Abstract View
Dispersion Normalized PMF Provides Insights into the Significant Changes in Source Contributions to Atmospheric Particulate Matter after the COVID-19 Outbreak
Qili Dai, Yinchang Feng, PHILIP K. HOPKE, Nankai University
Abstract Number: 12
Working Group: Source Apportionment
Abstract
An effective source apportionment tool, factor analysis, utilizes the covariance of compositional variables to separate sources of ambient pollutants like particulate matter (PM). In addition to the variations in source emission rates, meteorology provides another important source of variation through transport and dilution. Conventional positive matrix factorization (PMF) loses information in the observation data due to variations in dilution. To reduce the influence of dilution, dispersion normalized PMF (DN-PMF) is proposed to incorporate the ventilation coefficient into the PMF analysis. This approach has been applied to hourly speciated particulate data measured at a suburban location in a field campaign that included the COVID-19 outbreak. Compared to standard PMF, the results from DN-PMF increased the morning peaks of coal combustion, and traffic rush hour peak of traffic emissions, lowered the daytime peak of soil and aged sea salt and a point source of waste incinerator. It is provided more subtlety defined source directionality. DN-PMF enhanced the local influence of coal combustion, traffic emissions and incinerator, and highlighted the regional transport nature of soil and aged sea salt. The enhanced emission patterns indicated that the DN-PMF is a useful addition to current source apportionment methods. This work also highlights the significant changes in source contributions after the outbreak of COVID-19. During this unprecedented pandemic, secondary inorganic aerosol (SIA) was the predominant source of PM2.5, with averaged mass contribution of 50.5% that formed via gaseous precursors mostly emission from coal combustion, followed by firework emissions (32.0%), primary emission of coal combustion (13.3%), primary traffic emissions (2.1%), soil and aged sea salt (1.2%) and incinerator (0.9%). The traffic contribution has decreased dramatically (70%) compared to other sources. Soil and aged sea salt contributions decreased by 68%, also likely related to decreased traffic volume.