Hydrochemical Characteristics of Karst Groundwater in the Mountains of Northern Bazhong City, China

Abstract

To study the hydrogeochemical characteristics and formation mechanism of groundwater in a karst development transition zone in southern and northern China, 25 groundwater samples were collected from the Shuangfengya area in the northern part of Bazhong City. Descriptive statistics, coefficients of variation, Schoeller diagrams, Sukalev classification, Piper diagrams, and Gibbs and ion scale coefficients were used to analyze the karst water chemistry and distribution characteristics. The main processes controlling the chemical evolution of the groundwater are also discussed. The research shows that the degree of groundwater mineralization in the study area is generally low, with mostly neutral water and alkaline water. There are some differences in groundwater between the northern and southern regions; the anions and cations in the groundwater in the northern area were mainly HCO3-, Ca2+, and Mg2+, with HCO3-Ca·Mg being the main water chemistry type; the anions and cations in the groundwater in the northern area were mainly HCO3-, and Ca2+, and HCO3-Ca was the main water chemistry type. The chemical character of groundwater was controlled by rock weathering and alternate cation adsorption, and evaporation crystallization in the southern region was more significant than in the northern region. Furthermore, rainfall in the northern region had a more significant effect on groundwater geochemistry than in the south. The differences in climate and lithology between the northern and southern region are the dominant factors influencing the differences in hydrochemistry.