Alkaline tailings as novel soil forming substrates: Reframing perspectives on mining and refining wastes

Abstract

Historically, tailings management plans have focused largely on confinement and containment, with little regard to long term alteration of the chemical, physical, and biological properties of tailings materials. Management strategies are now moving towards in situ remediation of tailings to mitigate environmental risks associated with long term storage, and return occupied land areas to an alternative, productive land use. Creating a stable, sustainable ecosystem in tailings storage areas requires shifting our perspective to think of tailings as a novel soil forming material rather than as a waste. This review presents a conceptual model of soil formation (pedogenesis) in alkaline tailings and mineral processing residues, which can be used to guide rehabilitation efforts and identifies key knowledge gaps for future research. Although tailings and mine wastes exhibit chemical, physical, and biological properties greatly different to those of bedrock-derived parent materials, they experience the same drivers of soil formation (climate, organisms, relief, time) as bedrock parent materials, and understanding how these drivers interact is of importance in accelerating natural processes of soil formation and attainment of a desired ecosystem endpoint. Individual processes (desiccation, mineral precipitation) early in pedogenesis in alkaline wastes are relatively well understood; however, the interactions between these processes (particularly between abiotic and biotic processes) in guiding and controlling the rates of soil development in alkaline tailings remain a priority for future research.