Assessment of heavy metals and metalloid in soils, sediments and water from pristine and major mining areas in Ghana- data to aid geochemical baseline setting.

Abstract

The distribution, risks and geochemical baseline analysis of the heavy metals in soils, sediments and water in pristine and major mining areas in Ghana were investigated. The surface soils, sediment and water were pulverized, acid digested, and analyzed for the major and minor elements using (ICP QQQMS). The average metals and metalloid (As, Cd, Pb and Zn) concentrations from the mining sites were higher than the pristine sites (p>0.05) with many of the metals not detected in pristine water samples. The natural geogenic metals however, showed varied concentrations in both the pristine and the mining areas. The total heavy metals concentrations from the study ranged from 0.OHO.01 (Cd) to 86859.36±47.07 (Fe) in the soils and sediments and 0.002±0.00 (As) to 0.929±0.06 mg/L (Fe) in the waters. With the exception of Al, Fe, Mn and As, the metals levels in the water samples were generally found to be below the WHO, EC and USEPA guideline limits. For the soils and sediments, the concentrations of Cd, Pb and Zn were below the guideline limits. However, As showed exceptionally high concentrations in samples from the mining areas, especially those from Obuasi and Kwabeng mining areas, indicating a potential biological effect. Elevated human health risk indices (>10“4) were obtained for As and Cr with the severity of the metals and metalloid in the soils and sediment ranked as As >Cr> Pb> Cd. The multi-criteria ranking, employing PROMETHEE and GAIA, indicated that the pristine sites have low degree of contamination which is suitable for setting the geochemical baseline values for the metals and metalloid in the pristine areas. The proposed geochemical baseline values will be applied for speedy identification of sites that could be affected by heavy metals contamination.