土壤中不同有机质组分对纳米铁作用下多氯联苯降解特性的影响

Extensive research findings have showed that nanoscale zero-valent iron had a certain effect on the dechlorination of chlorinated organic compounds. However,the current studies were mostly concentrated on the degradation process and mechanism of PCBs in water. The studies about the reductive dechlorination of the chlorinated organic pollutants in soils were rare,especially further study about the effect of organic matter in soils on the degradation characteristics of polychlorinated biphenyl by nanoscale zero-valent iron were not made. Considering the candidate’s experience in the zero-valent iron and organomineral complexes, the applicaation of the project will start the research from this point. The project would select peat soil having high organic matter as the study object. Humic acid, fulvic acid and humin would be extracted from the humus through the method of chemical fractionation. Organomineral aggregates were separated by physical method. The experimental results of the reduction degradation of PCBs by nanoscale zero-valent iron would combined with the results of nuclear magnetic resonance, infrared spectral analysis and X ray diffraction to analysis the degradation kinetics, explain the effects of different organic matter fractions and organomineral aggregates to the reductive dechlorination of PCBs, and discuss the degradation mechanism of PCBs in soil by nanoscale zero-valent iron. Therefore, the study is of practical importance for providing the basic science base for the remediation of different types of soil contaminated by PCBs.

大量研究成果表明纳米铁对含氯有机化合物具有一定的脱氯效果，但目前的研究多集中于对水体中含氯有机污染物降解过程及机理的研究，对土壤中含氯有机污染物还原降解的研究还比较少，特别是关于土壤中有机质对纳米铁作用下多氯联苯降解行为影响的研究还不多见。本课题结合申请者在零价铁、有机矿质复合体等方面的研究基础，以此为切入点展开研究。申请项目选用有机质含量丰富的泥炭土为研究对象，采用化学分级法提取腐殖质中腐殖酸、富里酸和胡敏素，通过物理分级方法提取土壤有机矿质复合体组分，进行纳米铁还原降解实验，结合核磁共振、红外光谱分析、X射线衍射等仪器表征结果，分析土壤中多氯联苯在纳米铁作用下的降解反应动力学、探讨土壤中不同的有机质组分及有机质与矿物质的结合体对多氯联苯还原脱氯的影响，初步探讨多氯联苯在纳米铁作用下的降解反应机理，从而为不同类型多氯联苯污染土壤的修复提供基础科学依据。

大量研究成果表明纳米铁对含氯有机化合物具有一定的脱氯效果，但目前的研究多集中于对水体中含氯有机污染物降解过程及机理的研究，对土壤中含氯有机污染物还原降解的研究还比较少，特别是关于土壤中有机质在纳米铁作用下对多氯联苯降解行为影响的研究还不多见。本课题选用有机质含量丰富的泥炭土和黑土为研究对象，提取土壤中的有机质组分，分析土壤中多氯联苯在纳米铁作用下的降解反应动力学、探讨土壤中不同的有机质组分对多氯联苯还原脱氯的影响，并初步探讨多氯联苯在纳米铁作用下的降解反应机理，从而为不同类型多氯联苯污染土壤的修复提供基础科学依据。实验结果表明，纳米级零价铁、镍铁双金属和微米级零价铁均可降解土壤中的六氯联苯PCB138，降解过程符合一级反应动力学方程。PCB138在黑土胡敏酸中降解速率最快。降解产物实验分析及电荷分布计算结果表明PCB138还原脱氯反应中C原子的活性大小顺序为：邻位＞对位＞间位。PCBs的还原降解速率与分子结构的定量结构-性质关系模型结果表明，Ehomo、△fHθ、△fGθ和Polar是影响体系中多氯联苯降解速率的主要分子结构参数。此模型可以较好地预测多氯联苯污染场地土壤化学修复过程中多氯联苯各同系污染物的化学降解潜力和残留趋势，具有实践意义。