Comparison between Spatially Resolved Airborne Flux Measurements and Emission Inventories of Volatile Organic Compounds in Los Angeles
Abstract
Los Angeles is a major hotspot for ozone and particulate matter air pollution in the United States. Ozone and PM_(2.5) in this region have not improved substantially for the past decade, despite a reduction in vehicular emissions of their precursors, NOₓ and volatile organic compounds (VOCs). This reduction in "traditional" sources has made the current emission mixture of air pollutant precursors more uncertain. To map and quantify emissions of a wide range of VOCs in this urban area, we performed airborne eddy covariance measurements with wavelet analysis. VOC fluxes measured include tracers for source categories, such as traffic, vegetation, and volatile chemical products (VCPs). Mass fluxes were dominated by oxygenated VOCs, with ethanol contributing ∼29% of the total. In terms of OH reactivity and aerosol formation potential, terpenoids contributed more than half. Observed fluxes were compared with two commonly used emission inventories: the California Air Resources Board inventory and the combination of the Biogenic Emission Inventory System with the Fuel-based Inventory of Vehicle Emissions combined with Volatile Chemical Products (FIVE-VCP). The comparison shows mismatches regarding the amount, spatial distribution, and weekend effects of observed VOC emissions with the inventories. The agreement was best for typical transportation related VOCs, while discrepancies were larger for biogenic and VCP-related VOCs.
Copyright and License
© 2022 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0.
Acknowledgement
The authors thank Dennis Baldocchi, Glenn Wolfe, Erin Delaria, and Tianxin Wang for insightful discussions about vertical flux divergence, Matthew Coggon, Chelsea Stockwell, and Carsten Warneke for valuable discussions on PTR-ToF-MS VOC corrections, the Regional Chemical Modeling Group of NOAA CSL for help with weather forecasting, and the Modeling and Meteorology Branch at CARB for providing their inventory. We gratefully acknowledge Greg Cooper for excellent mission support, the pilots Bryce Kujat and George Loudakis for flight planning and execution, and Robert Weber and Erin Katz for logistical support. We acknowledge the following funding sources: California Air Resources Board Contract numbers 20RD003 and 20AQP012, NOAA Climate Program Office's Atmospheric Chemistry, Carbon Cycle, and Climate program, grant number NA22OAR4310540 [UCB]/ NA22OAR4310541 [AD], Office of Naval Research Defense University Research Instrumentation Program grant number N00014-19-1-2108, Presidential Early Career Award for Scientists and Engineers (PECASE), and EPA-STAR grant (84001001). EP was supported by an Alexander von Humboldt Foundation Feodor Lynen Fellowship. The views expressed in this article are those of the authors and do not necessarily represent the views or policies of the U.S. Environmental Protection Agency. EPA does not endorse any products or commercial services mentioned in this publication.
Conflict of Interest
The authors declare no competing financial interest.
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acs.est.3c03162.pdf
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Identifiers
- ISSN
- 1520-5851
Related works
Funding
- California Air Resources Board
- 20RD003
- California Air Resources Board
- 20AQP012
- National Oceanic and Atmospheric Administration
- NA22OAR4310540
- National Oceanic and Atmospheric Administration
- NA22OAR4310541
- Office of Naval Research
- N00014-19-1-2108
- Environmental Protection Agency
- 84001001
- Alexander von Humboldt Foundation