title: Light-source-dependent role of nitrate and humic acid in tetracycline photolysis: kinetics and mechanism.
abstract: To elucidate the environmental fate of tetracycline (TC), we reported the light-source-dependent dual effects of humic acid (HA) and NO3(-) on TC photolysis. TC photolysis rate was highly pH- and concentration-dependent, and was especially enhanced at higher pH and lower initial TC concentrations. Under UV-254 and UV-365 irradiation, HA inhibited TC photolysis through competitive photoabsorption or reactive oxygen species (ROS) quenching with TC; under solar and xenon lamp irradiation, TC photolysis was enhanced at low HA concentration due to its photosensitization, whereas was suppressed at high HA concentration due to competitive photoabsorption or ROS quenching with TC. Similarly, the effect of NO3(-) on TC photolysis varied with light irradiation conditions. Even under the same light irradiation conditions, the effects of HA or NO3(-) on TC photolysis varied with their concentrations. The electron spin resonance spectrometer and ROS scavenger experiments demonstrated that TC photolysis was involved in O2(-)-mediated self-sensitized photolysis. The photolysis pathways were involved in hydroxylation and loss of some groups. More toxic intermediates than TC were generated under different light irradiation conditions. These results can provide insight into the potential fate and transformation of TC in surficial waters.
authors.affiliation: State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, PR China. junfengn@bnu.edu.cn
authors.forename: Junfeng
authors.initials: J
authors.lastname: Niu
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Wenlong
authors.initials: W
authors.lastname: Wang
mesh_terms: D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009566:Nitrates / Q000737:chemistry*; D010776:Photobacterium / Q000187:drug effects; D010782:Photolysis; D017382:Reactive Oxygen Species / Q000737:chemistry; D013472:Sunlight; D013752:Tetracycline / Q000737:chemistry* / Q000633:toxicity; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000633:toxicity
chemical_list: D006812:Humic Substances; D009566:Nitrates; D017382:Reactive Oxygen Species; D014874:Water Pollutants, Chemical; D014867:Water; D013752:Tetracycline
keywords: Humic acid; Light conditions; Nitrate; Photolysis; Tetracycline