A034-0015
Influence of Anthropogenic Emission Reduction during COVID-19 on PM2.5 in California’s San Joaquin Valley: Concentrations and Chemical Properties
Tuesday, 8 December 2020
Poster
Shang Liu1, William Vance1, Toshihiro Kuwayama1, Chenxia Cai1, Jianjun Chen1, Jeremy Avise1, Michael FitzGibbon1, Elizabeth Scheehle2, Lijuan Li3, Ryan Nilsson Farley3, Christopher Niedek3, Qi Zhang3, Christopher D Cappa4 and Sally E. Pusede5, (1)California Air Resources Board, Sacramento, CA, United States, (2)California Environmental Protection Agency Air Resources Board, Sacramento, CA, United States, (3)University of California Davis, Department of Environmental Toxicology, Davis, CA, United States, (4)University of California, Department of Civil and Environmental Engineering, Davis, CA, United States, (5)University of Virginia, Department of Environmental Science, Charlottesville, VA, United States
Abstract:
California’s San Joaquin Valley (SJV) experiences high levels of ambient PM
2.5 pollution despite decades of emission controls. To examine the mechanisms that lead to high PM
2.5 episodes in the SJV, the non-refractory organic and inorganic (nitrate, sulfate, and ammonium) components of PM
2.5 have been continuously measured using an Aerosol Chemical Speciation Monitor at the Fresno Supersite since October 2018. In addition, black carbon has been measured with a seven-wavelength Aethalometer since March 2019. The long-running measurements captured the changes in speciated PM
2.5 levels before and after the California Governor’s shelter-in-place order in response to the 2020 COVID-19 pandemic, thereby enabling us to evaluate the impact of reduced anthropogenic emissions on air quality in the SJV.
Based on the dataset adjusted for the interannual variability in PM2.5 species, we estimated that the PM2.5 species decreased by about 50% on average after the shelter-in-place order compared to the same period in 2019. Additional analysis will be conducted to evaluate the change of PM2.5 level using historical data. Despite this substantial reduction, the overall chemical composition and aerosol properties, such as acidity, did not change with statistical confidence. In addition, source apportionment analysis was performed to evaluate the influence of changing source activities to ambient PM2.5. The results suggested that primary air pollutant emission controls will continue to hold strong implications for reducing secondary PM in the SJV. Furthermore, the results suggested that reduction in ambient PM2.5 levels will likely not shift the PM formation mechanisms, providing confidence that current air quality evaluation strategies can be used to study the efficacy of the PM control measures on future air quality, climate, and human health. Additional modeling analysis using the dataset can further evaluate the sensitivity of emission reduction in mitigating PM2.5 in the SJV.
