Sensitization Of Six Flavonoids On Photolysis Of Chlorothalonil In Water

Chlorothalonil is a conventional polychlorinated aromatic fungicide in agriculture and is toxic to many aquatic species.The aim of this study is to find a kind of natural compounds which are non-toxic,efficient,abundant and can promote photodegradation of chlorothalonil in water.This study was designed study the enhancing effects of six flavonoids on photolysis of chlorothalonil under sunlight and high-pressure mercury lamp irradiation(HPML).The photodegradation products of chlorothalonil were qualitatively and quantitatively analyzed by HPLC,the active oxidized species in the photolysis system were detected by EPR and the characteristics of flavonoids promoting photolysis of chlorothalonil were analyzed.The experimental results are summarized as follows:1.Six flavonoids accelerated photolysis of chlorothalonil under sunlight and artificial lights for 6.7-18.3 and 2.4-7.5 times,respectively.The enhanced effect of six flavonoids under sunlight irradiation was greater than that under HPML.2.The photodegradation of chlorothalonil in pure water and flavonoid aqueous solution accorded with the first-order degradation kinetics.Under HPML and sunlight,the photodegradation rate of chlorothalonil showed the same rule: under the action of Cyanidin chloride,the photodegradation rate of chlorothalonil was the fastest,the fastest was 0.1235 min-1;luteolin was the slowest,the slowest was 0.0242 min-1;under the action of other flavonoids,the photodegradation rate of chlorothalonil was in the order of Kaempferol> Morin> Quercetin> Galangin.3.Chlorothalonil underwent photo-reductive dechlorination and no hydroxy product was formed in the presence of flavonoids under sunlight and artificial lights.Three chlorinated products of 2,4,5-trichloroisophtalonitrile,2,5-dichloroisophtalonitrile and 5-chloroisophtalonitrile are produced.4.Hydroxyl and hydrogen radicals were confirmed the reactive species in absence and presence of cyanidin under light irradiation by electron spin resonance spectroscopy.5.Cyanidin chloride showed more significant photolysis enhancement than luteolin,galangin,quercetin,morin and kaempferol.The different structure characteristics of flavonoids led to different enhancement effects.The enhancement mechanism of the flavonoids on photolysis of chlorothalonil might be attributed to their hydrogen donation capacity.The obtained results benefited utilizing flavonoids to manage aquatic toxicity and pollution remediation and also have potential reference value to predict degradation of chlorothalonil on different plants.