Soil potentially toxic elements contamination in different rural - urban fringe land uses in Edo state, Nigeria

Abstract

The study investigated soil potentially toxic elements contamination in different rural - urban fringe land uses in Edo State, Nigeria. The objectives were to determine the level of PTEs in the soils, their contamination status and implications. Nine soil samples were collected from mechanic workshop, secondary forest, block molding site, oil palm production site, fire wood processing site, cassava farm, back yard farm, cooking gas plant site and oil palm plantation respectively at 0-15cm soil depth. Each soil sample was analyzed for lead, chromium, cobalt, arsenic, cadmium, vanadium and nickel using USEPA method 3050B. Data obtained was analyzed using index of geoaccumulation, contamination factor and single element pollution indices. The results revealed that the status of Lead (Pb), Chromium (Cr), Cobalt (Co), Arsenic (As), Cadmium (Cd), Vanadium (V) and Nickel (Ni) in the soils were low. Backyard farm had higher Co, As, V and Ni levels compared to the other examined land uses. Contamination factor showed very slight contamination (< 0.1) while Single Element Pollution Indices indicated low contamination (> 1). Index of Geoaccumulation demonstrated that the soils’ were unpolluted (0 < Igeo ≤ 1). The findings also indicated that backyard farm had higher levels of PTEs (Co, As, V and Ni), followed by oil palm plantation (Cr and Cd), firewood processing site (Pb) and secondary forest (V) respectively. The study concluded that the PTEs status of the soils was not toxic and that the soils in the investigated land uses were not severely contaminated. It recommended intervallic monitoring in the existing land uses while further researches should focus on the evolving ones.