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Volume 165, 2013
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Organic aerosol formation photo-enhanced by the formation of secondary photosensitizers in aerosols

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Secondary organic aerosols (SOA), which are produced by the transformations of volatile organic compounds in the atmosphere, play a central role in air quality, public health, visibility and climate, but their formation and aging remain poorly characterized. This study evidences a new mechanism for SOA formation based on photosensitized particulate-phase chemistry. Experiments were performed with a horizontal aerosol flow reactor where the diameter growth of the particles was determined as a function of various parameters. In the absence of gas-phase oxidant, experiments in which ammonium sulfate seeds containing glyoxal were exposed to gas-phase limonene and UV light exhibited a photo-induced SOA growth. Further experiments showed that this growth was due to traces of imidazole-2-carboxaldehyde (IC) in the seeds, a condensation product of glyoxal acting as an efficient photosensitizer. Over a 19 min irradiation time, 50 nm seed particles containing this compound were observed to grow between 3.5 and 30 ± 3% in the presence of either limonene, isoprene, α-pinene, β-pinene, or toluene in concentrations between 1.8 and 352 ppmv. The other condensation products of glyoxal, imidazole (IM) and 2,2-bi1H-imidazole (BI), also acted as photosensitizer but with much less efficiency under the same conditions. In the atmosphere, glyoxal and potentially other gas precursors would thus produce efficient photosensitizers in aerosol and autophotocatalyze SOA growth.

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Publication details

The article was received on 20 Mar 2013, accepted on 26 Apr 2013 and first published on 26 Apr 2013

Article type: Paper
DOI: 10.1039/C3FD00044C
Citation: Faraday Discuss., 2013,165, 123-134

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    Organic aerosol formation photo-enhanced by the formation of secondary photosensitizers in aerosols

    K. Z. Aregahegn, B. Nozière and C. George, Faraday Discuss., 2013, 165, 123
    DOI: 10.1039/C3FD00044C

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