Abstract
Soil samples were collected from floodplain sediment in Enugu Urban, Nigeria to investigate the speciation and bioavailability of some trace metals, namely; iron, manganese, copper, zinc, lead, nickel and cadmium. Extracts from the soil were obtained by sequential extraction as described by Horowitz et al. The metals occurred with the following percentage bioavailability: Fe(67.00%), Mn(65.10%), Cu(44.70%), Zn(52.90%), Pb(53.80%), Ni(53.90%) and Cd(8.30%). Exchangeable metals and metals bound to carbonates accounted for over 50% of the total fractions. Metals bound to Fe-Mn oxides and humic materials accumulated 4.50% and 7.96% respectively, while residual metals bounded 34.93% of the sediment fraction. Lead had the highest distribution in exchangeable, carbonate and residual fractions while zinc was partitioned mostly in reducible and oxidizable forms. The high concentration of lead in both the carbonate and exchangeable forms depict its greater mobility tendency in the soil and consequently, bioavailable to biota. The results of the finding indicated that these trace metals with exception of cadmium were readily bioavailable in this urban soil, therefore, phytoremediation is advocated.
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