Three years of elevated [CO2] reduce cadmium bioavailability in contaminated paddy soils by modifying dissolved organic matter

Background and aim

Elevated atmospheric CO (eCO ) and cadmium (Cd) contamination collectively threaten rice safety and soil ecosystem stability. Soil dissolved organic matter (DOM), a critical mediator of biogeochemical processes, regulates heavy metal mobility and bioavailability, yet the interplay between eCO and Cd pollution on DOM dynamics remains unclear, particularly regarding its implications for Cd bioavailability under future climate scenarios.

Methods

We employed a series of characterization techniques, along with Pearson correlation analysis, to explore the impact of eCO on the content and structure of DOM in Cd-contaminated paddy soil, as well as the correlation between the molecular composition of DOM and the bioavailability of Cd.

Results

The research findings show that eCO increased the concentration of DOC by 25.58% and 7.04% in low and high Cdcontaminated paddy soil, respectively. In addition, eCO increased the aromaticity, hydrophobicity, and humicity of DOM in low Cd-contaminated paddy soils by about 3.84%, 5.07%, and 5.12%, respectively. Exposure to eCO resulted in a 2.56% decrease in C1cotent, an 18.30% increase in C2 content and complicated DOM structure. In high Cd-contaminated soils, the structure of DOM becomesbecame relatively simpler. Correlation analysis further revealed that the increased complexity of DOM could reduce the bioavailability of Cd.

Conclusion

Three years of eCO reduced cadmium bioavailability in contaminated paddy soils by modifying dissolved organic matter. This will contribute to a better understanding of rice Cd uptake under future climate conditions, thus promoting the development of climate-crop-soil models and the accurate prediction of food security.