基于EDCs氯消毒副产物紫外吸收红移效应的太阳光直接降解机制研究

Environmental endocrine disrupting chemicals (EDCs) are ubiquitous in rivers, lakes and coastal waters. The municipal wastewater treatment plants (WWTPs) effluents are the main sources of chlorination byproducts of EDCs in the receiving waters. Although they are frequently detected in effluents and natural waters, up to now, few studies have been made on the environmental behaviors of these chlorinated EDC products in waters. Our recent experiments have shown that the UV light absorption of the chlorination byproducts of EDCs shifts to longer wavelength compared to the parent compounds, and partially overlaps the solar spectrum. Therefore, the direct photodegradation may become an important pathway for the transformation of chlorinated EDCs in waters. The effect of water quality of effluents on the photodegradation of chlorinated EDCs will be investigated. The estrogenic activity of chlorinated EDCs before and after photodegradation will also be examined. A series of experiments including the quenching of reactive species, kinetics modeling of photodegradation, and determination of reactive intermediates and photoproducts will be conducted to elucidate the mechanisms of photodegradation. The correlation studies on the generation of chlorinated disinfection byproducts and direct photodegradation of chlorinated EDCs will supply basic data for the ecological risk assessment and prediction of the persistence of chlorinated EDCs. Meanwhile, it will help for the optimization of the process parameters of chlorination disinfection in WWTPs.

环境内分泌干扰物（EDCs）广泛存在于河流、湖泊、海洋等天然水体，城镇污水处理厂排放为受纳水体EDCs主要来源。尽管EDCs的氯消毒副产物存在于污水厂出水及受纳水体，但迄今为止仍没有研究报道这些氯消毒副产物在水体中的环境化学行为。根据我们最新的实验结果，EDCs的氯消毒副产物紫外吸收相对于母体化合物发生了明显的红移，并与地面太阳光谱部分重叠，使得EDCs的氯消毒副产物在水中直接光降解成为重要的迁移转化途径。本项目拟考察污水厂出水水质对氯代EDCs的光降解影响，测试氯代EDCs光降解前后雌激素活性变化；根据活性物种猝灭实验、光降解动力学模拟、反应过程中活性自由基中间体和产物的识别，揭示氯代EDCs在水中的光降解作用机制。通过消毒过程中氯代EDCs的生成与太阳光直接降解关联研究，为污染物的生态风险评估和环境持久性预测提供基础数据，同时为优化污水厂氯消毒工艺参数提供依据。

雌酮、雌二醇、雌三醇和乙炔基雌二醇、双酚A、对羟基苯甲酸酯类是常见的内分泌干扰物（EDCs），它们被使用后最终排放到城镇污水处理厂，这些内分泌干扰物并不能被传统工艺完全被去除。污水处理厂二沉池出水氯消毒过程中，它们与水中的氯消毒剂反应生成雌激素活性更强的氯代EDCs。本项目研究表明：1）氯代EDCs紫外可见光谱发生明显红移，最终红移至300 nm以上，与辐射到地面的太阳光谱重叠；2）相比难以直接光降解的EDCs而言，太阳光照射下氯代EDCs发生快速直接光降解；3）氯代EDCs光降解途径主要为苯环氯原子被羟基取代生成羟基化产物，其进一步开环生成相应的羧酸和醇类化合物；4）氯代EDCs在模拟太阳光下直接光降解主要由于自身激发三线态与单线态氧（1O2）的作用，羟基自由基（•OH）对其直接光降解几乎没有影响；5）重组人雌激素受体（h-ER）酵母试验对含有EDCs的原样品和光解以后的样品进行测试，发现光解后产物雌激素效应可以忽略。本项目研究成果意义在于：1）揭示氯代EDCs的形成过程及光化学反应机制；2）为氯消毒后难降解有机微污染物提供高效节能去除方法；3）提供一种异于高级氧化方法的难降解有机无污染物处理工艺。