大连大魏家水源地海水入侵过程中水文地球化学作用分析及定量模拟

摘要

大连大魏家水源地位于中国北方典型滨海岩溶地区。近年来，地下淡水不合理开采造成的地下水位降落漏斗引发了严重的海水入侵。本文以大魏家水源地海水入侵为研究对象，通过大量的水文地质调查和水化学样品测试分析，探讨了海水入侵形成的水动力条件，通过绘制Piper图、以Cl^-为天然示踪剂计算了海水和地下淡水的混合比例、实际浓度和理论浓度的对比、水化学组成特征分析等方法，探讨了该区岩溶含水层在海水入侵过程中所发生的主要水文地球化学作用，并对其进行了定量模拟，进而阐明了岩溶含水层中的海水入侵机理。研究结果表明，研究区微成水和成水并不是地下水淡水和海水简单混合而成。利用反向水文地球化学模拟揭示了控制滨海岩溶含水层中水化学演化的主要水文地球化学反应有方解石、蒙脱石和石膏的溶解作用，伊利石的沉淀作用以及Ca—Na离子交换作用，伴随着CO2的释放，石膏的溶解并没引起白云石化作用。%The Daweijia wellhead field is located at the coastal Karst area in north China. Unsustainable groundwa- ter exploitation in recent decades has found severe seawater intrusion in this area.Employing hydrogeological inves-tigations,hydrodynamic monitoring and hydrogeochemical texting, An attempt toidentify the geochemical processes of seawater intrusion in the coastal aquifer wascarried out using methods of ionic deltas accounting to the mix pro- portion of seawater and groundwater by Cl-tracer. The contrasts of effection concentration and theory concentration and hydrogeological simulation, and delineated the mechanism of seawater intrusion in this area.The research re-sults suggest that brackish and saline groundwater is not a simple mixture between seawater and fresh groundwater. Inverse hydrogeochemical model can be used to reveal the main hydrogeochemical reactions controlling the hydro-chemical evolution of coastal karst aquifers in the study area, including the dissolution of calcite, montmorillonite and gypsum, the precipitation of illite and Ca-Na cation exchange with CO2 extrication and there is no dolomitiza-tion in this zone.