title: Photodegradation of the azole fungicide climbazole by ultraviolet irradiation under different conditions: Kinetics, mechanism and toxicity evaluation.
abstract: Climbazole (CZ) has been known to persist in various environmental media, and may cause potential risks to aquatic organisms. This study investigated the photodegradation of CZ by ultraviolet (UV, 254nm) under different conditions. The results revealed that CZ could be effectively degraded in aqueous solutions under UV-254 irradiation with a half-life of 9.78min (pH=7.5), and the photodegradation followed pseudo-first-order kinetics. pH had almost no effect on its rate constants and quantum yields; but the water quality of natural waters could affect the photolysis of CZ, and the coexisting constituents such as Fe(3+), NO3(-), and HA obviously inhibited its photolysis. The addition of different radical scavengers also inhibited the photodegradation of CZ due to the reduction of reactive oxygen species (ROS). CZ underwent direct and self-sensitized photolysis involving ROS. Based on the identified photodegradation by-products, the proposed pathways included hydroxylative dechlorination, dechlorination and de-pinacolone. Moreover, toxicity evaluation using duckweed found significant toxicity reduction in the photodegradation system of CZ after the irradiation of UV-254, and the remaining by-products did not pose extra toxicity compared with CZ itself. These findings from present study suggest that CZ in effluent could be further reduced by applying UV photolysis treatment.
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Wang-Rong
authors.initials: WR
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China. Electronic address: guang-guo.ying@gig.ac.cn.
authors.forename: Guang-Guo
authors.initials: GG
authors.lastname: Ying
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Jian-Liang
authors.initials: JL
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: You-Sheng
authors.initials: YS
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Li-Xin
authors.initials: LX
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Yao
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Yan-Qiu
authors.initials: YQ
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, PR China.
authors.forename: Fei
authors.initials: F
authors.lastname: Tian
mesh_terms: D004350:Drug Residues / Q000032:analysis; D005659:Fungicides, Industrial / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity*; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity*; D007700:Kinetics; D017382:Reactive Oxygen Species; D014466:Ultraviolet Rays; D014865:Waste Disposal, Fluid; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification; D060753:Water Quality; D014881:Water Supply / Q000592:standards
chemical_list: D005659:Fungicides, Industrial; D007093:Imidazoles; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; C108286:climbazole
keywords: By-products; Climbazole; Photodegradation; Reactive oxygen species; Toxicity