Dynamics of Organic Carbon Stabilization by Minerals during Pedogenesis of Mine Tailings: A Conceptual Model

Ecological engineering of soil formation in mine tailings provides a sustainable approach for rehabilitating thousands of hectares of global tailings landscapes. In this process, tailings are parent material to be developed into soil-like substrates (i.e., technosols), where mineral weathering and organic carbon (OC) stabilization are crucial. Existing knowledge of mineral-OC interactions primarily concerns naturally formed soils with stable mineral compositions. However, eco-engineered pedogenesis in tailings is marked by the rapid formation of secondary minerals through primary mineral weathering, driven by tolerant microbes and pioneer plants. A key question is how mineral weathering during eco-engineered pedogenesis influences the formation and stabilization of OC in tailings. This paper proposes a conceptual model to explain the stabilization and transformation of OC during mineral weathering in eco-engineered tailing systems. The model suggests that as pedogenesis progresses, the molecular diversity of OC and microbial derived OC increase. Furthermore, OC stabilization through organo-mineral association and soil aggregation increases with the continual generation of secondary minerals during primary mineral weathering. The conceptual model provides a comprehensive framework for understanding the OC dynamics and stabilization in the tailings undergoing ecological rehabilitation. Further studies are needed to validate this conceptual model. This knowledge would not only lay the foundation for developing tailings rehabilitation technologies but also help increase the OC stock capacity in rehabilitated tailings landscapes in the future.