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Indexed by:期刊论文

Date of Publication:2016-04-15

Journal:JOURNAL OF HAZARDOUS MATERIALS

Included Journals:SCIE、EI、PubMed

Volume:307

Page Number:344-349

ISSN No.:0304-3894

Key Words:Methoxylated polybrominated diphenyl ethers; Photodegradation; Singlet oxygen; Superoxide anion radical; Hydrodebromination

Abstract:Photodegradation has been proved to be a crucial way of elimination for polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDEs (HO-PBDEs). However, it is still unknown whether methoxylated PBDEs (MeO-PBDEs) can also undergo photodegradation. In this study, 4'-MeO-BDE-17, 5-MeO-BDE-47, 5'-MeO-BDE-99, 6-MeO-BDE-47 and 6-MeO-BDE-85 were selected as targets to investigate their photodegradation in water. Meanwhile, the effects of dissolved oxygen on the photoreactions of MeO-PBDEs were also unveiled. Simulated sunlight experiments indicate that 6-MeO-BDE-47 resisted photodegradation for 20 h, while other MeO-PBDEs underwent relatively fast photodegradation, which was greatly susceptible to the substitution patterns of methoxyl and bromine. Photo-excited MeO-PBDEs (except 6-MeO-BDE-47) can sensitize dissolved oxygen to generate singlet oxygen (O-1(2)) and superoxide anion radical (O-2(-center dot)). The generated O-1(2) cannot degrade the MeO-PBDEs, whereas O-2(-center dot) was reactive with MeO-PBDEs. The contribution of dissolved oxygen to the photodegradation of 4'-MeO-BDE-17 and 6-MeO-BDE-85 was negligible; while the negative contribution was observed for 5-MeO-BDE-47 and 5'-MeO-BDE-99. Hydrodebromination was a crucial photodegradation pathway for MeO-PBDEs (excluding 4'-MeO-BDE-17 and 6-MeO-BDE-47). Eventually, direct photolysis half-lives of MeO-PBDEs except 6-MeO-BDE-47 in the surface waters at 40 N latitude were calculated to be 1.35-3.46 d in midsummer and 6.39-17.47 d in midwinter. (C) 2016 Elsevier B.V. All rights reserved.