西吉县第三系承压水中硫酸盐的水文地球化学特征及其来源

宁夏自治区西吉县地下水中硫酸盐(SO₄^2-)含量普遍超标，为了查明地下水中SO₄^2-的来源，对区内36件地下水样品的水化学组成、21件岩石样品的易溶盐组分和10件地下水样品硫同位素组成进行了测试分析。结果表明：SO₄^2-是区内地下水中主要阴离子组分，在区域上具有北部低，中部和南部高的明显的分带性，并且沿着地下水流向SO₄^2-含量逐渐升高；SO₄^2-也是区内第三系地层中主要的易溶盐组分，以石膏和芒硝形式存在；区内地下水中SO₄^2-主要来源于地层中石膏和芒硝（所占比例平均为83%），其次是地层中的硫化物（所占比例平均为17%）。

Hydrochemical characteristics and sources of sulfate in Xiji teritary confined groundwater

The hydrochemical compositions of 36 groundwater samples, the soluble salt components of 21 rock samples and the sulfur isotope compositions of 10 groundwater samples were analyzed so as to identify the origin of SO₄^2- in groundwater in Xiji County of Ningxia where the content of SO₄^2- in groundwater was generally excessive. The results showed that SO₄^2- was the main component of anion in the study area, and the concentration of sulfate in groundwater increased gradually from north to south along with the flow path of groundwater. The soluble components in Teritary strata were dominated by sulfate in the forms of gypsum and mirabilite. There were two sources of sulfate in groundwater: about 83% was originated from gypsum and mirabilite in rocks, and the rest was from sulfide in aquifers.