Integrated Cartographic Inventory of Solid Mining Wastes to Support Environmental Rehabilitation: The São Domingos Mine (Portugal)

Historical mining districts contain heterogeneous waste accumulations whose spatial distribution and characteristics complicate environmental assessment and rehabilitation planning. This study develops an integrated, unit-based methodology for the cartographic inventory and environmental characterization of solid mine wastes, using the historical São Domingos Mine in the Portuguese Iberian Pyrite Belt as a case study. The workflow combines remote sensing, UAV imagery, terrain data, field verification, targeted laboratory analyses, and GIS, with individual waste accumulations as the basic spatial units. The methodology identified 40 waste units, comprising 23 waste dumps and 17 landfill deposits, covering 148.34 ha and classified into seven waste categories. Industrial residues, volcanic rock-derived wastes, and schist-dominated wastes account for 79.8% of the inventoried area. However, spatial extent does not necessarily reflect environmental relevance: washed ore represents only 1.8% of the area but displays very high integrated reactivity. Residual sulfides and secondary alteration products in representative units further demonstrate the importance of combining spatial delineation with mineralogical and weathering information. The methodological contribution lies in linking the geometry of individual waste units with information on origin, material characteristics, mineralogy, weathering, and reactivity within a common spatial framework. This provides a consistent basis for comparing heterogeneous mine wastes and supporting environmental screening, targeted investigation, and rehabilitation planning. The workflow can be adapted to different geological, mining, environmental, and data conditions.