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

Thomas, Daniel A. and Coggon, Matthew M. and Lignell, Hanna and Schilling, Katherine Ann and Zhang, Xuan and Schwantes, Rebecca H. and Flagan, Richard C. and Seinfeld, John H. and Beauchamp, Jesse Lee (2016) Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols. Environmental Science and Technology, 50 (22). pp. 12241-12249. ISSN 0013-936X. doi:10.1021/acs.est.6b03588.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Information
Thomas, Daniel A.0000-0001-9415-5991
Coggon, Matthew M.0000-0002-5763-1925
Lignell, Hanna0000-0001-7049-1659
Schwantes, Rebecca H.0000-0002-7095-3718
Flagan, Richard C.0000-0001-5690-770X
Seinfeld, John H.0000-0003-1344-4068
Beauchamp, Jesse Lee0000-0001-8839-4822
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.
Funding AgencyGrant Number
Department of DefenseUNSPECIFIED
Subject Keywords:Fenton, Oxalate, Iron, Aerosol, Glycolaldehyde, Oxidation, Oxalic, Aqueous
Issue or Number:22
Record Number:CaltechAUTHORS:20161021-115049301
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Official Citation:Real-Time Studies of Iron Oxalate-Mediated Oxidation of Glycolaldehyde as a Model for Photochemical Aging of Aqueous Tropospheric Aerosols Daniel A. Thomas, Matthew M. Coggon, Hanna Lignell, Katherine A. Schilling, Xuan Zhang, Rebecca H. Schwantes, Richard C. Flagan, John H. Seinfeld, and J. L. Beauchamp Environmental Science & Technology 2016 50 (22), 12241-12249 DOI: 10.1021/acs.est.6b03588
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:71344
Deposited By: Tony Diaz
Deposited On:21 Oct 2016 19:14
Last Modified:11 Nov 2021 04:43

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