鄂尔多斯盆地摩林河水化学成分的形成机制

Study on the Formation Mechanism of Chemical Constitution of Stream Water of the Molin River in the Ordos Basin

根据在流域内采集的19个河水及地下水化学分析样品、18个氢氧稳定同位素分析样品,对河水成分沿着流程的变化进行了研究。比较了河水的TDS、主要离子的浓度、水化学类型以及1δ8O和δD沿流程的变化,使用水溶组分平衡分布模型计算了方解石、白云石和石膏等矿物的饱和指数,使用质量平衡模型计算并分析了河水成分沿流程的变化机理。结果表明:石膏的溶解、方解石的沉淀、离子交换、混合过程以及蒸发作用在河水化学成分的形成过程中均起着重要的作用。

The Molin River is a small continental river in the arid region near Hangjin County of Inner Mongolia, China, it is 81 km in length, its drainage area is 5 220 km^2, and its annual runoff volume is 1.8 × 10^7 m^3. In this paper, the chemical institution of stream water of the Molin River is lucubrated based on introducing the hydrogeologic conditions and analyzing 19 stream water and groundwater samples 18 oxyhydrogen stable isotopic samples collected in the drainage basin. Moreover, the changes of TDS, concentration of the main ions, hydrochemical properties, δ^18O and δD of stream water along stream flow are compared, the saturation indexes of calcite, dolomite, gypsum, etc. are calculated with hydrotropic component balance distribution model, and the change mechanism of chemical institution of stream water along stream flow is calculated and analyzed with the mass balance model. The results show that the dissolution of gypsum, precipitation and ion exchange of calcite and mixing and evaporation of stream water play an important role in the formation of chemical institution of stream water; in the positive ions, Na^＋ is dominant; in the negative ions, HCO3^- is dominant, and then Cl^- and SO4^2-. Stream water is in HCO3 · Cl- Na type in the upper and middle reaches but in HCO3 · SO4 · Cl - Na in the lower reaches of the Molin River.