Evolution and Key Drivers of Typical Air Pollutants in Binzhou, China: A Case Study of the Yellow River Delta's Central City (2019-2024).

In recent years, combined pollution of PM2.5 and O3 has emerged as a major constraint on improvement of air quality in urban China. This study investigates Binzhou, an industrial-agricultural city within the Beijing-Tianjin-Hebei air pollution transport corridor. Based on air quality monitoring and socioeconomic data from 2019 to 2024, we analyze the temporal variations, driving mechanisms, and economic effects of PM2.5-O3 compound pollution. Results show that the annual mean PM2.5 concentrations decreased initially and then increased, while O3 levels exhibited a fluctuating increase. Seasonal patterns were distinct: PM2.5 pollution was more severe in autumn and winter, and O3 dominated in spring and summer. The number of compound pollution days decreased from 24 in 2019 to 12 in 2024, with a notable concentration in spring (March-May), accounting for 40-54% of the annual total, highlighting this period as critical for coordinated control. Correlation analysis revealed a weak positive association between PM2.5 and O3 in spring, summer, and autumn (strongest in summer) but a weak negative correlation in winter. Economic development demonstrated a phased decoupling from pollution: Binzhou's GDP grew by 38.6% cumulatively during the study period, while compound pollution days declined, with significant decoupling in 2020 and 2022. However, pollution rebounded with economic recovery. Key drivers identified include coal combustion and industrial emissions, while industrial restructuring and regional joint prevention policies have contributed to pollution mitigation. This study provides scientific support for formulating differentiated air quality strategies tailored to seasonal and regional characteristics, thereby supporting both clean air and high-quality development.