Toward a new paradigm for tailings phytostabilization – nature of the substrates, amendment options and anthropogenic pedogenesis

Base metal tailings (BMT) are normally sulfidic and contain high abundance of residue metals. Their adverse impacts on the environment can last for decades to centuries if without appropriate stabilization. While in situ phytostabilization has been thought to be a promising approach to stabilize surface tailings, few studies have reported a success in constructing a sustainable plant community in BMT so far, implying that a new paradigm involving a sophisticated understanding of the nature of BMT is needed for BMT phytostabilization. Using a property database of BMT worldwide built in this study as a backdrop, this review explores how BMT are different from normal soils and how these differences influence the strategies of BMT phytostabilization. It is found that BMT are mineralogically and chemically different from natural soils, which endows BMT with unstable geochemistry and inherent extreme toxicity. Studies have documented that amendment options and soil development in BMT phytostabilization are largely constrained by these abiotic factors. From a viewpoint of pedogenesis, BMT can be seen as novel parent materials rather than soil. Accordingly, we propose that in BMT phytostabilization, extensive engineering efforts are required to increase the biocapacity of tailings (i.e., anthropogenic pedogenesis) rather than focus on the selection and establishment of plants