Heavy Metal Contamination of Soil and Surface Water in the Arufu Lead-Zinc Mining District, Middle Benue Trough, Nigeria

This paper is aimed at investigating the nature of heavy metals dispersion in soil and surface water around the Arufu leadzinc mine, Middle Benue Trough, Nigeria. Rock samples from mine pits and adjoining outcrops as well as water samples from mine pits and adjacent streams were collected and analyzed. Also analysed were soil samples collected from mine waste and adjoining areas as well as from a forest to serve as control. All samples were analysed for Fe, Zn, Mn, Cu, Pb, Cr, As, Cd and Ag, using atomic absorption spectrophotometer (AAS). Organic Matter (OM) content of the soil samples, and the pH of both soil and water samples were also determined. The results show that the OM content of soil was generally low (4 + 1.1%) and both soil and water samples were characterized by moderate pH values of 6.30 to 8.00 and 5.60 to 7.80 respectively. Furthermore, soils developed over bedrock show normal (background) levels of heavy metals, while soils developed over mine waste are enriched in Zn (181 + 83 mg/kg); Pb (40 + 28 mg/kg) and Cd (3 + 2 mg/kg). Also, water samples from mine ponds are enriched in Pb (0.02 – 0.10 mg/1) and Cd (0.02 – 0.04 mg/1). The sources of these heavy metals are most probably sulphides in the mine waste. Tailing and mine pits may therefore represent point sources of heavy metal contaminants and should therefore be reclaimed to prevent further contamination.