典型污染场地浅层地下水体系中氯代烃自然衰减规律及其环境响应机制

Chlorinated hydrocarbons (CHs) were widely used as industrial solvents and cleaning agents. Because of the improper usa and disposal, CHs have polluted thousands sites of soil and groundwater in the industrialized country worldwide. The contaminated sites will be developed for commercial and residential usage which leads to the serious risk to ecological environment and public health by the residues of the high toxic CHs plume. Thus, it is necessary to remediate the contaminated sites effectively. The in situ bioremediation technology with the advantages of low-cost and environment-friendly is becoming the most popular contaminated sites remediation technology. To study the CHs natural attenuation and its environmental response mechanism is very important to the bioremediation of CHs contaminated sites. This project focus on the interdisciplinary topic of the CHs natural attenuation rules and the reductive dechlorinating bacterial community diversity and function at typical contaminated sites in the eastern coastal area of China. This study plan to determine the CHs attenuation process by carbon stable isotope fractionation, illustrate dechlorinating microbial ecosystem and community sucession by genomic and proteomics technique, and reveal the reductive dechlorinating microbial community composition, ecological distribution and mechanism of environmental adaption. The results will further indicate the scientific topic of the relationship between CHs plume migration and transformation process-hydrogeological condition-environment factors-biological effects, and deep into the understand of CHs plume migration and transformation regularity based on the flow field properties and biodegradation process, which contributes to provide scientific basis for breaking through the bottlenecks of the CHs contaminated sites bioremediation theory and technology.

氯代烃曾广泛用于工业溶剂和清洗剂，使用和处置不当造成全球数千个场地土壤和地下水污染。氯代烃污染场地开发作商用和民用，严重威胁生态环境和人居环境安全，亟需进行污染场地修复。氯代烃原位生物修复技术环保、低成本，已经成为各国关注的热点，研究氯代烃在地下水中的自然衰减规律和环境响应机制，对污染场地原位生物修复过程具有重要意义。本课题针对我国东部沿海地区典型污染场地地表过程中氯代烃污染物的自然衰减规律与还原性脱氯菌群多样性和功能研究的交叉科学问题，采用稳定同位素法测定氯代烃衰减过程，基因组学和蛋白组学分析脱氯功能微生物生态系统，查明脱氯菌群的演替规律，揭示脱氯菌群的组成、生态分布及其环境响应机制。目的是探索污染场地氯代烃迁移转化过程与水文地质条件、环境因素及生物作用耦合关系的科学问题，基于污染场地流场性质和生物降解过程预测氯代烃的迁移转化规律，为突破氯代烃污染场地原位修复理论和技术瓶颈提供科学依据。

本课题针对我国东部沿海地区典型污染场地地表过程中氯代烃污染物的自然衰减规律与还原性脱氯菌群多样性和功能研究的交叉科学问题，选取上海浦东典型的三氯乙烷（TCA）污染场地，采用长期跟踪调查和地下水污染迁移转化模型模拟，研究了污染场地的自然衰减的潜在能力，发现了氯代烃污染物主要存在于地下2-6 m的土层中，并在场地含水层中发生了明显的自然衰减过程。TCA自然衰减的产物主要包括DCA、CA、1,1-DCE和VC等，其中以DCA和CA为主要降解产物，推测主要发生了取代、消去、及氢解等非生物降解作用以及生物降解作用，其中负责生物降解的微生物菌群主要包括4种类型：Proteobacteria，Spirochaetes，Clostridia和Bacteroidetes。模拟结果表明场地地下水流场较为稳定且水力梯度较小，联合吸附作用共同导致了污染物的缓慢迁移扩散，同时在吸附作用和生物降解作用下，利用等温吸附实验和自然衰减模拟实验，计算得到三氯乙烷在含水层土壤中分配系数0.06 m3/kg和准一级降解动力学参数0.005 d-1。利用Visual MODFLOW软件模拟，预测污染区域的高浓度三氯乙烷的衰减过程，证明5年后三氯乙烷的最高浓度将低于300 μg/L。本研究结果对于深入阐明土壤地下水环境中的氯代烃污染物迁移转化规律和自然衰减机理，并在此基础上创新污染物的原位自然衰减控制技术具有重要意义。