A048-04
Aerosol Composition in Pasadena, CA, During the COVID-19 Pandemic

Tuesday, 8 December 2020: 10:42
Virtual
Christopher M Kenseth1, Benjamin Schulze1, Yuanlong Huang1, Harrison Parker1, John D Crounse2, Paul Van Rooy3, Barbara Barletta4, Simone Meinardi4, Donald Ray Blake4, Kelley Barsanti3, Paul O Wennberg2 and John Seinfeld1, (1)California Institute of Technology, Pasadena, CA, United States, (2)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States, (3)University of California Riverside, Riverside, CA, United States, (4)University of California Irvine, Irvine, CA, United States
Recorded Presentation
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 volatile organic compound (VOC) emissions associated with transportation and economic activity. Here, we present measurements of submicrometer aerosol at Caltech (Pasadena, CA) from April 8 to July 19, 2020 using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), scanning mobility particle sizer (SMPS), and 12-h filter samples analyzed off-line with liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS). The extended deployment (102 days) 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 secondary organic aerosol (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.
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