贺兰山至吉兰泰盐湖的水化学特征及演化规律

在对吉兰泰盐湖南部地下水化学组分特征分析的基础上,利用PHREEQC软件对水文地球化学演化规律进行模拟研究。结果表明,从贺兰山西侧山前到吉兰泰盐湖,水化学类型由HCO-3型过渡到Cl-—SO2-4型、最后变为Cl-型;Ca2+、Mg2+与SO2-4相关分析表明发生石膏溶解出的Ca2+置换了MgCO3中Mg2+,从而产生了CaCO3沉淀的水岩反应,而白云石、石膏、岩盐、CO2(g)的溶解是常量离子增加的物质来源,同时伴有强烈的蒸发浓缩作用及阳离子交换作用。特别是深层地下水具有较高的mNa/Cl值与较低的mCa/Na值,表明发生强烈的阳离子交换作用,这对认识吉兰泰盐湖地区及干旱区沙漠地区水体发生的水岩相互作用与演化机制具有借鉴作用。

Hydrogeochemical Properties and Evolution of Groundwater from Helan Mountain to Jilantai Salt Lake

The PHREEQC software is applied to simulate the groundwater spatial pattern from the Helan Mountain to the Jilantai Salt Lake based on analysis of hydrochemical properties. Results show that groundwater evolves gradually from HCO-3 type to Cl--SO2-4 type and eventually to Cl- type from the front of western Helan Mountain to Jilantai Salt Lake. Correlation between Ca2+, Mg2+ and SO2-4 shows that Ca2+, which dissolved from gypsum, substitutes Mg2+ of MgCO3, so that CaCO3 is produced in the process. The increase of major ions comes from the dissolution of dolomite, gypsum, halite and CO2(g), which is strongly influenced by evaporation and cation exchange process. The deep groundwater have high value of mNa/Cl (2.12) and low value of mCa/Na(0.09), which indicate a dramatic cation exchange process. It is very helpful to the understanding of the water-rock interactions and groundwater evolution in the arid desert zone and Jilantai Salt Lake.