Demarcation of Coordinated Prevention and Control Regions in the Yangtze River Delta Based on Spatio-Temporal Variations in PM2.5 and O-3 Concentrations

The PM2.5 and O-3 pollution situation in the Yangtze River Delta (YRD) region is increasingly complex. Existing coordinated prevention and control programs are demarcated according to administrative regions, making fine-scale pollution control difficult. This study proposed a method for delineating regional control and pollution types based on the analysis of PM2.5 and O-3 pollution characteristics. Four key indicators were used to comprehensively evaluate regional pollution trends: PM2.5 concentration rho(PM2.5), O-3 concentration rho(O-3), and the rates of change r(PM2.5) and r(O-3). Our results demonstrate that from 2015 to 2020, cities in the YRD show a transition in the main pollution type from PM2.5 to O-3. By 2020, the main types of pollution in the YRD region are co-pollution (rho(PM2.5) > 35 mu g/m(3) and rho(O-3) > 100 mu g/m(3)), O-3 pollution (rho(PM2.5) < 35 mu g/m(3) and rho(O-3) > 100 mu g/m(3)), and low pollution (rho(PM2.5) < 35 mu g/m(3) and rho(O-3) < 100 mu g/m(3)), accounting for 41.9%, 26.3%, and 30% of the study area, respectively, which is roughly consistent with the remote sensing results (40.4%, 25.6%, and 33.7%, respectively). The proposed method can predict future trends in pollution and assist in decision-making for the coordinated prevention and control of PM2.5 and O-3 pollution.