分级研究珠江水环境中皮质激素的赋存形态、多介质间的运移及作用机制

Corticosteroids are a class of “emerging” environmental endocrine disruptors. The concern about their pollution has been increasing in recent years. Most of the previous studies were focusing on the corticosteroid pollution in point-sources such as sewage treatment plants, and the systematic research on the occurrence of these pollutants and their geochemical behaviors in natural environment is limited. Their speciation and fate in aquatic environments are in lack of understanding as well, which is setting back the risk evaluation of corticosteroids. In this project, the presence of corticosteroids and their spatial and temporal distribution will be investigated in the Pearl River Delta though the field survey, sampling and lab analysis. Based on the fractionation of samples, their occurrence, migration, and accumulation in the multi-medium environment (water, colloids, particles, sediments, plankton and fish) and the controlling factors are further to be studied on different scale. Furthermore, the interaction between corticosteroids and natural organic matters will be studied based on fractionation methods, and the binding mechanisms are to be explored as well. The project implementation will develop the research on speciation and environmental behaviors of endocrine disruptors, and provide scientific basis to the endocrine-disrupting pollution regulation and ecological risk assessment in the Pearl River basin.

作为一类“新兴”的环境内分泌干扰物，皮质激素的污染问题在近几年开始受到关注。此前的研究工作主要围绕污水处理厂等点源污染状况而开展，对污染物在天然环境中的存在状况和地球化学行为缺乏系统研究和科学定量。关于水环境中皮质激素的形态分布和界面间的运移机制等重要基础理论问题尚缺乏认识，难以深入开展风险评估。本课题选择珠江三角洲流域作为典型研究区域，通过系统的野外观察、采样和实验室分析，研究皮质激素的区域时空分布规律；对环境样品进行分级处理，从不同尺度探究典型皮质激素在珠江水体中的赋存形态、多介质（水、胶体、颗粒物、沉积物、浮游生物/鱼）界面间的迁移、累积规律及其主控因子；分级研究天然有机质与典型皮质激素间的相互作用，探索其微观作用机制。该课题的开展将不仅拓展环境内分泌干扰物的形态和环境行为研究，相关成果亦将为珠江流域的内分泌干扰物污染调控和生态风险评价提供科学依据，具有重要的理论和现实意义。

通过系统的野外观察、采样和实验室分析，揭示皮质激素（CSs）在珠三角流域区域时空分布规律和季节性变异；对CSs污染来源进行解析，并开展了流域尺度的生态风险评估。分级研究了CSs在水体多介质中的赋存状况，分析测定了代表性CSs的原位分配系数、富集系数，揭示了CSs在不同相态间的运移趋势及其主控因子；探索了天然有机质与典型CSs间的相互作用。研究发现，CSs广泛存在于珠三角河流各介质中，其浓度水平呈现出上游向中游或下游增加，然后向河口衰减的趋势并且枯水期浓度高于丰水期、支流高于干流的分布特征；其时空分布主要受到人类活动、水文条件以及DO、Chl a、DOC等水环境参数影响。CSs主要来源于城市新排放的未经处理的生活污水，可的松和醋酸氟氢可的松可分别作为天然和合成CSs来源的潜在指示物。珠三角河流中总体处于中至高生态风险水平，贡献主要来自合成皮质激素。约55.3%、36.2%、8.5%的CSs分别赋存于水相、颗粒相、沉积相，其中粗颗粒级分中的占比略高于细颗粒物级分。CSs的颗粒物/水、沉积物/水、藻/水的logKd值分别为2.62±0.54、2.45±0.43、1.68±0.22，各介质对水体中CSs的迁移作用呈现出颗粒物＞沉积物＞藻（浮游生物）的趋势，TOC和DO是其中的关键影响因子。与雌激素情况不同，疏水作用并非CSs与天然有机质间的主要作用机制。