As economic activity resumes in China following the first wave of the coronavirus pandemic, levels of the air pollutant nitrogen dioxide (NO2) are rising to traditional standards for the first time this year.
According to NASA’s Earth Observatory reports, in February of 2020 scientists using NASA and European satellites identified there was a significant reduction in NO2 over the country after COVID-19 shutdown regulations took effect.
With the conclusion of stringent health mandates, just three months later scientists saw their anticipated rebound.
When nitrogen dioxide is closer to the Earth's surface, it can turn into ozone that decreases air quality and makes breathing conditions unhealthy. When higher in our atmosphere, NO2 can form acid rain.
Data collected by the Tropospheric Monitoring Instrument (TROPOMI) on the European Space Agency's Copernicus Sentinel-5P satellite marked notable changes in levels of nitrogen dioxide in the troposphere over China during periods during and after shutdowns.
Yet, during the pandemic, this increase was delayed by several weeks.
In February and March 2020, NO2 levels over Wuhan and some other Chinese cities were well below long-term trends. By April levels bounced back, reaching the long-term norm for the season.
That said, NASA's Earth Observatory noted that increasing sunlight shortens the lifetime of the gas near the ground, and shifting weather patterns can temper NO2 to disperse without resistance from the air.