The response in air quality to the reduction of chinese economic activities during the COVID-19 outbreak

On the basis of measurements made at the monitoring stations operated by the China National Environmental Monitoring Center, we quantify the reduction in surface PM2.5, NO2, CO, and SO(2)concentrations in northern China during the lockdown, which started on 23 January 2020.

We find that, on the average, the levels of surface PM(2.5)and NO(2)have decreased by approximately 35% and 60%, respectively, between the period 1 and 22 January 2020 and the period 23 January and 29 February 2020. At the same time, the mean ozone concentration has increased by a factor 1.5-2. In urban area of Wuhan, where drastic measures were adopted to limit the spread of the coronavirus, similar changes in the concentrations of PM2.5, NO2, and ozone are found.