Statistical characteristics and the urban spillover effect of haze pollution in the circum-Beijing region

This study analyzes the statistical characteristics of the major pollutant distribution in 7 cities in the circum-Beijing region based on the daily PM2.5 concentration indices over the past 3 years, and Granger causality test is used to discuss the PM2.5 spillover effect within the region. The results indicate that significant regional differences exist in the PM2.5 concentration distribution in the circum-Beijing cities, with higher values in the southern cities than in the northern cities. Moreover, the PM2.5 concentrations in the different cities are the highest in the winter and at its lowest in summer, with a bimodal structure in the monthly distribution. The PM2.5 indices of the cities do not follow a normal distribution but present a skewed distribution with a sharp peak and heavy tail. Furthermore, strong inter-correlation and autocorrelation are found among the PM2.5 indices of the cities, indicating the regional consistency and strong continuity of the haze pollution in this region. A PM2.5 spillover effect exists in the circum-Beijing cities and present a seasonal difference. The spillover effect is most significant with a lag of 2-3 days and becomes weaker with increasing confidence levels. Additionally, cities close to each other easily formed a PM2.5 spillover in a short time period but additional accumulation time is required for distant cities to form a spillover effect.