地下水中氯代乙烷的化学还原与生物刺激协同降解机理研究

Chlorinated ethane is a kind of saturated chlorinated hydrocarbon which is harmful and difficult to degrade in groundwater. The coordination of chemical reduction and biological action has been proved to be a potential combined technology for the degradation of chlorinated hydrocarbons. At present, most of remediation technologies focus on the pollution of chlorinated ethene such as trichloroethylene, tetrachloroethylene and the research on mechanism of chlorinated ethane degradation was scarce. At the same time, sulfate is the key parameter restricting the efficiency of dechlorination, and its mechanism has not been elucidated. In this project, the contaminated groundwater in the transitional zone of sandy aquifer is taken as the object, and the batch and anaerobic microcosm experiment will be carried out under the condition of chemical reduction of ZVI, biological stimulation and cooperative remediation of the two methods, respectively. Then the degradation mechanism of chlorinated ethane and environmental chemical behavior of SO42- will be studied. Through routine laboratory analysis techniques, modern molecular biology methods, carbon stable isotope analysis and ZVI interface characterization, the dechlorination process and regularity of chlorinated ethane in groundwater will be elucidated, the synergistic mechanism of ZVI chemical reduction and biostimulation will be revealed, and the mechanism of the SO42- influence for dechlorination process will be discussed, which provides scientific bases for the development and application of remediation technology.

氯代乙烷是一类地下水中危害较大且难以降解的饱和氯代烃。近年来，化学还原协同生物作用被证实是最具潜力的脱氯手段，然而国内外研究热点大多聚焦于三氯乙烯、四氯乙烯等氯代烯烃污染，缺乏对氯代乙烷的关注及降解机理研究。同时，硫酸根是制约脱氯效率的关键参数，其作用机制亦未被阐明。本项目拟以砂质含水层过渡带中的污染地下水为研究对象，采用批试验和厌氧微宇宙实验体系，开展零价铁（ZVI）化学还原、生物刺激及二者协同作用条件下，氯代乙烷的降解机理及硫酸根环境化学行为研究。通过实验室常规分析技术、现代分子生物学手段、碳稳定同位素分析及ZVI界面表征，阐明氯代乙烷在地下水中的脱氯过程及规律，揭示化学还原与生物刺激的协同增效机制，探讨硫酸根影响协同降解的微观机理，为氯代烃污染地下水修复技术的开发和应用提供科学依据。

氯代乙烷是一类地下水中危害较大且难以降解的饱和氯代烃。近年来，化学还原协同生物作用被证实是最具潜力的脱氯手段，然而国内外研究热点大多聚焦于三氯乙烯、四氯乙烯等氯代烯烃污染，缺乏对氯代乙烷的关注及降解机理研究。同时，硫酸根是制约脱氯效率的关键参数，其作用机制亦未被阐明。本项目通过采集实际污染场地地下水及含水层土壤，开展化学还原、生物刺激及二者协同作用条件下，氯代乙烷的降解动力学及土著微生物归趋研究。结果表明：①化学还原条件下，C、O、S、Cl等杂质含量及比表面积是影响铁还原颗粒活性的主要因素，环境因子SO42-在零价铁(ZVI)表面形成配合物的结构特性导致不同粒径ZVI对氯代乙烷的降解存在差异；②氯代乙烷的生物刺激降解效率高于铁还原颗粒，电子供体类型对细菌群落的影响比其浓度更为显著，SO42-的存在则会抑制生物脱氯效率；③微米ZVI-生物刺激协同可使氯代乙烷的降解速率较化学还原提高1个数量级，1,1,2-三氯乙烷的半衰期可缩短至13.86 d，通过Fe0快速改善地下水环境加快生物脱氯的启动时间是该协同体系增效的主导机制；④纳米ZVI-生物刺激协同体系中，SO42-浓度为200-400 mg/L时，产物氯乙烯的深度脱氯效率可提升5.44%-13.59%，推测SO42-通过强化nZVI表面硫化作用提升了后期氯代乙烷的非生物脱氯效率。研究结果初步形成了基于污染地块特征可调控的深度脱氯技术，有利于实现氯代烃污染地下水的低成本环境安全控制。