Estudo isotópico e hidroquímico das águas superficiais e subterrâneas no semi-árido cearense em área de preservação ecológica no município de Aiuaba

Abstract

Surface waters from small dams and groundwater from dug wells located in alluviums, in the township of Aiuaba, in the semi-arid region of Ceará, were studied to avaluate their quality and process of salination, and isotope models (2H) were used for assessing losses through infiltration and through evaporation of the Boqueirão dam. Results from chemical analyses of waters and soils show that in neighbouring areas to the Boqueirão dam infiltration of rainfall water is reduced due to caulinitic clay soils. In four out of eight samplings pH of Boqueirão dam water was found to be alkaline with values up to 9.4, due to water/soil ion exchange. The major part of hydrochemical values for surface and groundwaters show that these are chemically suitable for human consumption. However, in spite of the area being of environmental protection, antropic influence is revealed through + NH4 and − NO3 in dam waters. Dissolved salts originate, principally, from water/rock interaction but also from atmospheric precipitation; evaporation is the process responsable for increasing concentration in both surface and groundwater stable isotope models applied to Boqueirão dam waters identified, for the three months of observations, an elevated loss through evaporation of 60.7% and 13.4% through infiltration of the volume stored. The respective absolute heights for these processes were 614 mm and 106 mm.