潜水含水层隔水底板中TCE-DNAPL的自然衰减机制研究

以三氯乙烯（TCE）为代表的氯代烃是地下水有机污染的重要类型，隔水层中TCE-DNAPL的反向扩散引是决定含水层污染羽存续时间的关键，是地下水污染防治和风险管理的难点。本研究以隔水层低渗透介质中的TCE-DNAPL为研究对象，利用高精度超声扫描、micro-CT和激光共聚焦扫描显微镜精细刻画低渗透介质的物理结构和TCE-DNAPL的分布特征；在此基础上进行低渗透介质中TCE-DNAPL反向扩散的动力学研究，厘清吸附控制的反向扩散动力学机理；通过TCE及其降解产物、多维同位素、水化学和水环境因子综合数据解析，探明低渗透介质中TCE-DNAPL生物降解的过程机理，提出自然衰减的判断依据，建立TCE-DNAPL及其降解产物的解吸-反向扩散-生物降解多步耦合动力学方程，形成自然衰减量化评估模型并进行场地验证，从微观分布特征、反向扩散和生物降解角度揭示隔水层中TCE-DNAPL的自然衰减机制。

Chlorinated solvent contaminants, represented by trichloroethene (TCE), are important contaminants of concern in groundwater. The persistence of contaminant plumes mainly depends on the back diffusion rate of TCE-DNAPL from the low permeability region to higher permeability aquifer. Therefore, understanding the back diffusion process is the main difficulty and key point of groundwater contaminant prevention and risk management. In this study, high-resolution ultrasound scanner, micro-CT and laser confocal scanning microscope will be used to well characterize the physical structure of the low permeability media and the distribution characteristics of TCE-DNAPL. The kinetics of TCE-DNAPL back diffusion from the low permeability media to the higher permeability zone will be studied, to clarify the mechanism of adsorption controlled back diffusion kinetics. The comprehensive studies of TCE and its degradation products, multidimensional isotopes, water chemistry, and water environmental factors will be conducted to identify the mechanism of TCE-DNAPL biodegradation in the low permeability media and to propose the criterion for evaluating the natural attenuation. In addition, the multi-step kinetic equation, including desorption, back diffusion, and biodegradation of TCE-DNAPL and its degradation products will be established. The quantitative assessment model for the natural attenuation will be built and applied to the field site for verification. The project will provide a comprehensive understanding of the natural attenuation mechanism of TCE-DNAPL in the unconfined aquifer by investigating micro-distribution characteristics, back diffusion, and biodegradation.