Spatiotemporal Heterogeneity of Redox Characteristics and Molecular Assembly Mechanisms of Dissolved Organic Matter during Landfill Stabilization: Insights from Integrated Molecular and Ecological Models.

As the most mobile and reactive organic fraction, the spatiotemporal evolution of dissolved organic matter (DOM) governs the stabilization of municipal solid waste landfills and critically regulates their ecological risk trajectories. However, the spatiotemporal heterogeneity in molecular assembly mechanisms and redox characteristics of DOM remains unclear, hindering the mechanistic understanding of landfill stabilization. Here, we develop a novel molecular modeling approach integrated with an ecological model to elucidate DOM molecular chemical heterogeneity, redox properties, and assembly dynamics across 20 year landfill layers. Ar-OH, quinone, Ar-COO-, Ar-SH, and Ar-NH2 are key redox sites. The enhanced electron transfer capacity of DOM during stabilization arises from synergistic electronic-structural interactions throughout its entire molecular framework rather than isolated redox sites, including ortho-positioned -NH2 and -OH, electron-withdrawing -COO- and electron-donating -OH adjacent to -SH on benzene rings, and π-π stacking. Molecules containing multiple redox sites and featuring extensively π-conjugated systems play a crucial role in enhancing the long-term stability of landfills. Ecological models revealed that stochastic processes dominate DOM molecular dynamics (>90%), while deterministic processes slightly strengthened with the stabilization process (from 8.55% to 9.18%), governing its chemical and redox properties. This research advances molecular-level insights into waste stabilization processes that will inform refined waste management strategies to mitigate landfill ecological impacts.