Chemical characteristics of groundwater in the dispersed drainage system of Yangshui anticline in central Guizhou

The dispersed drainage system of Yangshui anticline is located in Jinzhong town, Kaiyang county, Guizhou Province. As one of the main producing areas of phosphate deposits in Guizhou, this area is concentrated with phosphorus mines, phosphorus chemical industry and phosphogypsum storage sites. Therefore, the study on the chemical characteristics of groundwater in this area is of great significance for the rational development, utilization and protection of groundwater resources. This study takes the karst groundwater system, which has relatively independent conditions of groundwater recharge, runoff and discharge, as the research object. The main samples of karst springs, bedrock fissure springs, boreholes and mine drains are collected, and the hydrogeochemical research methods such as ion comparison method and main ion ratio method are used to analyze the chemical components and main ion sources of groundwater. The results show that contents of main cations of K⁺、Na⁺、Ca²⁺ and Mg²⁺ are listed as: mine drainage>carbonate karst water>bedrock fissure water; contents of ${\rm{HCO}}_3^{-}$ and ${\rm{SO}}_4^{2-}$ in main anions, mine drainage>carbonate karst water>bedrock fissure water; Ion content of Cl⁻, mine drainage>bedrock fissure water>carbonate karst water; TDS, mine drainage>carbonate karst water>bedrock fissure water. HCO₃-Ca·Mg is the main chemical type of karst water in carbonate rocks; the hydrochemical type of bedrock fissure is HCO₃-Ca; the chemical type of mine water is mainly SO₄-Ca·Mg followed by SO₄·HCO₃-Ca·Mg. There are significant differences in hydrochemical composition among carbonate karst water, bedrock fissure water and mine water in the study area. The main chemical components of karst water in carbonate rocks come from the leaching of dolomite and dolomitic limestone. The content of the main chemical components of bedrock fissure water is the result of the joint action of calcareous mudstone leaching and atmospheric precipitation. The main chemical components of mine water come from the leaching of dolomite and dolomitic limestone and the foreign ions brought by intensive human engineering activities. This study not only provides a scientific basis for the rational development and utilization of groundwater resources in this area, but also helps to protect groundwater resources and maintain the regional ecological environment.