Analyzing COVID-19 Impacts on Vehicle Travels and Daily Nitrogen Dioxide (NO2) Levels among Florida Counties

Abstract

The COVID-19 outbreak and ensuing social distancing behaviors resulted in substantial reduction on traffic, making this a unique experiment on observing the air quality. Such an experiment is also supplemental to the smart city concept as it can help to identify whether there is a delay on air quality improvement during or after a sharp decline on traffic and to determine what, if any, factors are contributing to that time lag. As such, this study investigates the immediate impacts of COVID-19 causing abrupt declines on traffic and NO2 concentration in all Florida Counties through March 2020. Daily tropospheric NO2 concentrations were extracted from the Sentinel-5 Precursor satellite and vehicle mile traveled (VMT) estimates were acquired from cell phone mobility records. It is observed that overall impacts of the COVID-19 response in Florida have started in the first half of the March 2020, two weeks earlier than the official stay-at-home orders, and resulted in 54.07% and 59.68% decrease by the end of the month on NO2 and VMT, respectively. Further, a cross-correlation based dependency analysis was conducted to analyze the similarities and associated time lag between 7-day moving averages of VMT and NO2 concentrations of the 67 counties. Although such reduction is unprecedented for both data sets, results indicate a strong correlation and this correlation increases with the identification of a time lag between VMT and NO2 concentration. Majority of the counties have no time lag between VMT and NO2 concentration; however, a cluster of South Florida counties presents earlier decrease on NO2 concentration compare to VMT, which indicates that the air quality improvements in those counties are not traffic related. Investigation on the socioeconomic factors indicates that population density and income level have no significant impact on the time lag between traffic and air quality improvements in light of COVID-19.

Counterfactual time series analysis of short-term change in air pollution following the COVID-19 state of emergency in the United States

“… Citation Geographic locations COVID19 related intervention Confounding adjustment Statistical approach Results Berman et al 22 United States (all counties in the U.S. with both NO 2 and PM 2.5 monitors) Reduced traffic and mandated business closures between March 13-April 21. March 13th being when U.S. reported cases exceeded 2000 and the first enacted state-wide social distancing order None Two-sided t-tests paired by county (α = 0.05) 25.5% reduction (4.8 ppb) in NO 2 was observed during the COVID-19 period NO 2 decline was statistically significant regardless of when mandated business closures were implemented 11.3% statistically significant reduction (0.7 μg/m 3 ) of PM 2.5 in counties from states that instituted early non-essential business closures Gillingham et al 28 (Commentary) United States (785 monitors) Shutdowns Weather and seasonality Global polynomial and a two-step local regression PM 2.5 concentrations have decreased by around -0.5 μg/m 3 since the start of the shutdowns Estimated 11% NOx decrease in daily local emissions There is insufficient evidence to prove that there was a significant decrease in PM 2.5 concentrations in the U.S Goldberg et al 24 20 cities in North America COVID-19 Physical distancing measures (lockdown) (15 March to 30 April post-covid-19 period) Solar zenith angle and meteorological conditions over very short time scales Average differences Adjusted for seasonality and meteorology, NO 2 had a median drop of 21.6% before and after COVID‐19 physical distancing Karaer et al 25 Florida COVID-19 social distancing behaviors (March 2020) Population density and income A cross-correlation based dependency analysis …”

Projecting daily travel behavior by distance during the pandemic and the spread of COVID-19 infections – Are we in a closed loop scenario?

“…Using the travel data in China, Kraemer et al, 2020 , Chinazzi et al, 2020 found that travel restrictions issued by the Chinese government have reduced the spread of COVID-19 in that country. Regarding travels in the United States, a study by Karaer et al (2020) showed that COVID-19 reduced vehicle travels in all Florida counties, which resulted in a significant reduction in traffic. Finally, Yilmazkuday (2020) focused on inter-county travels and found that strict restrictions on travels across counties in the United States reduced the number of new cases and new deaths.…”

On the impact of the COVID-19 pandemic on air quality in Florida

“…These include particulate matter with aerodynamic diameter less than 2.5 μm (PM 2.5 ), nitrogen and sulfur dioxides (NO 2 and SO 2 , respectively), carbon monoxide (CO), and ozone (O 3 ). NO 2 is a primary pollutant that is mainly produced from vehicular emissions, and has therefore exhibited wide reductions during the lockdowns ( Hoang et al, 2021 ), as evident from ground-level measurements ( Berman and Ebisu, 2020 ; Zangari et al, 2020 ) and remote sensing data ( Karaer et al, 2020 ; Elshorbany et al, 2021 ). CO is also a primary pollutant, emitted directly due to combustion, that has displayed a decline in its concentrations during the lockdowns ( Chen et al, 2020 ).…”

“…As a result, a few studies have attempted to characterize the impact of the COVID-19 pandemic lockdowns on air quality in the state. However, these were conducted either by using remote sensing data ( Elshorbany et al, 2021 ; Karaer et al, 2020 ), or on a relatively low temporal resolution (Bekbulat et al, 2021), or focused primarily on few criteria pollutants (e.g., Karaer et al, 2020 ). Hence, these studies lack the capability to explain the overall processes that govern air quality on a city level.…”