Direct photolysis mechanism of pesticides in water

Abstract

Photodegradation is one of the most important abiotic transformations for pesticides in the aquatic environment, and the high energy of sunlight causes characteristic reactions such as bond scission, cyclization, and rearrangement, which are scarcely observed in hydrolysis and microbial degradation. This review deals with direct photolysis via excitation of a pesticide by absorbing natural or artificial sunlight in order to know its basic photochemistry, and indirect photolysis meaning either sensitization by dissolved organic matters or oxidation by reactive oxygen species is basically excluded. Several experimental approaches including spectroscopic techniques together with theoretical calculations are first discussed from the viewpoint of the reaction mechanisms in direct photolysis. Then, the typical photoreactions of pesticides are summarized by chemical classes and/or functional groups and discussed as far as possible in relation to their mechanisms.

[Retracted] Effective Remediation Strategy for Xenobiotic Zoxamide by Pure Bacterial Strains, Escherichia coli, Streptococcus pyogenes, and Streptococcus pneumoniae

“…Zoxamide displays mediocre toxicity towards aquatic creatures [ 8 ]. Zoxamide dissipation usually occurs through hydrolytic action and photolysis [ 9 ]. It is virtually immobilized in terms of its lesser potential for groundwater movement [ 10 ].…”

Theoretical and organic chemical approaches to environmental behavior and metabolism of pesticides

“…By absorbing sunlight at a wavelength >290 nm, a pesticide molecule is activated to excited states and undergoes chemical reactions, called direct photolysis. 7,26) Another degradation process is indirect photolysis, typically chemical reactions with photogenerated reactive species, such as hydroxyl radical (•OH) and singlet oxygen ( 1 O 2 ). 26) The usual photolysis experiments with a pesticide to examine its dissipation and transformation products do not directly give any information on reactive species, which is needed to scrutinize the photoreaction mechanism.…”

Reducing Water and Pesticide Movement in Nursery Production

“…Pesticides at the ground surface and in ponds are subject to photolysis (the breakdown of pesticides in response to sunlight), which is the primary degradation pathway for certain pesticides, such as the insecticide pirimicarb and the herbicide oxyfluorfen (Mantzos et al, 2014;Pirisi et al, 1996). The photodecomposition of pesticides occurs in either a direct or an indirect manner, with the former resulting from the compound reaching a photo-excited state, and the latter in response to reactions driven by light-induced reactive oxygen species present in water (Katagi, 2018). Pesticides may degrade in water via hydrolysis (Linde, 1994) or, based on the Henry's Law constant of a given compound, may volatilize, which is a physico-chemical process that results when a compound enters a gaseous state through either evaporation from water or sublimation from a solid form (Bedos et al, 2002).…”