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<p>Atmospheric CO₂ concentration is rising at an unprecedented rate, posing a multifaceted challenge to global agricultural ecosystems and food security. This short-term pot study, using two rice cultivars grown in soils with three cadmium (Cd) levels under ambient and elevated CO₂ conditions, demonstrated how elevated CO₂ (eCO₂, 620&#xa0;ppm) influenced Cd bioavailability in paddy soils. The results showed that eCO₂ enhanced rice biomass by up to 27.05%, increased soil dissolved organic carbon (DOC) concentrations by 8.54%–20.51%, and induced soil acidification. Spectral analyses revealed that eCO₂ shifted dissolved organic matter (DOM) composition toward greater aromaticity and humification. These changes were closely associated with Cd mobilization: eCO₂ significantly elevated the concentrations of diethylenetriaminepentaacetic acid-extractable cadmium (DTPA-Cd) by 13.49%–23.91% and increased DOM-complexed Cd, leading to a 4.44%–23.84% increase in root Cd accumulation. Strong positive correlations between DOM aromaticity indices and total Cd or Cd fraction content, together with a significant negative correlation between soil pH and total Cd or Cd fraction content, indicated that the joint effects of soil acidification and modified DOM characteristics were important drivers of enhanced Cd mobility and bioavailability under eCO₂. These findings highlight an increased risk of Cd uptake by rice under future climate conditions.</p>

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Elevated CO₂ Increases Cadmium Bioavailability in Paddy Soils via Soil Acidification and DOM Transformation

  • 期刊论文

  • 发表日期：

    2026年4月29日

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  • Hongyan Yu,
  • Zuyu An,
  • Xulei Geng,
  • Yunlong Han,
  • Jinyan Lan,
  • Yanxun Qiu,
  • Xuejia Bai,
  • Xingchen Hao,
  • Yue Teng

摘要

Atmospheric CO₂ concentration is rising at an unprecedented rate, posing a multifaceted challenge to global agricultural ecosystems and food security. This short-term pot study, using two rice cultivars grown in soils with three cadmium (Cd) levels under ambient and elevated CO₂ conditions, demonstrated how elevated CO₂ (eCO₂, 620 ppm) influenced Cd bioavailability in paddy soils. The results showed that eCO₂ enhanced rice biomass by up to 27.05%, increased soil dissolved organic carbon (DOC) concentrations by 8.54%–20.51%, and induced soil acidification. Spectral analyses revealed that eCO₂ shifted dissolved organic matter (DOM) composition toward greater aromaticity and humification. These changes were closely associated with Cd mobilization: eCO₂ significantly elevated the concentrations of diethylenetriaminepentaacetic acid-extractable cadmium (DTPA-Cd) by 13.49%–23.91% and increased DOM-complexed Cd, leading to a 4.44%–23.84% increase in root Cd accumulation. Strong positive correlations between DOM aromaticity indices and total Cd or Cd fraction content, together with a significant negative correlation between soil pH and total Cd or Cd fraction content, indicated that the joint effects of soil acidification and modified DOM characteristics were important drivers of enhanced Cd mobility and bioavailability under eCO₂. These findings highlight an increased risk of Cd uptake by rice under future climate conditions.