摘要:
由于2,4-二氯酚(2,4-dichlorophenol,简称2,4-DCP)具有“三致”作用及潜在的生态风险，其光化学降解机理及产物的生态毒理效应目前成为人们关注的焦点。本研究采用理论化学计算手段，系统阐明了2,4-DCP在水环境中·OH介导的间接光化学转化机理、动力学和转化产物的生态毒性变化特征。结果表明2,4-DCP很容易被·OH氧化降解，其降解主要通过·OH-加成和H-迁移路径进行。在低温条件下·OH-加成路径将占主导，主要形成4,6-二氯苯-1,3-二酚；而当温度超过313 K时，·OH提取酚羟基上的氢原子为主要降解途径，主要形成2-氯苯-对苯醌。尤其在活性物种浓度较低的高温环境中，H-迁移路径有可能生成二噁英。计算毒理学结果表明：H-迁移产物的水生毒性超过·OH-加成产物，甚至超出母体2,4-DCP一个毒性等级。因此，我们建议在以后的环境监测以及风险评估过程中，关注2,4-DCP及其转化产物特别是H-迁移路径的转化产物的生态毒理学问题。
Abstract:
Recently, the photochemical degradation mechanisms of 2,4-dichlorophenol (2,4-DCP) and the consequent toxicities of its intermedates cause a worldwide concern due to its potential carcinogenesis, teratogenesis, and mutagenesis as well as ecotoxicological effects. Herein, the·OH- initiated indirect photochemical transformation mechanism, environmental fate and aquatic toxicity of 2,4-DCP as well as its degradation intermediates in water environment were theoretically calculated in detail. The results show that 2,4-DCP can be degraded readily via·OH- addition and H- abstraction pathways. The·OH- addition was the predominant pathway at low temperature (<313 K), mainly producing 4,6-dichlorobenzene-1,3-diol; whereas the phenolic hydroxyl H atom was predominantly abstracted by·OH at high temperature, mainly forming 2-chlorobenzene-p-benzenequinone. What's more, dioxin would be also formed via the H- abstraction pathway in the high temperature water environment with limited concentration of reactive species. Furthermore, the computational toxicology results indicate that the transformation products from H- abstraction pathways possess an increased aquatic toxicity to fish compared with·OH- addition products, and even exceeds one toxic level than 2,4-DCP. Therefore, more attentions should be paid to photochemical products as well as the original 2,4-DCP, particularly those products from H- abstraction pathways.
点击查看大图
下载:
