泾源县地下水演化及其地球化学模拟

Evolution and Geochemical Modeling of Groundwater in Jingyuan County

以揭示泾源县地下水水化学场的形成机理为主要研究目的,在了解泾源县水文地质条件的基础上,分析了地下水水化学演化特征,选择3条模拟路径,应用PHREEQC软件对其进行了水-岩作用的地球化学模拟,定量分析研究了该区地下水的演化过程、形成机理。结果表明:各种矿物在3条模拟路径上具有相同的溶解沉淀趋势。TDS沿模拟路径的变化主要是由SO42-含量的变化引起的。在模拟路径1和3上,钠长石、岩盐、钠蒙脱石、钾长石和CO2发生了溶解作用,白云石、方解石和石膏发生了沉淀作用,同时还发生了Na+、Ca2+之间的阳离子交换作用,在路径2上,发生的是钠长石、岩盐、钠蒙脱石、石膏和钾长石的溶解以及Na+、Ca2+之间的阳离子交换,白云石和方解石发生了沉淀作用。在这些溶解沉淀作用综合作用下,地下水水化学成分发生了变化。

Based on the hydrogeological conditions in the Jingyuan County, Ningxia, the regional chemical evolution characters of groundwater were analyzed. By the PHREEQC software a geochemical modeling for water-rock interaction was performed and the quantitative analysis for the evolution process and forming mechanism of groundwater were made. The conclusions were that the minerals in the three selected simulated paths showed the same dissolution and precipitation trends. TDS changes along the simulated path were due to the changes of SO2-4 concentrations. In path 1 and 3, the main reactions occurred were the dissolutions of sodium feldspar, rock salt, sodium montmorillonite, k-feldspar, dolomite and CO2; the precipitations of calcite and gypsum; and the cation exchange between Na＋ and Ca2＋. In the path 2, the main reactions occurred were the dissolution of sodium feldspar, rock salt, gypsum, sodium montmorillonite, K-feldspar; the cation exchange between Na＋ and Ca2＋, and the precipitations of dolomite and calcite. Groundwater chemical composition changes under the effects of the dissolution and precipitation of various minerals.