Deciphering China’s shifting skies: a spatial-temporal analysis of air quality across 337 cities (2015–2023)

The spatial-temporal evolution of six key air pollutants (PM2.5, PM10, CO, NO2, SO2, O3) across 337 Chinese cities between 2015 and 2023 was analyzed based on the provided figure set. The period represents a critical juncture encompassing the implementation and intensification of China’s ambitious national air pollution action plans. Using annual average concentration data visualized through spatial mapping, we conducted a comparative analysis of pollutant distributions for 2015, 2020, and 2023, identifying regional hotspots and temporal trends. Significant reductions were observed for most pollutants: PM2.5 decreased by 46.3% in the Beijing–Tianjin–Hebei (BTH) region and by 24.5% in the Fenwei Plain (FWP); SO2 declined by over 79% in BTH and FWP; CO fell by 62.9% in BTH. NO2 showed slower reductions, particularly in urban corridors, highlighting persistent traffic-related emissions. However, O3 increased by 14% in BTH and 12% in the Yangtze River Delta (YRD), with over 50% of BTH cities exceeding 180 μg/m³ by 2023, highlighting the complex atmospheric chemistry involved. The analysis underscores the effectiveness of targeted policy interventions for primary pollutants but emphasizes the urgent need for multi-pollutant, regionally tailored strategies to address the evolving air quality landscape, particularly the rising O3 threat.