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Background and aims <p>Cadmium (Cd), a highly mobile trace metal in paddy soils, is readily absorbed and translocated by rice, resulting in elevated grain Cd accumulation and increased dietary risk. Although lime application is widely employed to immobilize Cd, its efficacy under heterogeneous chloride (Cl⁻) backgrounds in soil remains poorly constrained.</p> Methods <p>Experiments were conducted in two field sites to investigate the role of soil Cl⁻ as a key determinant of amendment performance in stabilizing Cd along the soil–root–grain continuum.</p> Results <p>Under low-Cl⁻ regimes, lime application elevated soil pH by 0.63 units and reduced diethylenetriaminepentaacetic acid (DTPA)-extractable soil Cd by 20–57%, whereas high-Cl⁻ conditions restricted alkalization to 14.8% and DTPA-extractable Cd reductions to 15–30%, owing to Cl⁻-induced acidification and the formation of stable soluble Cd–Cl complexes that weakened chemical immobilization. Elevated Cl⁻ further curtailed iron plaque formation by 19.2–41.7%, compromising its capacity as a crucial apoplastic barrier. At the molecular scale, high Cl⁻ markedly upregulated <i>OsNramp1</i>, <i>OsNramp5</i>, and <i>OsHMA2</i>, enhancing root Cd uptake and internal transport, consistent with the pronounced inward Cd<sup>2</sup>⁺ flux observed in cultivar YX2292. Moreover, under high-Cl⁻ conditions, transfer factors across different rice tissues of rice tissues were increased, highlighting Cl⁻-mediated amplification of root-to-shoot Cd transfer. Collectively, these results demonstrated Cl⁻ as a key determinant of Cd behavior and uptake in paddy systems, emphasizing the importance of considering soil Cl⁻ levels when implementing lime amendments for effective and sustainable Cd risk mitigation.</p> Graphical Abstract <p></p>

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Chloride attenuates lime-induced cadmium immobilization in the soil-rice system

  • 期刊论文

  • 发表日期：

    2026年7月11日

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  • Jingxia Guo,
  • Madinai Abulimiti,
  • Yuqing Wu,
  • Chenghao Ge,
  • Dongmei Zhou,
  • Yanhui Chen

摘要

Background and aims

Cadmium (Cd), a highly mobile trace metal in paddy soils, is readily absorbed and translocated by rice, resulting in elevated grain Cd accumulation and increased dietary risk. Although lime application is widely employed to immobilize Cd, its efficacy under heterogeneous chloride (Cl⁻) backgrounds in soil remains poorly constrained.

Methods

Experiments were conducted in two field sites to investigate the role of soil Cl⁻ as a key determinant of amendment performance in stabilizing Cd along the soil–root–grain continuum.

Results

Under low-Cl⁻ regimes, lime application elevated soil pH by 0.63 units and reduced diethylenetriaminepentaacetic acid (DTPA)-extractable soil Cd by 20–57%, whereas high-Cl⁻ conditions restricted alkalization to 14.8% and DTPA-extractable Cd reductions to 15–30%, owing to Cl⁻-induced acidification and the formation of stable soluble Cd–Cl complexes that weakened chemical immobilization. Elevated Cl⁻ further curtailed iron plaque formation by 19.2–41.7%, compromising its capacity as a crucial apoplastic barrier. At the molecular scale, high Cl⁻ markedly upregulated OsNramp1, OsNramp5, and OsHMA2, enhancing root Cd uptake and internal transport, consistent with the pronounced inward Cd2⁺ flux observed in cultivar YX2292. Moreover, under high-Cl⁻ conditions, transfer factors across different rice tissues of rice tissues were increased, highlighting Cl⁻-mediated amplification of root-to-shoot Cd transfer. Collectively, these results demonstrated Cl⁻ as a key determinant of Cd behavior and uptake in paddy systems, emphasizing the importance of considering soil Cl⁻ levels when implementing lime amendments for effective and sustainable Cd risk mitigation.

Graphical Abstract