title: Transformation of acesulfame in water under natural sunlight: joint effect of photolysis and biodegradation.
abstract: The transformation of acesulfame in water under environmentally relevant conditions, including direct and indirect photolysis, biodegradation, and hydrolysis, was systematically evaluated. Under natural sunlight, both direct and indirect photolysis of acesulfame were negligible in sterilized systems at neutral or alkaline pH, whereas direct photolysis occurred at pH of 4 with a rate constant of 0.0355 d(-1) in deionized water. No significant reduction in acesulfame contents was found in the dark controls or in the incubation experiments, indicating acesulfame was resistant to hydrolysis and biodegradation. In unsterilized systems, photolysis was substantially enhanced, implying that there was a joint effect of photolysis and biodegradation or that the sterilization process had the secondary effect of inactivating some photosensitizers. The near-surface summer half-life of acesulfame in the water from the Haihe River was 9 d. Specific experiments revealed the involvement of (1)O2/(3)DOM* in acesulfame photolysis, whereas OH exhibited only a slight contribution in the presence of DOM or bicarbonate. As indicated by the total organic carbon data, no significant mineralization occurred in both sterilized and unsterilized systems after acesulfame was irradiated under simulated sunlight for 7 d, suggesting the generation of persistent intermediates. Finally, major degradation intermediates were analyzed, and the degradation pathways of acesulfame under environmentally relevant conditions were proposed for the first time.
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Gan
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China. Electronic address: sunhongwen@nankai.edu.cn.
authors.forename: Hongwen
authors.initials: H
authors.lastname: Sun
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Ruonan
authors.initials: R
authors.lastname: Wang
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Hu
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Zhang
authors.affiliation: MOE Key Laboratory of Pollution Processes and Environmental Criteria, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
authors.forename: Xinhao
authors.initials: X
authors.lastname: Ren
mesh_terms: D001673:Biodegradation, Environmental; D002681:China; D006207:Half-Life; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D010782:Photolysis; D013472:Sunlight; D013549:Sweetening Agents / Q000737:chemistry*; D013843:Thiazines / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D013549:Sweetening Agents; D013843:Thiazines; D014874:Water Pollutants, Chemical; D014867:Water; C006362:acetosulfame
keywords: Acesulfame; Natural sunlight; Photolysis; Transformation intermediates; Transformation pathways