Significant concurrent decrease in PM(2.5) and NO(2) concentrations in China during COVID-19 epidemic

The strict control measures and social lockdowns initiated to combat COVID-19 epidemic have had a notable impact on air pollutant concentrations. According to observation data obtained from the China National Environmental Monitoring Center, compared to levels in 2019, the average concentration of NO(2) in early 2020 during COVID-19 epidemic has decreased by 53%, 50%, and 30% in Wuhan city, Hubei Province (Wuhan excluded), and China (Hubei excluded), respectively. Simultaneously, PM(2.5) concentration has decreased by 35%, 29%, and 19% in Wuhan, Hubei (Wuhan excluded), and China (Hubei excluded), respectively. Less significant declines have also been found for SO(2) and CO concentrations. We also analyzed the temporal variation and spatial distribution of air pollutant concentrations in China during COVID-19 epidemic. The decreases in PM(2.5) and NO(2) concentrations showed relatively consistent temporal variation and spatial distribution. These results support control of NO(x) to further reduce PM(2.5) pollution in China. The concurrent decrease in NO(x) and PM(2.5) concentrations resulted in an increase of O(3) concentrations across China during COVID-19 epidemic, indicating that coordinated control of other pollutants is needed.