Influence of Waste Type on Heavy Metal Enrichment in Dumpsite Soils in Ijebu-Ode, Southwestern Nigeria

Abstract

Heavy metals occur naturally in soils, but their concentrations may be elevated by anthropogenic activities such as improper disposal of waste. Dumpsites are particularly significant sources as various waste streams can release different metal assemblages into soils. In this study, we investigate concentration and distribution of heavy metals in soils around different dumpsites in Ijebu-Ode, southwestern Nigeria. The idea is that dumpsites dominated by synthetic and mixed domestic wastes, especially plastic-related waste, would show higher heavy-metal enrichment than other dumpsites. Five soil samples collected from five dumpsites associated with different types of waste were analyzed for their elemental concentration using X-Ray Fluorescence (XRF). The results were evaluated using contamination indices such as Contamination Factor (CF), Geo-accumulation index ( I geo ) and Pollution Load Index (PLI). Results reveal the following range of values of metal concentration: Copper (Cu) 54 - 3637 ppm, Zinc (Zn) 13 - 1342 ppm, Arsenic (As) 49 - 112 ppm, and Lead (Pb) 2 - 38 ppm. The highest concentrations of heavy metals, which were Cu and Zn, occurred at the plastic-waste dumpsite, suggesting that waste composition influences metal enrichment in dumpsite soils. High CF of 2.57 - 173.19, 24.50 - 56.00, 0.94 - 9.65 were recorded for Cu, As and Zn, respectively. Pollution Load Index (PLI) values revealed that the soil quality at all sampled dumpsites was deteriorated as their PLI values were higher than 1 in the soil (2.63 - 7.42). The findings indicate that dumpsite soils in the study area are environmentally degraded and may serve as secondary sources of metal exposure to surrounding soils, surface runoff, plants and human populations. And that the type of waste may influence heavy metal concentration of soil.