HYDROCHEMICAL CHARACTERISTICS OF GROUNDWATER IN KARST MOUNTAINOUS AREAS OF GUIZHOU PROVINCE

Based on the water quality test data of 1 067 boreholes from the water-searching drilling project in Guizhou Province, the study uses the methods including descriptive statistical analysis, variation coefficient, Piper diagram, Schukalev classification, Gibbs diagram and ion ratio coefficient to analyze the hydrochemistry and distribution characteristics of karst water in the study area, and discusses the sources and formation of major ion compositions. The results show that the cations in the groundwater of study area are mainly Ca²⁺ and Mg²⁺, and the anions mainly HCO₃^-. The hydrochemical type of the groundwater is mainly of HCO₃-Ca·Mg. The chemical compositions of the groundwater are mainly derived from the lixiviation of carbonate rocks, with Ca²⁺ and Mg²⁺ mainly from the dissolution of carbonate rock minerals, which constrain the content of Ca²⁺ and Mg²⁺. The main source of Na⁺ and K⁺ is affected by the lixiviation of rock salt, as well as other Na- and K-bearing minerals and human activities, while the cation exchange and adsorption has less effect. The anion of SO₄^2- is mainly derived from the leaching of evaporation salts such as gypsum.