Is rhizosphere remediation sufficient for sustainable revegetation of mine tailings?
BACKGROUND
Revegetation of mine tailings (fine-grained waste material) starts with the reconstruction of root zones, consisting of a rhizosphere horizon (mostly topsoil and/or amended tailings) and the support horizon beneath (i.e. equivalent to subsoil - mostly tailings), which must be physically and hydro-geochemically stable. This review aims to discuss key processes involved in the development of functional root zones within the context of direct revegetation of tailings and introduces a conceptual process of rehabilitating structure and function in the root zones based on a state transition model.


METHODS
Field studies on the revegetation of tailings (from processing base metal ore and bauxite residues) are reviewed. Particular focus is given to tailings' properties that limit remediation effectiveness. Aspects of root zone reconstruction and vegetation responses are also discussed.


CONCLUSIONS
When reconstructing a root zone system, it is critical to restore physical structure and hydraulic functions across the whole root zone system. Only effective and holistically restored systems can control hydro-geochemical mobility of acutely and chronically toxic factors from the underlying horizon and maintain hydro-geochemical stability in the rhizosphere. Thereafter, soil biological capacity and ecological linkages (i.e. carbon and nutrient cycling) may be rehabilitated to integrate the root zones with revegetated plant communities into sustainable plant ecosystems. A conceptual framework of system transitions between the critical states of root zone development has been proposed. This will illustrate the rehabilitation process in root zone reconstruction and development for direct revegetation with sustainable plant communities. Sustainable phytostabilization of tailings requires the systematic consideration of hydro-geochemical interactions between the rhizosphere and the underlying supporting horizon. It further requires effective remediation strategies to develop hydro-geochemically stable and biologically functional root zones, which can facilitate the recovery of the microbial community and ecological linkages with revegetated plant communities.
University of Queensland, Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, Brisbane, Queensland 4072, Australia. l.huang@uq.edu.au
Longbin
L
Huang
Thomas
T
Baumgartl
David
D
Mulligan
D000537:Aluminum Oxide / Q000633:toxicity; D001673:Biodegradation, Environmental; D003247:Conservation of Natural Resources / Q000379:methods*; D017753:Ecosystem; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007220:Industrial Waste; D019216:Metals, Heavy / Q000633:toxicity; D008906:Mining; D018517:Plant Roots / Q000187:drug effects / Q000382:microbiology*; D010944:Plants / Q000187:drug effects / Q000382:microbiology*; D058441:Rhizosphere; D012988:Soil Microbiology
D007220:Industrial Waste; D019216:Metals, Heavy; D000537:Aluminum Oxide