The geo-environmental influence on hydrogeochemical conditions in the Tanjaknangsi volcanic region

Abstract

Groundwater in volcanic areas flows from the recharge to the discharge, and dissolving rock minerals undergo hydrochemical changes. Anthropogenic influences in the form of increasing built-up land and plantation activities in upstream areas raise concerns about changes in groundwater hydrochemistry. Hydrogeochemical and environmental characterization of groundwater in volcanic regions is essential to trace the rock-water interaction. This study aimed to determine the geo-environmental influence on the hydrogeochemical conditions in Tanjaknangsi volcanic areas. The methods used were statistical analysis, bivariate analysis, and Piper diagram. During the dry season, 16 groundwater samples were taken, consisting of five dug wells, nine drilled wells, and two springs. The hydrogeochemical process of major ions in groundwater volcanic regions is characterized by the weathering of silica. The concentrations of cations were Ca2+ > Na+> K+> Mg2+, while the anion were HCO3 −> Cl−> SO4 −. The correlation analysis shows that Ca2+, Mg2+, and Na+ cations strongly correlated with the HCO3 − anion. Hierarchical dendrogram analysis shows groundwater was influenced by the rock-water interaction and anthropogenic influences; the piper diagram shows the dominant hydrogeochemical facies in the study area were CaCl, CaMgCl, CaMgHCO3, and NaHCO3. Groundwater in the upstream area was dominated and influenced by the groundwater-rock interaction, while anthropogenic factors influenced groundwater in the downstream area. Residues of anthropogenic activities such as agriculture, plantations, and livestock will increase the levels of NH4-N, Cl− and SO4 2- ions.