粘性土弱透水层孔隙水渗流过程及演变机制研究

滨海平原粘性土弱透水层是古海（咸）水聚集的主要场所，影响并威胁着含水层的水质安全。认识弱透水层孔隙水的水质特征、空间分布及运移规律，可以把握地下水咸化机制与演变规律。粘性土层与含水层交互沉积，量化分析孔隙水-地下水相互作用，可以探讨含水层的补给与更新。本课题以莱州湾滨海平原晚更新统第Ⅰ、第Ⅱ承压水及其间的粘性土为研究对象，测定弱透水层-含水层系统水化学-同位素-稀有气体-年龄组成，绘制其垂向图谱。利用稀有气体，综合多种环境同位素，揭示孔隙水的起源、演化、古环境记录及其与含水层的相互作用。利用天然示踪剂Cl和4He剖面形态，分析孔隙水的运移模式；以粘性土层上下含水层为边界，建立孔隙水垂向一维对流扩散模型，结合古沉积环境及地下水地层学，定量模拟晚更新世以来孔隙水的扩散运移过程，揭示含水层的（古）补给与更新过程。本课题提出粘性土孔隙水的环境记录可为含水层地下水演化提供新的研究手段。

Clayey aquitard is capable to trapped paleo-seawater (or saline water) in the coastal plain, which is a major threat for aquifer groundwater. Understanding the geochemistry, distribution and transport of aquitard porewater, it will be helpful to know the salinization and evolution regime of adjacent aquifer groundwater. In the coastal plain, clay formation is usually interbedded deposited with sand layer. Based on the quantitative study of porewater-groundwater interaction, the recharge and alternation of groundwater can be analyzed by environmental record of aquitard porewater. In this study, the aquitard and groundwater samples in the Late Pleistocene will be collected from the first and second confined aquifer and the clay formation between them in the coastal plain, Laizhou bay, by drilling. Based on the detailed clay porewater – aquifer groundwater geochemistry, isotopes, noble gas and age profiles, the porewater origin, evolution and implications on paleo-environment, and the interaction with aquifer groundwater will be elaborated. According to the profile shape of natural tracers Cl and 4He, porewater transport model will be revealed. Taking the upper and under aquifers as boundaries, the one-dimensional vertical advection-diffusion model of aquitard porewater will be constructed. Combined with paleo-sedimentation condition and groundwater dating, the diffusion process of aquitard porewater since the late Pleistocene will simulated and the recharge and alternation of groundwater will be showed. Using the environmental record of aquitard porewater to study groundwater evolution is a new method in the hydrogeology.