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Risk Assessment of Heavy Metal Pollution of Topsoil in the Proposed Land for UNIOSUN Teaching Hospital

Heavy metals which are released to the soil are found to be deleterious to environment and biota. Such soil quality, particularly in residential proximities, must be assessed periodically. This study investigated nine (9) heavy metals (Cu, Pb, Cd, Fe, Cr, Zn, As, Mn, Ni) in the surface soil of an agrarian land for Osun State University Teaching Hospital, Osogbo, with a view to establishing their potential threat. They were measured in twenty (20) composite soil samples of the site by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results showed that the average concentrations of Cu (6.5 mg/kg), Pb (5.4 mg/kg), Fe (5831 mg/kg), Cr (22 mg/kg), Zn (14.8 mg/kg), As (1.4 mg/kg), Mn (575 mg/kg), Ni (2.6 mg/kg) were within the permissible range and posed no ecological risk. However, Cd ranging 0.1–1.3 mg/kg (average, 0.6 mg/kg) moderately posed ecological risk due to its positive geo-accumulation index and constituted 86.5% of risk index of all the metals. Applications of agrochemicals, fertilizers in the previous agricultural activities could be the primary sources of the elevated concentration of Cd measured in the soil. The overall pollution assessment of the surface soil indicated moderate pollution of the site soil by the heavy metals.