Characterization of the waste dump at La Soterraña mine (Spain): Foundation for a sustainable restoration plan

To assess the needs and condition of the waste dump at La Soterraña, researchers carry out a soil characterization. Previous data indicate widespread metal(loid) contamination throughout the area, which was once a mining site. The waste dump remains unrestored, barren of vegetation, and its material is classified as spolic technosol. In the laboratory, the soil of the waste dump undergoes various treatments to reveal its physical and chemical properties. The findings show a significant imbalance compared to healthy soil, with alarming levels of arsenic and mercury. The total concentrations of As reach 910 mg/kg, far exceeding all generic reference levels established for this area. Similarly, the total concentrations of Hg are 15 mg/kg, once again surpassing the established generic reference levels for the region. These conditions pose serious risks, including the spread of contaminants that endanger human health and ecosystems, and the inability to sustain vegetation due to nutrient deficiency, lack of structure, low organic matter, and contamination by As and Hg. The study outlines potential restoration phases to address these critical issues.