Particulate Oxalate-to-Sulfate Ratio as an Aqueous Processing
Marker: Similarity Across
Field Campaigns and Limitations
Miguel Ricardo A. Hilario1, Ewan
Crosbie2,3, Paola Angela Bañaga4,5,
Grace Betito4,5, Rachel A. Braun6,†,
Maria Obiminda Cambaliza4,5, Andrea F.
Corral6, Melliza Templonuevo
Cruz4,7, Jack E. Dibb8, Genevieve
Rose Lorenzo1, Alexander B.
MacDonald6, Claire E. Robinson2,3,
Michael A. Shook2, James Bernard
Simpas4,5, Connor Stahl6, Edward
Winstead2,3, Luke D. Ziemba2, and
Armin Sorooshian1,6
1 Department of Hydrology and Atmospheric Sciences,
University of Arizona, Tucson, AZ 85721, USA, 2 NASA
Langley Research Center, Hampton, VA, USA, 3 Science
Systems and Applications, Inc., Hampton, VA, USA, 4Manila Observatory, Quezon City 1108, Philippines, 5Department of Physics, School of Science and Engineering, Ateneo de
Manila University, Quezon City 1108, Philippines, 6Department of Chemical and Environmental Engineering, University of
Arizona, Tucson, AZ 85721, USA, 7 Institute of
Environmental Science and Meteorology, University of the Philippines,
Diliman, Quezon City 1101, Philippines, 8 Earth
Systems Research Center, Institute for the Study of Earth, Oceans, and
Space, University of New Hampshire, Durham, NH, USA
Corresponding author: Armin Sorooshian
(armin@email.arizona.edu)
† Now at: Healthy Urban Environments Initiative,
Global Institute of Sustainability and Innovation, Arizona State
University, Tempe, AZ, USA
Key Points:
- Oxalate-sulfate mass ratios show similarity across multiple
environments (95% confidence interval: 0.0154 – 0.0296; R = 0.76; N
= 2948)
- Oxalate-sulfate mass ratio is biased towards higher values in presence
of coarse aerosol particles and/or biomass burning
- Ground-based, size-resolved
measurements reveal that the ratio can be robust within the mixed
layer for the submicrometer mode
-
Abstract
Leveraging aerosol data from multiple airborne and surface-based field
campaigns encompassing diverse environmental conditions, we calculate
statistics of the oxalate-sulfate mass ratio
(median: 0.0217; 95% confidence
interval: 0.0154 – 0.0296; R = 0.76; N = 2948). Ground-based
measurements of the oxalate-sulfate ratio fall within our 95%
confidence interval, suggesting the range is robust within the mixed
layer for the submicrometer particle size range. We demonstrate that
dust and biomass burning emissions can separately bias this ratio
towards higher values by at least one order of magnitude. In the absence
of these confounding factors, the 95% confidence interval of the ratio
may be used to estimate the relative extent of aqueous processing by
comparing inferred oxalate concentrations between air masses, with the
assumption that sulfate primarily originates from aqueous processing.