银川平原地下水水化学特征及演变研究

Study on the Hydrochemical Characteristics and Evolution of Groundwater in Yinchuan Plain

为科学认识银川平原地下水水化学特征的演化规律,合理开发利用、保护地下水资源,根据银川平原2021年度地下水水质资料,采用统计法、三线图法、图解法及离子来源分析法对研究区地下水水化学特征及演化规律进行分析。结果表明:银川平原潜水中阴离子以HCO_(3)^(-),SO_(4)^(2-),Cl^(-)为主,阳离子以Na^(+),Mg^(2+),Ca^(2+)为主。第一承压水中阴离子以HCO_(3)^(-),Cl^(-),SO_(4)^(2-)为主,阳离子以Na^(+)为主。第二承压水中阴离子以Cl^(-),HCO_(3)^(-),SO_(4)^(2-)为主,阳离子以Na^(+),Mg^(2+)为主。大部分地下水的成分主要受岩石风化作用的影响,潜水受蒸发浓缩作用的影响略大于承压水,潜水中总溶解性固体物质(TDS)较承压水偏高。研究区存在着地下水中Na^(+),K^(+)与含水层颗粒表面吸附的Ca^(2+),Mg^(2+)的离子交换,从而使地下水中的Na^(+),K^(+)质量浓度逐渐减少,Ca^(2+),Mg^(2+)的质量浓度逐渐增多。研究区地下水发生了白云石沉淀,方解石平衡及岩盐、石膏溶解作用。第一承压水的Cl^(-)和SO_(4)^(2-)来源于潜水的越流补给。

In order to scientifically understand the evolution of hydrochemical characteristics of groundwater in the Yinchuan Plain,and to rationally develop,utilize,and protect groundwater resources,the hydrochemical characteristics and evolution patterns of groundwater in the study area were analyzed using statistical methods,trilinear diagrams,graphical methods,and ion source analysis methods,based on the groundwater quality data of the Yinchuan Plain in 2021.The results show that in the phreatic water of the Yinchuan Plain,the main anions are HCO_(3)^(-),SO_(4)^(2-),and Cl^(-),while the main cations are Na^(+),Mg^(2+)and Ca^(2+).In the first confined aquifer,the main anions are HCO_(3)^(-),Cl^(-),SO_(4)^(2-),with Na^(+)being the predominant cation.In the second confined aquifer,the main anions are Cl^(-),HCO_(3)^(-),SO_(4)^(2-),with Na^(+)and Mg^(2+)being the main cations.The composition of most groundwater is mainly influenced by rock weathering,with the phreatic water being slightly more affected by evaporation and concentration than the confined water;the total dissolved solids(TDS)in the phreatic water are relatively higher than in the confined water.There is ion exchange between Na^(+)and K^(+)in the groundwater and Ca^(2+)and Mg^(2+)adsorbed on the surface of aquifer particles in the study area,which leads to a gradual decrease in the mass concentration of Na^(+)and K^(+)and an increase in the mass concentration of Ca^(2+)and Mg^(2+).There has been dolomite precipitation,calcite equilibrium,and the dissolution of halite and gypsum in the groundwater of the study area.The Cl^(-)and SO_(4)^(2-)in the first confined water come from the overflow recharge of the phreatic water.