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Are organic films from atmospheric aerosol and sea water inert to oxidation by ozone at the air-water interface?

DOI: 10.1016/j.atmosenv.2017.04.025 DOI Help

Authors: Stephanie Jones (Royal Holloway, University of London; STFC, Central Laser Facility) , Martin D. King (Royal Holloway, University of London) , Andrew D. Ward (STFC, Central Laser Facility) , Adrian R. Rennie (Uppsala University) , Alex C. Jones (Royal Holloway, University of London) , Thomas Arnold (Diamond Light Source)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Atmospheric Environment

State: Published (Approved)
Published: April 2017
Diamond Proposal Number(s): 8744 , 9632

Abstract: The heterogeneous oxidation of thin films of organic material extracted from real aerosol and sea-water samples was studied at the air-water interface using X-ray reflectivity. Oxidation of thin films of organic material extracted from real aerosol and sea-water are important in further understanding the impact of coated aerosols on the climate. Surface active insoluble organic material extracted from the atmosphere was found to form stable films at the air-water interface. On exposure of the films to gas-phase ozone, no reaction (or change in the relative scattering length of the interface) was observed, indicating a potential lack of unsaturated organic material in the samples. Gas chromatography and electrospray ionization mass spectrometry showed the presence of saturated compounds in the samples. It is therefore proposed that the amount of unsaturated compounds as compared to saturated compounds in the atmospheric material is so low that the mass spectrometry analyses, as well as gas-phase oxidation are dominated by saturated material. A reaction was observed on exposure of the same films to aqueous phase hydroxyl and nitrate radicals and a film thinning mechanism is proposed to explain the change in scattering length of the film at the air-water interface. It can be suggested tentatively that oxidation by gas-phase ozone is not important in the atmosphere for organic films on aqueous atmospheric aerosol and that further studies should focus on radical induced oxidation of saturated organic material instead of unsaturated proxies that are typically studied.

Journal Keywords: Atmospheric aerosol; Sea-water; Thin film; Heterogeneous oxidation; Ozone; OH radical; X-ray reflectivity

Subject Areas: Earth Science, Environment, Chemistry

Instruments: I07-Surface & interface diffraction

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