Assessment of potentially toxic elements in mine tailings and their categorization and prioritization as environmental liabilities in gold mining areas of Antioquia, Colombia.

In El Bagre, Nechí, Zaragoza, and three other municipalities that comprise the Bajo Cauca region of Antioquia, an estimated total of 28.000 ha have been affected by illegal gold mining, where environmental liabilities such as mine tailings are distributed throughout the area. Urban areas, especially the main urban centers, may be exposed to environmental contaminants and their associated adverse effects. Studies that contribute to the characterization and prioritization of environmental liabilities are necessary to improve environmental management and public policies. The aim of this study was to assess the presence of As, Cd, Cr, and Pb associated with mine tailings in El Bagre, Nechí, and Zaragoza and to implement a methodology for their characterization and prioritization through the calculation of risk index (RI) values. The RI considered both the concentrations of potentially toxic elements (PTEs) and the proximity of mine tailings to sensitive receptors, including urban areas and environmental features such as surface water bodies. Spatial distribution maps of PTE concentrations and RI values were subsequently developed to identify priority environmental liabilities for management. One of the main results of the study is the identification of five mining tailings as prioritized environmental liabilities for environmental management, which was unknown prior to the completion of this study. No environmental liabilities classified as high risk were identified in any of the three municipalities. In El Bagre, 9/11 environmental liabilities were classified as low risk, while 2/11 were classified as medium risk. In Zaragoza, 4/7 environmental liabilities were classified as low risk and 3/7 as medium risk. In Nechí, 6/6 environmental liabilities were classified as low risk. To the best of our knowledge, this study is the first to apply a methodology for the classification and prioritization of mining tailings in the study area. Another important result was the spatial mapping of the distribution of PTEs across the three municipalities, as this outcome allows the spatial identification of PTE concentrations and serves as an input for environmental planning of the territories. In conclusion, the results provide scientific evidence that will contribute to the development of a methodology for the categorization and prioritization of environmental liabilities associated with gold mining, serving as a resource for environmental authorities and guiding decision-making based on scientific and technical evidence.