Impact of COVID-19 pandemic lockdown on air pollution in 20 major cities
around the world
Abstract
In order to fight against the spread of COVID-19, the most hard-hit
countries in the spring of 2020 implemented different lockdown
strategies. To assess the impact of the COVID-19 pandemic lockdown on
air quality worldwide, we use Air Quality Index (AQI) data to estimate
the AQI change in 20 major cities on six continents. Our results show
significant declines of AQI in NO2, SO2,
CO, PM2.5 and PM10 in most cities,
mainly due to the reduction of transportation, industry and commercial
activities during lockdown. This work shows the reduction of primary
pollutants, especially NO2, is mainly due to lockdown
policies. However, preexisting local environmental policy regulations
also contributed to declining NO2, SO2
and PM2.5 emissions, especially in Asian countries. In
addition, higher rainfall during the lockdown period could cause decline
of PM2.5, especially in Johannesburg. By contrast, the changes of AQI in
ground-level O3were not significant in most of cities,
as meteorological variability and ratio of VOC/NOx are
key factors in ground-level O3 formation.