How Does Air Pollution Change during COVID-19 Outbreak in China?

According to the corresponding historical averages of air quality during each month of BF, AF1, and AF2 period (in Fig In general, it shows more notable variations in air quality during the AF1 period than that of the AF2 period [ ]we will go through some detailed air quality variation in the AF1 period here According to the low normalized concentration in the BF period, SO2 concentration shows significant decrease throughout China in recent years, especially over northern China, indicating the importance of coal desulfurization and nationwide emission reduction Considering O3, the concentration of which is driven by two major classes of directly emitted precursors, i e , NOx and volatile organic compounds (VOCs), except for the Guangxi Province, O3 over the other provinces and areas increased significantly with the outbreak of coronavirus