A recent satellite analysis suggests that the COVID-19 lockdown is reducing two pollutants but increasing another. With so many people working from home or sheltering in place, a reduction in automobile emissions is one potentially positive outcome of the pandemic, even if it is temporary.
The American Geophysical Union’s journal Geophysical Research Letters recently published two papers that take a look at the effect of lockdowns on air quality.
They show that, on the one hand, levels of nitrogen dioxide and particulate matter pollution over China, Western Europe, and the United States have fallen dramatically due to lockdown measures. However, on the other hand, levels of surface ozone in China have increased.
Atmospheric scientist Jenny Stavrakou, of the Royal Belgian Institute for Space Aeronomy in Brussels, notes: “Maybe this unintended experiment could be used to understand better the emission regulations. It is some positive news among a very tragic situation.” Stavrakou is co-author of the paper focusing on levels of nitrogen dioxide.
The first paper: Nitrogen dioxide
The researchers behind this paper studied satellite measurements of air quality over several major coronavirus epicenters: China, South Korea, Italy, Spain, France, Germany, Iran, and the U.S.
Perhaps because each country had a different response to the coronavirus, the reduction in nitrogen dioxide levels varied by locale. For example, levels were down by 40% over urban areas in China, 20% over Belgium and Germany, and 19–40% in different areas of the U.S.
Experts have not observed reductions of such magnitude since satellite-based air quality monitoring began in the 1990s, according to Stavrakou.
The observed reductions, while widespread, did not occur everywhere. There was no decrease in nitrogen dioxide over Iran, one of the countries that COVID-19 has most affected. The authors hypothesize that this is due to a less stringent lockdown. After Iranian New Year, nitrogen dioxide levels did go down, but only to the levels that scientists see every year after this holiday.
The second paper: Particulate matter and surface ozone
The second paper focused on China, as no other country has had to deal with coronavirus for longer or on a larger scale.
Atmospheric scientist Guy Brasseur of the Max Planck Institute for Meteorology in Hamburg, Germany, led the team of researchers, who measured the levels of nitrogen dioxide, particulate matter, and surface ozone in northern China after the lockdown began on January 23, 2020.
Although the authors reported a 60% reduction in nitrogen dioxide and a 35% reduction in particulate matter, secondary pollutant surface ozone increased by 150–200%.….. Continue Reading……