Hydrochemical Characteristics and Controlling Mechanisms of Groundwater in Dongping Lake

ABSTRACT

Dongping Lake is a key regulating and storage lake on the Eastern Route of the South‐to‐North Water Diversion Project, and characterizing the hydrochemistry of groundwater around the lake is essential for safeguarding regional water security. We collected 70 groundwater samples in the Dongping Lake area and used a combination of statistical analysis, self‐organizing maps (SOMs), Piper and Gibbs diagrams, ion ratios, and positive matrix factorization (PMF) to identify the hydrochemical characteristics and controlling mechanisms of the groundwater. The groundwater is weakly alkaline and oxidizing, with HCO ₃ ‐Ca as the dominant hydrochemical type. Freshwater prevails, but anthropogenic impacts are already detectable. SOM clustering resolved four groundwater groups: natural background water, transitional water, agriculturally polluted water, and mixed polluted water. Water–rock interactions—chiefly the weathering and dissolution of silicate, carbonate, and evaporite minerals—exert the primary control on hydrochemical composition, with cation exchange also playing an important role. Evaporative concentration and precipitation infiltration have comparatively weak effects. PMF further identified four source factors: natural geological background, urban domestic pollution, carbonate and evaporite dissolution, and agricultural nonpoint source pollution. These findings illuminate the mechanisms driving groundwater chemical evolution under the combined influence of natural processes and human activities and provide a basis for regional groundwater protection, pollution control, and sustainable utilization.