Sustainable Minerals Institute, The University of Queensland, Brisbane, Queensland, 4072, Australia.
School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.
Environ Pollut. 2019 Jul;250:676-685. doi: 10.1016/j.envpol.2019.04.100. Epub 2019 Apr 22.
Phytostabilization of sulfidic PbZn tailing landscapes may be one of interim options of tailings management, but which is limited by acute phytotoxicity of heavy metals in the tailings. The present study aimed to investigate the effectiveness of soluble phosphate (i.e., KHPO) in immobilizing soluble Pb, Cd and Zn and lowering their acute phytotoxicity. The addition of soluble phosphate improved the growth of native plants Acacia chisholmii and survival rate of A. ligulata, where the latter exhibited 100% survival rate. This was in contrast to effects of conventional organic amendment in the tailings on metal solubility (e.g., elevated metal levels in porewater) and plant survival (e.g., only 42%). Organic amendment with mulch did not lower the levels of water-soluble Cd, Pb and Zn and their concentrations in plant tissues after 56 days of plant growth in the treatment. In contrast, the tailings amended with KHPO significantly decreased metal concentrations in the porewater and plant tissues by about 80-92% and 56-88%, respectively. The metal immobilization by phosphate was due to the formation of insoluble or sparingly soluble metal (Pb, Cd and Zn)-phosphate minerals in the tailings with circumneutral pH conditions, as revealed by using X-ray diffraction and scanning electron microanalyses. The reduced metal concentrations in roots and shoots of Acacia species after direct root contact with the KHPO amended tailings suggested that metals (i.e., Pb, Cd and Zn) were effectively immobilized by the phosphate treatment of the tailings. These findings indicate that addition of high dosage of soluble phosphate may provide a low cost option to treat sulfidic PbZn tailings for rapid phytostabilization of the tailings surface, as an interim option to manage environmental risks of sulfidic PbZn tailings.
硫化物 PbZn 尾矿景观的植物稳定化可能是尾矿管理的临时选择之一，但受到尾矿中重金属的急性植物毒性的限制。本研究旨在探讨可溶性磷酸盐（即 KHPO）在固定可溶性 Pb、Cd 和 Zn 并降低其急性植物毒性方面的有效性。添加可溶性磷酸盐可改善本地植物金合欢（Acacia chisholmii）的生长和金合欢（A. ligulata）的存活率，后者的存活率达到 100%。这与传统有机改良剂在尾矿中对金属溶解度（例如，孔隙水中金属水平升高）和植物存活率（例如，仅 42%）的影响形成对比。有机改良剂加覆盖物并不能降低 56 天植物生长处理后孔隙水中和植物组织中可溶 Cd、Pb 和 Zn 的水平及其浓度。相比之下，KHPO 改良的尾矿显著降低了孔隙水和植物组织中金属的浓度，分别约为 80-92%和 56-88%。在 pH 值接近中性的条件下，磷酸盐在尾矿中形成了不溶性或难溶性金属（Pb、Cd 和 Zn）-磷酸盐矿物，从而固定了金属，这是通过 X 射线衍射和扫描电子微分析揭示的。在直接与 KHPO 改良的尾矿接触后，金合欢属植物的根和茎中的金属浓度降低，表明金属（即 Pb、Cd 和 Zn）通过磷酸盐处理有效地固定在尾矿中。这些发现表明，添加高剂量的可溶性磷酸盐可能为处理硫化物 PbZn 尾矿提供一种低成本的选择，以便快速稳定尾矿表面，作为管理硫化物 PbZn 尾矿环境风险的临时选择。
