| Title: | Contribution of carbonyl photochemistry to aging of atmospheric secondary organic aerosol |
| Author(s): | Mang SA; Henricksen DK; Bateman AP; Andersen MP; Blake DR; Nizkorodov SA; |
| Address: | "Department of Chemistry, University of California, Irvine, California 92697, USA" |
| ISSN/ISBN: | 1520-5215 (Electronic) 1089-5639 (Linking) |
| Abstract: | "The photodegradation of secondary organic aerosol (SOA) material by actinic UV radiation was investigated. SOA was generated via the dark reaction of ozone and d-limonene, collected onto quartz-fiber filters, and exposed to wavelength-tunable radiation. Photochemical production of CO was monitored in situ by infrared cavity ring-down spectroscopy. A number of additional gas-phase products of SOA photodegradation were observed by gas chromatography, including methane, ethene, acetaldehyde, acetone, methanol, and 1-butene. The absorption spectrum of SOA material collected onto CaF2 windows was measured and compared with the photolysis action spectrum for the release of CO, a marker for Norrish type-I photocleavage of carbonyls. Both spectra had a band at approximately 300 nm corresponding to the overlapping n --> pi* transitions in nonconjugated carbonyls. The effective extinction coefficient of freshly prepared SOA was estimated to be on the order of 15 L mol(-1) cm(-1) at 300 nm, implying one carbonyl group in every SOA constituent. The absorption by the SOA material slowly increased in the visible and near-UV during storage of SOA in open air in the dark, presumably as a result of condensation reactions that increased the degree of conjugation in the SOA constituents. These observations suggest that photolysis of carbonyl functional groups represents a significant sink for monoterpene SOA compounds in the troposphere, with an estimated lifetime of several hours over the continental United States" |
| Keywords: | "Acetaldehyde/chemistry Acetone/chemistry Aerosols/*chemistry Air Pollutants/*chemistry Chromatography, Gas/methods Cyclohexenes/chemistry Filtration/instrumentation/methods Limonene Organic Chemicals/*chemistry Ozone/chemistry Particle Size *Photochemistr;" |
| Notes: | "MedlineMang, Stephen A Henricksen, Dana K Bateman, Adam P Andersen, Mads P Sulbaek Blake, Donald R Nizkorodov, Sergey A eng Research Support, U.S. Gov't, Non-P.H.S. 2008/08/15 J Phys Chem A. 2008 Sep 11; 112(36):8337-44. doi: 10.1021/jp804376c. Epub 2008 Aug 14" |
