Resilience of soil fauna to pesticide contamination in areas impacted by mining tailings.

We aimed to assess the intrinsic toxicity of iron mining tailings-impacted soil and the recovery capacity of invertebrates when exposed to pesticides. The study was developed in two phases, and the soil used was collected in areas impacted by the Fundão dam rupture. In the first phase, the intrinsic toxicity was investigated by exposing Folsomia candida, Enchytraeus crypticus, and Eisenia andrei to tailings-impacted and no-impacted soils (reference). In the second phase, chronic tests involved using F. candida and E. crypticus, exposed to imidacloprid. Exposure concentrations were 0, 0.25, 0.50, 1, 2, and 4 mg·kg-1 for F. candida, and 0, 4, 8, 16, 32, and 64 mg·kg-1 for E. crypticus. Effect concentrations (EC₁₀ and EC₅₀) were estimated for the soil reference and tailing of both the low-impact and high-impact scenarios. Invertebrate sensitivity to tailings varied by species: F. candida was the most sensitive, E. crypticus exhibited moderate tolerance, and E. andrei was unaffected compared to the reference soil. For F. candida, EC₁₀ values were 0.07, 0.01, and 0.009 mg·kg-1, and EC₅₀ values were 0.27, 0.07, and 0.06 mg·kg-1. For E. crypticus, EC₁₀ values were 5.02, 0.30, and 0.13 mg·kg-1, and EC₅₀ values were 13.09, 1.47, and 0.90 mg·kg-1. Toxicity increased by 3.8-16.7-fold and 4.5-38.6-fold in low- and high-impact tailings, respectively. In general, tailings increase the risk of soil contamination, heightening the vulnerability of fauna and compromising biodiversity and resilience. These results highlight the need for integrated management strategies to preserve ecological integrity and facilitate sustainable recovery after anthropogenic disturbances.