First monitoring data of the post-project of geomorphological and geochemical rehabilitation in Lousal (Portugal)

Abstract

The rehabilitation of the Lousal mine in Portugal, carried out during September-November 2021 within the framework of the LIFE RIBERMINE project, is the first designed and built rehabilitation project in Europe where geomorphic reclamation methodologies have been combined with solutions aimed at addressing the problems caused by the generation of acid mine drainage and the mobilisation of potentially toxic elements (PTE).To assess the success and impact of the rehabilitation actions on the hydrochemistry of surface and groundwater in Lousal, four groundwater samples and two surface water samples were collected in May 2022. In each of the water samples, in situ dissolved oxygen, pH, conductivity was measured and PTEs and cation-anion content analysis were carried out by ICP - MS in an external laboratory. The post mine rehabilitation effects of recent less acidic leachates with lower metallic loads have not yet reflected correction to the pH or EC values, but they are significant in terms of oxidation reduction potential and presence of PTEs.The geomorphic evolution and development of vegetation in the reclaimed area has been monitored since the conclusion of the reclamation actions in November 2021. After the completion of the rehabilitation work, localised rilling processes were observed in areas where surface run-on entered the rehabilitation topography from adjacent areas. These erosive forms were corrected by extending limestone blocks over the eroded areas to create additional open limestone channels that manage incoming surface runoff and minimise its erosive potential. Throughout 2022, no signs of active erosion have reappeared in the restored area, demonstrating the success of the physical stabilisation actions applied in the intervention area.Vegetation has successfully developed during the year 2022, after manual sowing in November 2021. Currently, the intervention area is almost completely covered with herbaceous vegetation, with the exception of some small areas where the density of vegetation is lower.It is expected that the data and information obtained from the continued monitoring of this pioneering mine rehabilitation project will provide new knowledge and methodological innovations that can be applied to future mine rehabilitation projects around the globe with characteristics similar to those of the Lousal mine.