Determination of Toxic Heavy Metals of a Selected Dumpsite (Asunle Dumpsite), Ibadan, Oyo State, Nigeria

Levels of toxic heavy metals (Pb, As, Cd, Ni, Cr, and Hg) were determined in surface soilsfrom the Asunle dumpsite (Ibadan, Nigeria), adjacent receptor areas, and a background controlsite using Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES).Concentrations for all metals were in the ppb (μg/kg) range and below established residentialsoil limits. However, a consistent gradient was observed: receptor samples concentrationsgreater than dumpsite sample concentrations greater than control sample concentrations,indicating outward migration of contaminants from the waste body. Indices of contamination(e.g., contamination factor, ecological risk factor, and geo-accumulation index) corroboratedanthropogenic enrichment, with receptor soils showing the strongest signals—particularly forPb, Cd, and Cr—despite absolute concentrations remaining low. Site activities such as informalscavenging and dismantling of materials likely contribute to localized hotspots andredistribution. Although current levels do not exceed guideline thresholds, the pattern ofenrichment at receptors highlights the potential for progressive accumulation and associatedecological and health risks. Routine monitoring, improved leachate control, and targetedremediation of receptor soils are recommended to prevent long-term deterioration of soilquality and to protect nearby communities and ecosystems.