With the onset of the COVID-19 pandemic, reports of air quality improvements around the world resulting from the stay-at-home orders were widespread. However, for Chicago, no significant air quality improvements occurred despite large reductions in private vehicle transportation due to the lack of commuters. The city of Chicago is a nexus for long-haul transportation by trucks and trains, which did not decrease during the pandemic. These transportation sources use mostly diesel fuel engines and emit NOX, a precursor to tropospheric ozone, and PM2.5, both of which are harmful air pollutants. Using open access EPA air quality data for the Chicago region, three sites of interest were chosen due to the proximity to the city and location in urban, suburban, and rural areas. The concentration of PM2.5 remained elevated at the urban site but not the suburban site during the COVID timeframe, supporting the hypothesis that long-haul transportation emissions dominate poor air quality in Chicago. The suburban site during the COVID timeframe measured statistically significantly higher concentrations of ozone compared to the Non-COVID timeframe most likely due to the complexity of NOX chemistry and its “lag” effect. This would mean that reductions locally around the suburban site yielded a decrease in concentrations, but the long-haul emission of NOX around the urban site would lead to the consistent or great concentrations of ozone at the suburban site. While the concentrations of ozone were significantly higher during the COVID timeframe for half of the analyzed months, the site did experience a significant decrease in ozone concentration immediately after lockdown measures were implemented.
Steffeck, Adam W.T.
"Insignificant Impacts of COVID-19 Stay-At-Home Orders on Chicago Air Quality,"
DePaul Discoveries: Volume 10, Article 2.
Available at: https://via.library.depaul.edu/depaul-disc/vol10/iss1/2