Hydrochemical characteristics and genesis analysis of typical aquifer system in Karst Critical Zone of central Yunnan Platea

The study of hydrogeochemical processes in Karst Critical Zone (KCZ) is of great significance for scientific understanding of their internal evolutionary environment and structural characteristics. Karst groundwater is the main information carrier after water-rock interaction. Quantitative analysis of its hydrochemical characteristics and causes is an effective means to reveal the medium environment and hydrodynamic conditions of aquifer system in KCZ. In this paper, three typical karst aquifer systems in the KCZ of central Yunnan Plateau are taken as the research objects. Through field sampling and laboratory testing of karst springs exposed by different aquifer systems, mathematical statistics analysis, hydrochemical diagram, ion ratio coefficient and hydrogeochemical simulation are comprehensively used to deeply analyze the characteristics of hydrochemical components, genesis and aquifer medium of karst groundwater in each aquifer system, and the internal relationship and law between water cycle and hydrochemistry in the key belt are discussed. The results show that : (1)  HCO₃⁻ and Ca²⁺ are the highest and stable ion components in regional karst groundwater, and Mg²⁺ is the key factor to control the alienation of hydrochemical types in each aquifer system ; (2)  The rock weathering and mineral dissolution of carbonate rocks are the main causes of the chemical composition characteristics of karst water in each aquifer system, and the karst groundwater dissolution on the aquifer of Huaning aquifer system is still occurring. The alternation of cation adsorption and the weathering and dissolution of silicate rocks are the main sources of Na⁺ and K⁺ in regional karst groundwater. (3)  The development intensity of regional karst, the exposed condition of karst aquifer and the lithology and connectivity of aquifer medium jointly shape the groundwater chemical characteristics of different aquifer systems in the KCZ of central Yunnan Plateau.