Chemistry Characteristics and Formation Mechanisms of the Surface Water in the Danghe River Basin, Subei County, Gansu Province

The Danghe River is regarded as the "mother river" of Subei County and Dunhuang City. The surface water in the Danghe River basin Subei County is of great significance for the reasonable development and protection of water resources in Subei County and Dunhuang City. Taking Danghe River in Subei County as the research object, the spatial distribution characteristics and genetic mechanism of hydrochemical components of surface water were comprehensively analyzed by means of mathematical statistics, correlation coefficient method, Piper three-graph, Gibbs chart and ion ratio. The results show the surface water in the Danghe River basin of Subei County is weakly alkaline with low mineralization. The cations are mainly Ca²⁺, Na⁺ and Mg²⁺, and the average mass concentration was Ca²⁺ > Na⁺ > Mg²⁺ > K⁺ from high to low. The anions are mainly HCO₃⁻ and SO₄²⁻, and the average mass concentration is HCO₃⁻ >SO₄²⁻ >Cl⁻ >NO₃⁻ from high to low. The TDS changes are consistent with the concentration changes of the main ions. The water chemistry types are mainly HCO₃-Ca·Mg, SO₄·HCO-Ca·Mg, and HCO₃·SO₄-Mg·Na. The influence of ion exchange and human activities on the hydrochemical process is weak, which is mainly controlled by the dissolution of carbonate minerals such as calcite and dolomite and silicate minerals such as potassium albite, while a small number of ions are affected by the dissolution of evaporative salt rocks such as gypsum.