Photodegradation of Strobilurin Fungicide Mandestrobin in Water

摘要

Photodegradation of a new strobilurin fungicide, mandestrobin, was investigated in buffered aqueous solution and synthetic humic water (SHIN) under continuous irradiation with artificial sunlight (lambda 290 nm). In both aquatic media, the direct photolysis preferentially proceeded via homolytic bond cleavage at the benzyl phenyl ether, and the subsequent recombination of geminate radicals in a solvent cage gave the photo-Claisen rearrangement products. A radical mechanism in the photochemical rearrangement was strongly supported by a radical-trapping technique using a novel nitroxide spin label combined with electron spin resonance (ESR) and liquid chromatography-mass spectrometry (LC-MS) analyses. Photosensitized generation of hydroxyl radical in SHIN might significantly contribute to enhancing the formation of a benzyl alcohol derivative. The series of photolysis products steadily degraded and finally mineralized to carbon dioxide.