Investigation of the hydrogeochemical processes and regional evolution of karst groundwater in Liulin Spring catchment, northern China

The Liulin Spring catchment in Shanxi Province has abundant karst groundwater resources that play a supporting role in the economic and social development of the Lvliang region. Research on the factors controlling the chemical evolution of karst groundwater can be of great significance for the sustainable utilization and effective protection of groundwater resources in the basin. In this study, the major ions of karst groundwater have been studied to identify the hydrogeochemical processes and regional evolution using 29 samples that were collected in 2014 from the recharge area, throughflow area, discharge area and stagnant area of the catchment. The results showed that the temperature and the concentrations of Na⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃⁻ and SO₄²⁻ increased with the increasing distance from the recharge area to the throughflow area, to the discharge area and then to the stagnant area. The chemical composition of karst groundwater in both recharge area and throughflow area was mainly derived from carbonate dissolution, while it was largely controlled by the weathering of silicate minerals in the discharge area, and dominated by the dissolution of both silicates and gypsum in the stagnant areas. The K⁺, Na⁺ and Cl⁻ were mainly sourced from the dissolution of salt rock, while the Ca²⁺, Mg²⁺, HCO₃⁻, and SO₄²⁻ were mainly derived from the dissolution of calcite, dolomite, and gypsum. The hydrochemical types of karst groundwater changed from HCO₃-Ca • Mg type in the recharge area to HCO₃ • SO₄-Ca • Mg type in the throughflow area and to HCO₃ • SO₄-Ca • Na • Mg type in the discharge area, and finally evolved into Cl • HCO₃-Na • Ca, Cl • HCO₃-Na type and Cl-Na • Ca type in the stagnant area. The results of this study will be useful to effectively guide the sustainable utilization and the integrated planning of water resources in the Liulin Spring catchment.