Hidroquímica das águas subterrâneas da folha Amargosa – sd.24-vd-ii, Centro Sul da Bahia

Abstract

Hydrogeochemical investigations were carried out to identify the processes that affect the chemistry of groundwater in the region that comprises the Amargosa sheet. This area is located in the Center-South portion of Bahia, is delimited by the parallels 13°00'S and 13°30'S and the meridians 39°30'W and 40°00'W, and has an area of approximately 2,996 km². The geological units that compose it are part of the tectonic context of the Jequié Block, one of the Archean geotectonic entities appurtenant to the São Francisco Craton, structured after the Paleoproterozoic collision. To reach the objectives, physicochemical analyses of 49 representative wells were used and interpreted according to the main ion chemistry, conventional and bivariate graphs. The wide range of hydrochemical facies demonstrates the heterogeneity of the aquifer environment, with HCO3- facies predominating in regions of sub-humid climate and active flow, while Cl facies occur in semi-arid and slow flow conditions. The mechanisms of water-rock interaction and evaporation control the groundwater chemistry, highlighting the geochemical weathering processes of silicates (plagioclases, pyroxenes and biotite); chlorine-alkaline imbalance, common in the HCO3- facies and base exchange reaction, representative of the Cl facies. The results of this research made it possible to increase the knowledge of a complex system and establish the basis for a more rational exploration of anisotropic aquifers.