LAUSR

Abstract The severity of urban air pollution problems in China increases with the city's size and population density. Outdoor air pollution not only affects indoor air quality but also increases building energy consumption. We analyzed the characteristics of urban air pollution in China based on long-period monitoring data with high temporal resolution (hourly) recorded between September 1, 2014 and August 31, 2019. We compared five key regions in detail: “2 + 26 cities,” the Yangtze River delta (YRD), the Pearl River delta (PRD), the Northeast China Plain (NECP), and the Sichuan Basin (SCB). The results show decreases in the annual mean concentrations of particulate matter, PM2.5 and PM10, SO2, and CO but an increase in the O3 concentration. The increasing O3 rate in the 2 + 26 cities region was nearly 14 times that of the global rate. In terms of diurnal variation, NO2 and CO reached maxima between 8:00 and 9:00 a.m. due to morning rush hour traffic, which was approximately 1 h before the PMs and SO2 reached their maxima. In the monthly variation profiles, the SO2 concentration magnitudes in the NECP were similar to those of the 2 + 26 cities during winter heating periods and the YRD region during the non-heating periods. Minima associated with “plum rain” and the rainy season were also observed in the O3 monthly variation profiles of the YRD and SCB regions, respectively. In the 2 + 26 cities region, each pollutant showed significantly large temporal variation relative to the spatial variation, which is indicative of the regional air pollution trend.