losing HClO 2 and HOCl from the intermediate adduct of MC-ClO 2 -OH, respectively, which was first formed around the sulfur center of methiocarb [49]. Pergal, et al [16] studied the ClO 2 oxidation of two organophosphorus pesticides and found the successive attack on the amide group and the sulfide group in azamethiphos, leading to the break of the amide group and S-C bond, and the hydroxylation of the phosphinothioyl and then decarbonyl in dimethoate.…”

Feasibility of biodegradation of Azamethiphos; odour and fly controlling chemical used in open solid waste dumpsite at Karadiyana, Colombo, Sri Lanka

“…In order to minimize environmental risks originating from the presence of the pesticide, it would be judicious to develop effective technologies that ensure successful and simple degradation of these compounds (Pergal et al, 2020). Biodegradation is an efficient green remediation method of many types of xenobiotic chemicals by microorganisms that grow in different ecosystems including incompatible extreme conditions (Sarnaik, 2004).…”