Multivariate data analysis applied to groundwater geochemical characterization, Central Pacific, Costa Rica

Abstract

This research has allowed to provide new information about the geochemical groundwater composition in the Central Pacific of Costa Rica, a place with an important commercial, touristic, and real estate development with a continues water resource demand. Previous reports of iron and manganese elevated concentrations, and flow water rate decrease in production wells, turn the area into an object of hydrogeological studies as the resource demand increases. The main objective of this research was to provide information about the quality and composition of the groundwater, and to understand the relationship with the geological and structural context. A total of 25 groundwater samples were collected, subsequently hierarchical clustering method were applied to analyze chemical concentrations and characterized the groundwater. Results showed some samples with atypical trace elements concentrations such as Al, Mn, and Fe, which are above the water quality limits. After applied the hierarchical clustering, results evidence the presence of two main clusters, which one cluster have samples with high temperatures and mineralized waters in common. The groups are distributed between three major neotectonics faults Barranca, Jesús María, and Tárcoles that creates a complex structural context that provides pathways movement for the contribution of thermal waters which can strongly dissolve the rocks, and provide a certain water chemical composition related with the presence of volcanic rocks with high concentrations of K, Mg, Mo, P, Rb, Si, Fe, Mn, F and U, and sedimentary rocks with high concentrations of B, Ba, Ca, Cu, Fe, Ge, Li, Na, S, SO4 and Zn.