Exploration of the Reasons for the Decreases in O3 Concentrations in Tai’an City Based on the Control of O3 Precursor Emissions

Due to the “One City, One Policy” for air pollution prevention and control measures, Tai’an City was the only city in Shandong Province with a year-on-year decrease in O3 concentrations in 2022. In this study, the WRF-CMAQ model was used to simulate the O3 concentrations in Tai’an and other inland cities in Shandong Province in September 2022, and the model evaluation method was applied to discover the differences in the O3 concentrations between Tai’an and other cities. During the periods of high maximum daily 8 h average O3 (MDA8 O3), the model only overestimated the O3 concentrations in Tai’an by 3.4% and underestimated those in other inland cities by −11.0% to −2.2%. Dozens of O3 simulation scenarios were designed on the basis of the control of O3 precursor emissions, and the results indicate that the O3 precursor emissions in Tai’an were at a lower level. On this basis, the impacts of meteorological conditions and O3 precursor emission changes on O3 concentrations in Tai’an were quantified. Adverse meteorological conditions and changes in emissions from other inland cities led to a 49.5 µg/m3 increase in the mean MDA8 O3 in Tai’an during the study period. However, the local emission reduction measures in Tai’an, to some extent, offset these adverse effects, reducing the mean MDA8 O3 by 5.8 µg/m3. In summary, the Tai’an City might implement effective emission reduction measures during periods of high MDA8 O3, thereby achieving a reduction in overall O3 concentrations. This effort secured its leading position in Shandong Province’s O3–8h-90per ranking in 2022.