Hidroquímica da água subterrânea na zona urbana de Manacapuru, Amazonas, Brasil

Abstract

Groundwater plays a very important role in the potential of water resources in Brazil and in the world and, in the State of Amazonas, studies are needed on the growing threat of groundwater contamination. In view of this scenario, this study aims to characterize the hydrochemistry of groundwater in the municipality of Manacapuru – AM, to present the spatial distribution of the physical and chemical variables of the water, to verify the existence of geogenic or anthropogenic contaminants and to seek to relate the lithological characteristics with the hydrochemistry. To achieve these objectives, two water samples were collected at different times. The first was carried out in November 2021, with collections made in deep tubular wells, totaling twenty wells of the Water Supply and Sewage Service company - SAAE in the municipality of Manacapuru. The second collection was carried out in five shallow piezometers in June 2022. In both cases, the following parameters were measured in-situ: pH, electrical conductivity, dissolved oxygen, salinity and temperature. Alkalinity was determined by titration. Analyses of cations, anions and silica were carried out at the Geochemistry Laboratory of the Federal University of Amazonas. The waters of the region are calcium or magnesian bicarbonate, with a high concentration of carbonate and bicarbonate, especially in the deep wells. The concentrations of the parameters at depths greater than 200 meters present different hydrochemistry from the shallower region waters, with the deep waters characterized by greater mineralization, containing higher concentrations of ions such as calcium and bicarbonates, due to the longer residence time in the aquifers, while the shallow waters have lower concentrations of ions, being waters of rapid circulation. The characteristics of these waters at different depths can be influenced by geological and lithological formation, highlighting that no contaminants were found in the groundwater of Manacapuru.