Assessment of heavy metals contamination of soil and water around abandoned Pb-Zn mines in Yelu, Alkaleri Local Government Area of Bauchi State, Nigeria

Abstract

Heavy metal contamination of soil, water, and crops, and their health impact on residents, is a persistent social issue, and several studies have identified health risks of residents living near abandoned mines. The concentration of selected heavy metals (Cd, Cu, Pb, Zn, and Fe) in soils and water around abandoned Pb-Zn mines in Yelu in Bauchi State, Northern Nigeria was investigated. Results of the atomic absorption spectrophotometric (AAS) analysis of samples of the soils revealed that for heavy metals, the concentrations in the soils are above background levels and permissible limits recommended for soils in some countries as indicated by the following mean concentration ranges (mg/kg): Cu, 42.01-111.60; Pb, 65.80 –291; Zn, 185.56-373; Cd, 12.62-20.70, and Fe, 0.583-0.781 with a variation pattern in the order: Zn>Pb>Cu>Cd>Fe. The contamination of Cu, Pb and Zn were high while Cd and Fe in the soil samples were low. Zn, Cu and Pb concentrations exceeded the Dutch target values (Zn: 50 mg/kg, Cu: 30 mg/kg, and Pb: 85mg/kg) in all the sampling sites. The results of the analysis of the water samples were Pb(16.63±2.63),Cu(6.049.16±0.22), Zn(9.66±4.59), Cd(0.0012±0.06) and Fe(0.189±0.450) in mg/l respectively. The Pb, Zn and Cu concentration in water were higher than WHO standards which indicated significant contamination of the water, while the values for Fe and Cd were below permissible limit. The results from the study indicated that the mining had a direct impact on the concentrations of the heavy metals determined, hence, the level of contamination of soil and water (with the exception of borehole water) samples around the abandoned Zn-Pb

Keywords: Heavy metals, solid minerals, concentration, water, mining and mine sites