To slow the spread of coronavirus, countries imposed lockdown measures, significantly reducing vehicle gas emissions. Atmospheric chemists took the opportunity to study atmospheric changes during the pandemic.
The American Chemical Society described initial findings in Chemical & Engineering News. The team hopes that their research could help with the global issue of climate change and air quality.
Since China was the first to impose lockdown measures in January, they had the first atmospheric changes due to reduced emissions. After the first three weeks of staying at home, there was already a significant reduction in emissions.
As the rest of the world followed similar lockdown measures within months, there was a similar pattern. While researchers remained at home, some installed spectrometers on their roofs or kept track of data from sensor networks.
As human economic activity was put on hold, researchers observed the significant impact that vehicle traffic has on atmospheric conditions. Atmospheric Chemist Ronald Cohen from the University of California-Berkley shared that he and other researchers had the opportunity to test their ideas without waiting years for significant atmospheric changes.
How Traffic Affects Gas Emissions
Traffic-related emissions contribute to nitrogen dioxide and carbon dioxide emissions. Carbon dioxide is a significant contributor to climate change, while nitrogen dioxide affects how ozone is produced in the atmosphere.
In New Zealand, when traffic was reduced by 80 percent due to lockdown measures, radiocarbon scientist Jocelyn Turnbull and her team analyzed roadside carbon dioxide sensors. Simultaneously, the team had also been studying how local lawns absorb carbon dioxide from fossil fuels as part of the natural carbon cycle. They discovered that fossil fuel carbon emissions decreased at the same as traffic activity at nearly 80 percent.
In the San Fransico Bay Area, analysts revealed that as traffic activity was reduced by 45 percent, carbon emissions fell by 25 percent compared to six weeks before. In India, previous images of the India Gate in New Delhi are surrounded by haze compared to an image from April 8, 2020, where the sky and the air were both cleared. Cohen shared that the significant changes in the atmosphere during lockdown is a useful model for what it may look like if 50 percent of vehicles were switched to electric cars.
Reduced Nitrogen Levels
Nitrogen dioxide levels also significantly dropped. Traffic is the primary source of nitrogen gas emissions at nearly 45 percent to 50 percent, according to the Copernicus Atmosphere Monitoring Service (CAMS). CAMS satellite imaging revealed that almost 65 percent of nitrogen dioxide levels dropped in China after weeks of lockdown.
However, according to another recent study from the University of Liverpool, reduced levels of nitrogen emissions do not necessarily mean better air quality. Data from Air Quality sensors in the UK revealed that while nitrogen emissions reduced, there was a significant increase in sulfur dioxide. Their results prove that the atmosphere is complex, and although reducing gas emissions are critical, further investigations need to be made to understand the driving factors of different air pollutants.
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