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<p>Uranium-cadmium (U-Cd) co-contamination is prevalent in uranium mining and tailings-impacted regions and represents a persistent environmental concern due to the high mobility, long-term persistence, and combined toxicity of these metals. Although phytoremediation has been widely applied to mitigate uranium pollution, the post-harvest fate of metal-enriched plant residues remains insufficiently understood, particularly with respect to secondary uranium remobilization during decomposition. In this study, <i>Syngonium podophyllum</i> (SP), a plant species with documented uranium tolerance and accumulation capacity, was used to investigate residue decomposition dynamics and U-Cd release behavior under single and combined contamination conditions. A 128d litterbag decomposition experiment was conducted under controlled conditions. Biomass loss, nutrient release, soil physicochemical properties, uranium speciation, and microbial community structure were systematically quantified. Exposure to high uranium concentration (20&#xa0;mg/L) significantly suppressed early-stage decomposition, reducing the initial mass loss rate by approximately 15% relative to the control. Both uranium and cadmium inhibited nutrient release, with cumulative release rates of C, N, P, and K decreasing by 10–25%. Notably, cadmium co-contamination enhanced uranium remobilization, increasing the uranium release rate from 70.4 ± 3.2% under uranium-only conditions to 75.42 ± 2.8% under combined U-Cd exposure. Sequential extraction revealed a pronounced shift in soil uranium speciation following residue decomposition, characterized by increases in organically bound and labile uranium fractions. Concurrently, microbial community analysis indicated substantial restructuring under metal stress, with marked enrichment of metal-tolerant taxa, particularly Proteobacteria (32.61–55.88%) and Firmicutes (7.00–47.19%). These results demonstrate that decomposition of phytoremediation residues under U-Cd co-contamination can substantially enhance uranium mobility through coupled microbial activity and speciation transformation. The findings highlight the necessity of post-harvest biomass management strategies to mitigate secondary uranium contamination and ensure the long-term effectiveness of phytoremediation in uranium-impacted environments.</p>

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Characterization of Plant Residue Decomposition and Uranium Release from U–Cd-Contaminated Plants

  • 期刊论文

  • 发表日期：

    2026年4月1日

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  • Han jiangyue,
  • Zhang haojie,
  • Tan jinlong,
  • Xie yuqi,
  • Chen binbin,
  • Deng qinwen

摘要

Uranium-cadmium (U-Cd) co-contamination is prevalent in uranium mining and tailings-impacted regions and represents a persistent environmental concern due to the high mobility, long-term persistence, and combined toxicity of these metals. Although phytoremediation has been widely applied to mitigate uranium pollution, the post-harvest fate of metal-enriched plant residues remains insufficiently understood, particularly with respect to secondary uranium remobilization during decomposition. In this study, Syngonium podophyllum (SP), a plant species with documented uranium tolerance and accumulation capacity, was used to investigate residue decomposition dynamics and U-Cd release behavior under single and combined contamination conditions. A 128d litterbag decomposition experiment was conducted under controlled conditions. Biomass loss, nutrient release, soil physicochemical properties, uranium speciation, and microbial community structure were systematically quantified. Exposure to high uranium concentration (20 mg/L) significantly suppressed early-stage decomposition, reducing the initial mass loss rate by approximately 15% relative to the control. Both uranium and cadmium inhibited nutrient release, with cumulative release rates of C, N, P, and K decreasing by 10–25%. Notably, cadmium co-contamination enhanced uranium remobilization, increasing the uranium release rate from 70.4 ± 3.2% under uranium-only conditions to 75.42 ± 2.8% under combined U-Cd exposure. Sequential extraction revealed a pronounced shift in soil uranium speciation following residue decomposition, characterized by increases in organically bound and labile uranium fractions. Concurrently, microbial community analysis indicated substantial restructuring under metal stress, with marked enrichment of metal-tolerant taxa, particularly Proteobacteria (32.61–55.88%) and Firmicutes (7.00–47.19%). These results demonstrate that decomposition of phytoremediation residues under U-Cd co-contamination can substantially enhance uranium mobility through coupled microbial activity and speciation transformation. The findings highlight the necessity of post-harvest biomass management strategies to mitigate secondary uranium contamination and ensure the long-term effectiveness of phytoremediation in uranium-impacted environments.