ASSESSMENT OF SOME SELECTED HEAVY METALS IN ORE METROPOLIS, SOUTHWESTERN, NIGERIA

Abstract

Findings have shown that heavy metal assessment and monitoring is at barest minimum in Ore metropolis and that increasing anthropogenic activities could significantly raise the level of heavy metals, thereby posing hazardous effects. To investigate the contributions of anthropogenic activities and pollution status of the area, soil samples were collected from four (4) sites, namely; dumpsite (DS), metal fabrication workshop (MF), mechanic workshop (MW), river sediment (RS), and Control sample (CT). A 5-steps (fractions) sequential extraction and total metal extraction were carried out and Nickel (Ni), Lead (Pb), Cadmium (Cd) and Chromium (Cr) concentrations were determined. The sequential extraction result shows that Cd and Cr were found to be mostly concentrated in the exchangeable and carbonated fractions which supports their mobility and anthropogenic sources, as against Ni and Pb metals which were more associated with Fe-Mg and organic fractions; a more natural source and less mobile forms. Heavy metals concentrations were found to decrease in the trend; Cr as MF>DS>RS>MW; Cd as MW>DS>MF>RS; Pb as MW>MF>DS>RS and Ni as MW>DS>MF>RS. The Ni concentrations were found to be above the DPR target values in MF and MW, while Cd concentrations were above the DPR target values in MW & DS; and above DPR intervention value in MW. The mobility factor values of metals decreases in the order of Cd>Cr>Ni>Pb; while the Pollution load index (PLI) results were all above 1, in the order: MW>MF>DS>RS. Geoaccumulation index (Igeo) result showed that the sites ranged from practically uncontaminated to extremely-contaminated, implying that some of the sites need urgent intervention. The percentage recovery ranged between 73.81100%, showing the efficiency of process and method of analysis. The research is imperative for regulatory and monitoring purposes