Hydrogeochemical Tracing of Interactions Between Lake Dongping and Groundwater: Mechanisms and Processes

Lake eutrophication is a global environmental issue influenced not only by surface pollution but also by subsurface hydrological connectivity. This study investigates Dongping Lake, a typical lake system, by integrating Piper diagrams, hydrochemical analysis, the Gibbs model, Euclidean distance, and hydrogeological profiling to elucidate the distinct roles of natural processes and human activities in shaping water chemistry and hydrological connections. Results indicate that natural weathering processes, particularly carbonate dissolution, dominate the ion composition of karst and bedrock fissure water. In contrast, human activities, such as agricultural fertilization and domestic wastewater discharge, drive significant evolution in pore water toward SO₄ ^2- and Cl-Na types, with high ion variability (CV > 30%). Hydrologically, Dongping Lake exhibits close connectivity with adjacent karst water and the Daqing River, while interaction with the Yellow River is limited. A closed-loop water cycle is identified, wherein the Yellow River laterally recharges Quaternary pore water, which then vertically exchanges with karst water before discharging into Dongping Lake. This study underscores the coupled impacts of natural geochemical processes and anthropogenic inputs on lake systems, providing a scientific basis for integrated water resource management in similar watersheds.