Assessment of hydrogeochemical characteristics of groundwater quality in the vicinity of Okpara coal and Obwetti fireclay mines, near Enugu town, Nigeria

Hydrogeochemical assessments were carried out in the vicinity of Okpara coal and Obwetti fireclay mines, Enugu, Nigeria to investigate the hydrogeochemical characteristics and constituents of shallow groundwater. A total of 12 representative shallow groundwater samples were collected and analyzed for major cations and anions as well as trace metals like Fe and Mn. Distribution of major ions in these groundwater samples was calculated and the general trend among cations and anions was found to be Ca → Na → Mg → K and SO4 → NO3 → Cl → HCO3, respectively. This means that water moving through the ground will react to varying degrees with the surrounding minerals (and other components), and it is these rock–water interactions that give the water its characteristic chemistry. Piper trilinear diagrams classified the hydrogeochemical facies into Ca–Mg–Cl, Ca–Fe–Mg–SO4 and Ca–Mg–Na–K–Cl–SO4 water types. Ratios of Cl to Na, K and Mg generally increased compared to those of Cl to Ca and SO4 which decreased indicating ion adsorption/exchange processes due to the dissolution of drainage materials. The aquiferous units mainly in the northwestern region of the study area yield water of better quality than those toward the southeastern region.