鄂尔多斯盆地南部马莲河流域地下水中锶富集特征及成因分析

马莲河流域地处鄂尔多斯盆地南部黄土高原区,按储水介质和埋藏条件可将地下水分为黄土潜水、基岩潜水和基岩承压水三类,利用2015—2018年流域的295组地下水水化学数据,分析了地下水中锶(Sr²⁺)的质量浓度水平、垂向分布及沿流向分布的特征,并采用因子相关性研究地下水中Sr²⁺的来源和富集成因。结果表明:马莲河流域地下水富锶现象显著,黄土潜水、基岩潜水和基岩承压水中锶的平均质量浓度分别为1.14 mg/l、1.39 mg/l和5.24 mg/l;地下水中锶富集成因主要是含锶矿物天然状态下的水-岩作用,黄土潜水、基岩潜水和基岩承压水三类地下水中Sr²⁺的主要来源分别为碳酸盐岩与铝硅酸盐岩、碳酸盐岩与硫酸盐和碳酸盐矿物的溶滤作用;地下水中Sr²⁺的质量浓度沿流向呈逐渐增大的趋势,在不同区域中随深度变化的趋势不一致。

Characteristics and Formation Mechanism of Strontium-rich Groundwater in Malian River Drainage Basin,Southern Ordos Basin

The Malian River drainage basin is located at the loess plateau in the southern Ordos Basin, in which the groundwater can be divided into the loess phreatic water, bedrock phreatic water and bedrock confined water based on the storage medium and burial conditions. Using 295 sets of groundwater hydrochemical data collected from 2015 to 2018, we analyze the Sr²⁺ concentration level, vertical and downstream distribution characteristics in the groundwater, and study the source and enrichment cause of Sr²⁺ in groundwater through factor correlation analysis. The results indicate that the groundwater Sr enrichment in the Malian River drainage basin is distinct, with the average Sr concentrations in the loess phreatic water, bedrock phreatic water, and bedrock confined water being 1.14 mg/l, 1.39 mg/l, and 5.24 mg/l, respectively. The Sr enrichment is mainly led by the water-rock interaction of Sr-bearing minerals. Major sources of Sr²⁺ in the loess phreatic water, bedrock phreatic water, and bedrock confined water are leaching from the carbonates and aluminosilicates, carbonates and sulfates, and carbonate minerals, respectively. The Sr²⁺ concentration in groundwater gradually increases along the flow direction, but varies with depth in different areas.