Impacts of COVID-19 control measures on tropospheric NO$_2$ over China, South Korea and Italy

TL;DR

This study uses satellite data to analyze how COVID-19 lockdowns significantly reduced tropospheric NO$_2$ levels over China, South Korea, and Italy, demonstrating the environmental impact of human activity restrictions.

Contribution

It provides the first detailed satellite-based quantification of NO$_2$ reductions during COVID-19 lockdowns across multiple countries, linking policy measures to atmospheric changes.

Findings

Over 40% reduction in NO$_2$ over China, South Korea, and Italy.

NO$_x$ emissions decreased by up to 20% during lockdowns.

NO$_2$ levels returned to normal within 50-70 days after measures ended.

Abstract

Tropospheric nitrogen dioxide (NO$_2$) concentrations are strongly affected by anthropogenic activities. Using space-based measurements of tropospheric NO$_2$, here we investigate the responses of tropospheric NO$_2$ to the 2019 novel coronavirus (COVID-19) over China, South Korea, and Italy. We find noticeable reductions of tropospheric NO$_2$ columns due to the COVID-19 controls by more than 40% over E. China, South Korea, and N. Italy. The 40% reductions of tropospheric NO$_2$ are coincident with intensive lockdown events as well as up to 20% reductions in anthropogenic nitrogen oxides (NO$_x$) emissions. The perturbations in tropospheric NO$_2$ diminished accompanied with the mitigation of COVID-19 pandemic, and finally disappeared within around 50-70 days after the starts of control measures over all three nations, providing indications for the start, maximum, and mitigation of intensive controls. This work exhibits significant influences of lockdown measures on atmospheric environment, highlighting the importance of satellite observations to monitor anthropogenic activity changes.