Slowdown in activity during the period including the initial coronavirus outbreak and the Chinese New Year led to massive reductions in VOC emissions – revealing local air quality baselines in Chinese megacities.
The ambient concentrations of volatile organic compounds (VOC) were measured by Vocus Elf PTR-TOF in a megacity in eastern China.
Factor analysis of sixteen of these VOCs suggested five major groups of compounds.
Two strong emission factors, traffic and industry, account for most of the VOC measured during the “business as usual” scenario. Traffic emissions (top, red) generally peak during the day and are identified by their rich content of aromatics from gasoline and other fuels.
Industrial emissions (yellow) are identified by a key compound known to be released by local industry, and are characterized by intense enhancements over periods of minutes to hours.
A background factor containing acids, other oxygenates, and possibly some alkanes (light blue) and a regional chemistry factor (dark blue) with ketones show longer-term, slower changes.
The remaining VOC intensity (black) shows fast, spikey behavior and likely comes from small sources (such as individual cars) passing near the measurement station.
Traffic and industrial emissions decrease substantially during the Chinese New Year Holiday and after a government-issued advisory concerning coronavirus. Ambient total VOC concentration fell by more than 50% from the average during the “business as usual” time period (9 Jan to 16 Jan), and traffic and industrial emissions decreased by 87% and 72%, respectively.