Seasonal patterns, vertical profiles, and sensitivity analysis of long-term O3 pollution observations in Hefei City, China

Atmospheric pollution in China has reduced significantly due to emission reduction measures. However, major pollution incidents often occur in the Yangtze-Huaihe region. In this study, based on long-term observation of the concentrations of surface pollutants and O3, measured using lidar, we explore the spatiotemporal variability of air pollutants in Hefei City, an important city in the Yangtze-Huaihe region, Anhui Province, China, spanning from 2015 to 2022. The results indicate that, from 2015 to 2022, the concentrations of PM2.5, PM10, O3, NO2, SO2, and CO decreased by 58.3 %, 37.8 %, −29.1 %, 23.0 %, 59.7 %, and 12.2 %, respectively. Over the eight years, O3 was the only pollutant that increased in concentration (from around 55.9 to 72.2 μg·m−3), and the study identifies external transport as a significant contributor to the high level of O3 pollution in the area. The generation of O3 in Hefei City is mainly associated with the emission of volatile organic compounds (VOCs). Since 2018, China has intensified efforts to prevent and control VOCs pollution, resulting in a reduction in O3 pollution. However, more effective control measures for VOCs are still needed in Hefei City. The analysis of O3 production in the area revealed that O3 pollution was dominated by local chemical generation during the daytime, with a minor amount of O3 being transported outside the region. O3 concentration was consumed in the area during the night through two mechanisms: transport to the other areas and surface chemical consumption. Investigating the long-term changes in O3 and related pollutants in Hefei City enhances our understanding of the spatial and temporal characteristics of O3 and the factors affecting O3 pollution. Additionally, such an investigation provides a theoretical basis for the prevention and control of O3 pollution in the Yangtze-Huaihe region.