Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published November 15, 2016 | public
Journal Article Open

Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols


The complexation of iron (III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron (II) and the carbon dioxide anion radical. Importantly, iron (III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown. This study utilizes glycolaldehyde as a model organic species to examine the oxidation pathways and evolution of organic aerosol initiated by the photodissociation of aqueous iron (III) oxalate complexes. Hanging droplets (radius 1 mm) containing iron (III), oxalic acid, glycolaldehyde, and ammonium sulfate (pH ~ 3) are exposed to irradiation at 365 nm and sampled at discrete time points utilizing field-induced droplet ionization mass spectrometry (FIDI-MS). Glycolaldehyde is found to undergo rapid oxidation to form glyoxal, glycolic acid, and glyoxylic acid, but the formation of high molecular weight oligomers is not observed. For comparison, particle-phase experiments conducted in a laboratory chamber explore the reactive uptake of gas-phase glycolaldehyde onto aqueous seed aerosol containing iron and oxalic acid. The presence of iron oxalate in seed aerosol is found to inhibit aerosol growth. These results suggest that photodissociation of iron (III) oxalate can lead to the formation of volatile oxidation products in tropospheric aqueous aerosols.

Additional Information

© 2016 American Chemical Society. Publication Date (Web): October 12, 2016. This work was supported by the Beckman Institute at Caltech and by the NSF grants CHE-1508825 and AGS-1523500. K.A.S. acknowledges support from the Department of Defense SMART program. The authors thank Kevin M. Barraza, Xinxing Zhang, and Prof. Mitchio Okumura for assistance with radiant flux measurements. Author Contributions: The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. D.AT. and M.M.C. contributed equally to this work. The authors declare no competing financial interest.

Attached Files

Accepted Version - acs_2Eest_2E6b03588.pdf

Supplemental Material - es6b03588_si_001.pdf


Files (2.7 MB)
Name Size Download all
1.5 MB Preview Download
1.2 MB Preview Download

Additional details

August 19, 2023
August 19, 2023