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Abstract Nigeria is facing the problem of soil degradation as a result of continuous deposition of spent oil in the soil. The physiochemical properties, including heavy metals concentrations, of spent oil contaminated soils and adjacent control soils were investigated at 0–15 and 15–30 cm depths at Ladipo and Berger auto-mobile Markets in Lagos, southwest Nigeria. The soils were collected in triplicate and analyzed in a 2 (location) * 2 (study site) * 2 (soil depth) factorial experiment. The results showed a uniform soil texture in both study sites and at both soil depths, with loamy sand at Ladipo and sandy loam at Berger. Bulk density was significantly decreased, while the total porosity (46.44%), organic C (21.79 g kg− 1), available P (16.48 mg kg− 1), Na+ (0.72 cmolc kg− 1) and K+ (0.81 cmolc kg− 1) increased in the contaminated site compared to the control site. Soil pH was higher at Ladipo (8.4) than at Berger (7.4). However, the soil pH and available P concentration decreased in the contaminated soil compared to the control at both locations, resulting in a decrease in available P concentration of more than 300% and 100% at Ladipo and Berger, respectively. At the Ladipo location, the concentration of Ca2+ was higher in the control than in the contaminated counterpart, while the opposite was true at the Berger location. The concentrations of the heavy metals Pb and Zn in the contaminated soils were low, while the Cu concentration was high. Although the concentrations of these heavy metals were below the standards for potential environmental risks, the high Cu concentration at both locations poses a potential ecological risk and may affect soil and human health as Cu accumulates in critical levels in the soil due to the continued irresponsible disposal of spent oil on the ground.

The present study investigated the distribution of elements and potentially toxic elements (PTEs) in soil profiles in the southeastern region of Nigeria, where unrefined and primitive mining practices are common. Soil samples were collected from mine and non-mine sites in Ameka and Nkalagu and analyzed for total elemental concentration using portable X-ray fluorescence (pXRF). The results showed that the Ameka mine-affected soils were heavily polluted, while the Ameka non-mine-affected soils were moderately polluted. The Nkalagu mine and non-mine-affected soils were also moderately polluted. The potential ecological risk (PER) was high in the Ameka mine-affected site due to elevated As, Cu, and Pb levels, while the Ameka non-mine-affected site had a low PER. The enrichment factor (EF) values indicated more enrichment of PTEs in the mine-affected sites compared to the non-mine-affected sites. The geoaccumulation index (Igeo) showed moderate to extreme contamination in the Ameka mine-affected site with Cu, Zn, As, and Pb. In contrast, the Nkalagu mine-affected site had considerably lower contamination. The regression model showed that site characteristics alone were insufficient to explain elements and PTEs distribution, emphasizing the importance of considering soil properties in understanding their spatial patterns. The study highlights the higher concentrations of As, Cu, and Pb in the mine-affected sites compared to the non-mine areas and recommends remediation strategies for these elements and PTEs, especially in the vicinity of mine sites. Further laboratory analysis is recommended to understand the mobility of PTEs with depth for better remediation approaches.