中文摘要：

民勤盆地地下水化学演化特征主要以Na＋、Mg2＋、SO42-、Cl-和HCO3-浓度升高,Ca2＋浓度降低及TDS值升高为主。利用PHREEQC软件对此演化机理进行了质量平衡模拟研究,结果表明：沿水流路径方解石、白云石的饱和指数大于零,有沉淀出溶液的趋势;而石膏、岩盐的饱和指数小于零,有继续溶解的趋势。其水-岩作用以吸收CO2,溶解石膏和氯化物,析出方解石为主要特征,这些矿物相的溶解、析出和蒸发作用共同控制着地下水水化学的演化。从研究区上游往下,由于地层岩性颗粒逐渐变细,水中矿物相迁入、迁出的数量逐渐增大,水-岩作用逐渐增强。研究区水-岩作用主要受蒸发浓缩作用的影响。

英文摘要：

In the Minqin Basin,the chemical evolution characteristics are mainly that the content of Na＋、Mg 2＋ 、SO 2-4、Cl-and the value of TDS increase and Ca 2＋ content are reduced with the increase of the groundwater flowroute. The mass balance of the chemical properties of groundwater is simulated by using PHREEQC. The results show that the saturating indexes of calcite and dolomite are positive,having the tendency of precipitation,but that of gypsum and halite are negative,continuing dissolution to some extent. The characteristics of the water-rock interaction are the solutes of CO2,gypsum and halite ,the precipitation of calcite with the increase of the groundwater flowroute. In study area,from upstream area to downstream area,because lithology granularity becomes fine gradually,the dissolution or precipitation amount of minerals in groundwater increases gently,the water-rock interaction becomes intense accordingly. The water-rock interaction undergoes the influence of evaporation mainly.