水质净化厂出水溶解性有机质介导类固醇类雌激素光降解机制研究

The photodegradation mediated by natural dissolved organic matter (NDOM) have been identified as major reduction pathways for steroid estrogens (SEs) in aquatic environment. And this reduction pathway is always affected by effluent dissolved organic matter (EfOM), which is discharged from water purification plants. The effects of EfOM on the photodegradation of SEs are still unclear due to the difference from NDOM on composition, structure and physicochemical properties, such as SUVA, larger fluorescence index and response peak of protein like organic matter in three-dimensional fluorescence spectrum. Herein, we selected 17α-ethynylestradiol (EE2) and 17β-estradiol (E2) as targeted contaminant, and aim to study: (1) the effects of EfOM with different sources and properties on the photodegradation of SEs; (2) the effects of environmental factors, including dissolved oxygen, pH, and ionic strength on the photodegradation meditated by EfOM; (3) the main reactive oxygen species and their roles in meditating the EE2 and E2 photodegradation as well as their contributions; (4) the effect of combination between EfOM and SEs on photochemical processes and the estrogenic activity variation of EE2 and E2 leaded by the photochemical processes. This study can provide scientific basis for the environmental behaviors and ecological risks assessment of SEs.

前期研究表明天然溶解性有机质（NDOM）介导的光降解过程是环境水体类固醇类雌激素（SEs）的主要削减途径之一。由于SEs主要随水质净化厂出水进入环境，这一途径必然受水质净化厂出水溶解性有机质（EfOM）的影响。由于EfOM具有特征性的紫外吸收值、更大荧光指数值及三维荧光光谱中明显的类蛋白有机质响应峰等与NDOM显著不同的组成、结构和理化性质，其促进EfOM介导SEs光降解的机制不清。本项目以17α-乙炔基雌二醇（EE2）和17β-雌二醇（E2）为对象，阐明不同性质的EfOM对EE2和E2光降解的介导效应和机制，及受环境因子溶解氧、pH和离子强度等的影响；EfOM光生活性氧物质（ROS）主要类型及其在EE2和E2光降解中的作用及相对贡献；阐明EfOM与SEs的结合作用对EfOM介导SEs光降解效率及光降解产物雌激素活性变化的影响规律。为SEs的环境行为研究及生态风险评价提供科学基础。

本项目以17α-乙炔基雌二醇（EE2）和17β-雌二醇（E2）为内分泌干扰物的代表物质，系统研究了水质净化厂出水受纳水体环境中雌激素的光化学转化过程。以水质净化厂出水中所含EfOM为切入点，在实验室模拟太阳光条件下，研究了EfOM介导下雌激素的光降解速率和效率，通过分子探针等技术明确了EfOM在光照条件下可以产生较高浓度3DOM*，1O2及•OH等活性物质，并且明确了光降解起主要贡献的自由基为3DOM*和1O2。通过降解产物分析，推导了雌激素的光转化途径。探明了DO、pH和离子强度通过影响ROS的产生间接影响EE2和E2的光降解过程。通过荧光淬灭手段探讨了EfOM与雌激素的结合机理，明确了静态结合是EfOM与EE2直接相互作用的关键途径；揭示了EfOM通过结合作用增加雌激素溶解度进而提升其降解的作用机制。通过对比分析明确了不同疏水性和分子量大小的EfOM介导雌激素光化学效能和机制。同时，对不同来源及性质的EfOM进行体外细胞毒性评估，并考察了EfOM介导雌激素光降解产物的生态毒性，综合评价污水出水进入受纳水体后的环境风险。研究成果为雌激素在水质净化厂受纳水体中的环境行为和生态风险评价提供理论依据。