Hydroxylated polyhalogenated diphenyl ethers (HO-PXDEs) have been recognized as a group of widely detected emerging contaminants in natural waters. Photolysis was proved to be an important transformation pathway for these compounds and their direct phototransformation results in highly toxic dioxins. However, the roles of excited states and reactive oxygen species in the photochemical transformation of these compounds are still unclear. In this study, 2'-HO-2,4,4'-trichlorodiphenyl ether (triclosan) and 2'-HO-2,4,4'-tribromodiphenyl ether (2'-HO-BDE-28) were selected as model compounds to investigate their phototransformation processes. Results showed that the direct photolysis reactions of both triclosan and 2'-HO-BDE-28 occurred via their respective excited singlet states, leading to the generation of dioxins. In addition, the energy and electron transfer reactions between excited states of model compounds and molecular O2 can lead to the generation of (1)O2 and OH, which results in self-sensitized photolysis. We also found that both the k, Φ dioxin yield for anionic triclosan were higher than those of anionic 2'-HO-BDE-28. This study revealed the roles of the excited states in direct photolysis and the generation pathway of reactive oxygen species in self-sensitized photolysis of HO-PXDEs, which is important for understanding the phototransformation mechanisms of HO-PXDEs.

中文翻译：

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洞察三氯生和2'-HO-BDE-28的光化学转化途径。

羟基化的多卤代二苯醚（HO-PXDEs）已被公认为是在自然水域中广泛检测到的新兴污染物。事实证明，光解是这些化合物的重要转化途径，它们的直接光转化导致产生剧毒的二恶英。但是，仍然不清楚激发态和活性氧在这些化合物的光化学转化中的作用。在这项研究中，选择2'-HO-2,4,4'-三氯二苯醚（三氯生）和2'-HO-2,4,4'-三溴二苯醚（2'-HO-BDE-28）作为模型化合物以研究其光转化过程。结果表明，三氯生和2'-HO-BDE-28的直接光解反应是通过它们各自的激发单线态发生的，从而导致了二恶英的产生。此外，模型化合物的激发态与分子O2之间的能量和电子转移反应会导致（1）O2和OH的生成，从而导致自敏光解。我们还发现，阴离子三氯生的k，Φ二恶英产率均高于阴离子2'-HO-BDE-28。这项研究揭示了激发态在直接光解中的作用以及活性氧的生成途径在HO-PXDEs自敏光解中的作用，这对于理解HO-PXDEs的光转化机理具有重要意义。阴离子三氯生的Φ二恶英收率高于阴离子2'-HO-BDE-28。这项研究揭示了激发态在直接光解中的作用以及活性氧的生成途径在HO-PXDEs自敏光解中的作用，这对于理解HO-PXDEs的光转化机理具有重要意义。阴离子三氯生的Φ二恶英收率高于阴离子2'-HO-BDE-28。这项研究揭示了激发态在直接光解中的作用以及活性氧的生成途径在HO-PXDEs自敏光解中的作用，这对于理解HO-PXDEs的光转化机理具有重要意义。