Particulate Oxalate-To-Sulfate Ratio as an Aqueous Processing Marker: Similarity Across Field Campaigns and Limitations

Miguel Ricardo A. Hilario, Ewan Crosbie, Paola Angela Bañaga, Grace Betito, Rachel A. Braun, Maria Obiminda Cambaliza, Andrea F. Corral, Melliza Templonuevo Cruz, Jack E. Dibb, Genevieve Rose Lorenzo, Alexander B. MacDonald, Claire E. Robinson, Michael A. Shook, James Bernard Simpas, Connor Stahl, Edward Winstead, Luke D. Ziemba, Armin Sorooshian

Research output: Contribution to journalLetterpeer-review

11 Scopus citations


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 = 2,948). 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 toward 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.

Original languageEnglish (US)
Article numbere2021GL096520
JournalGeophysical Research Letters
Issue number23
StatePublished - Dec 16 2021


  • CAMPEx
  • Oxalate
  • cloud processing
  • secondary organic aerosol
  • sulfate

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


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