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Contribution of carbonyl photochemistry to aging of atmospheric secondary organic aerosol.
- Source :
-
The journal of physical chemistry. A [J Phys Chem A] 2008 Sep 11; Vol. 112 (36), pp. 8337-44. Date of Electronic Publication: 2008 Aug 14. - Publication Year :
- 2008
-
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.
- Subjects :
- Acetaldehyde chemistry
Acetone chemistry
Chromatography, Gas methods
Cyclohexenes chemistry
Filtration instrumentation
Filtration methods
Limonene
Ozone chemistry
Particle Size
Quartz chemistry
Terpenes chemistry
Time Factors
Ultraviolet Rays
Volatilization
Aerosols chemistry
Air Pollutants chemistry
Organic Chemicals chemistry
Photochemistry
Subjects
Details
- Language :
- English
- ISSN :
- 1520-5215
- Volume :
- 112
- Issue :
- 36
- Database :
- MEDLINE
- Journal :
- The journal of physical chemistry. A
- Publication Type :
- Academic Journal
- Accession number :
- 18700731
- Full Text :
- https://doi.org/10.1021/jp804376c