天然水体中胶体颗粒物与内分泌干扰物的微界面作用机制研究

Natural waters are complex systems. In terms of the component size, they are composed of solutes, dissolved organic matters, trace pollutants, colloidal and particulate materials including organic matter and inorganic minerals, as well as microorganisms. Natural aquatic colloids are usually defined as naturally occurring particles with one dimension in the size range 1 nm and 1μm. It is becoming increasingly apparent that natural colloidal materials play a crucial role as an intermediary in environmental and biogeochemical processes e.g. C, N and P cycling, aggregation and sedimentation, as well as pollutant fate, transport and ecotoxicology. Despite the obvious importance there is a lack of quantitative understanding of the structure of aquatic colloids and how this relates to their environmental 'function' in regulating trace pollutant behavior. Numerous studies have been performed on the sorption of highly hydrophobic organic chemicals (HOCs) onto sediments (or soil). In comparison, natural colloid study is only limited to the phase distribution of trace metals. .Of particular environmental concern are the so-called endocrine disrupting chemicals (EDCs), which may be defined as "exogenous substances that cause adverse health effects in an intact organism or its progeny, consequent to endocrine function". It has been shown that these EDCs may be released directly or indirectly to the aquatic environment, leading to the alternations of normal hormone function and physiological status in wildlife and humans. The different types of EDCs with various levels have been detected in some water systems in China. Unfortunately, little data are available to assess the significance of natural aquatic colloids and nanoparticles in affecting the speciation, transport and fate of these EDCs in the aquatic environment. .Therefore, the overall aim of this project is to investigate the interfacial interactions of selected EDCs onto natural aquatic colloids in order to better understand the role of colloidal particles in influencing the environmental behavior of selected EDCs in aquatic systems. The following specific objectives are addressed: (1) To physical-chemically characterize the nature of colloidal particles that are most important in binding EDCs; (2) To examine the sorption thermodynamic and kinetic properties of selected EDCs onto natural colloidal particles, which include the assessment of controlling factors e.g. solution conditions, colloidal nature and size effect; (3) To investigate the interaction mechanisms with molecular-scale between selected EDCs and colloidal particles; (4) To develop the binding modeling to quantitatively describe the sorption behavior of EDCs onto colloids. .The project will generate novel data sets on the interactions between colloids and EDCs, in terms of thermodynamics, kinetics, mechanism, controlling factors, and provide implications for the transport, long-term fate and toxicity of EDCs in aquatic systems.

天然水体中粒度在1nm到1μm的胶态粒子，由于其特殊的物理化学性质，在各类物质的生物地球化学循环、聚集和沉降以及微量污染物的迁移、转化、归宿和生态毒理中起着重要的作用。EDCs是一类对生物体包括人体具有内分泌干扰作用的持久性有毒有害物，在我国许多的水域中都有不同种类和浓度的检出。本项目就是围绕着天然水体胶态颗粒物在污染物的环境行为中的作用问题，深入开展几种EDCs在胶态粒子界面上的复杂反应机制研究。采用多种仪器分析手段探讨胶体颗粒的物化特性并考察目标EDCs在各胶体界面上的吸附热、动力学特性以及微观作用机制，在此基础上建立相互作用机理模式及动力学模型。通过研究，明确目标EDCs界面吸附特性与胶体颗粒物化特性的定性定量关系及内在影响因素，揭示各胶体组分与目标EDCs的界面反应过程、反应机理及形态转化。该项目研究对预测EDCs的水环境行为具有重要的指导作用。

天然水体是一个复杂的分散体系，天然水体中的胶态粒子由于其特殊的物理化学性质，在各类物质的生物地球化学循环、聚集和沉降以及微量污染物的迁移、转化、归宿中起着重要的作用。EDCs是一类对生物体包括人体具有内分泌干扰作用的持久性有毒有害物。本项目围绕着天然河流中胶态颗粒物与目标EDCs的界面作用研究为核心，采用仪器分析手段测定了辽河流域中典型河流（蒲河、细河、海城河）水体胶体颗粒的荧光光谱特性、颗粒粒度大小分布特征、胶体颗粒中常见阴阳离子、微量金属以及胶态有机碳含量；充分调查了水体中目标EDCs分布特征，开展了EDCs在各胶体界面上的吸附过程以及微观作用机制研究，揭示了各胶体组分与目标EDCs的界面反应过程、相互反应的影响因素及形态转化。结果表明，河流中主要EDCs为双酚A(BPA)、乙炔雌二醇（EE2）、雌二醇（E2）、雌酮（E1）和邻苯二甲酸酯（PAEs）,其在水体中各相间分布特征随环境条件及人类活动而变化；典型河流水体中大部分胶体的形貌为粒径小于6 nm的圆型颗粒，偶有纤维状物存在，主要与有机质含量相关，平均粒径大小细河为1.43 nm、蒲河为1.53 nm、海城河2.22 nm；这些水体中类腐殖质荧光组分多分布在真溶液或小胶体中（1-100 kDa），类蛋白荧光组分在大胶体中（100 kDa-0.7 µm）占的比例较大，表明类蛋白物质在水体中明显的凝聚作用；胶体-EDCs作用动力学研究表明，所选EDCs在胶体表面几分钟之内达到吸附平衡，其校正碳分配系数（log Koc）范围为4.17-4.73，各污染物的分配系数与其辛醇水分配比没有相关性，表明憎水作用并非是目标污染物与胶体的作用机制，胶态Fe和Mn对EDCs在天然胶体上吸附具有增强作用，其作用机制是通过分子中所含羟基与水合铁锰氧化物表面结合位的配位交换而相互作用的，另一方面，Mn、Fe氧化物具有氧化特性，在有机物存在下被诱导还原，同时有机物被氧化降解。通过研究，揭示了复合胶体上的界面吸附行为。该项目的完成为胶体颗粒在天然水体中污染物的迁移转化及归宿中的作用提供一个科学意义上的解释和描述。