Terrestrial species exposed to mining tailings: Assessing the potential ecotoxicological impacts of the Fundão Dam collapse in Brazil

Abstract

Background

In 2015, the Fundão dam in Mariana, Brazil, collapsed, leading to the discharge of iron mining tailings (MT) that caused significant damage to the environment and human health. This study aimed to evaluate the potential effects of MT on four terrestrial species, including the soil invertebrates Folsomia candida (Collembola), Enchytraeus crypticus (Oligochaeta), and the plants Avena strigosa and Brassica rapa, after the Fundão dam collapse.

Methods

MT samples were collected from the topsoil of a contaminated site, and the total concentrations of potentially toxic elements (PTE) were determined. Soil organisms were exposed to different proportions of MT (0 % as the control, 25 %, 50 %, 75 %, and 100 %) in two soil types, including a background soil (BS) from a non-contaminated site in the area of study, and a natural soil (NS) from a well-documented place where there is no evidence of contamination.

Results

The study found that the addition of MT increased soil pH and influenced the toxicity of MT to invertebrates, with F. candida reproduction being more impacted in background soil (BS) and E. crypticus being more affected in natural soil (NS). Reproduction of F. candida and E. crypticus significantly decreased at 100 % of MT exposure. Furthermore, exposure to MT caused phytotoxicity in plants, and B. rapa was found to be more sensitive than A. strigosa, suggesting it is a suitable bioindicator. B. rapa showed significant reductions in most measured endpoints at 100 % of MT, while A. strigosa had declines in shoot length and dry biomass at 75 % of MT. Chromium was a PTE of environmental concern since its concentration in MT surpassed its prevention limit (75 mg kg⁻¹) and exceeded even its thresholds for industrial areas (400 mg kg⁻¹).

Conclusion

The findings can contribute to future strategies for the management of MT and underscore the importance of considering sublethal effects (e.g., reproduction) in environmental risk assessments. However, further research is needed to develop effective strategies for mitigating the negative impacts of MT on soil ecosystems.