Avaliação hidroquímica e geofísica do aquífero Alter do Chão de áreas de lava jatos de Santarém, Pará

Abstract

This study aimed to analyze the water quality in nine car wash wells that collect water from the Alter do Chão aquifer, in the urban area of Santarém PA. The purpose of this analysis is to verify the influence of wastewater from washing vehicles on the aquifer water through physical ch emical analyzes of the water from these wells in conjunction with the GPR analysis of the preferential area of flow and infiltration of the washing water. The geophysical method used via GPR was the electromagnetic one, which allows observing the regions o f interest in the subsurface. For the groundwater physical chemical technique, the water sample was collected in triplicate during the rainy season of 2019, following the CETESB methodology. Temperature, tolerated oxygen, electrical conductivity, pH and to tal solids measurements were measured in situ, using a portable multiparameter probe AKSO AK88, while physical chemical analyzes of alkalinity and total hardness, ions, and heavy metals and arsenic were carried out in the laboratories of Environmental Biol ogy/Ufopa, Multianalysis/Belém PA, Hydrochemistry/Ufpa and Geochemistry and Water/Unb DF, respectively. The results obtained by the GPR show that seven of the nine wells studied had, from a depth of 1.5 m, attenuated zones detected by low reflection method s, possibly related to infection caused by residual fluids from the washing processes. Groundwater was classified as sodium chlorinated, acidic (average pH of 3.73 0.30), with average temperatures of 30.01°C, soft and a little hard (average hardness of 4 8.00 mg/L 12.47 CaCO3), mineralized (average EC of 252.50 μS/cm 49.33 μS/cm), little oxygenated (average OD of 3.37 mg/L 10.56), clear and transparent (average STD of 112, 42 mg/L 27.47) within the recommended range for drinking water. The ionic co mposition of Mg2+, Ca2+, Na+, K+, and SO42 was within the range allowed by the national resolution for drinking water, as well as the concentrations of metals Cr, Pb, As, Cu and Zn. On the other hand, all wells had water with a relatively high concentrati on of NO3 and Al, with values above the limit established by Ordinance of the Ministry of Health No. 888/2021. It is concluded that the water from the studied wells poses risks to human health, both because of its ionic and metallic composition, and becau se of the presence of underground contamination plumes.