Seasonal Assessment of Heavy Metal Contamination and Drinking Water Suitability of Surface and Groundwater in Okaba-Odagbo Coal Mining Community, Ankpa, Kogi East, Nigeria

Abstract

Coal mining activities are recognized as significant sources of heavy metal contamination, posing serious threats to surface water, groundwater, and public health in mining communities. This study assessed the seasonal occurrence of heavy metal contamination and evaluated the suitability of surface and groundwater for human consumption in the Okaba-Odagbo coal mining community, Ankpa, Kogi East, Nigeria. Primary data were obtained through field sampling during the dry and rainy seasons. Surface water samples were collected from three strategic locations (upstream, middle course, and downstream) to determine the influence of mining activities along the flow path, while groundwater samples were collected from two functional community boreholes selected using simple random sampling. In total, ten water samples comprising six surface water and four groundwater samples were analyzed for selected heavy metals, including cobalt, fluorine, cadmium, copper, silicon, and selenium, alongside selected physicochemical parameters. Descriptive statistics (mean, standard deviation, and coefficient of variation) were used to summarize the data. The results revealed marked spatial and seasonal variations in heavy metal concentrations. Surface water recorded higher concentrations of heavy metals at the middle course and downstream sections than at the upstream location, indicating the influence of mine effluent discharge, runoff, and sediment transport. Groundwater samples also contained detectable concentrations of heavy metals, suggesting contaminant migration from mining areas into the aquifer system. Although the concentrations of the analyzed heavy metals were generally within the permissible limits prescribed by the World Health Organization (WHO) and the Federal Ministry of Environment (FME), most water samples exhibited acidic pH values below the recommended range and elevated total hardness at several sampling locations. The study concludes that coal mining activities have adversely influenced the quality of both surface water and groundwater in the Okaba-Odagbo mining community. Although most heavy metal concentrations remained within regulatory limits, the combined effects of acidic water conditions and detectable heavy metal concentrations indicate that the affected water sources are unsuitable for long-term human consumption without appropriate treatment. The study recommends continuous environmental monitoring, effective treatment of mine effluents, provision of safe alternative water supplies, and stricter enforcement of environmental regulations to safeguard water resources and protect public health in mining communities.