Assessment of anthropogenic contaminants (microbiological and glyphosate) and hydrochemical composition of shallow groundwater in Sergipe, Brazil

Abstract

This study assessed the presence of anthropogenic contaminants and characterized the hydrochemical composition of shallow groundwater at the Sergipe Hydrogeological Research Site (SEHRES), in São Cristóvão, Sergipe. Fifteen tubewell samples were analysed in July 2024, focusing on the detection of thermotolerant coliforms, Escherichia coli, and glyphosate, as well as the ionic composition (HCO₃⁻, CO₃²⁻, Cl⁻, SO₄²⁻, Ca²⁺, Mg²⁺, Na⁺, and K⁺). Microbiological analyses were performed using the membrane filtration method, while ions and herbicide were determined by ion chromatography. Thirteen samples contained thermotolerant coliforms and E. coli, indicating fecal contamination and diffuse source pollution. The hydrochemical classification revealed a predominance of chloride-rich sodic waters, with secondary occurrence of mixed types upstream. The marked presence of chloride was associated with marine influences on rainwater. A reduction in bicarbonate and carbonate ions was observed in the direction of groundwater flow, suggesting precipitation of carbonate minerals. One well showed glyphosate contamination and anomalous potassium concentrations, indicating a possible point source in an area of ​​agricultural use. The results reinforce the need for systematic monitoring and protection of vulnerable aquifers, especially in urban areas with direct recharge, and contribute to the Sustainable Development Goals (SDGs) focused on water security.