彭州通济地区水文地球化学特征及成因分析

Hydro-geochemical Characteristics and Formation Reason of Shallow groundwater in Tongji Area of Pengzhou

彭州地区是"5.12"地震灾区,其震后的水文地球化学特征还未有相关研究,本文利用以热力学为基础的水文地球化学平衡理论与方法对彭州通济地区震后浅层地下水化学特征及其形成进行了分析,为研究地震对浅层地下水的影响提供基础信息。分析表明:研究区水化学场受到地形地貌的控制,水化学类型以HCO3--Ca型为主;HCO3-、Ca2+普遍含量较高,CO2分压控制碳酸盐的溶解度及水中的pH值;其浅层地下水相对于石英处于过饱和状态,相对于非晶质SiO2处于未饱和状态,CO2气体参与硅酸盐矿物水解,产生可溶SiO2;矿物溶解及与水中化学组分平衡的非硅铝酸盐矿物主要为方解石,硅铝酸盐矿物主要为长石,其次是高岭石、蒙脱石。水化学平衡理论与方法可以较好的用于研究地下水所处的水文地球化学环境以及判断SiO2的来源和矿物溶解过程。

Pengzhou is one of the seismic disastrous areas during ＂5.12＂ earthquake.Related research on the hydro-geochemical characteristics of Pengzhou has not been done after the earthquake.Hydro-geochemistry equilibrium theory and method,based on the thermodynamic,are used in analyzing the shallow ground-water of Tongji area in this study,which shows that the groundwater chemical field of study area is controlled by topography.The concentrations of HCO3-and Ca2＋ are high in most study area,so the main hydro-geochemical type is HCO3-Ca type.Carbonate solubility and pH value are controlled by CO2 partial pressure.Quartz is oversaturated in shallow groundwater,and amorphous SiO2 is not saturated,CO2 is involved in hydrolysis of silicate minerals,producing soluble SiO2.Calcite is the main non-aluminosilicate mineral in mineral dissolution and water chemical equilibrium,and feldspar is the main aluminosilicate minerals,followed by kaolinite and montmorillonite.Hydro-geochemistry equilibrium theory and method are suitable for the study of groundwater hydro-geochemistry environment and determining the source of SiO2 and mineral dissolution proccess.