The odor nuisance of urban surface water after rainfall events has aroused public concerns and threaten the aquatic organisms. Herein, the first study to investigate 150 odorants in storm sewer discharge was performed in humid regions of China. During rainfall events, the total concentrations of odorants at storm sewer outlet increased by 1.3–2.1 fold from 1.7–9.4 μg/L to 2.1–20.0 μg/L with 37 odorants having detection frequencies above 50 % on rainy days, and the concentrations of total odorants in air also significantly increased resulting in worse odor nuisance. The accumulation of odorants in sewer sediment and the remobilization of sewer sediment were factors resulting in more intensified emission of odorants from storm sewer on rainy days. More than half of odorants discharged during rainfall were contributed by sewer sediment. Thioethers, indoles, 2-isopropyl-3‑methoxy pyrazine, acetophenone and coumarin exhibited high sediment-accumulation. Quantitative structure-property relationship models revealed that enhanced sediment-accumulation of chained aliphatic and aromatic odorants can be explained by the electrostatic attraction and topological characteristic, respectively. The multicriteria analysis was further introduced for relative odorants ranking by considering the variations in hazard criteria of environmental occurrence, ecotoxicity, persistence, odor nuisance and sediment accumulation. Among priority odorants, thioethers and indoles were attributed by their distinct sediment-accumulation and odor nuisance potential, while chlorinated anisole and pinenes prioritized due to their higher ecotoxicity. These findings provide novel insights into the odorants from storm sewer discharges and explore the environmental behaviors of odorants in sewer sediment.

The illicit connections between sewage and stormwater pipes result in the discharge of untreated sewage into receiving rivers, posing significant odor and health hazards. While thioethers are recognized as key odorants in sewage systems, their distribution in stormwater systems remain poorly characterized. This study analyzed 12 types of thioethers in stormwater pipes sampled at 21 sites in China. Advanced analytical techniques, including Mantel analysis and Structural Equation Modeling, were employed to examine the relationships between overlying water properties, sediment microbial characteristics, and thioether concentrations. Results showed that sediment thioether loads (36.77 ± 50.14 μg S/m; range: 7.24–99.96 μg S/m) were substantially higher than those in the overlying water (12.02 ± 42.52 μg S/m; range: 0.03–92.76 μg S/m), highlighting sediment as a critical pollution reservoir. Dissolved oxygen, NH₃-N, and terrestrial-derived dissolved organic nitrogen were identified as key factors shaping sediment microbiome composition, particularly fermentative, sulfate-reducing, and denitrifying bacteria, which in turn drives thioether formation. Specifically, dominant compounds like dimethyl disulfide and dimethyl trisulfide were found to be produced through the anaerobic fermentation of methionine and redox conversion of methanethiol, as well as the anaerobic fermentation of cysteine and methylation of polysulfides. Humic substances could facilitate methanethiol redox conversion and polysulfide methylation by serving as methyl donors and enhancing electron transfer efficiency. Additionally, NH₃-N may promote microbial metabolism by providing amino groups essential for the synthesis of metabolic precursors. Therefore, effective mitigation of odorous thioethers in stormwater systems necessitates integrated strategies targeting both sulfur-containing organic precursors and nitrogen-rich pollutants.