Mine waste constitutes one of the biggest environmental and management problems, both due to its quantity and its danger when they are rich in toxic elements. There is a wide variety of waste from the oxidation of ores in metal mining areas, both metal sulphide and other minerals. These residues may be enriched in potentially toxic elements that can spread and contaminate ecosystems, farmland and villages. This study has focused on the characterization and evaluation of residues derived from metal-bearing mining waste in abandoned mining areas. Mineralogy and geochemical characteristics were determined by XRD, WDXRF and TG-MS techniques. In addition, DIN 38414-S4 leaching tests were carried out to assess the risk and mobility of potentially toxic elements. Silicates and oxides were found as the main mineral groups, followed by sulphates. These tailings were particularly enriched in Zn, Pb, As, Sb and Cd, while their leachates had high or extreme metal content. Consequently, these mining wastes are considered toxic and hazardous, even for landfills. Sulphides, as the primary source, and sulphates from their oxidation, were the main sources of these pollutants. Sulphates, As, Zn, Cd and Cu determined the specific environmental impact of the different tailing types, which were grouped into different clusters according to their mineralogy and geochemistry. These results provided a better understanding of the environmental hazards associated with the different types of metal mining waste in the area studied.

Salt efflorescences from metal sulphides and their waste are important drivers of pollution both in and around mining areas. However, little is known about these supergene minerals, particularly in the mining areas of the Mediterranean. This study aims to characterise saline efflorescences and their leachates from a Mediterranean mining area located in Southeast Spain. The physicochemical characteristics were determined using stereomicroscopy and compositional analysis, with the following techniques: XRD, WDXRF and TG-MS. Additionally, to assess the risk and potential mobility of their analytes, the samples were subjected to the leaching test DIN 38414-S4. The results showed that the salt efflorescences presented a wide range of crystalline habits and colours. Sulphates were by far the largest mineral group, followed by silicates, oxides and sulphides. Their geochemistry was dominated by elements such as S or Fe, although other potentially toxic elements such as Cd, As, Zn, Pb, Ni and Cu were also present. Due to their high metal(loid) concentrations, the salt crusts studied may act as sources of environmental contaminants, demonstrating that their leachates pose a considerable risk to soil and drinking water quality. An analysis of the correlations and provenances of the components of the salt efflorescences revealed the possible presence of some rare supergene minerals of great interest, such as cuprocopiapite and Pb-As-jarosite.