汉中盆地地下水水化学特征及其成因研究

为研究汉中盆地地下水的水化学特征及成因，在丰水期共采集56件潜水样品，综合运用数理统计、相关性分析、Piper三线图、Gibbs模型和离子比等方法，分析了汉中盆地地下水的水文地球化学特征、各化学参数的空间变化规律、主要离子的控制因素及来源。结果表明，汉中盆地地下水阳离子以Ca2+为主，阴离子以HCO3–为主。从离子空间变化规律上来看， K+波动最为剧烈，且从中下游开始逐渐降低，Cl−和Na+变化规律一致，呈波动变化；HCO3−、Ca2+、Mg2+以及SO42−的从中上游至中下游含量逐步降低，至下游含量增加；TDS值为128.5～590 mg/L，平均值为282.67 mg/L，在中下游含量明显增加；pH平均值为7.17，为弱碱性，在中上游波动剧烈，至下游逐渐降低。地下水水化学类型以HCO3–Ca和HCO3–Ca·Mg型为主，受碳酸盐岩和硅酸盐岩的溶解共同控制，阳离子交替吸附作用较弱，Na+和K+主要来源于钾长石、钠长石等硅铝酸盐矿物的溶解和部分盐岩的风化溶解，Ca2+除来自碳酸盐岩的溶解外，还有大量硅酸盐岩的溶解；方解石及少量白云石等碳酸盐岩的风化溶解对Mg2+和HCO3−贡献较大。查明汉中盆地地下水水化学特征及成因机制，可为汉中地区地下水饮水安全提供有力科学依据。

Hydrochemical Characteristics and Genesis of Groundwater in the Hanzhong Basin

In order to study the hydrochemical characteristics and genesis of the groundwater in the Hanzhong Basin, 56 unconfined groundwater samples were collected during the high water period to analyze the hydrogeochemical characteristics of groundwater, the spatial variation of each chemical parameter and control factors and sources of major ions by means of mathematical statistics, correlation analysis, Piper triangular diagrams, Gibbs model and ion ratio and other methods. The results show that Ca2+ is the main cation and the main anion is dominated by HCO3–. From the perspective of spatial variation, K+ fluctuates most violently, and gradually decreases from the middle and downstream. While Cl− and Na+ have the same change law, showing a fluctuation variation. The contents of HCO3−, Ca2+, Mg2+ and SO42− decrease gradually from the middle and upper reaches to the middle and lower reaches, and increase in the lower reaches. TDS ranges from 128.5 mg/L to 590 mg/L, with an average of 282.67 mg/L. The average value of pH is 7.17, showing weakly alkaline, which fluctuates violently in the middle and upper reaches, and gradually decreases in the lower reaches. The hydrochemical types of groundwater are mainly HCO3–Ca and HCO3–Ca·Mg, which are jointly controlled by the dissolution of carbonate rock and silicate rock. The cationic alternate adsorption is weak. Among all the chemical composition of groundwater, Na+ and K+ mainly come from the dissolution of aluminosilicate minerals such as potash feldspar and albite, and the weathering and dissolution of some salt rocks. In addition to the dissolution of carbonate rocks, Ca2+ also comes from the dissolution of a large amount of silicate rocks. Weathering and dissolution of carbonate rocks such as calcite and a small amount of dolomite have a greater contribution to Mg2+ and HCO3−. Identifying the hydrochemical characteristics and genetic mechanism of groundwater in the Hanzhong Basin can provide a strong scientific basis for groundwater drinking water safety in the Hanzhong area.