广汉市平原区浅层地下水化学演化及其控制因素

Shallow Groundwater Hydrogeochemical Evolution Process and Controlling Factors in Plain Zone of Guanghan City

为在广汉市城乡规划过程中提供地下水资源开发利用的基础信息,采用矿物风化系统分析、相关性分析、主成分分析和PhreeQC反向水文地球化学模拟等方法对广汉市平原区的浅层地下水的地下水水化学组分进行分析,确定了浅层地下水的水化学演化及控制因素,完成了地下水资源的质量及时空分布特征分析。分析表明:Gibbs图显示岩石风化主导该区地下水水化学特征,风化过程产生离子和次生矿物又经历水解作用,在矿物风化系统稳定场图中显示水样中铝硅酸盐矿物逐渐趋于溶解,碳酸盐矿物处于饱和状态;PhreeQC反向水文地球化学模拟结果显示在水流模拟路径上主要发生了钙蒙脱石、钾长石溶解和高岭石、石英、钠长石的沉淀,以及Ca-Na_2之间的阳离子交换吸附作用;离子相关性和主成分分析进一步的验证了溶滤作用、蒸发浓缩作用和阳离子交换吸附作用是引起浅层地下水水化学过程和矿物组成改变的主要原因。研究区地下水水质总体不会对人体健康造成不良影响。

Four methods,including mineral weathering system analysis,correlation analysis,principal component analysis and inverse hydrogeochemical simulation by Phree QC are used to analyse the chemical composition,identify hydrogeochemical evolution processes and controlling factors,then complete analyzing quality and spatial temporal distribution of shallow groundwater in the plain of Guanghan City,which providesbasic data for developing and utilizing groundwater resources exsisting in urban and rural planning process. The analysis showes that Gibbs plots indicate that the groundwater hydrochemical characteristics are dominated by rock weathering, the weathering processes produce ions and then secondary minerals undergo hydrolysis;aluminosilicate minerals of water samples tend to dissolve gradually in the mineral weathering system stability diagram; carbonate minerals are saturated. Phree QC inverse hydrogeochemical simulation results show what mainly happen in the water flow path simulation are the dissolution of calcium montmorillonite and K-feldspar,the precipitation of kaolinite,quartz and albite,and the cation exchange adsorption between Ca-Na_2; The analysis of ion correlation and principal component analysis verifies that leaching,evaporation and concentrating,and cation exchange adsorption are the main cause of hydrochemical process and mineral composition in the shallow groundwater. The groundwater quality in the study area generally will not cause adverse effects on human health.