title: More toxic and photoresistant products from photodegradation of fenoxaprop-p-ethyl.
abstract: The photodegradation pathway of the commonly used herbicide fenoxaprop-p-ethyl (FE) was elucidated, and the effects of the photodegradation on its toxicity evolution were investigated. Under solar irradiation, FE could undergo photodegradation, and acetone enhanced the photolysis rates significantly. The same photoproducts formed under the irradiation of lambda > 200 nm and lambda > 290 nm through rearrangement, loss of ethanol after rearrangement, de-esterification, dechlorination, photohydrolysis, and the breakdown of the ether linkages. One of the main transformation products, 4-[(6-chloro-2-benzoxazolyl)oxy] phenol (CBOP), was resistant to photodegradation under the irradiation of lambda > 290 nm, and its photolysis rate was seven times slower than the parent under the irradiation of lambda > 200 nm. Among the metabolites, CBOP (48 h EC50 of 1.49-1.64 mg/L) and hydroquinone (48 h EC50 of 0.25-0.28 mg/L) were more toxic to Daphnia magna than the parent FE (48 h EC50 of 4.2-6.9 mg/L). Thus, more toxic and photoresistant products were generated from photolysis of the herbicide. Ecotoxicological effects of phototransformed products from pesticides should be emphasized for the ecological risk assessment of these anthropogenic pollutants.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), Department of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lin
authors.forename: Jingwen
authors.initials: J
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiyun
authors.initials: X
authors.lastname: Cai
authors.forename: Xiaoxuan
authors.initials: X
authors.lastname: Wei
authors.forename: Xianliang
authors.initials: X
authors.lastname: Qiao
mesh_terms: D000818:Animals; D003621:Daphnia / Q000187:drug effects; D006540:Herbicides / Q000737:chemistry* / Q000633:toxicity*; D007700:Kinetics; D008027:Light; D010080:Oxazoles / Q000737:chemistry* / Q000633:toxicity*; D010777:Photochemistry; D010782:Photolysis; D011422:Propionates / Q000737:chemistry* / Q000633:toxicity*
chemical_list: D006540:Herbicides; D010080:Oxazoles; D011422:Propionates; C416661:fenoxaprop ethyl