Phosphate treatment alleviated acute phytotoxicity of heavy metals in sulfidic Pb-Zn mine tailings. (July 2019)

• Record Type: Journal Article
• Authors: Saavedra-Mella, Felipe; Liu, Yunjia; Southam, Gordon; Huang, Longbin
• Is Part Of: Environmental pollution. Volume 250(2019)
• Page Start: 676
• Page End: 685
• Publication Date: 2019-07
• Subjects: Phytostabilisation -- Zn-phosphate -- Hydrogeochemical stabilization -- Sulfidic Pb-Zn tailings -- Native plants; Pollution -- Periodicals; Pollution -- Environmental aspects -- Periodicals; Environmental Pollution -- Periodicals; Pollution -- Périodiques; Pollution -- Aspect de l'environnement -- Périodiques; Pollution -- Effets physiologiques -- Périodiques; Pollution; Pollution -- Environmental aspects; Periodicals; Electronic journals; 363.73
• DOI: 10.1016/j.envpol.2019.04.100
• Languages: English
• ISSNs: 0269-7491

Abstract

Abstract: 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., K2 HPO4 ) 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 K2 HPO4 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 K2 HPO4 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. Graphical abstract: Image 1 Highlights: Soluble phosphate alleviated acute phytotoxicity of sulfidic PbZn tailings. Cd, Pb, Zn solubility was lowered by formation of sparingly soluble metal-phosphate minerals. Organic amendment of sulfidic PbZn tailings was ineffective in lowering Cd, Pb and Zn solubility. Soluble phosphate treatment may be optimized to manage geochemical risks of sulfidic tailings.