QUALITY ASSESSMENT OF GROUNDWATER AROUND INEC HEADQUARTERS GOLD MINING SITE, MINNA NIGER STATE, NORTH-CENTRAL NIGERIA

This study evaluates the physicochemical, heavy metal, and microbial characteristics of groundwater around the INEC Headquarters Gold Mining Site, Minna, with the aim of determining its suitability for domestic use and identifying potential sources of contamination. Geological field mapping revealed that the study area is underlain by granite and schist, with quartz veins hosting gold mineralization. A total of ten groundwater samples, comprising both hand-dug wells and boreholes, were collected and analyzed for major ions, physicochemical parameters, heavy metals, and microbial indicators. Parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), hardness, chloride, sulphate, nitrate, and bicarbonate were measured in accordance with APHA (2017) standards, while atomic absorption spectrophotometry (AAS) was used to determine heavy metals including arsenic (As), lead (Pb), cadmium (Cd), mercury (Hg), chromium (Cr), nickel (Ni), copper (Cu), and zinc (Zn). Microbial tests were carried out to detect total coliforms and Escherichia coli. Results indicated that most physicochemical parameters were within the World Health Organization (WHO, 2017) and Nigerian Standard for Drinking Water Quality (NSDWQ, 2015) limits, although localized increases in EC and TDS were observed near mining pits. Hydrochemical facies classification showed that groundwater in the area is predominantly of the Ca–Mg–HCO₃ type, reflecting rock–water interaction within Basement Complex aquifers. However, samples near artisanal mining sites showed a shift toward Na–Cl and Ca–SO₄ types, suggesting the influence of sulphide mineral oxidation and anthropogenic contamination. Concentrations of As, Pb, Cd, and Hg exceeded permissible limits in several samples, indicating contamination from mine tailings and weathering of mineralized schist. Microbial analysis revealed the presence of coliforms and E. coli in some wells, signifying faecal pollution due to poor sanitation practices and infiltration from surface sources. The study concludes that groundwater in the area is moderately mineralized but suffers from localized heavy metal and microbial contamination, making it unsafe for direct consumption without treatment. It recommends regular groundwater monitoring, improved sanitation, and environmental regulation of artisanal mining activities to mitigate contamination risks and protect public health.