Characterization and evaluation of the effects of mine discharges on surface water resources for irrigation: a case study of the Enyigba Mining District, Southeast Nigeria

Abstract

Mining activities generate much wastes which degenerate into various geochemical components and affect the natural composition of surface water resources. They cause Acid Mine Drainage (AMDs) and influence the hydrochemical evolution of the hydrogeological systems. This study employed hydrochemical parameters to characterize and evaluate the effects of mine discharges on irrigation surface water in the mining district of Enyigba, SE Nigeria. Twenty-four water samples were collected from surface water sources used for subsistence irrigation farming and analyzed for pH, total dissolved solids (TDS), electrical conductivity (EC), sodium (Na+), potassium (K), calcium (Ca2+), magnesium (Mg2+), bicarbonate (HCO3−), chloride (Cl−) and sulfate (SO42−), while various irrigation parameters including Soluble Sodium Percentage (SSP), Magnesium Adsorption Ratio (MAR), Sodium Percentage (Na %), Sodium Adsorption Ratio (SAR), Permeability Index (PI), Total Hardness (TH), Kelly Ratio (KR) and Electrical Conductivity (EC) were deduced. Result indicates hydrogeochemical trend of Cl− > Mg2+ > Ca2+ > SO42− > HCO3− + CO3 > Na+ + K+, while hydrogeochemical facies from Piper Trilinear plot, Durov and Schoeller plots shows that the dominant ionic species are the Mg2+, Cl−, and SO42−. Irrigation parameters such as SSP, MAR, Na %, SAR, PI, KR and EC indicate that majority of water sample are very good to moderately suitable for irrigation. Five samples around Amorie and Ameka are within the hard category for TH, which could be attributed to the high concentration of dissolved magnesium and calcium ion in the area. Apart from mine discharges, rock water interaction also affects the composition of surface water resources of the area.