Impact of COVID-19 Lockdowns on a Global Sample of Surface PM2.5 Monitor Measurements

Abstract:

The lockdowns imposed in early 2020 in many countries around the world to reduce the spread of COVID-19 offered an unusual opportunity to study the impact of human activity on the environment. Residents around the globe were required to stay home, and both transportation and industrial activity were significantly curtailed for weeks. This shutdown is hypothesized to have led to a reduction in the emission from these sources of pollutants including particulate matter aerosols with diameters smaller than 2.5 microns (PM2.5). However, in some locations, it was recognized that residents may have returned to homes in the countryside, leading to an increase in emissions from the burning of wood for heating and cooking. As an initial step to exploring the impacts of the lockdown, data were examined from a global distribution of PM2.5 surface monitors run by the U.S. Department of State (DOS). DOS operates a network of Beta Attenuation Monitors (BAMs) located at over 60 of their embassies and consulates around the world. These monitors operate on a continuous basis measuring the PM2.5 concentration on hourly intervals and reporting back in near real-time to the U.S. Environmental Protection Agency (EPA). The EPA performs quality control on the data and openly publishes on its airnow.gov website the raw concentration, as well as the corresponding color-coded U.S. Air Quality Index (AQI). Twenty of the DOS monitors were identified to be operating during country-wide lockdowns occurring between March and June of 2020 as well as during the same period in 2019 used as a reference period for analysis. PM2.5 concentration data from these monitors were averaged to daily values for the country-specific lockdown periods and differences were explored between measurements occurring in 2020 and those in the previous year. Since PM2.5 concentrations can also be impacted by weather events, daily precipitation amounts and average wind speeds for the locations were obtained and used to group the observations into different categories for interpretation. Preliminary analyses show 15% to 50% decreases in observed PM2.5 concentrations across selected cities. Further studies of these data are warranted to better understand the impact of the lockdowns on air quality.