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<p>This study systematically evaluated the performance and underlying mechanisms of chitosan-functionalized biochar in arsenic (As)-contaminated soil–rice systems, with particular emphasis on the effects of natural aging. Specifically, four biochar-based amendments were prepared: fresh biochar (BC), chitosan-functionalized biochar (CBC), naturally aged biochar (NBC), and naturally aged chitosan-functionalized biochar (NCBC). Chitosan functionalization and natural aging collectively increased the abundance of oxygen/nitrogen-containing functional groups (e.g., C = O and N–H/O–H) and modified biochar surface properties. The CBC decreased soil-available As by 21.1%, whereas BC and NBC increased As bioavailability in soils. Notably, both CBC and NCBC decreased As accumulation in rice roots (48.1% vs. 37.1%) and grains (43.1% vs. 32.8%) compared to the control. Subcellular fractionation showed that both CBC and NCBC enhanced As sequestration in root and leaf cell walls, while reducing its distribution in soluble fractions and organelles. Micro-X-ray fluorescence (μ-XRF) analysis showed strong spatial As–Fe co-localization, indicating that Fe-mediated sequestration was associated with As stabilization, particularly for aged chitosan-functionalized biochar. Additionally, chitosan-functionalized biochars reduced the levels of glutathione and proline while increasing low-molecular-weight organic acids. Structural equation modeling suggested root architecture as an important factor in rice growth, and implied that As-induced root impairment may represent a pathway linking As stress to yield reduction. While natural aging attenuated CBC’s As immobilization performance in soils, the material maintained a significant ability to promote root growth, modulate phytohormones, and control As uptake. These findings suggest that chitosan-functionalized biochar may serve as a promising approach for mitigating As contamination in paddy soils, warranting further field-scale validation.</p> Graphical Abstract <p></p>

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Chitosan-functionalized biochar modulates arsenic speciation, distribution, and stress tolerance during rice growth in contaminated paddy systems: role of natural aging

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月9日

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  • Meng Li,
  • Jianhong Li,
  • Hongni Xiong,
  • Jiayi Li,
  • Xiaokai Zhang,
  • Williamson Gustave,
  • Weijie Xu,
  • Lizhi He,
  • Xing Yang,
  • Shengdao Shan,
  • Hanbo Chen,
  • Xu Yang,
  • Hailong Wang

摘要

This study systematically evaluated the performance and underlying mechanisms of chitosan-functionalized biochar in arsenic (As)-contaminated soil–rice systems, with particular emphasis on the effects of natural aging. Specifically, four biochar-based amendments were prepared: fresh biochar (BC), chitosan-functionalized biochar (CBC), naturally aged biochar (NBC), and naturally aged chitosan-functionalized biochar (NCBC). Chitosan functionalization and natural aging collectively increased the abundance of oxygen/nitrogen-containing functional groups (e.g., C = O and N–H/O–H) and modified biochar surface properties. The CBC decreased soil-available As by 21.1%, whereas BC and NBC increased As bioavailability in soils. Notably, both CBC and NCBC decreased As accumulation in rice roots (48.1% vs. 37.1%) and grains (43.1% vs. 32.8%) compared to the control. Subcellular fractionation showed that both CBC and NCBC enhanced As sequestration in root and leaf cell walls, while reducing its distribution in soluble fractions and organelles. Micro-X-ray fluorescence (μ-XRF) analysis showed strong spatial As–Fe co-localization, indicating that Fe-mediated sequestration was associated with As stabilization, particularly for aged chitosan-functionalized biochar. Additionally, chitosan-functionalized biochars reduced the levels of glutathione and proline while increasing low-molecular-weight organic acids. Structural equation modeling suggested root architecture as an important factor in rice growth, and implied that As-induced root impairment may represent a pathway linking As stress to yield reduction. While natural aging attenuated CBC’s As immobilization performance in soils, the material maintained a significant ability to promote root growth, modulate phytohormones, and control As uptake. These findings suggest that chitosan-functionalized biochar may serve as a promising approach for mitigating As contamination in paddy soils, warranting further field-scale validation.

Graphical Abstract