Multivariate statistical analysis of the hydrochemical characteristics of a volcano sedimentary aquifer in Saraburi Province, Thailand

Study region: The study area is located in the southwest Kaeng Khoi district and the east Muang District, Saraburi Province, Thailand. Based on its hydrostratigraphic characteristics, the aquifer in this area can be divided into an unconsolidated floodplain deposit aquifer (Qfd) and a volcanic aquifer (Vc). Study focus: This research investigated the hydrogeological characteristics and hydrogeochemical parameters of 42 groundwater samples obtained in the summer and rainy seasons. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to identify the natural and anthropogenic impacts that likely influenced groundwater quality. New hydrological insights for the region: The groundwater type in Qfd and Vc is mainly Ca-Na-HCO3, suggesting that the hydrochemical groundwater of both aquifers is affected by the same sources. This study found evidence of ion exchange between Ca2+ and Na+ in both seasons. The five principal components had a cumulative variance greater than 76.11 and 77.88 % in the rainy and summer seasons, respectively. Based on correlation analysis and PCA, the sources of the groundwater chemistry are generally silicate and calcite weathering from geological formations, including alkali feldspar and Ca2+- and Mg2+- rich minerals. Moreover, some ions arose from anthropogenic activities, typically irrigation water and sewage wastewater. The presence of photphate (PO43-) may be related to the dissolution of apatite and associated with anthropogenic activities, causing an increase in PO43- in the rainy season.