OH-Initiated Oxidation Mechanisms and Kinetics of 2,4,4 '-Tribrominated Diphenyl Ether

2,4,4'-Tribromodiphenyl ether (BDE-28) was selected as a typical congener of polybrominated diphenyl ethers (PBDEs) to examine its fate both in the atmosphere and in water solution. All the calculations were obtained at the ground state. The mechanism result shows that the oxidations between BDE-28 and OH radicals are highly feasible especially at the less-brominated phenyl ring. Hydroxylated dibrominated diphenyl ethers (OH-PBDEs) are formed through direct bromine-substitution reactions (P1 similar to P3) or secondary reactions of OH-adducts (P4 similar to P8). Polybrominated dibenzo-p-dioxins (PBDDs) resulting from o-OH-PBDEs are favored products compared with polybrominated dibenzofurans (PBDFs) generated by bromophenols and their radicals. The complete degradation of OH adducts in the presence of O-2/NO, which generates unsaturated ketones and aldehydes, is less feasible compared with the H-abstraction pathways by O. Aqueous solution reduces the feasibility between BDE-28 and the OH radical. The rate constant of BDE-28 and the OH radical is determined to be 1.79 X 10(-12) cm(3) molecule(-1) s(-1) with an atmospheric lifetime of 6.7 days.