Hydrogeochemical Characteristics and Formation Mechanisms of Groundwater Around Ji’an City, Southern China

Understanding the occurrence and genesis of groundwater is vital for management and utilization. This study examines the hydrogeochemical characteristics and influencing factors of groundwater around Ji’an City, southern China, with 235 groundwater samples collected from pore, fissure–pore, karst, and bedrock fissure aquifers. Methods such as multivariate statistical analysis, Piper plot, Gibbs plots, and ion ratio coefficient were used for data analysis. Results indicated that groundwater hydrochemical types primarily were HCO 3 -Ca, HCO 3 ·Cl-Na·Ca, and HCO 3 -Na·Ca. The TDS and pH values ranged from 139.92 to 329.66 mg/L and from 4.7 to 8.5, respectively, indicating freshwater with a weakly acidic to neutral nature. Groundwater composition was shaped by a combination of rock weathering/dissolution, cation exchange, and anthropogenic activities. Karst water was notably affected by carbonate rock weathering/dissolution, whereas bedrock fissure water was primarily influenced by silicate rock weathering. Human activities showed a minimal impact on karst and bedrock fissure water, while pore and red-bed fissure–pore water were significantly impacted. The contributions of natural and anthropogenic input to groundwater chemistry were constrained by PCA, showing the rate was 78.09% 15.79%, respectively. Our findings provide insights into the distinct hydrogeochemical processes within different aquifer systems, contributing valuable data and methodologies for groundwater research and management in multi-aquifer systems.