Atmospheric Chemistry Program Seminar
Measurements of Volatile Organic Compounds during the COVID-19 Lockdown in Changzhou, China
"The COVID-19 outbreak in January 2020 prompted strict lockdowns, reduced human activity, and reduced emissions of associated pollutants. These reduced emissions have been estimated via remote and in-situ methods, but detailed measurements of volatile organic compounds (VOCs) are lacking. We measured VOCs in Changzhou, a Chinese city on the Yangtze River, during the local COVID-19 lockdowns from 8 January through 27 March, including periods of pre-lockdown, strict measures (level 1), and more relaxed measures accompanied by the return to work (level 2). VOCs were measured using a new, compact model of the Vocus proton-transfer-reaction time-of-flight mass spectrometer (Vocus Elf PTR-TOF-MS). We used positive matrix factorization to attribute VOCs to sources and employ an ensemble approach to determine uncertainties in the measured emission reductions. These uncertainties were further informed by satellite remote sensing and in-situ monitoring measurements of criteria pollutants, where we had measurements from previous years. Four factors of interest were resolved: textile industrial emissions (62±10%; average reduction during level 1 relative to pre-lockdown), pharmaceutical industrial emissions (40±20%), fresh traffic emissions (69±10%), and aged traffic emissions (73±14%). The quantified changes in the factors due to the lockdowns serve to constrain emission inventories and inform models, particularly for sectors where activity data are sparse, as the effects of lockdowns on air quality are explored."