Identification of hydrogeochemical processes in shallow groundwater using multivariate statistical analysis and inverse geochemical modeling

Identifying key factors that control the chemical evolution of groundwater along groundwater flow direction is essential in ensuring the safety of groundwater resources in upper watersheds and lower plains. In this study, the ion ratio, multivariate statistics, and inverse geochemical modeling were used to investigate and explore the chemical characteristics of groundwater and factors driving the formation of groundwater components in the plain area of Deyang City, China. The chemical type of groundwater in the area was dominated by the HCO₃-Ca type, and the variation in groundwater chemical composition was mainly affected by water-rock interaction and human interference. The water-rock interaction process includes carbonate dissolution, oxidation-reduction reactions, and cation exchange. Furthermore, inverse geochemical modeling revealed that the dissolution of evaporite minerals, dissolution/precipitation of carbonate minerals, and weathering of silicate minerals play a key role in the hydrogeochemical evolution of groundwater. Owing to dissimilar geological and hydrological conditions, hydrogeochemical evolution processes differ along different and similar paths. Overall, this study not only provides a conceptual framework for hydrochemical evolution in plains but also has important implications for the sustainable management of groundwater resources in other basins within plains.