关键词: 水源地;水文地球化学特征;水-岩相互作用;矿物溶解作用;华北平原;

Abstract: With a series of measures, such as reducing groundwater extraction, replenishing water through the South-to-North Water Diversion Project, and ecological water replenishment in river channels, there have been significant changes in the groundwater environment of the water source areas in the North China Plain.Taking the water source area of Langfang City in the North China Plain as an example, we used statistical analysis, piper trilinear diagram, ion composition ratio, and other methods to analyze the hydrogeochemical characteristics and evolution mechanism of groundwater.The results indicated that:(1) From the initial stage of groundwater extraction to the intensive extraction period, the regional groundwater exhibited strong dynamic conditions.The dominant hydrochemical process in groundwater was mineral dissolution, and the hydrochemical types were mainly HCO3-Na and HCO3·Cl-Na types.After the implementation of the South-to-North Water Diversion Project, the dynamic conditions of groundwater relatively were weakened, so the dominant hydrochemical process in groundwater shifted to cation exchange adsorption, and the hydrochemical types were mainly HCO3-Na and HCO3·SO4-Na types.(2) Hydrogeochemical simulation results showed that the mineral dissolution amounts in groundwater were 0.17,1.43 mmol/L and 0.21 mmol/L in 1974,1995 and 2019 respectively.The water-rock interaction exhibited a weak-strong-weak trend.The water quality changes in the deep groundwater of the study area were mainly influenced by the dissolution of fluorite minerals, carbonate minerals, silicate minerals, and cation exchange adsorption.This indicated that regional geological and hydrogeological conditions as well as human activities, affected the groundwater flow field and altered the degree of water-rock interaction.The research findings can provide scientific basis for the development and utilization of groundwater resources in the North China Plain.

Key words: water source; hydrogeochemical characteristics; water-rock interaction; mineral dissolution; North China Plain;