中文摘要：

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。

英文摘要：

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 envi-ronment 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 Habstraction 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.