Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China.
Shanghai Key Lab for Urban Ecological Processes and Eco-Restoration, School of Ecological and Environmental Sciences, East China Normal University, Shanghai 200241, China; Shanghai Engineering Research Center of Biotransformation of Organic Solid Waste, Shanghai 200241, China; Technology Innovation Center for Land Spatial Eco-restoration in Metropolitan Area, Ministry of Natural Resources, 3663 N. Zhongshan Road, Shanghai 200062, China.
J Hazard Mater. 2021 Jan 5;401:123884. doi: 10.1016/j.jhazmat.2020.123884. Epub 2020 Sep 6.
Halogenated organic compounds, also termed organohalogens, were initially regarded to be of almost exclusively anthropogenic origin. However, recent research has demonstrated that photochemical reactions are important abiotic sources of organohalogen compounds in sunlit surface waters. Halide ions (X, X represents Cl, Br and I) are common anions in natural waters and might be oxidized by reactive species originated from photochemistry of dissolved organic matter (DOM) or inorganic photoactive species. The resulting reactive halogen species may react with organic substances with diverse bimolecular reaction rate constants, depending on the complexity and structure of organic substances. Therefore, the chemical mechanism of halogenation remains challenging to be fully elucidated. To better understand the trends in the existing data and to identify the knowledge gaps that may merit further investigation, this review gives an integrative summary on the sources of reactive oxygen species (ROS) and halogen radicals (X/X). Photochemical halogenation of phenolic compounds and formation of methyl halide and brominated organic pollutants are highlighted. By evaluating existing literature and identifying some uncertainties, this review emphasizes the environmental significance of sunlight-driven halogenation and proposes further research directions on mechanistic investigation and rational experimental design close to natural systems.
卤代有机化合物，也称为有机卤代物，最初被认为几乎完全是人为来源的。然而，最近的研究表明，光化学反应是阳光照射地表水中有机卤代化合物的重要非生物来源。卤素离子（X，X 代表 Cl、Br 和 I）是天然水中常见的阴离子，可能会被溶解有机物（DOM）或无机光活性物质的光化学产生的活性物质氧化。由此产生的活性卤素物种可能会与具有不同双分子反应速率常数的有机物质反应，这取决于有机物质的复杂性和结构。因此，卤化的化学机制仍难以完全阐明。为了更好地了解现有数据的趋势，并确定可能值得进一步研究的知识空白，本综述对活性氧物种（ROS）和卤素自由基（X/X）的来源进行了综合总结。着重介绍了酚类化合物的光化学卤化作用以及甲基卤化物和溴化有机污染物的形成。通过评估现有文献并确定一些不确定性，本综述强调了阳光驱动卤化的环境意义，并就接近自然系统的机制研究和合理实验设计提出了进一步的研究方向。
