U003-03
Early Implications of the COVID-19 Shelter-in-Place Restrictions on Urban Air Quality in the Los Angeles Basin

Tuesday, 8 December 2020: 07:25
Kelley Barsanti1, Jeremy Avise2, Bart Eric Croes3, Joost A de Gouw4, Sina Hasheminassab5, Cesunica Ivey6, Jessica L. Neu7, Olga Pikelnaya5, Stanley Sander7, Yuk L Yung8, Zhao-Cheng Zeng9 and Paul O Wennberg10, (1)University of California Riverside, Chemical & Environmental Engineering, Center for Environmental Research & Technology, Riverside, CA, United States, (2)California Air Resources Board, Sacramento, CA, United States, (3)California Energy Commission, Sacramento, CA, United States, (4)University of Colorado, CIRES and Department of Chemistry, Boulder, CO, United States, (5)South Coast Air Quality Management District, Diamond Bar, CA, United States, (6)University of California Riverside, Chemical and Environmental Engineering, Riverside, United States, (7)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (8)California Institute of Technology, Pasadena, CA, United States, (9)University of California, Los Angeles, Pasadena, CA, United States, (10)California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Abstract:
COVID-19 shelter-in-place restrictions have led to disproportionate changes in human activities and associated emissions. The impacts of these changes on air quality and human health are spatially variable and moderated by chemistry and meteorology. Comparisons of historical data, and data collected during shelter-in-place restrictions, have provided unprecedented opportunities to: 1) test hypotheses regarding major sources and ambient levels of air pollutants and their precursors (including volatile organic compounds, nitrogen oxides, ozone (O3), and fine particulate matter (PM2.5); 2) evaluate fundamental understanding and model representation of how changes in emissions and meteorology drive changes in O3 and PM2.5; and 3) assess the efficacy of air pollution mitigation strategies in reducing pollutants and minimizing human health effects. The Los Angeles Basin has experienced dramatic reductions in several air pollutants over decades. Recently however, trends in ambient O3 and PM2.5 have leveled. This pollution and mitigation history has led to several long-term data sets that are useful for interpreting historical trends and current observations. Analyses of these data reveal that while there have been reductions in transportation sector activity and emissions, the responses of secondary pollutants vary significantly and are highly influenced by meteorology. Across the Basin, O3 levels largely showed no significant decreases, but showed strong correlations with temperature. There is also evidence for changes in O3 production and peak O3 location due to changes in emissions during shelter-in-place. Regional-scale models reproduced the sensitivity of O3 to temperature, but additional sources and detailed chemical modeling were required to represent O3 observations at individual locations. Averaged across the Basin, median PM2.5 levels showed statistically significant decreases, even when accounting for heavy rainfall events. Compositional analysis by site provided insight into changes in PM2.5 levels in response to localized changes in emissions. The data collected and analyzed during this unprecedented pause in human activity will support development of optimized strategies to reduce air pollutants and evaluation of potential health benefits associated with those reductions.
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