Introduction: Mining poses ecological and human health risks through heavy metal contamination. This study assessed contamination, ecological risk, potential sources, and human-health implications in soils surrounding the Osole gold mining area, Sidama, Ethiopia.
Methods: Eleven metals (As, Cd, Hg, Pb, Ni, Cr, Fe, Co, Zn, Mn, and Cu) were quantified using inductively coupled plasma optical emission spectrometry (ICP–OES). Contamination was evaluated using CF, Cdeg, mCdeg, and PLI, and ecological risk using ER and ERI. Pearson’s correlation, principal component analysis (PCA), and hierarchical cluster analysis (HCA) assessed metal associations and potential sources. Human-health risks were evaluated using the USEPA framework.
Results: Metal concentrations followed the order Fe > Mn > Zn > Cr > Cu > Ni > Pb > Co > Cd > Hg > As. Cd and Hg exceeded agricultural soil guideline values at all sites and were the principal contributors to contamination and ecological risk. Contamination indices indicated high to very high contamination, while ER and ERI indicated very high ecological risk. Multivariate analyses suggested geogenic and anthropogenic inputs associated with mining activities. Individual non-carcinogenic risks were below the acceptable threshold (HQ < 1), but cumulative risk exceeded the acceptable level for children. Ni and Cr were the principal contributors to carcinogenic risk, with potential lifetime cancer risks for children at all sites and adults at SG1 and SG3.
Conclusion: Cd and Hg were priority contaminants, and children were the most vulnerable receptor. The findings support improved mine-waste management and protection of mining-affected agricultural soils.