Currently, urban wet weather overflow pollution has become one of the key factors restricting the improvement of urban water environment quality. Conducting research on the traceability of overflow pollution is of great significance for revealing the output patterns of pollutants and achieving precise control of overflow pollution. This study systematically monitored the overflow sewage at an overflow outlet of the Qinghe River in Beijing and the surface runoff in the nearby area in July 2024. Three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) combined with parallel factor analysis (PARAFAC) was employed to trace the sources of dissolved organic matter (DOM) in the overflow sewage. The results indicate that the pollutant concentration in surface runoff is higher than that in overflow sewage at the initial stage of rainfall. However, as the rainfall continues, the pollutant concentration in surface runoff gradually decreases and eventually becomes lower than that in overflow sewage. Three fluorescent components are detected in the overflow sewage, namely, the fulvic acid-like component C1, the mixed component C2 of aromatic protein-like substances and humic acid-like substances, and the tyrosine-like component C3, accounting for 37.20%, 49.29%, and 13.51% of the total fluorescent components, respectively. The traceability analysis further reveals that pipeline sediments contribute the most to the DOM in overflow sewage, representing its primary source.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |