Assessment of Heavy Metal Contamination by Mine Dumps in Enyigba Lead/Zinc District, South Eastern Nigeria

Abstract

Nineteen {19} samples of mine waste dumps were collected from the lead/zinc mining areas of Enyigba, Ameri and Ameka in the Abakaliki area of Ebonyi State, south-eastern Nigeria and analysed for As, Cd, Cu, Pb, Zn, Ni, Co, Mn, Ca and pH. The physico-chemical analyses show that pH varied from fairly acidic to basic (4.8 - 11.6), resulting from the dissolution of the sulphide minerals in the waste dumps. The heavy metal mean trend indicates that As > Cd > Zn > Cu > Pb > Ni > Co. The variations observed indicate heavy metals contamination due to Pb-Zn mining operations in the area. Possible contamination by mine dumps is assessed on the basis of enrichment factor (EF) and contamination factor (CF). The results of enrichment factor (EF) show that using Mn concentration in the background value, As show extremely high enrichment, Cd has significant to extremely high enrichment, Pb, Zn and Co show significant enrichment. The enrichment of Cu and Ni are moderate to low. The CF values for the dumps indicate the very high contamination factor for As and Cd, while the concentration for Pb and Zn are Cu, Co, Ni and Co show low contamination. These levels of contamination and values indicate that under the prevailing conditions and environmental regulations in Nigeria, the mining district would face major and hazardous discharges of these metals from the dumps into the soil and water sources, and needs remediation.