Composição físico-química de águas subterrâneas das zonas norte e leste de Manaus-AM

Abstract

Groundwater constitutes an important source of drinking water supply worldwide, playing a key role in public distribution systems in cities such as Manaus, Brazil. However, these waters are susceptible to contamination from anthropogenic sources, mainly due to inadequate sanitation infrastructure, which may compromise their potability and pose risks to both human health and aquatic ecosystems. Previous studies conducted in Manaus have reported groundwater quality impairment, particularly highlighting the presence of Escherichia coli, a direct indicator of contamination. In this context, this study aimed to evaluate the quality of groundwater from wells located in the North and East zones of Manaus through the analysis of physicochemical, microbiological, inorganic ions, and potentially toxic metals parameters, comparing the results with the standards established by Brazilian legislation (Ordinance GM/MS No. 888/2021). A total of 24 tubular wells were sampled, equally distributed between the two study areas, during four sampling campaigns representing the dry and rainy seasons. The results indicated overall compliance with drinking water standards when considering mean values. However, point-specific analyses revealed nitrate concentrations exceeding the regulatory limit (10 mg L-1 as N–NO₃⁻), suggesting possible influence from anthropogenic sources. Additionally, parameters such as chloride and sodium, although below the maximum allowable limits, showed elevated values at specific sites, indicating environments under anthropogenic influence, corroborated by the correlations observed among nitrate, chloride, and sodium. The detection of total coliforms and Escherichia coli at specific locations indicates localized microbiological contamination, demonstrating that, although not widespread, groundwater is vulnerable to contamination from anthropogenic sources. Seasonal statistical analysis showed no significant differences for most evaluated parameters between dry and rainy periods, indicating low seasonal influence on groundwater quality. Overall, the findings demonstrate that, despite general compliance with drinking water standards, groundwater in the study area is vulnerable to anthropogenic contamination.