Hydrogeochemistry and Impact of Iron Ore Mining on groundwater Quality in Itakpe and its Environs, Kogi State, Central Nigeria

ABSTRACT This work is a hydrogeochemical study of groundwater and the impact of over twenty five years of iron ore exploration and mining on groundwater quality in Itakpe and environs. Measurements were carried out on water samples from eight shallow hand dug open wells, four deep boreholes and a seasonal river flowing through the mine area. Groundwater in the area occurs within weathered rocks, fractured and faulted terraces. Depths to water level in the open wells were generally below 15m. Chemical and physical analyses were carried out on the groundwater samples collected from the study area. Parameters measured include pH, temperature, electrical conductivity, concentration of cations, anions and trace metals. Groundwater in Itakpe is slightly acidic with pH values between 6.03 and 6.80 and temperatures between 28OC and36"C. Statistical analysis using pie charts, stiff plots Schoeller semi-logarithmic diagram and piper trilinear diagrams were used to characterize the groundwater in Itakpe. Three water types were commonly found to characterize the area. They include Ca-Mg-CI-SO4 type water, Na-K-CI-SO4 type water and mixtures of Ca - Mg- Na - K- CI - SO4 waters with no single cation dominating. Results of the analysis were compared with an apriori data of groundwater analysis from the area as well as world health organization (WHO) standards for portable water. Water in the study area has increased in acidity, electrical conductivity, hardness and concentrations of major cations and trace metals over time. Concentration of iron (0.9mgll - 1.63mgll) and manganese (0.2mgll- 0.44mgll) was found to be well above WHO 0.1 mgll iron and 0.05mgll manganese recommended for portable water respectively. Recommendations were made on how to reduce and control the impact of iron ore mining activities on groundwater at Itakpe.