[Molecular Chemo-diversity of the Dissolved Organic Matter Occurring in Urban Stormwater Runoff]

Stormwater runoff pollution occurring in urban areas can be a notable threat to the ecological environments of receiving water bodies. Dissolved organic matter (DOM) constitutes the primary type of pollutant in stormwater runoff, and tracking of its components and sources can provide valuable scientific bases for the future abatement of stormwater runoff pollution. In this study, aiming to demonstrate the characteristics and sources of the contained DOM in both pavement runoff (PR) and greenland runoff (GR), we applied ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to analyze the molecular chemo-diversity of their DOM, as well as Spearman rank correlations between the molecular chemo-diversity and water quality indicators including suspended solids (SS), total nitrogen (TN), dissolved organic carbon (DOC), and dissolved lead (Pb). The results show:① When the molecular accumulation reaches a saturated state, the cumulative number of molecules of PR-DOM (12498) is much larger than that of GR-DOM (7015). The molecular distribution of PR-DOM (150-750) is smaller yet more concentrated than that of GR-DOM (150-850). ② According to the molecular composition characterization and Spearman rank correlation analysis, the sources of the components of PR-DOM and GR-DOM are remarkably different. PR-DOM can be greatly influenced by human activities, and its primary element component (CHOS) contains a large number of substances that were recognized to be from the surfactant sulfonic acid. Additionally, the significant aliphatic components that emerged were from traffic pollution. In contrast, GR-DOM is less affected by human activities, and its primary element component (CHO) gives priority to natural organic matter (NOM). The most abundant substance component that occurred in GR-DOM, i.e., the highly unsaturated and phenolic compound that generally originates in the degraded humus, is initially formed by the plant residue and flushed by rainfall runoff.