Hydrogeochemistry of aquifers in the northern portion of the Lagoa Santa Karst Environmental Protection Area and surroundings, state of Minas Gerais, Brazil

• Published in: Journal of South American earth sciences 2024-09, Vol.144, p.105042, Article 105042
• Main Authors: Barbosa, Débora Maria Diniz, De Paula, Rodrigo Sérgio, Velásquez, Leila Nunes Menegasse, Pena, Matheus Alonso Castelo
• Format: Article
• Language: English
• Subjects: Environmental management; Groundwater; Hydrochemical markers; Hydrogeology; Multivariate analysis; Water sampling; Water sustainability
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2024.105042

The studied region, located in the central part of Minas Gerais state, Brazil, encompasses the northern portion of the Lagoa Santa Karst Environmental Protection Area (APA) and adjacent areas to the west. It is notable for harboring important karstic aquifers and archaeological and paleontological sites of global significance. The research aims to define the key parameters that characterize the waters of the aquifers, quantifying their most frequent maximum and minimum concentrations. For this purpose, water sampling and hydrochemical analyses were conducted at 51 water points. Hierarchical clustering analysis facilitated the association of samples with aquifer units. Utilizing Piper and Stiff diagrams, boxplot graphs, and proportional symbol maps enabled the classification of water and the determination of its hydrochemical signatures. All sampled waters are bicarbonated, with 87% being calcic. Waters associated with metacalcareous rocks exhibit higher concentrations of calcium (Ca2⁺), bicarbonate (HCO₃⁻), electrical conductivity (EC), total dissolved solids (TDS), and hydrogenionic potential (pH) compared to waters associated with non-carbonate rocks. Waters from the Lagoa Santa Member differ from those of the Pedro Leopoldo Member by higher concentrations of Ca2⁺ and HCO₃⁻ and slightly lower concentrations of sodium (Na⁺), magnesium (Mg2⁺), and silica (SiO₄2⁻). Non-carbonate waters related to granite-gneisses differ from those associated with metapelites by slightly higher concentrations of potassium (K⁺), sodium (Na⁺), silica (SiO₄2⁻), and barium (Ba2⁺). Additionally, hydrochemical variations have been linked to the regional groundwater flow (from west to east). The results obtained have enabled advancements in the hydrogeochemical understanding of the study area and can be valuable for comparative studies in other karst regions, contributing to more effective water resource management aimed at environmental conservation and water sustainability, a growing global concern. •Advancement of hydrogeochemical studies in a karst area of great environmental relevance.•Chemical classification of groundwater and multivariate analysis of data.•Identification of hydrochemical markers characterizing hydrogeological units.•Definition of the maximum and minimum values of hydrochemical markers for each aquifer.•Determination of groundwater flow from hydrochemical data.