For more than a year, the COVID-19 pandemic transformed many employees’ daily commute from a miles-long car trip to a several-yard, barefoot shuffle to the home office. The environmental impact of this change in transportation habits is something that Shannon Capps, PhD, assistant professor of civil, architectural and environmental engineering, is studying closely. Capps leads the Atmospheric Modeling at Drexel group, which conducts outdoor air quality modeling to estimate influences of emissions sources; evaluate health, ecosystem and climate impacts of pollutants; and assimilate satellite-based observations to improve models.
Using satellite imagery and ground-level air quality monitors, Capps and her group studied the concentration of nitrogen dioxide (NO2), a byproduct of fossil fuel combustion found from vehicle exhaust, in the air over ten U.S. metropolitan areas at different points before and after March of 2020.
“We know that weather affects the concentration of NO2 in the air,” Capps says. “But wanted to look to see if there were additional differences as a result of behavioral changes brought on by COVID lockdowns.”
The group linked the changes in NO2 up to data from Google location services and requests to Apple Maps for driving directions. They found that changes in travel behavior were associated with improved air quality more so in cities where cars and trucks contribute more NO2. In fact, a change as small as 20 to 30 percent of the population not traveling or driving when they do can make a difference large enough that it can be measured from sensors in space.
Additionally, Capps’ group has recently added ammonia emissions as an area of focus. A common emission from livestock manure and commercial fertilizers, ammonia is a major contributor to the formation of fine particulate matter in the air that can cause breathing and other health problems. The United States does not have reliable methods to identify the greatest sources of ammonia emissions. Capps hopes that, between satellite imagery, the sparse ground monitoring available, and their modeling, meaningful change could be made.
“Once we have better ammonia emissions estimates, states and local governments can use the same models to design more efficient ways to reduce fine particulate matter,” Capps says. “By valuing human health and leveraging satellite-based observations, we can make more substantial changes to our behaviors and our regulations.”
