饱和多孔介质内多组分非水相有机物溶解传递机制研究

A persistent pollutant source will be formed when the non-aqueous phase liquids (NAPLs) contaminants are released into the underground environment and dissolved in groundwater. Dissolution and mass transfer mechanisms of NAPLs in saturated porous media are still not thoroughly understood so far. Three typical organic pollutants methyl tert-butyl ether, xylene and trichlorethylene are selected in the study. The interaction between multi-components in the process of non-aqueous phase organic dissolution in saturated porous media will be analyzed. Impact of factors including characterization of the porous media, initial concentration of NAPLs, groundwater velocity, and the dissolved organic matter or surfactant in water on the process will be investigated. Combined with the dissolution kinetics and mass transfer parameters obtained from experiments or data fitting, a coupled mathematical model will be established, consists of the continuity equation, momentum equation, pollution source NAPLs mass conservation equation, and the role of the dissolution, adsorption, degradation written in the source and sink terms. Dissolution and transfer processes of non-aqueous contaminants in groundwater will be quantified by numerically solving and parameter sensitivity analysis of the theory models using finite element method the theory models using parameters obtained from dissolution kinetics and mass transfer experiments. Results of this study will be of great significance for the establishment and improvement of the theoretical principles on contaminants fate and transport in groundwater, which will serve as theory basis for the environmental risk assessment and remediation of organic contaminants in groundwater.

进入地下环境中的非水相（NAPLs）有机污染物会随着其自身的不断溶解逐渐释放到地下水体环境中，形成持久的污染源。目前，多组分NAPLs在饱和多孔介质中的溶解传递过程机制尚未完全清晰。本项目选取典型有机污染物甲基叔丁基醚、对二甲苯和三氯乙烯为研究对象，分析饱和多孔介质非水相有机物溶解过程中多组分间的相互作用，探讨多孔介质性质、NAPLs初始浓度、地下水流速及水中可溶性有机物和表面活性剂对该过程的影响机制；结合溶解动力学和传质实验获得或拟合得到的参数，建立由连续方程、动量方程、污染源NAPLs质量守恒方程组成的耦合数学模型，将溶解、吸附、降解等作用写入源汇项，运用有限元方法对该模型进行数值求解和参数敏感度分析，从而对地下水中非水相污染物溶解和传质过程做出量化判断。本研究有助于建立和完善地下水中污染物传递和运移过程的理论基础，并可为我国地下水环境中有机污染的环境评价和修复治理工作提供理论依据。

随着工业化进程的加快，有机物对地下环境的污染已经成为一个全球性的问题。进入地下环境的有机物会通过不断溶解过程形成大范围的、持久的污染源，因而溶解过程往往是非水相流体(NAPL)在地下环境污染迁移的关键。本研究首先通过实验方法测定了多孔介质本身的水力学性质及其对有机物的吸附特性，为后续的溶解过程分析讨论提供参数。采用一维土柱和二维砂箱实验模拟NAPL在饱和多孔介质内溶解传质过程，分别探讨了NAPL初始饱和度、水相流速、介质尺寸等因素对MTBE溶解过程的影响，并获得了MTBE溶解动力学。选取地下水中经常检测到的三氯乙烯和对二甲苯，探讨了多组分共存时对MTBE溶解过程的影响。采用非离子型表面活性剂Tween 80、阴离子型表面活性剂SDBS和水溶性的乙醇，完成了水中可溶性有机物和表面活性剂对NAPL溶解过程影响机制的探索。本研究有助于建立和完善地下水中污染物传递和运移过程的理论基础，为地下水环境中有机污染的环境评价和修复治理工作提供理论依据。