HYDROCHEMICAL CHARACTERIZATION OF THE BARREIRAS-ITAPECURU AQUIFER SYSTEM GROUNDWATER ON THE MARANHÃO ISLAND, IN THE NORTH COAST OF BRAZIL
Hydrochemical characterization of the Barreiras-Itapecuru Aquifer System groundwater in the Maranhão Island, North Coast of Brazil
DOI:
https://doi.org/10.5016/geociencias.v41i02.15700Abstract
This work analyzes the hydrochemistry of the groundwater of the Barreiras-Itapecuru Aquifer System on the Ilha do Maranhão, northern Brazilian coast. Records of 100 tubular wells were subjected to ionic balance; plotted on a Piper diagram; spatialized through Kriging procedures; grouped into class ranges; and compared to the maximum permitted values established in the environmental legislation. Ionic concentrations occur in the order Cl- > HCO3- > Na+ > NO3- > SO4-2 > Ca+ 2 > K+ > Mg+ 2. The first three ions represent 67.5% of the average ionic concentration; give groundwater the hydrochemical facies sodium chloride and sodium bicarbonate; and they probably originate from marine aerosols and from the dissolution of soil carbon dioxide by meteoric water and subsequent ionization. Groundwater is classified as sweet and fast circulating (93% of samples showing STD <500mg / L) and originated in rainfall, with lower/higher ionic concentration in regions of higher/lower elevations, qualifying them as probable areas charging/discharging. Potability standards for human consumption are met in 47% of the samples; in 53% they are not attended, mainly in relation to nitrate concentrations > 10mg / L. This worrying scenario points to the fragility of sanitation policies in the area investigated.