Using Eddy Covariance to Measure COVID-19's Impact on CO2 Emissions in Indianapolis, IN

Abstract:

The goal of this project is to determine if carbon dioxide eddy covariance measurements at a tower in suburban Indianapolis are sensitive to traffic patterns on a nearby highway. An additional goal is to quantify any effects of the COVID-19 lockdown on the area’s CO₂ emissions. Daily and hourly traffic numbers were acquired from the Indiana Department of Transportation in order to analyze activity before and after COVID-19 lockdowns began. CO₂ fluxes were measured at a tower in Indianapolis and the portion of CO₂ attributed to human sources was found by using a technique based on eddy diffusivity. Average anthropogenic CO₂ flux by hour of the day was calculated across four weeks before lockdown in Indianapolis (February 5th to March 3rd, 2020) and during lockdown (March 25th to April 21st, 2020), using only measurements that were taken when wind was blowing from the direction of the highway. Comparisons of this analysis to traffic data for the same time periods showed that flux measurements have a similar pattern to traffic (correlation coefficients of 0.76 and 0.61, respectively). Results suggest CO₂ emissions decreased by about 58% during lockdown within the tower’s footprint, while traffic decreased by about 43%. Hourly CO₂ emissions during daylight hours averaged by week also decreased during the COVID-19 lockdown, but the correlation coefficient with traffic patterns was only 0.26, likely due to small sampling sizes. If the tower had been located predominantly downwind of the highway, the sample size would have been almost 3 times greater. The tower’s original purpose was to monitor the urban forest to the west rather than the highway to the east. These findings indicate that eddy covariance is an effective method of monitoring human emissions and detecting sudden changes in human activity such as the one precipitated by the COVID-19 pandemic.