Component changes of dissolved organic matter during organic materials decomposition and their comple-xation with cadmium.

Dissolved organic matter (DOM) released from organic materials plays a vital role in regulating soil ecological functions and remediating heavy metal contamination. We conducted a 120-day decomposition experiment with three types of organic materials, including composted pig manure, corn stover, and biochar. Using three-dimensional fluorescence spectroscopy and parallel factor analysis (EEM-PARAFAC), we analyzed the compositional change of DOM during decomposition and its complexation characteristics with Cd. Results showed that the DOM content of all materials decreased over time and stabilized after 28 days. Throughout the experiment, the DOM content of the corn stover treatment remained significantly higher than other two types. The humification index (HIX) of DOM from all materials positively correlated with decomposition time, with the HIX of corn stover, biochar, and composted pig manure being increased by 50.0%, 6.3%, and 24.5% after 120 days, respectively. Biochar DOM was primarily composed of fulvic acid-like (C2, accounting for 24.0%-29.0%) and humic acid-like (C3, accounting for 52.0%-60.0%) components, while composted pig manure and corn stover DOM were dominated by protein-like components (C1, accounting for 47.0%-63.0% and 44.0%-52.0%, respectively) during the first 28 days and shifted to C2 and C3 components thereafter. EEM-PARAFAC and Ryan-Weber model analysis revealed that the complexation capacity of DOM with Cd followed the order: corn stover > composted pig manure > biochar, with C2 components playing a dominant role. At 28 days of incubation, corn stover DOM exhibited the strongest complexation capacity with Cd. In summary, compared to composted pig manure and biochar, corn stover decomposed for 28 days demonstrated potential advantages in remediating Cd-contaminated soils.