宁夏海原盆地地下水水化学特征及其演化规律

结合宁夏海原盆地已有的地质、水文地质资料,基于水化学、同位素数据分析了研究区的水文地球化学特征。总体上当地的地下水化学场从补给区到径流区到排泄区具有明显的分带性,符合干旱区盆地的水质演化规律;地球化学模拟表明当地水岩相互作用从补给区的以溶滤-混合作用为主逐渐演变成排泄区的以溶滤-蒸发为主。水中的溶解性总固体含量升高主要由岩盐和石膏的溶解引起,第三系岩性及径流条件对地下水水质有很大的影响。同位素特征表明西华山—南华山断裂控制着当地地下水的补给,地下水开采对深层地下水水质的影响尚不明显;在有些地区,由于地下水开采加速了地下水径流,水质有变好的趋势。

Hydrogeochemical Characteristics and Evolution Laws of Groundwaterin Haiyuan Basin, Ningxia

Based on the hydrochemical and isotopic data,this paper analyzes the hydrological geochemistry characteristics of Haiyuan basin combining with the existed geological and hydrogeological data of this area.As a whole,the chemical fields of local groundwater have the obvious zonation patterns from the recharge area to the runoff area,and to the discharge area,which are in conformity with the evolution law of water quality in arid basin.Geochemistry simulation shows that the local water-rock interaction changes gradually from the dissolution-mixture action in the recharge area into the dissolution-evaporation action in the discharge area,chemical compositions of the Tertiary strata and the circulation condition have a great influence on the groundwater quality.Isotopic features show that the Nanhua Mountain-Xihua Mountain fault controls the groundwater recharge of Haiyuan basin,so far,there is little impact of exploitation on the quality of deep groundwater.In some sites,the improved water quality with the exploitation of groundwater was observed,one explanation for this is that the increasing velocity of local water shortens the water-rock interaction time.