Environmental and Health Risk Assessment of Soil Adjacent to a Self-Burning Waste Pile from an Abandoned Coal Mine in Northern Portugal

Abstract

Abandoned mines and disposal of mining residues can be responsible for the release of potentially toxic elements (PTEs) into the environment causing soil and water contamination, with potential ecological damage and human health hazards. The quantification of the apportionment of PTEs in soils and the study of the associated ecological and human health risks are essential. This study aims to assess the environmental and human health risk of the soils surrounding an abandoned coal mine in São Pedro da Cova, whose waste pile has been affected by self-combustion for over 17 years. The soil environmental characterization of the study area regarding PTEs was accessed by different pollution indices, considering the elementary crustal abundance and the determined regional soil geochemical background. The soil contamination degree was evaluated using indices such as the contamination factor (Cf) and geoaccumulation index (Igeo), inferred for all soil samples, and the potential ecological risk index (PERI) was also accessed. The human health risk was evaluated for adults and children, considering the non-carcinogenic and carcinogenic risks. The pollution indices calculated for the PTEs using distinct reference values showed significant differences, resulting in lower pollution indices when using the regional reference values. The regional background proved to be a much more reliable geochemical baseline for environmental assessment. Regarding Igeo, the soils were found to be unpolluted to moderately polluted for most of the studied PTEs. The determined PERI for the soils surrounding the abandoned mine classifies them as low ecological risk. The evaluation of the non-carcinogenic and carcinogenic risks, resulting from exposure to the studied soils, suggests that there is no potential human health risk for children or adults regarding the considered PTEs.