title: Accelerated photo-transformation of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) in water by dissolved organic matter.
abstract: The ubiquitous dissolved organic matter (DOM) has an important influence on transformation of organic contaminants through the production of reactive substances, such as (•)OH, (1)O(2), and (3)DOM*. The photolysis of a higher chlorinated polychlorinated biphenyl (PCB) congener (2,2',4,4',5,5'-hexachlorobiphenyl, PCB 153) under simulated sunlight in presence of humic acid (HA) was investigated. Degradation of PCB 153 was accelerated significantly by the addition of HA, with a rate constant of 0.0214, 0.0413, and 0.0358 h(-1) in the initial 18 h of irradiation in presence of 1, 5, and 20 mg/L HA, respectively. The main photodegradation products analyzed by gas chromatography mass spectrometry were 4-hydroxy-2,2',4',5,5'-pentaCB and 2,4,5-trichlorobenzoic acid. Main reactive species involved were determined by the electron spin-resonance spectroscopy, including (1)O(2) and (•)OH. Special scavengers were added to elucidate the photolysis mechanisms. By using the specific scavengers, it turned out that (•)OH accounted for 29.3 % of the degradation, and the intra-DOM reactive species ((1)O(2), (•)OH, and (3)DOM*) accounted for 59.6 % of the degradation. Photo-transformation sensitized by DOM, which involves both aqueous and intra-DOM reactions of PCBs with reactive species, may be one of the most important mechanisms for natural attenuation of PCBs.
authors.affiliation: College of Environmental and Resource Sciences, Zhejiang University, 388 Yuhangtang Road, Hangzhou, 310058, People's Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.forename: Chaofeng
authors.initials: C
authors.lastname: Shen
authors.forename: Minmin
authors.initials: M
authors.lastname: Zhou
authors.forename: Xianjin
authors.initials: X
authors.lastname: Tang
authors.forename: Yingxu
authors.initials: Y
authors.lastname: Chen
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D008401:Gas Chromatography-Mass Spectrometry; D006812:Humic Substances / Q000528:radiation effects; D007700:Kinetics; D010782:Photolysis; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000378:metabolism*; D013472:Sunlight; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D006812:Humic Substances; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls; C014024:2,4,5,2',4',5'-hexachlorobiphenyl