Heavy Metal Pollution of Topsoil in the Vicinity of an Industrial Estate Co-Located with a Housing Estate in Southwestern Nigeria

摘要

Heavy metals were determined in topsoils around a major industrial estate co-located with a housing estate in the southwestern region of Nigerian. Samples were collected on three-monthly basis for 18 months, from the industrial waste dumpsites, industrial area, residential area, around an effluent channel, outskirts of the estate and control sites. Average levels of Cu (2850 ± 3340 mg/kg), Pb (768 ± 450 mg/kg) and Ni (105 ± 30 mg/kg) at the dumpsites were significantly higher than other locations. At the industrial area and effluent channels, Pb and Cr levels were slightly elevated compared with other metals. Metal levels at the residential area and outskirts of the estate were about the levels in the control. Generally, the degree of contamination within the vicinity of the estate was of the order Cu>Pb>Ni>Cd>Co>Cr. Average total bioavailable (non-residual) fraction of the metals consisted of 52.0% of the metal load, with this fraction for Cd and Pb being 73.9% and 60.7% respectively. Topsoils around the dumpsite were evidently polluted with high levels of copper and lead. Seepage of leachate from the dumpsite has the potential of contaminating ground water reserves. Improper disposal of industrial solid wastes appears to be the likely source of metal pollution in the industrial estate. Heavy metal pollution in the estate can therefore be significantly reduced by prompt and proper disposal of generated solid wastes, and the application of particulate scrubbers in the industries.