Toxic potential of the soil from sites with mining waste in San Luis Potosí, Mexico

Purpose

The aim of this study was to evaluate the toxic potential of mining residues by 1) evaluating the concentrations of heavy metals and arsenic in soil and earthworm’s samples from impacted and reference sites in Charcas and Villa de la Paz, San Luis Potosí, México; and 2) evaluating effects by laboratory bioassays and the comet assay in the earthworm Eisenia andrei.

Methods

The quantification of metals in soils was carried out by the Thermo Scientific Niton XL3t Gold Serie 500 environmental analyzer for X-ray fluorescence (XRF), and in the earthworm tissue through ICP-MS. The evaluation of the genotoxic potential of soils was assessed through movility and exposure bioassays with earthworms, determining DNA damage using the comet assay at the end of the bioassays.

Results

In Charcas, the concentrations in soils of heavy metals from highest to lowest were: Pb > Cu > Mn > Cd (Impacted); and Mn > Pb (Reference). In Villa de la Paz, the concentrations were: As > Mn > Cu > Pb (Impacted) and Mn > Pb > As (Reference). The exposure pattern to heavy metals in earthworms in Charcas was: Pb > As (Impacted and Reference); and in Villa de la Paz it was: As > Mn > Pb > Cu > Cd (Impacted), y Pb > As (Reference). In both mining districts, the magnitude of DNA damage in earthworms was: Impacted > Reference > Control.

Conclusion

The results indicate that the impacted soils of both sites represent a significant source of exposure to edaphic organisms, with a notable genotoxic potential.