Meteorological Drivers and Chemical Evolution of Ozone Pollution in the North China Plain

Over the past decade, stringent emission control policies have been implemented in the North China Plain, fundamentally altering regional air pollution profiles. This study investigates the long-term temporal evolution (2015–2025) and chemical reconstruction of air pollutants in Jinan, China. Benefiting from rigorous emission controls, annual median concentrations of PM2.5, SO2, and CO decreased significantly by 64%, 81%, and 54%, respectively. Conversely, NO2 exhibited a slower decline (47%), and the maximum 8-hour daily average (MDA8) ozone (O3) increased by 23%. Generalized additive model (GAM) analysis identified solar radiation, temperature, relative humidity, and NO2 as the primary factors strongly associated with O3 variations. The amplified atmospheric oxidation capacity driven by O3 has triggered a profound chemical reconstruction of secondary inorganic aerosols (i.e., SO42-, NO3-, and NH4+), with a significant increase in sulfur and nitrogen oxidation ratios (SOR and NOR), which may continue to intensify the combined pollution trend of ozone and PM2.5. These findings emphasize that coordinated reductions in nitrogen oxides and volatile organic compounds must be achieved in future air quality management while also taking into account the promoting effect of climate warming on ozone generation.