基于反向地球化学模拟的地下水形成作用: 以安徽省泗县为例

在了解安徽省泗县水文地质条件基础上,分析了区域水文地球化学特征及类型,探讨了其空间分布特征。根据开采条件下的地下水动力场条件,选择了3条模拟路径,采用PHREEQC软件进行了水文地球化学模拟研究,定量分析了地下水的形成机理及演化。结果表明,路径Ⅰ发生了岩盐、石膏以及伊利石的溶解,高岭土、石英、白云石、萤石发生了沉淀;钙蒙脱石、方解石不参与反应,NaX解吸,CaX_2被吸附;路径Ⅱ发生了岩盐、石膏、伊利石、石英等的溶解以及钙蒙脱石、方解石的沉淀,NaX解吸,CaX_2被吸附;路径Ⅲ发生的反应基本与路径Ⅰ相同,不同之处在该路径上的白云石发生了溶解,其原因可能是地下水在径流过程中溶解CO_2,使其继续溶解白云石以及受沉淀滞后的影响。研究结果表明地下水开采条件下,泗县地下水化学组分主要受到了岩盐和石膏等矿物的溶解作用、钙钠离子交换作用以及钙蒙脱石、方解石沉淀作用的控制。

Formation of Groundwater Based on Inverse Geochemical Modeling: A Case Study from the Sixian County,Anhui Province

Based on regional hydrogeological conditions, the hydrogeochemical characteristics, water type and spatial distribution of groundwater in Sixian County,Anhui Province were analysed and discussed. According to the characteristics of hydrodynamic field under groundwater exploitation, three paths were selected to simulate. The hydrogeochemical simulation was carried out using PHREEQC, and the formation and evolution of groundwater were quantitatively analysed. The results showed that the halite, gypsum and illite were dissolved; kaolinite, quartz, dolomite, calcite, fluorite were precipitated; calcic montmorillonite did not participate in the reaction; NaX desorption or CaX₂ adsorption occurred in Path Ⅰ. Halite, gypsum, illite, quartz were dissolved; calcic montmorillonite and calcite were precipitated; NaX desorption and CaX₂ adsorption occurred in Path Ⅱ. Reactions of Paths Ⅰ and Ⅲ are largely the same; the difference is the presence of dolomite dissolution in Path Ⅲ. The reason for this difference may be that dolomite dissolution is affected by precipitation CO₂ and precipitation hysteresis in groundwater runoff. The results show that the groundwater composition is mainly influenced by dissolution of rock salt and gypsum, Ca-Na ionic exchange and calcic montmorillonite, calcite in groundwater mining conditions of Sixian County.