Heavy Metal Speciation in Some Selected Farms Treated with Urban Solid Waste, in Jos South, Plateau State, Nigeria

Abstract

The speciation of metals in environmental samples is a serious factor in appraising the potential environmental impacts, before their disposal. The six step extraction procedure previously proposed by Obasi et al. was used with modification to systematically study the speciation of Cd, Cu, Mn, Pb, Zn, Fe and Cr in a farm treated with the dumpsite soils. The speciation study revealed higher distribution of the metals in the residual fractions except Cd which had 70.18% in the exchangeable fraction. The results also showed that there were low tendency of bioavailability and reactivity in the environment. The results of the newly introduced extractants (BeCl2, mixture of BeCl2/BaCl2 and CaCl2/NH4Cl), revealed that these reagents could be used for the leaching of the exchangeable fraction in speciation analysis. BeCl2 extracted 0.6499 mg/kg of the exchangeable Cd while the conventional MgCl2 extract 0.010 mg/kg (Cd). The results also revealed that the mixture BeCl2/BaCl2 extracted 0.4384 mg/kg of Cd. The use of the mixture of BeCl2/BaCl2 and CaCl2/NH4Cl extractants leached exchangeable Ni more than the conventional single extractants. BeCl2, NH4Cl and the mixture of BeCl2/BaCl2, reagents were better extractants for the exchangeable Mn in soil samples.