Ecological Risk, Contamination Indices, and Plant Uptake of Metals in Soils from Abandoned and Existing Gold Mines in Ijesa, Osun State, Nigeria

Abstract

Gold mining (GM) can introduce or mobilize potentially toxic elements in soils, with implications for ecological quality and food-chain transfer. This study evaluated soils from abandoned and existing gold mining sites by comparing waste soil, rhizospheric soil, and plant matrices. Metals (Fe, Cu, Zn, Pb, Mn, Sn, Al) were assessed, and contamination and ecological risk were quantified using contamination factor (CF), ecological risk factor (Er), potential ecological risk index (PERI), and geo-accumulation index (Igeo). Abandoned versus existing waste-soil means were also compared using Welch’s t-test from summary statistics. Using average shale background values, CF values were <1 for all metals and PERI values were low (Abandoned: 0.236; Existing: 0.138), indicating low potential ecological risk. Igeo values were ≤0 for all metals in both groups (unpolluted class). Although overall abandoned–existing differences were not statistically significant for key parameters (p>0.05), transfer factors (plant/waste soil) suggested comparatively higher apparent accumulation for Fe, Mn and Pb in abandoned-site samples. The results provide an index-based baseline for soil management and support targeted monitoring of bioavailable fractions and food-chain pathways in GM communities.