Developing alternative approaches to cap and rehabilitate the large areas of tailings landscapes is critical for sustainable development of mining industry. This study revealed the potential of an in-situ hardpan-based duplex soil system as an un-conventional approach to rehabilitate sulfidic Cu-Pb-Zn tailings. Under a shallow silicious soil cover, a massive and consistent hardpan horizon had been formed in-situ at the surface layer of tailings across the trial area, which physically separated root zones (i.e., silica soil cover) from the un-weathered tailings underneath, prevented capillary enrichment of acidity and soluble solutes into the root zones, and sustained native plant growth for more than a decade. Precipitation of Si-rich ferric complexes were attributed to the stabilisation/solidification of the sulfidic tailing. The hardpan layer possesses a highly compacted texture, a low-percolating pore network, and extreme resistance to water movement in the hardpan horizon. Further, the hardpans directly interfacing with plant roots in the soil cover were geochemically stabilised and attenuated, with very low levels of soluble metal(loid)s and a circumneutral pH condition. This case study would serve as a good incentive to develop bio-chemical engineering methodology building on current knowledge for achieving sustainable rehabilitation of sulfidic and metallic tailings in future.

开发替代方法来限制和恢复大面积尾矿景观对于采矿业的可持续发展至关重要。这项研究揭示了原位硬质复相土壤系统作为一种非常规方法来修复硫化铜-铅-锌尾矿的潜力。在浅层硅质土壤覆盖下，原位形成了巨大而一致的硬质层在整个试验区尾矿的表层，将根区（即硅土覆盖层）与下面未风化的尾矿物理分离，防止酸性和可溶性溶质通过毛细管富集到根区，并维持原生植物的生长十多年。富硅铁配合物的沉淀归因于硫化尾矿的稳定/固化。硬质层具有高度致密的质地、低渗透的孔隙网络和对硬质层中水运动的极强抵抗力。此外，与土壤覆盖中植物根部直接接触的硬质盘在地球化学上得到稳定和减弱，可溶性金属（类）含量非常低，pH 值处于中性水平。