黄土高原中部浅层地下水化学特征及影响因素

通过采集黄土高原中部沿黄流域57个浅层地下水水样，采用定性（Gibbs模型、Na端元和离子相关关系）和定量（正向演替模型）分析方法探究了该地区地下水水化学特征、沿程变化规律和控制因素.结果表明，黄土高原中部沿黄流域浅层地下水均呈弱碱性；优势阴阳离子分别为HCO₃^-和Na⁺；水化学类型以HCO₃-Ca-Mg为主，占40%.研究区地下水主要离子自北向南变化趋势有所差异，其中Cl^-浓度保持动态稳定，SO₄^2-、HCO₃^-、Mg²⁺和Na⁺浓度沿程增加，而NO₃^-、Ca²⁺和K⁺浓度沿程降低，矿产资源开发是研究区地下水SO₄^2-重要来源，而强烈的阳离子交替吸附作用是引起Na⁺富集的重要因素.研究区地下水溶质来源主要受岩石风化作用控制，以硅酸盐岩石风化为主；大气输入、人类活动和岩石风化对地下水溶质的相对贡献分别为5%±3%、6%±13%和89%±13%.此外，下垫面因素改变、人类活动以及气候变化通过改变地下水补给与排泄等过程直接或间接的影响了地下水水量和水质.本研究结果将为黄河流域和其他类似地区当前和未来的地下水质量管理项目提供参考.

Hydrochemical characteristics and controlling factors of shallow groundwater in the Chinese Loess Plateau

The 57 shallow groundwater samples along the Yellow River in the middle of Chinese Loess Plateau were collected, and the qualitative (Gibbs, Na-normalized molar ratios and ions correlation methods) and quantitative methods (forward derivation modeling) were used to explore the hydrochemical characteristics, the variation rules along the channels, and the controlling factors. The results showed that the shallow groundwater samples were weakly alkaline; the dominant anion and cation was HCO₃^- and Na⁺, respectively; the major groundwater type was HCO₃-Ca-Mg (accounted for 40%). There was a difference of variation trend of major ions of shallow groundwater from north to south in the research areas. The Cl^- level kept dynamic stability along the way, SO₄^2-, HCO₃^-, Mg²⁺, and Na⁺ increased, while NO₃^-, Ca²⁺, and K⁺ decreased. Mineral exploitation was an important source of SO₄^2-, while the Na⁺ enrichment was caused by strong cation exchange. Moreover, the source of groundwater solutes was mainly controlled by rock weathering, primarily silicate weathering. The relative contribution of groundwater solutes by atmospheric input, human activity, and rock weathering was 5% ±3%, 6% ±13%, and 89% ±13%, respectively. Furthermore, the change of underlying surface conditions, human activities, and climate change directly or indirectly affected the groundwater quantity and quality by changing the processes of groundwater recharge and discharge. Our findings will inform current and future groundwater quality management programs for the Yellow River catchment and other similar area.