Geogenic characterisation of airborne particles from the former Regoufe mining area

Mining operations contribute to higher environmental contaminant levels, such as particulate matter (PM) hosting potentially toxic elements (PTE). This study aimed to comprehensively characterise atmospheric PM in an environment impacted by former tungsten-tin mining exploration at Regoufe mine (Arouca, Portugal). Although this is a deactivated mine, its location near population clusters and integration into a Geopark belonging to the "World Geoparks Network" with frequent presence of hikers highlight the importance of air quality monitoring to keep its Geopark classification. A seasonal and cumulative sampling approach was used, with samples collected over a seasonal period, between April 2022 and April 2023, through passive sampling, wet and dry sedimentation, and air mass filtration. All samples were analysed using SEM-EDS for detailed imaging. Samples from wet deposition and filtration were also analysed with ICP-MS to determine the concentration of the inorganic elements. The PTE determined in the atmospheric particulate matter of the studied area occurs in variable concentrations as a function of the sampling period. The mineralogy of the PM sampled includes Sn- and W-minerals, pyrite, quartz, phosphates, sulfates, and As-oxides. These materials are typical in the site's soils, suggesting their resuspension by the wind and transported to nearby areas. Angular to sub-angular dense particles indicate limited transportation, depositing closer to their emission source. The smaller particles (<25 μm) tended to be angular with sharp edges. Our results emphasise the importance of monitoring potentially toxic elements in atmospheric particulate matter of abandoned mining areas for developing mitigation strategies to reduce impacts on human health and surrounding environments.