银北平原浅层地下水的水化学特征及成因分析

结合银北平原已有的地质、水文地质资料,基于水化学数据、室内释放试验,分析了浅层地下水的水文地球化学分布特征及成因。结果表明:银北平原浅层地下水水化学类型具有一定的分带性,从山前至平原,阴离子由西南向东北从HCO3型过渡到HCO3.SO4(SO4.HCO3)型,再逐渐向HCO3.SO4.Cl、HCO3.Cl(Cl.HCO3)型转化,阳离子则由Ca(Ca.Na、Ca.Mg)型向Na.Mg(Na)型转化;山前洪积倾斜平原地处边山地带,受地形地貌、地层岩性等因素影响,溶滤作用是控制地下水水化学变化的主要形式;冲洪积和河湖积平原则受气候、灌溉活动等作用,蒸发浓缩、蒸发浓缩-混合作用控制着平原内水化学的变化;地层岩性为地下水质的基本组成提供重要的物源。

Hydrochemical Characteristics and Formation Analysis of Unconfined Groundwater of Northern Yinchuan Plain

Based on the hydrochemical data and release experiment,this paper analyzed the hydrological geochemistry characteristics and formation of unconfined groundwater of Northern Yinchuan Plain,combining with the existing geological and hydrogeological data of this area.The results indicate that: a) the hydrochemical distribution of unconfined groundwater of Northern Yinchuan Plain presents a considerate zonation.From mountainfront to the plain,negative ions transform from HCO3 type to HCO3·SO4(SO4·HCO3) type from southwest to northeast,then converting to HCO3·SO4·Cl(HCO3·Cl,Cl·HCO3) type gradually.Positive ions transform from Ca(Ca·Na,Ca·Mg) type to Na·Mg(Na) type at the same time.b) The sloping flood plain locates mountain edge zone,influenced by topography,stratigraphic lithology and other factors.Therefore,dissolve filter function is the controlling factor for the change of groundwater hydrochemical characteristics.c) Evaporation and concentration,mixed evaporation and concentration actions determine the hydrochemical formation in the plain because of weather conditions and irrigation actions in the alluvial and river lacustrine plains.d) The main components of ground water are controlled by stratigraphic lithology.