Heavy metal speciation in agricultural farmland in some selected local government areas of Benue State, Nigeria

This study investigates speciation of heavy metals (Cd, Co, Cu, Mn, Ni, Pb and Zn) in the cultivated farmland of three selected Local Government Areas of Benue state in Nigeria. Total of 31 selected sites and 9 controls have been sampled and five subsamples were taken in each site to create a composite sample. The seven metals have been analyzed for the sequential extraction procedure by atomic absorption spectrometry. Heavy metal speciation of soil samples from agricultural farmland indicates that the determined heavy metals are predominantly in the non-residual fractions thereby reflecting control by anthropogenic sources. The exchangeable Cd, Co, Pb, was not detected. The absence of mobile forms of Cd and Pb in all soil samples eliminates the toxic risk both in the tropic chain and from its migration downwards the soil profile.