Spatial Distribution and Health Risk Evaluation of some Potentially Hazardous Elements in Akure Urban Topsoil, Nigeria

Abstract

Indiscriminate solid waste disposal among the urban population has a new wave of metal pollution. This study was therefore carried out to understand the spatial distribution of selected potentially hazardous elements (Cd, Pb, Ni, Mn) in Akure metropolis, and their possible associated potential risk among the urban population. The whole metropolis was divided into grids from which fifty two (52) surface composite soil samples (0–15 cm) were collected. The samples were analyzed for physicochemical properties using standard procedures while PHEs was extracted with aqua regia and the extracts analyzed using Atomic Absorption Spectrophotometer (AAS) (Buck Scientific model 210) after appropriate sample preparation. The results showed that the Metropolis top soil has slightly alkaline pH averaging 7.79 with electrical conductivity of 307.89 µS/cm. Soil type is sandy clay loam with average composition of sand, clay and silt of 61.90%, 28.16% and 7.94% respectively with mean percentage organic content of 2.11%. The mean concentrations of selected PHEs in mg/kg are: Cd (0.18); Pb (21.48); Ni (20.96) and Mn (242.78). Environmental contamination indicators reveals that the top soils is uncontaminated to moderately contaminated with Pb, and Mn but highly contaminated with Cd in agroforest zone and with Ni where there is high vehicular activities. The health risk observed for Cd in the metropolis should be further investigated since Cd is known to be neurotoxic and its entrance into the food chain should be of concern.