Composição isotópica do carbono combinado com os íons (Ca+2, Mg+2, SO4 =) para avaliar a interação água-rocha no sistema aqüífero Salitre-Ba

Analysis of stable isotope composition (δC13) of carbon dissolved inorganic of carbonates and major ion concentration in groundwater from the Salitre basin in Bahia was carried out to investigate the water-rock interaction in the aquifers of that region. The important aquifers of the Salitre basin are the fractured metasedimentary rocks of Chapada Diamantina Group and the Karsts of the carbonates rocks of the Una Group and Caatinga Formation. The chemical data show a dear distinction between the two groups with a much lower concentration of dissolved salts in waters from the metasedimetary aquifers. The δC13 of carbon dissolved inorganic ranged from -4,3 to -13,2‰ with the water samples from the karst aquifers enriched in C13 indicating a higher interaction with the carbonate rocks. One sample very rich in sulfates from one well in metasedimentary rock rich in C13 shows that in some points the pyrite oxidation can be an important source for dissolution.