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Background and aims <p>The escalating climate crisis demands innovative carbon dioxide removal strategies, with biochar and enhanced rock weathering (ERW) emerging as promising carbon-negative solutions. However, their contrasting effects on iron (Fe) (hydr)oxide-organic carbon (OC) interactions, a key mechanism underlying mineral-mediated C persistence, remain poorly understood.</p> Methods <p>A pot experiment examined the effects of biochar and enhanced basalt weathering alone and in combination on Fe oxide phases, C-binding capacity, Fe-complexed OC characteristics, and shifts in Fe-oxidising and reducing microbial communities via 16S rRNA sequencing in a paddy soil.</p> Results <p>The Biochar and the Dual treatments consistently transformed Fe mineral, reducing organo-complexed Fe (Fe<sub>PP</sub>) by 26%–29%, while increasing amorphous Fe by 22%–41%. These shifts elevated C bound to Fe<sub>PP</sub> by 25%–28% with reduced aromaticity and the OC-to-Fe molar ratio by 73%–76%. Basalt alone generated the highest Fe-bound OC fraction (Fe-OC%, 26.2%), where biochar maximised SOC (+ 61%) but diluted Fe-OC% (16.6%). The Dual treatment enriched Fe-cycling bacteria, most notably stimulating <i>Geobacter</i> (21-fold) and <i>Desulfosporosinus</i> (&gt; 120%), and achieved the highest Fe-OC% (27.6%) after adjusting for biochar-C inputs.</p> Conclusion <p>The findings demonstrated that biochar prioritised SOC quantity and stability via direct recalcitrant C retention and stabilisation of labile C on residual Fe (hydr)oxides, while ERW enhanced Fe-bound OC persistence through organo-mineral associations without C gain. The strategic integration of biochar and basalt enhances both C stocks and stability, offering a practical route to improve C sequestration in anaerobic agroecosystems.</p>

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Microbial-driven iron transformation and carbon stabilisation in flooded soils: roles of biochar and rock weathering

  • 期刊论文

  • 发表日期：

    2025年12月11日

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  • Qiao Xu,
  • Gefeng Zhang,
  • Feifan Zhang,
  • Tharanga Bandara,
  • Hongyan Guo,
  • Meiling Xu,
  • Caixian Tang

摘要

Background and aims

The escalating climate crisis demands innovative carbon dioxide removal strategies, with biochar and enhanced rock weathering (ERW) emerging as promising carbon-negative solutions. However, their contrasting effects on iron (Fe) (hydr)oxide-organic carbon (OC) interactions, a key mechanism underlying mineral-mediated C persistence, remain poorly understood.

Methods

A pot experiment examined the effects of biochar and enhanced basalt weathering alone and in combination on Fe oxide phases, C-binding capacity, Fe-complexed OC characteristics, and shifts in Fe-oxidising and reducing microbial communities via 16S rRNA sequencing in a paddy soil.

Results

The Biochar and the Dual treatments consistently transformed Fe mineral, reducing organo-complexed Fe (FePP) by 26%–29%, while increasing amorphous Fe by 22%–41%. These shifts elevated C bound to FePP by 25%–28% with reduced aromaticity and the OC-to-Fe molar ratio by 73%–76%. Basalt alone generated the highest Fe-bound OC fraction (Fe-OC%, 26.2%), where biochar maximised SOC (+ 61%) but diluted Fe-OC% (16.6%). The Dual treatment enriched Fe-cycling bacteria, most notably stimulating Geobacter (21-fold) and Desulfosporosinus (> 120%), and achieved the highest Fe-OC% (27.6%) after adjusting for biochar-C inputs.

Conclusion

The findings demonstrated that biochar prioritised SOC quantity and stability via direct recalcitrant C retention and stabilisation of labile C on residual Fe (hydr)oxides, while ERW enhanced Fe-bound OC persistence through organo-mineral associations without C gain. The strategic integration of biochar and basalt enhances both C stocks and stability, offering a practical route to improve C sequestration in anaerobic agroecosystems.