Nonlinear impact of COVID-19 on pollutions – Evidence from Wuhan, New York, Milan, Madrid, Bandra, London, Tokyo and Mexico City

The majority of existing COVID-19 and pollution research are from a linear perspective, ignoring the nonlinear relationship between COVID-19 and pollution. This work is aimed to systematically investigate the nonlinear impact of COVID-19 lockdown on four typical pollutants (NO(2,) PM2.5, O(3) and SO(2)) in the selected eight cities (Wuhan of China, New York of the United States, Milan of Italy, Madrid of Spain, Bandra of India, London of United Kingdom, Tokyo of Japan and Mexico City of Mexico) using the updated data and spearman correlation function model. To a certain extent, the global lockdown caused by the coronavirus only reduces nitrogen dioxide and particles, but does not reduce ozone . Specifically, compared with the average concentration in the same period from 2017 to 2019, NO(2) in 2020 decreased by 40–50 %, PM(2.5) in 2020 decreased by 10–30 %, O(3) in 2020 increased by 17–20 % and SO(2) in 2020 increased slightly. In addition, the changes of new confirmed cases of COVID-19 and change of pollutants were not synchronized. On the contrary, there was a 0–7 days lag between the new confirmed cases and changes of pollutants.