Abstract Tailings storage facilities are disposal systems for storing the waste products of the mining industry consisting of a slurry mixture made of soil, rock and water that remain after the mineral values have been removed from the patent ore. Tailings dams are supposed to last forever, so after their deposition, tailings can experience aging processes with physical and chemical changes depending on the interactions between local conditions and source mineralogy. The consequences of these aging processes are increased interlocking of particles and oxidation processes, sometimes making previously safely held contaminants available and mobile. Among the long-term aging processes, the natural ionizing radiation (from radioactive isotopes of the soils, cosmic rays, and also ultraviolet rays from the sun) can be considered, as proposed in the current research. Furthermore, in many countries, tailings are beginning to be re-used as backfill, landscaping material or feedstock for cement and concrete. So if any, the long-term physical and chemical modifications could affect the hydraulic and mechanical behaviour of tailings with relevant economic consequences. For these reasons, wet and dry silty samples of tailings spilled out after the failure of the Stava tailings dam (Trentino Alto Adige, Italy) were exposed to gamma rays, as an accelerated aging technique to simulate the natural ionizing radiation, and then characterized. The modifications on physical and chemical properties were observed and, despite certain chemical stability, some physical changes were observed, particularly in terms of size particle distribution, inner porosity of the particles and specific surface.

Recentes acidentes envolvendo barragens de contenção de rejeitos de mineração e de resíduos industriais vêm despertando a atenção para essas estruturas, que crescem com o aumento da produção industrial. Em Minas Gerais, a Fundação Estadual do Meio Ambiente (FEAM) realiza cadastro e classificação dessas barragens através da metodologia de Potencial de Dano Ambiental. De acordo com essa classificação as barragens devem se submeter, periodicamente, a novas auditorias técnicas de segurança, com prazos de um, dois ou três anos. Em parceria com a FEAM, foram aplicados dados de 124 barragens de contenção de rejeitos de mineração e de resíduos industriais em um modelo de avaliação de potencial de risco, a princípio, desenvolvido para barragens convencionais. O modelo, que considera os fatores Periculosidade, Vulnerabilidade e Importância Estratégica, se apresenta como uma ferramenta adicional para subsidiar a tomada de decisões, permitindo focar atenção naquelas barragens que apresentarem situação mais crítica quanto ao potencial de risco e de dano ambiental. Os resultados mostraram que nenhuma barragem apresentou potencial de risco Muito Alto/Emergência. No entanto, 30% das barragens apresentaram potencial de risco Médio/Alerta, o que revela a necessidade de priorizar a atenção e a intervenção nessas estruturas.

Recent accidents involving tailings and industrial waste dams are attracting attention. This is because the number of these dams increases as industrial production increases. In Minas Gerais, the State Environmental Foundation (FEAM) conducts the registration and classification of dams according to the methodology called Potential Environmental Damage. According to this classification, the dams must be periodically submitted to technical and safety audits every one, two or three years. In partnership with FEAM, data from 124 tailings and industrial waste dam was applied in a model for potential-risk evaluation; in principle, developed for conventional dams. The model, which considers factors of danger, vulnerability and strategic importance, is presented as an additional tool to support decision-making, allowing focusing attention on those dams that present the most critical risk potential for environmental damage. The results showed that no dam presented the Very High/Emergency potential risk. However, 30% of the dams showed Medium/Alert potential risk, which shows the need to prioritize attention and intervention in these structures.