CHEMICAL FORMS OF Zn, Mn, Fe and Pb IN SOIL SAMPLES FROM THE VICINITY OF SOME MAJOR DUMPSITES IN GOMBE METROPOLIS, GOMBE STATE NIGERIA

Abstract

This research work is aimed at determining the chemical speciation of metals Zn, Mn, Fe and Pb in soil samples from three major dumpsites within Gombe metropolis, Gombe state. The renowned five steps Tessier sequential extraction method was employed in the extraction of the heavy metals. The metals were extracted into five fractions namely: Exchangeable (F1), carbonate bound (F2), Fe-Mn oxide bound (F3), Bound to organic matter (F4) and the residual fraction (F5) in order of decreasing mobility. The elemental analysis of the fractions was carried out using atomic absorption spectrometric technique. The results showed Zn was predominantly bounded to the exchangeable fraction with 32.66±0.31 mg/kg (54.18%) and least in the Fe – Mn oxide fraction with 0.01±0.00 mg/kg (0.02%). The trend in its abundance is in the order F1> F2>F5>F4>F3. Mn was predominantly associated with the bound to carbonates fraction with the value of 103.3.±3.30 mg/kg (56.14%) and least in the exchangeable with the value of 1.30±1.85mg/kg (2.13%) its occurred in the order F2>F3>F4>F5>F1. The concentration of Fe was highest in the residual fraction with the value of 25.90±1.75mg/kg (45.45%)and least in the carbonate bound fraction wi th 5.10±0.40 mg/kg (2.13%) the order is F5>F4>F3>F2>F1. Pb was not detected in most of the fraction but highest in bond to carbonate and bond to organic matter fraction with the values of 6.64±4.12 mg/Kg (70.64 %) and 2.76±0.10 mg/Kg (29.36 %) respectively in two different samples. It was however established that Zn, Mn and Pb were mostly associated with the first three fractions thus, showed high bio-availabilty whereas Fe was found in the residual fraction and is expected to be low in mobility and less bioavailable.