Special Issue on Carbonaceous Aerosols in the Atmosphere

Michael R. Olson This email address is being protected from spambots. You need JavaScript enabled to view it.1,2, Alexandra Lai2,3, Matthew Skiles2,4, James J. Schauer2 

1 California Air Resources Board, Sacramento, CA, USA
2 University of Wisconsin Madison, Water Science and Engineering Laboratory, Madison, WI, USA
3 Weizmann Institute of Science, Rehovot, Center District, Israel
4 The University of Texas at Austin, Austin, TX, USA


Received: November 27, 2023
Revised: February 4, 2024
Accepted: February 6, 2024

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.


Download Citation: ||https://doi.org/10.4209/aaqr.230292  


Cite this article:

Olson, M.R., Lai, A., Skiles, M., Schauer, J.J. (2024). Attribution of Source Specific 370 nm UV Light Absorption from Dust, Brown Carbon, and Black Carbon at Two Locations in the San Joaquin Valley. Aerosol Air Qual. Res. https://doi.org/10.4209/aaqr.230292


HIGHLIGHTS

  • Winter near-UV abs. is dominated by wood combustion in the San Joaquin Valley (SJV).
  • Vehicle BC & BrC emissions are key near-UV abs. sources in the SJV during summer.
  • Literature BrC MACs can be used to accurately reproduce ambient 370 nm absorption.
  • Source apportionment results are a vital tool to predict near-UV absorption.
 

ABSTRACT


Yearlong, one-in-three-day, source apportionment results were applied to literature values of source specific BrC, BC, and dust mass absorption cross-sections (MAC) to estimate the source contribution to 370 nm near-UV light absorption at Fresno and Bakersfield, San Joquin Valley (SJV), California. The reconstructed light absorption agreed well (r2 of 0.94 Fresno and 0.90 Bakersfield) with co-located AE33 aethalometer measurements. Near-UV absorption was attributed to total mobile, vegetative detritus, wood combustion, meat cooking, SOA and dust sources. Winter BrC absorption was dominated by wood combustion, accounting for 67% (Fresno) and 53% (Bakersfield) of light absorption at the sites. In summer, wood combustion only accounted for approximately 7% of the near-UV absorption in the SJV. Summer absorption, while significantly lower than winter values, was dominated by SOA and vehicle emissions. In Fresno, summer absorption was comprised of 35% SOA, 39% vehicle BC and 15% vehicle BrC. Bakersfield’s summer absorption was 27% SOA, 44% vehicle BC, and 14% Vehicle BrC. Total BrC absorption correlated well with OC concentrations, when segregated out by season, while the total BrC absorption was highly variable when compared to WSOC concentrations. The results indicate using source specific MAC values is an effective way to model near-UV light absorption associated with BrC sources and mitigation approaches that prioritize wood combustion in winter and vehicle emissions in summer would have the greatest effect in reducing near-UV light absorption in the SJV.


Keywords: Brown carbon, UV absorption, Source apportionment, Vehicle emissions, Biomass burning




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