越流过程中粘土弱透水层超滤作用机理研究

The semi-permeable membrane property of the low-permeability aquifer, an important part of the groundwater aquifer system, is significant to the solute and pollutant migration.The previous studies focus more on the process of hydrodynamic transmission in the aquifer, and there’s lack of research on the aquitard. By focusing on the semi-permeable membrane of the clay low-permeability aquifer, this study will conduct the field vertical hydrochemical and isotopic profile survey. By dint of indoor high pressure permeability test and isotopic labeling ,it will analyze factors that can influence the semi-permeable membrane property ,discuss the mechanism of hydrodynamics and electrochemistry during the flow of water and salt transport in the seepage process, and reveal the mechanism of salt hyperfiltration, thus trying to achieve new breakthrough in the mechanism of semi-permeable layer membrane effect. This study will not only enrich the basic theory of hydrogeology, but also provide theoretical basis for the deep water resources protection in North China Plain, which bears both theoretical and.practical significance.

弱透水层是地下水含水系统中的重要组成部分，弱透水层的半透膜性能对溶质和污染物迁移的阻截具有重要的意义。由于人们更关注含水层中的水动力传输过程，而缺少对弱透水层的研究。本项申请将针对粘土弱透水层的半透膜性能，通过野外实际弱透水层垂向水化学和同位素剖面调查，结合室内原状粘土高压渗透越流试验，以同位素作示踪剂，研究影响粘土半透膜作用发生的各种影响因素，探讨越流过程的水、盐运移过程中的动力学和电化学机制，揭示其对盐分“超滤”机理，力图在弱透水层膜效应机理认知方面取得新突破。不仅丰富水文地质学基本理论，而且为华北平原深层水资源开发保护提供理论依据，具有重要的理论与实际意义。

通过粘性土高压反渗透试验证实了粘性土弱透水层具有半透膜效应，阐明了氯同位素分馏证据，扫描电镜能谱分析证据。计算原状粘性土膜的截留系数(σ)介于0.052～0.2之间。分析了粘性土膜效应的影响因素：膜效应随粘土压密而增大，但不适用于超固结原状粘性土；随渗入液溶度的增大而减小；和阳离子交换容量（CEC）呈正相关性；随着渗透压力的增大而减小直至盐突破。拓展了越流过程中的溶质传输理论，揭示了电化学双电层对粘性土阻盐的机理。提出半透膜阻盐能力的有限性及随着地下水的开采其具有潜在灾难性盐突破的新认识。