Hydrochemical-environmental study of the low jaguaribe alluvial aquifer, Itaiçaba – Ceará

Abstract

In the countryside of the state of Ceará, groundwater is considered an important source of water, mainly from alluvial plains. The city of Itaiçaba (CE), located in the low Jaguaribe hydrographic basin, although supplied with treated water, relies on groundwater for its water supply. In the low Jaguaribe region, large shrimp farms and plantations are present, which together with poor sanitation can cause contamination and salinization. The objective of this study was to evaluate the quality of surface waters and groundwater, analyzing the physical and chemical parameters, and to provide preliminary data on the concentration DOI 10.5935/0100-929X.20180012 Nobre et al. 78 of heavy metals. For understanding the recharge process, δ18O was measured and the water balance was carried out. The reference values established by the Brazilian legislation were used to assess the level of water contamination. For all samples, some parameters of water quality were higher than those allowed for drinking water, among them, turbidity, nitrate, Fe, and total dissolved solids. Al, Ba, Mn, Ni metals were observed in all samples, but in concentrations generally below those recommended for drinking water. The positive values of δ18O indicated the infiltration of evaporated water into wells located in the shrimp farming area, which may, together with the poor sanitation, contribute to the input of salts and contaminants. The isotopic results show the entry of rainwater and surface waters from leaching of the salinized soil into the alluvial aquifer, increasing therefore the electrical conductivity. The relationship between salinity and saltwater intrusion in the studied area was not identified.