Composição isotópica (δ18O, δ2 H e δ13CCID) das águas subterrâneas dos municípios de Feira da Mata e Santana (BA)

Manuel Vitor Portugal Gonçalves, Rodrigo Alves Santos, Antônio Bomfim da Silva Ramos Junior, Flavio Souza Batista, Manoel Jerônimo Moreira Cruz, Alexandre Barreto Costa, Mônica Pringsheim da Cunha

Abstract


This research aimed to characterize the isotopic composition of the groundwater of the municipalities of Feira da Mata and Santana, in western Bahia, Brazil. Water was collected in fifteen wells drilled in the pellet-carbonate rocks of the Bambuí Group. The physico-chemical variables were measured in situ, using multiparameter probes, cations by ICP-OES and anions by titrimetry and spectrophotometry. The values of the isotopic ratio in δ2H and δ18O indicated the role of recharge by local rains, rapid infiltration and low evaporation. The groundwater of the municipality of Santana was the most evaporated. The isotopic composition in δ13CCID suggested a small residence time of the water in the aquifer, predominating values similar to the isotopic signature of plants of photosynthetic cycle C4 and carbonic rocks. The analysis of clusters showed that the hydrochemical groups were distinguished in relation to the values of the mineralization, saturation of the solution in the minerals calcite and dolomite and the isotopic composition in δ13CCID the samples of Feira da Mata or of Santana. The changes in these variables accompany the geochemical evolution of the bicarbonated calcium waters to the bicarbonate or sodium chlorate, from the base exchange reactions and the groundwater circulation in the aquifer. The integration of isotopic results, geochemical reasons, saturation index and multivariate statistics revealed the relevance of chemical weathering of carbonates and pellets to water quality.


Keywords


Stable Isotopes; Analysis of Clusters; Hydrochemical Types; Bambuí Aquifer.

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