Hydrochemical characteristics and genesis analysis of typical aquifer system in karst critical zone of Central Yunnan Plateau

Abstract

The study of hydrogeochemical processes in the karst critical zone (KCZ) is of great significance for the scientific understanding of their internal evolutionary environment and structural characteristics. Karst groundwater is the main information carrier after water-rock interactions. Quantitative analysis of its hydrochemical characteristics and causes is an effective means to reveal the medium environment and hydrodynamic conditions of the aquifer system in the KCZ. In this paper, three typical karst aquifer systems in the KCZ of the central Yunnan Plateau were 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 were comprehensively used to deeply analyze the characteristics of hydrochemical components, genesis and aquifer medium of karst groundwater in each aquifer system; the internal relationship and law between the water cycle and hydrochemistry in the key belt were discussed. The results showed that: ①HCO3- and Ca2+ were the highest and most stable ion components in regional karst groundwater, and Mg2+ was the key factor controlling the alienation of hydrochemical types in each aquifer system; ②The rock weathering and mineral dissolution of carbonate rocks were the main causes of the chemical composition characteristics of karst water in each aquifer system, and karst groundwater dissolution on the aquifer of the Huaning aquifer system was still occurring. The alternation of cation adsorption and the weathering and dissolution of silicate rocks were the main sources of Na+ and K+ in regional karst groundwater; ③The development intensity of regional karst, the exposed condition of karst aquifers and the lithology and connectivity of aquifer media jointly shaped the groundwater chemical characteristics of different aquifer systems in the KCZ of the Central Yunnan Plateau