Products from mining operations are of great economic importance to the state of Minas Gerais, Brazil. However, due to the extensive damage they may cause to biota, including soil fauna, recovery and biomonitoring of these areas and their surroundings are necessary. Considering the ecological importance of earthworms and their potential as bioindicators, the aim of this study was to evaluate the toxicity of arsenic to earthworms of the species Eisenia andrei Bouché in soils around gold mining operations in the Doce and São Francisco River Basins. Soil samples of these areas were characterized in terms of physical and chemical properties, including Fe, Al, Cu, Ni, Zn, Mn, and As contents. Bioassays evaluating the survival, reproduction, and biomass variation of organisms were also carried out in these samples. Tests were also conducted of E. andrei sensitivity to As added to artificial tropical soil and natural soil. A notable toxic effect on reproduction was highly correlated with high As concentrations in the samples (r = -0.80). These concentrations exceeded the limits of legislation (Conama Resolution no. 420/2009) in both areas, reaching 2,388.2 mg kg-1. Arsenic LC50 in artificial tropical soil (207.4 mg kg-1) was six times lower than in natural soil (1,248.1 mg kg-1). The lower bioavailability of As in natural soils was attributed to its association with iron ore in the samples. We conclude that soils around mining areas had a chronic toxic effect on E. andrei in terms of reproduction, demonstrating the potential damage of these mining activities on the fauna in the surrounding soil. The study also provided ecotoxicological information that may be useful in environmental risk assessments in tropical soils.
ecotoxicological bioassays; Doce River; São Francisco River; environmental risk
