Toward a New Paradigm for Tailings Phytostabilization—Nature of the Substrates, Amendment Options, and Anthropogenic Pedogenesis

Base metal tailings (BMTs) 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 success in constructing a sustainable plant community in BMTs so far, implying that a new paradigm involving a sophisticated understanding of the nature of BMTs is needed for BMTs phytostabilization. Using a property database of BMTs worldwide built in this study as a backdrop, this review explores how BMTs are different from normal soils and how these differences influence the strategies of BMTs phytostabilization. It is found that BMTs are mineralogically and chemically different from natural soils, which endows BMTs with unstable geochemistry and inherent extreme toxicity. Studies have documented that amendment options and soil development in BMTs phytostabilization are largely constrained by these abiotic factors. From a viewpoint of pedogenesis, BMTs can be seen as novel parent materials rather than soil. Accordingly, we propose that in BMTs 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.