应用同步辐射谱学技术研究典型有机污染物的土壤微界面过程

Investigation of the micro-interfacial processes of organic pollutants in soils at the molecular scale is one of the frontier topics in the field of environmental chemistry. The micro-interfacial processes of organic pollutants are believed to be controlled by the functional group composition and micro-structure of organic carbon in the soil environment to a great extent. Due to the complexity of soil matrices and limitation of analytical techniques, the knowledge on the soil micro-interfacial processes of organic pollutants is still to be further investigated. Because of their element-specific characteristics and unique spectral and spatial resolution, synchrotron based X-ray techniques have been the most effective ones for the qualitative and quantitative characterization of micro-interfacial processes of organic pollutants in the soil environment. Here we propose to study the micro-interfacial processes of organic pollutants in soils using synchrotron based X-ray techniques coupled with NMR and infrared spectroscopy and atomic force microscopy and select the characterization of functional group composition and micro-structure of soil organic carbon as an entry point and Br as a conservative tracer to indicate the speciation and sorption sites of some persistent organobromine pollutants in soils. The proposal mainly focuses on (a) the micro-interfacial processes of organic pollutants in soils and their relationship with the functional group composition and micro-structure of organic carbon, (b) the sorption sites, speciation and micro-distribution of some typical organobromine pollutants and their aging processes in the soil environment, and (c) how the relevant environmental factors affect the above processes in order to explore the reaction mechanisms involved in the micro-interfacial processes of typical organic pollutants and highlight the key factors controlling the micro-interfacial processes in the soil environment. This line of research will be an important step towards both a better understanding of the behaviors of persistent organic pollutants in the environment and the advancement of molecular environmental science.

在分子水平上研究有机污染物在土壤微界面上的反应过程是环境化学领域的前沿科学问题。有机污染物的土壤微界面过程在很大程度上受控于有机碳的官能团组成和微观结构。由于土壤基质复杂性及分析技术限制，关于有机污染物在土壤微界面上反应过程机制的认识仍有待深入。同步辐射谱学技术以其元素专一性、独特的光谱和空间分辨率而成为定性、定量表征有机污染物土壤微界面过程最有效的技术之一。本项目以土壤有机碳官能团组成和微观结构为切入点，以典型溴代有机污染物中Br为示踪原子，联合应用同步辐射谱学、核磁、红外及原子力显微镜等技术，分别从有机污染物的土壤微界面过程与有机碳官能团组成和微观结构关系，典型溴代有机污染物在土壤微界面上结合位点、赋存形态、微区分布及老化过程，以及相关环境影响因素等三个层次深入揭示典型有机污染物的土壤微界面过程反应机制，探讨影响有机污染物土壤微界面过程的关键因素，推动分子环境科学的进步。

在分子水平上研究有机污染物在土壤微界面上的反应过程是环境化学领域的前沿科学问题。有机污染物的土壤微界面过程在很大程度上受控于有机碳的官能团组成和微观结构。本课题基于同步辐射谱学技术，联合应用红外光谱、光电子能谱、分子排阻色谱等技术，以影响有机污染物土壤界面过程的关键因素：有机碳官能团组成作为研究切入点，分别开展了土壤腐殖质组分含碳官能团组成及磷酸根影响作用；生物质黑炭在碳化过程中官能团组成变化特征；典型溴代有机化合物在土壤界面结合位点、赋存形态及微区分布特征；典型硝基芳香化合物在土壤界面结合位点、微区分布及相关影响因素；生物质黑炭在土壤界面老化过程官能团组成变化及对有机化合物吸附的影响特征；以及硫素在土壤中赋存形态及相关影响因素等6方面的研究。通过以上工作，建立了基于同步辐射微束X射线荧光光谱和红外显微成像技术的典型有机污染物土壤界面过程的原位分析方法，实现从微纳米尺度、分子水平解析溴代有机污染物在土壤界面上赋存形态、结合位点及关键影响因素等反应机制；分析了具有不同极性硝基芳香化合物在土壤界面结合位点、微区分布，揭示了土壤芳香基碳以及黏土矿物在硝基芳香化合物土壤界面反应过程中的重要作用；明确了不同碳化温度对生物质黑炭官能团组成的影响特征：随着碳化温度升高，生物炭芳构化程度趋于增大，含氧官能团趋于降低；探讨了生物质黑炭在土壤界面老化过程中表面官能团组成变化特征及对有机污染物界面过程的影响机制，明确了可溶性有机碳在衰减生物质碳吸附有机污染物反应中的重要作用；比较了常见土壤前处理方式对土壤硫素形态分析的影响特征，并研究了长期施肥土壤中硫素、磷素的赋存形态和迁移、转化规律。研究结果为认识非离子型有机污染物土壤界面反应机制及相关影响因素提供了直接的证据，研究方法对于研究有机污染物在土壤界面反应过程具有重要的方法学意义，研究工作推动了有机污染物在土壤微界面上反应过程机制研究的进步。