Bioleaching of heavy metals from soils contaminated by military activities using Acidithiobacillus ferrooxidans

• Cu, Ni, and Pb predominated in real soils impacted by military activities. • Higher bioleaching efficiency was observed in more acidic soils. • A. ferrooxidans achieved higher Ni release than HNO 3 extraction in acidic soils. • Metal solubilization declined after 24 h due to incorporation into jarosite phases. • Jarosite phases were confirmed by SEM and XRD analyses This study compares the bioleaching efficiency of Acidithiobacillus ferrooxidans in real soils contaminated by military activities. Samples came from three sites with distinct histories: (i) debris from a 2014 munition storage explosion (MS), (ii) an infantry shooting range impact area (SR), and (iii) a grenade range throwing zone (GR). Bioleaching performance was benchmarked against nitric-acid extraction (HNO 3 ), and the total metal content was determined after soil mineralization. Copper (Cu), nickel (Ni), and lead (Pb) predominated. Cu and Pb mobilization were highest in SR, while Ni was most effectively mobilized in MS, reflecting site-specific contamination. Although MS is a Gleyic Luvisol and SR/GR are Modal Mesobasic Cambisols, soil type was not the primary driver. Soil acidity impacted outcomes: more acidic soils (SR) yielded higher solubilization, whereas the more alkaline GR showed limited leaching. Nickel exhibited a distinct temporal trend: while its dissolved concentration declined during extended bioleaching due to sequestration within secondary jarosite phases, the process nonetheless achieved an approximately fivefold higher solubilization efficiency compared to HNO 3 extraction. This suggests that bioleaching effectively circumvents the mineral passivation that limits HNO 3 efficacy in this specific soil matrix, even though late-stage Ni solubility is constrained by jarosite precipitation. Overall, bioleaching efficiency followed Cu ≥ Ni ≫ Pb. A. ferrooxidans -mediated bioleaching is a promising, environmentally friendly in-situ approach for removing Cu and Ni from acidic soils, including explosion sites and shooting ranges.