Concentration of Heavy Metals in Soils at the Municipal Dumpsite in Calabar Metropolis

Abstract

This research was carried out to investigate the levels of heavy metals in soils at the municipal dumpsite in Calabar, Cross River State, Nigeria. Composite soil samples were collected from five different landscape positions along a toposequence (crest, upper slope, middle slope, lower slope and valley/swamp) at the dumpsite in Calabar. The control sample was taken from an adjacent plot. The control soil was slightly acidic (5.6) while soils from the dumpsite were slightly acidic (6.7 -7.4) to slightly alkaline in reaction. In all the dumpsite locations the levels of Mercury (0.4-1.0 mg/kg), Chromium (0.66 - 200 mg/kg), Nickel (26 - 748.6 mg/kg), Lead (118 - 4548 mg/kg), and Zinc (1248 -2864 mg/kg) were above the permissible limits in soil whereas iron and copper concentrations were within soil limits. Generally the values of Mercury (Hg), Cadmium (Cd), Chromium (Cr), iron (Fe), Nickel (Ni), Lead (Pb), Zinc (Zn) and Copper (Cu) observed for the dumpsite were higher than the control soil. The metal contamination/pollution index assessment revealed that the soils in the dumpsite were excessively polluted with impending negative effect on plants animal, humans and the environment at large. It is expedient that necessary actions be put in place to sort at source, recycle and reuse wastes materials to minimize the quantity of these toxic metals in the environment.