Phytoremediation of Uranium-238 and Thorium-232 in Contaminated Soils Using Native Dryland Shrubs

Introduction: This study investigated the phytoremediation potential of Atriplex canescens, Haloxylon aphyllum, and Nitraria schoberi for decontaminating soil polluted with radioactive elements. Materials and Methods: Contaminated soil was collected from a uranium mine site. Compost and sawdust were used as soil amendments. Radionuclide activities and concentrations were determined using gamma spectrometry and ICP-MS. Results: H. aphyllum demonstrated the highest uptake of radioactive elements, accumulating 58 mg.kg-1 of Th-232 and 28.08 mg.kg-1 of U-238, respectively. Considering their initial concentrations, the thorium removal efficiency was higher than that of uranium, with a maximum of 85% for Th-232 achieved by H. aphyllum. Plant roots accumulated higher concentrations of radionuclides than the stems. A comparison of phytoremediation factors (TF, BAF, and BCF) indicated that H. aphyllum had a greater stabilization potential than the other two species. Furthermore, phytoextraction was identified as the dominant remediation mechanism. Conclusion: Compost application enhanced the phytostabilization potential of all three plants (e.g., as indicated by the increase in BCF, which reached a maximum of 0.45 for H. aphyllum). In contrast, sawdust had an inhibitory effect, likely due to the disruption of the C/N ratio, which prevented plant growth. H. aphyllum showed significant potential for radioactive soil rehabilitation, particularly when it was amended with compost.