Synergistic Evolution of PM2.5 and O3 Concentrations: Evidence from Environmental Kuznets Curve Tests in the Yellow River Basin

Air pollution, especially the synergistic pollution of PM2.5 and O-3, poses a severe threat to human life and production. The synergistic formation mechanism of PM2.5 and O-3 pollution is relatively confirmed, while research on their spatiotemporal synergy is urgent. Based on remotely sensed interpretation data from 90 cities in the Yellow River Basin, we analyzed the synergistic evolution of PM2.5 and O-3 concentrations during 2013-2020. Combined with the environmental Kuznets curve, we performed factor analysis using a panel regression model. The synergistic evolution pattern shows a gradual decrease in PM2.5 concentration and a gradual increase in O-3 concentration. There is a strong spatial auto-correlation in the two pollutants' concentrations. The relationship between economy and PM2.5 concentration shows an "N-shaped" curve, while that between O-3 concentration and economic development presents an inverse "N-shaped" curve. The environmental Kuznets curve shows that the deterioration of O-3 pollution takes place later than the mitigation of PM2.5 pollution. Various factors have obvious heterogeneous effects on PM2.5 and O-3 concentrations. Meanwhile, the sensitivity effect of per capita GDP on PM2.5 concentration in the midstream region is stronger than that in the upstream region, while the sensitivity effect of per capita GDP on O-3 concentration is strongest in the midstream region than that in upstream and downstream region.