In this study, Jiangmen City was selected as a case study to investigate the characteristics and causes of heavy ozone(O3)pollution days. Positive Matrix Factorization(PMF)and an observation-based model coupled with the CB06chemical mechanism(OBM-CB06)were employed as the analytical methods, integrating pollutant concentrations, meteorological data, photolysis data, and volatile organic compound(VOC)concentrations. The findings showed that heavy ozone pollution in Jiangmen resulted primarily from the early morning accumulation of precursors due to meteorological conditions, followed by enhanced photochemical reactions and poor dispersion after the O3 concentration peaked. Notably, early morning concentrations of nitrogen oxides(NOx)and carbon monoxide(CO)in Jiangmen were significantly higher than those in surrounding cities. VOCs source apportionment revealed that mobile sources(29.91% to 31.25%)and liquefied petroleum gas(LPG)usage(28.8% to 30.73%)were the major contributors. O3 sensitivity analysis demonstrated that O3 formation in Jiangmen was predominantly NOx-sensitive under heavy pollution conditions. A 20% reduction in NOx could effectively prevent heavy pollution, while a further 60% reduction might keep O3 concentrations within the mild pollution range. The relative incremental reactivity(RIR)of precursors also highlighted the importance of NOx control during heavy pollution days, as NOx exhibited the highest RIR values(0.95~0.99). O3 budget analysis revealed regional influences. Except at year-end, when stringent control measures effectively reduced regional impacts on heavy pollution days, heavy pollution episodes in other periods were largely influenced by upwind areas, particularly the central PRD region(e.g., Guangzhou-Foshan). Moreover, the regional contribution generally increased significantly after 15:00 on heavy pollution days, exceeding 60%. To mitigate heavy O3 pollution in Jiangmen, stricter control of NOx and other precursor emissions should be enforced. Furthermore, coordinated regional prevention and control measures should be implemented in collaboration with upwind cities, such as Foshan, Zhongshan, and Guangzhou.
| 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 |