TY - JOUR
T1 - Contribution of carbonyl photochemistry to aging of atmospheric secondary organic aerosol
AU - Mang, Stephen A.
AU - Henricksen, Dana K.
AU - Bateman, Adam P.
AU - Andersen, Mads Peter Sulbæk
AU - Blake, Donald R.
AU - Nizkorodov, Sergey A.
PY - 2008
Y1 - 2008
N2 - 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 I-butene. The absorption spectrum of SOA material collected onto CaF, windows was measured and compared with the photolysis action spectrum for the release of CO, a marker for Norrish type-1 photocleavage of carbonyls. Both spectra had a band at similar to 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 rim, 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.
AB - 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 I-butene. The absorption spectrum of SOA material collected onto CaF, windows was measured and compared with the photolysis action spectrum for the release of CO, a marker for Norrish type-1 photocleavage of carbonyls. Both spectra had a band at similar to 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 rim, 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.
U2 - 10.1021/jp804376c
DO - 10.1021/jp804376c
M3 - Journal article
C2 - 18700731
SN - 1089-5639
VL - 112
SP - 8337
EP - 8344
JO - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
JF - Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
IS - 36
ER -