Spatial and temporal differentiation of air quality and its influence factors in 16 cities in Shandong Province from 2019 to 2020

Ambient air quality is a complex dynamical system that is affected by a number of subsystems, such as particulate matter emission, meteorological factors, and socioeconomic factors. However, the mechanism of action of meteorological factors and socioeconomic factors and correlation between cities are unclear. The spearman correlation coefficient was used to analyze and explore the spatial and temporal differentiation of air quality (SO2, NO2, PM10, PM2.5, CO-95per and O3–8h), the proportion of days with heavy pollution (PDHP), the proportion of days without pollution (PDWP) and influencing factors (particulate matter emission, meteorological factors and socioeconomic factors) in 16 cities in Shandong Province in the period 2019–2020. The results indicated that the concentrations of SO2, NO2, PM10, PM2.5 and CO-95per showed a trend of “winter high, summer low”, while the concentration of O3–8h showed a trend of “winter low, summer high”. The air quality of coastal cities was better than that of inland cities. Temperature and precipitation were negatively correlated with the concentrations of SO2, NO2, PM10, PM2.5, CO-95per (P < 0.05). There were significant positive correlations between SO2 and the proportion of secondary industry, between PM10 and population density, and between PM2.5 and population density. The annual mean concentrations of PM2.5, PM10, NO2 and SO2 were positively correlated, and the positive correlation between PM10 and PM2.5 was extremely significant. The correlation between pollutants in the heating period and nonheating period was significantly different. PM2.5/O3–8h and PM2.5/NO2 had no correlation in the heating period but had a significant positive correlation in the nonheating period. The PDHP in the heating period was positively correlated with SO2, NO2, PM10, PM2.5 and CO-95per, indicating that the air pollutants released during the heating process in winter are important factors that affect the air quality. There was a significant positive correlation between different cities in Shandong Province, and the correlation was affected by the distance between cities and the type of pollutants.