Phototransformation of 2,3-Dibromopropyl-2,4,6-tribromophenyl ether (DPTE) in Natural Waters: Important Roles of Dissolved Organic Matter and Chloride Ion

Novel brominated flame retardants (NBFRs) have become ubiquitous emerging organic pollutants. However, little is known about their transformation in natural waters. In this study, aquatic photochemical behavior of a representative NBFR, 2,3-dibromopropyl-2,4,6-tribromophenyl ether (DPTE), was investigated by simulated sunlight irradiation experiment. Results show that DPTE can undergo direct photolysis (apparent quantum yield 0.008 +/- 0.001) and hydroxyl radical (center dot OH) initiated oxidation (second order reaction rate constant 2.4 x 10(9) M-1 s(-1)). Dissolved organic matter (DOM) promotes the photo degradation due to generation of excited triplet DOM and center dot OH. Two chlorinated intermediates were identified in the photo degradation of DPTE in seawaters. Density functional theory calculation showed that center dot Cl or center dot Cl-2(-) addition reactions on C-Br sites of the phenyl group and H-abstraction reactions from the propyl group are main reaction pathways of DPTE with the chlorine radicals. The center dot Cl or center dot Cl-2(-) addition proceeds via a replacement mechanism to form chlorinated intermediates. Environmental half-lives of DPTE relevant with photodegradation are estimated to be 6.5-1153.9 days in waters of the Yellow River estuarine region. This study provides valuable insights into the phototransformation behavior of DPTE in natural waters, which is helpful for persistence assessment of the NBFRs.