Insight into Redox Sites and Intermolecular Interactions of Soil Dissolved Organic Matter through Diverse-Compost Applications Using VSOMM2 and Schrödinger

Substituting chemical fertilizers with compost is anticipated to facilitate the disposal of organic waste and mitigate nonpoint source pollution. However, research investigating the impact of diverse-compost utilization on the chemical reactivity of soil at the molecular-level remains lacking. Herein, the quantification and identification of molecular-scale redox sites and intermolecular interactions of soil dissolved organic matter (DOM) using diverse composts during a crop rotation cycle were investigated using the unified theoretical modeling approach VSOMM2 and Schrödinger. Results showed that compost use considerably altered the molecular weight and composition of soil DOM. In particular, we successfully optimized the validity coefficient of the unit model's molecular number to construct 38 molecular models of DOM molecules to identify and quantify the distribution of redox sites and intermolecular interactions within soil DOM molecules. Moreover, the distinct roles of different composts in modulating redox molecules within the soil DOM were determined during a crop rotation cycle. The application of cow manure compost considerably increased the quinone, Ar–COOH, and Ar–SH contents in Model(EAC+), while application of food waste compost enhanced the Ar–OH and Ar–NH2 in Model(EDC+). Finally, rotatable bonds, cation−π interactions, aromatic H-bonds, π-stacking, and salt bridges were identified to facilitate electron transfer within the redox molecules of soil DOM, which can be further enhanced via compost use. The findings of this study provide insights into the environmental biochemical reactions involving microcatalysts, metal reduction fate, pollution fate, and molecular composition of soil, providing a theoretical basis for enhancing soil reactivity using organic fertilizers instead of chemical fertilizers.