鄂尔多斯沙区天然水体水化学组成及其成因

天然水体水化学组成及其成因分析既有助于重塑和预测区域水文地质环境及水文地球化学发展历史,也是水资源评价的基础。本文基于鄂尔多斯沙区天然水体水化学数据和前人在该地区的研究成果,利用多种水化学分析方法,对该地区天然水体的水化学组成及其成因进行分析。结果表明：鄂尔多斯沙区毛乌素沙地和库布齐沙漠虽然具有不同的沙漠景观,但其相同类型的天然水体具有相似的水化学性质和成因,该现象的出现可能和两者具有相似的蒸发量有关。鄂尔多斯沙区受蒸发影响较小的深层地下水水化学类型以Ca²⁺-HCO₃^-型为主,其水化学组成主要受控于岩石风化;湖水蒸发较强烈,水化学类型为Na⁺-Cl^-型,其水化学组成主要受控于蒸发—结晶过程的影响;浅层地下水和河水的水化学类型及其成因均处于两者之间,具有过渡特征。离子比例关系显示,蒸发岩风化、碳酸盐岩风化和硅酸盐岩风化在不同程度上影响着深层地下水、浅层地下水和河水的水化学组成。鄂尔多斯沙区地下水和河水虽然能满足灌溉水要求,但由于蒸发强烈,长期使用可能会引起盐碱化。本研究结果可为区域水资源可持续开发利用提供科学依据。

Hydrochemical compositions of natural waters in Ordos Deserts and their influencing factors

The analysis of hydrochemical compositions of natural waters and their influencing factors is helpful to understand the regional hydrogeological environment and hydrogeochemical development history. The Ordos Deserts, consisting mainly of the Mu Us Sandy Land and the Hobq Sand Sea, are located in the south of Hetao Plain, north to the Great Wall, surrounded by the Yellow River in the west, north and east, and adjacent to the Loess Plateau in the south. The Ordos Deserts make up the Ordos Plateau, with the same tectonic background, similar amount of precipitation and evaporation rates. There are a large number of lakes and rivers in these deserts. In this paper, based on the hydrochemical data of natural waters in the Ordos Deserts, the chemical compositions of natural waters and their influencing factors are analyzed, using various hydrochemical analysis methods. Results show that although Mu Us Sandy Land and Hobq Sand Sea have different landscapes, their natural waters of the same type have similar hydrochemical features, which should be related to their similar rates of evaporation. Deep groundwater in the Ordos Deserts is mainly Ca²⁺-HCO₃^- type and its chemical composition is mainly influenced by rock weathering. Due to strong evaporation, the hydrochemical nature of lakes in these regions is characterized with Na⁺-Cl^- contents. As for shallow groundwater and river waters, their hydrochemical features and influencing factors show transitional characteristics between deep groundwater and lake water. The ion ratios show that the weathering of evaporites, carbonate and silicate rocks affects the hydrochemical composition of deep groundwater, shallow groundwater and river water to a varying degree. Although the groundwater and river water in the Ordos Deserts are suitable for irrigation, an excessive use of them will cause salinization, which should be given attention timely.