title: Ozonation degradation of microcystin-LR in aqueous solution: intermediates, byproducts and pathways.
abstract: The intermediates and byproducts formed during the ozonation of microcystin-LR (MC-LR, m/z = 995.5) and the probable degradation pathway were investigated at different initial molar ratios of ozone to MC-LR ([O3]0/[MC-LR]0). Seven reaction intermediates with m/z ≥ 795.4 were observed by LC/MS, and four of them (m/z = 815.4, 827.3, 853.3 and 855.3) have not been previously reported. Meanwhile, six aldehyde-based byproducts with molecular weights of 30-160 were detected for the first time. Intermediates structures demonstrated that ozone reacted with two sites of MC-LR: the diene bonds in the Adda side chain and the Mdha amino acid in the cyclic structure. The fragment from the Adda side chain oxidative cleavage could be further oxidized to an aldehyde with a molecular weight of 160 at low [O3]0/[MC-LR]0. Meanwhile, the polypeptide structure of MC-LR was difficult to be further oxidized, unless [O3]0/[MC-LR]0 > 10. After further oxidation of the intermediates, five other aldehyde-based byproducts were detected by GC/MS: formaldehyde, acetaldehyde, isovaleraldehyde, glyoxal and methylglyoxal. Formaldehyde, isovaleraldehyde and methylglyoxal were the dominant species. The yields of the aldehydes varied greatly, depending on the value of [O3]0/[MC-LR]0.
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Jing
authors: J
authors: Chang
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Zhong-lin
authors: ZL
authors: Chen
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Zhe
authors: Z
authors: Wang
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China. Electronic address: shenjimin@hit.edu.cn.
authors: Ji-min
authors: JM
authors: Shen
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Qian
authors: Q
authors: Chen
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Jing
authors: J
authors: Kang
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Lei
authors: L
authors: Yang
authors: Institute of Municipal Engineering, College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China.
authors: Xiao-wei
authors: XW
authors: Liu
authors: State Key Laboratory of Urban Water Resource and Environment, School of Municipal & Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
authors: Chang-xin
authors: CX
authors: Nie
mesh_terms: D001427:Bacterial Toxins / Q000378:metabolism*; D002853:Chromatography, Liquid; D008401:Gas Chromatography-Mass Spectrometry; D008387:Marine Toxins; D052998:Microcystins / Q000378:metabolism*; D010126:Ozone / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000378:metabolism*; D018508:Water Purification / Q000379:methods*
chemical_list: D001427:Bacterial Toxins; D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; D010126:Ozone; C057862:cyanoginosin LR
keywords: Aldehyde-based byproducts; Degradation pathways; Intermediates; Microcystin-LR; Ozone