title: Transformation of acesulfame in chlorination: Kinetics study, identification of byproducts, and toxicity assessment.
abstract: Acesulfame (ACE) is one of the most commonly used artificial sweeteners. Because it is not metabolized in the human gut, it reaches the aquatic environment unchanged. In the present study, the reactivity of ACE in free chlorine-containing water was investigated for the first time. The degradation of ACE was found to follow pseudo-first-order kinetics. The first-order rate increased with decreasing pH from 9.4 to 4.8 with estimated half-lives from 693 min to 2 min. Structural elucidation of the detected transformation products (TPs) was performed by ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Integration of MS/MS fragments, isotopic pattern and exact mass allowed the characterization of up to 5 different TPs in the ultrapure water extracts analyzed, including two proposed new chlorinated compounds reported for the first time. Unexpectedly, several known and regulated disinfection by-products (DBPs) were present in the ACE chlorinated solution. In addition, two of the six DBPs are proposed as N-DBPs. Time-course profiles of ACE and the identified by-products in tap water and wastewater samples were followed in order to simulate the actual disinfection process. Tap water did not significantly affect degradation, but wastewater did; it reacted with the ACE to produce several brominated-DBPs. A preliminary assessment of chlorinated mixtures by luminescence inhibition of Vibrio fischeri showed that these by-products were up to 1.8-fold more toxic than the parent compound. The generation of these DBPs, both regulated and not, representing enhanced toxicity, make chlorine disinfection a controversial treatment for ACE. Further efforts are urgently needed to both assess the consequences of current water treatment processes on ACE and to develop new processes that will safely treat ACE. Human health and the health of our aquatic ecosystems are at stake.
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region; Key Laboratory of Tropical Agro-environment, Ministry of Agriculture of China, South China Agricultural University, Guangzhou 510642, China.
authors.forename: Adela Jing
authors.initials: AJ
authors.lastname: Li
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region; School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China.
authors.forename: Pengran
authors.initials: P
authors.lastname: Wu
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region.
authors.forename: Japhet Cheuk-Fung
authors.initials: JC
authors.lastname: Law
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region.
authors.forename: Chi-Hang
authors.initials: CH
authors.lastname: Chow
authors.affiliation: Water and Soil Quality Research Group, Department of Environmental Chemistry, Institute of Environmental Assessment and Water Research - Spanish National Research Council (IDAEA-CSIC), Jordi Girona 18-26, 08034 Barcelona, Spain.
authors.forename: Cristina
authors.initials: C
authors.lastname: Postigo
authors.affiliation: School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China. Electronic address: yingguo2004@jnu.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region; HKBU Institute of Research and Continuing Education, Shenzhen Virtual University Park, Shenzhen, China; School of Environment, Guangzhou Key Laboratory of Environmental Exposure and Health, Guangdong Key Laboratory of Environmental Pollution and Health, Jinan University, Guangzhou 510632, China. Electronic address: s9362284@hkbu.edu.hk.
authors.forename: Kelvin Sze-Yin
authors.initials: KS
authors.lastname: Leung
mesh_terms: D004203:Disinfection; D054879:Halogenation; D006801:Humans; D007700:Kinetics; D053719:Tandem Mass Spectrometry; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification
chemical_list: D014874:Water Pollutants, Chemical
keywords: Acesulfame; Chlorination; Disinfection by-products; Environmental fate; Kinetics