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Aerosol Composition in Pasadena, CA during the COVID-19 Pandemic
BENJAMIN SCHULZE, Christopher Kenseth, Yuanlong Huang, Harrison Parker, John Crounse, Paul Wennberg, John Seinfeld, California Institute of Technology
Abstract Number: 297
Working Group: Urban Aerosols
Abstract
The COVID-19 pandemic offers an unprecedented opportunity to evaluate the response of ambient aerosol in the Los Angeles Basin to dramatic reductions in NOx and VOC emissions associated with transportation and economic activity. Here, we present results of ongoing measurements of sub-micrometer aerosol at Caltech (Pasadena, CA) using an Aerodyne HR-ToF-AMS, SMPS, and 12-h filter samples analyzed offline with LC/ESI-MS. The extended deployment (April 8th–present) provides comparison of aerosol composition and concentration across a gradient of meteorological conditions and traffic levels. Decadal trends in aerosol abundance and speciation are also examined via comparison to measurements from the CalNex 2010 campaign. Established metrics are used to assess the efficiency of urban SOA formation (e.g., OA/∆CO vs. photochemical age) and extent of atmospheric evolution (e.g., van Krevelen diagram), while positive matrix factorization (PMF) is applied to AMS data to differentiate OA subtypes and possible sources based on their mass spectra, time series, diurnal/weekly cycles, and correlations with molecular tracers identified via LC/ESI-MS. This “unnatural” experiment affords a glimpse into a potential future of urban air quality in which vehicular emissions are significantly reduced due to the ongoing electrification of cars and trucks across North America, suggests new scientific challenges that complicate air-quality management, and will allow for more accurate prediction of the trajectory of air quality in the decades to come.