Processos de salinização da água subterrânea armazenada em meio poroso e em meio fraturado no Vale do Cariri

Abstract

Two aquifer systerns in the Cariri Valley, one porous (Interrnediate Systern) and the other one fractured (Lower Systern) were studied in order to understand the processes of salinization. The fractured systern underlies the porous one in the sarne area, then, being influenced by the sarne externai conditions. Groundwater frorn both systerns are of bicarbonate/rnixed character. They differ, however, with respect of the degree of salinization. The maximum value of the electrical conductivity for the porous systern was 540μS/crn cornpared to 976μS/crn for the fractured. The relation for the concentrations of Ca" and HCO3- is 1:2 indicating dissolution of calcite; the Calcite Saturation Index showed a super-saturation of 25% for the fractured systern. As Na+ concentration is uncorrelated with c1-, Na+-ca++ ion exchange is the probable source ofthis ion. CI" concentration is lower than O, 1 rneq/L in 92% of the 79 sarnples frorn the porous aquifer. SO4= concentration is lower than O, 1 rneq/L in 96% of the sarnples frorn the porous systern and in 60% of the fractured systern. Even through both systerns have pMC-values in the sarne range, salinization is higher in the fractured aquifer. This is true as well for young recharge waters.