title: Impact of dissolved organic matter on the photolysis of the ionizable antibiotic norfloxacin.
abstract: Norfloxacin (NOR), an ionizable antibiotic frequently used in the aquaculture industry, has aroused public concern due to its persistence, bacterial resistance, and environmental ubiquity. Therefore, we investigated the photolysis of different species of NOR and the impact of a ubiquitous component of natural water - dissolved organic matter (DOM), which has a special photochemical activity and normally acts as a sensitizer or inhibiter in the photolysis of diverse organics; furthermore, scavenging experiments combined with electron paramagnetic resonance (EPR) were performed to evaluate the transformation of NOR in water. The results demonstated that NOR underwent direct photolysis and self-sensitized photolysis via hydroxyl radical (OH) and singlet oxygen ((1)O2) based on the scavenging experiments. In addition, DOM was found to influence the photolysis of different NOR species, and its impact was related to the concentration of DOM and type of NOR species. Photolysis of cationic NOR was photosensitized by DOM at low concentration, while zwitterionic and anionic NOR were photoinhibited by DOM, where quenching of OH predominated according to EPR experiments, accompanied by possible participation of excited triplet-state NOR and (1)O2. Photo-intermediate identification of different NOR species in solutions with/without DOM indicated that NOR underwent different photodegradation pathways including dechlorination, cleavage of the piperazine side chain and photooxidation, and DOM had little impact on the distribution but influenced the concentration evolution of photolysis intermediates. The results implied that for accurate ecological risk assessment of emerging ionizable pollutants, the impact of DOM on the environmental photochemical behavior of all dissociated species should not be ignored.
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Liang
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China. Electronic address: zhaohuim@dlut.edu.cn.
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Minjie
authors.initials: M
authors.lastname: Deng
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Xie
authors.initials: X
authors.lastname: Quan
authors.affiliation: Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Chen
authors.affiliation: College of Fisheries and Life Science, Dalian Ocean University, Dalian 116023, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D009643:Norfloxacin / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*; D010782:Photolysis; D053719:Tandem Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D009643:Norfloxacin
keywords: Aquaculture industry; Dissociated species; Dissolved organic matters (DOM); Norfloxacin (NOR); Photolysis