银川地区地下水矿物的水文地球化学模拟

Hydrogeochemical modeling of minerals in groundwater in Yinchuan region

以银川地区为例,用水文地球化学模拟研究了地下水化学组分的存在形式和矿物的存在形态。通过对银川地区144组水化学常量组分的计算分析和水文地球化学模拟计算,系统研究了地下水化学组分和矿物饱和指数的变化。研究表明,1)在银川地区,山前洪积扇→冲洪积平原→河湖积平原→河漫滩,矿化度从西向东不断增高,由淡水向盐化水转化,水化学类型由HCO3.SO4-Ca.Mg向SO4.Cl-Na.Mg过渡;2)地下水从山前洪积扇到黄河漫滩,SO42-的存在对Ca2+和Mg2+的存在形式有很大影响,随着SO42-含量和矿化度的上升,络合组分CaSO40和MgSO40分别相对Ca2+和Mg2+呈逐渐升高的趋势,与之对应的是游离Ca2+和Mg2+的相对含量逐渐降低,CaSO40和MgSO40在黄河漫滩相对含量皆超过20%;3)方解石和白云石的饱和指数在整个地下水流动范围内均呈现过饱和状态,并从冲洪积平原和河湖积平原分别向山前洪积扇和河漫滩降低,石膏饱和指数小于0,从山前洪积扇向河漫滩逐渐升高,表明石膏处于不断溶解的状态。

As a case of groundwater study in Yinchuan region, the paper has produced the existing structural form of hydro-chemical components and mineral contents used in the region＇s hydro-geochemical modeling. In doing so, the paper has also given an analysis of the variation of hydro-chemical components and saturation indices of different minerals in correspondence with the 144 group chemical component contents and hydro-geochemical modeling structure. The results of the modeling indicate that, （1） The TDS has gradually been increasing as the fresh water turns into saline water and the hydro-chemical type evolutes from HCO3· SO4 - Ca· Mg to SO4· Cl Na · Mg, from piedmont pluvial fan to alluvial proluvial plain, and then to fluviolacustrine plain, and later to Huanghe alluvial flat in Yinchuan region; （2） The SO4^2- in the local groundwater contributes to the existing form of Ca^2 ＋ and Mg^2 ＋ from piedmont pluvial fan to the Huanghe alluvial flat. The compound components of CaSO4^0 and MgSO4^0 prove to increase with SO4^2- and TDS respectively while the free content of Ca^2 ＋ and Mg^2＋ decrease gradually. The content of CaSO4^0 and that of MgSO4^0 can be as high as over 20% in the alluvial flat; and, （3） the saturation indices of calcite and dolomite prove to be higher than zero in the total groundwater flowing system, though they may decrease gradually from the alluvial proluvial plain and the fluviolacustrine plain to piedmont pluvial fan and Huanghe alluvial flat, respectively. Nevertheless, the saturation indices of gypsum would be lower than zero, on the condition that they increase gradually from piedmont pluvial fan to the River＇ s alluvial flat. Therefore, the saturation indices of gypsum show that the gypsum in the groundwater system remains in the gradual dissolution.