石期河流域地下水化学特征及物质来源分析

为明确典型岩溶溶丘洼(谷)地区域地下水化学特征及其成因,以石期河流域为研究对象,运用Gibbs图、Piper图、端元分析及离子比例系数等方法,对地下水水化学特征及物质来源进行了定性和定量分析.结果表明,研究区内地下水pH值介于6.06～8.07之间,Ca~(2+)、 Mg~(2+)和HCO~-_3是地下水中的主要离子,其质量浓度范围分别为2.61～108.7、 0.54～27.61和8.1～370.74mg·L~(-1),符合岩溶水高钙弱碱性特征;地下水物质成分中, Ca~(2+)和Mg~(2+)主要受到碳酸参与的灰岩和白云岩风化作用的控制, Na~+主要来源于硅酸盐岩的溶解,同时, Ca~(2+)和Na~+在地下水流动过程中进行阳离子交替吸附作用; K~+、 Cl~-和NO~-_3主要受到农业化肥施放和生活废水排放的影响.此外,大气降水作为该区域地下水的主要补给来源,对当地地下水化学特征和物质来源也有一定的影响.

Chemical Characteristics of Groundwater and Material Sources Analysis in Shiqi River Basin

To investigate the chemical characteristics of groundwater and material sources in a typical karst hill (valley) depression, 41 groundwater samples were systematically collected in the Shiqi River basin. The statistical analysis of the conventional ion content in the groundwater shows that pH of the groundwater in the study area is between 6.06-8.07, the total solid solubility is between 18.21 mg ·L^-1 and 336.28 mg ·L^-1, and the charges of anions and cations in the water body are balanced. Ca²⁺, Mg²⁺, and HCO₃^- are the main ions in groundwater, with concentrations of 2.61-108.7 mg ·L^-1, 0.54-27.61 mg ·L^-1, and 8.1-370.74 mg ·L^-1, respectively. The groundwater characteristics in the study area are consistent with the high calcium and weak alkalinity characteristics of karst water. By using the Gibbs diagram, piper diagram, end-member analysis, and ion proportional coefficient, hydrochemical characteristics and material sources of groundwater were further analyzed. The results show that Ca²⁺ and Mg²⁺ are mainly controlled by the weathering of limestone and dolomite in which carbonic acid is involved. Na⁺ mainly comes from the dissolution of silicate rocks. At the same time, Ca²⁺ and Na⁺ undergo cationic exchange adsorption in the groundwater flow process. K⁺, Cl^-, and NO₃^- are mainly affected by agricultural fertilizer application and domestic wastewater discharge. The hydrogen and oxygen isotope analysis of groundwater shows that atmospheric precipitation is the main recharge source of groundwater in this region, which impacts the chemical characteristics and material sources of local groundwater. The results of this study show that the geological background of groundwater is the main factor that affects its hydrochemical characteristics and material sources in areas with relatively little anthropogenic activity.