 |
| Titel |
Inter-comparison of laboratory smog chamber and flow reactor systems on organic aerosol yield and composition |
| VerfasserIn |
E. A. Bruns, I. El Haddad, A. Keller, F. Klein, N. K. Kumar, S. M. Pieber, J. C. Corbin, J. G. Slowik, W. H. Brune, U. Baltensperger, A. S. H. Prévôt |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1867-1381
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 6 ; Nr. 8, no. 6 (2015-06-04), S.2315-2332 |
| Datensatznummer |
250116423
|
| Publikation (Nr.) |
 copernicus.org/amt-8-2315-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
A variety of tools are used to simulate atmospheric aging, including smog
chambers and flow reactors. Traditional, large-scale smog chambers age
emissions over the course of hours to days, whereas flow reactors rapidly
age emissions using high oxidant concentrations to reach higher degrees of
oxygenation than typically attained in smog chamber experiments. The
atmospheric relevance of the products generated under such rapid oxidation
warrants further study. However, no previously published studies have
compared the yields and chemical composition of products generated in flow
reactors and smog chambers from the same starting mixture.
The yields and composition of the organic aerosol formed from the
photo-oxidation of α-pinene and of wood-combustion emissions in a
smog chamber (SC) and two flow reactors: a potential aerosol mass reactor
(PAM) and a micro-smog chamber (MSC), were determined using aerosol mass
spectrometry. Reactants were sampled from the SC and aged in the MSC and the PAM
using a range of hydroxyl radical (OH) concentrations and then
photo-chemically aged in the SC.
The chemical composition, as well as the maximum yields and emission
factors, of the products in both the α-pinene and wood-combustion
systems determined with the PAM and the SC agreed reasonably well. High OH
exposures have been shown previously to lower yields by breaking
carbon–carbon bonds and forming higher volatility species, which reside
largely in the gas phase; however, fragmentation in the PAM was not
observed. The yields determined using the PAM for the α-pinene
system were slightly lower than in the SC, possibly from increased wall
losses of gas phase species due to the higher surface area to volume ratios
in the PAM, even when offset with better isolation of the sampled flow from
the walls. The α-pinene SOA results for the MSC were not directly
comparable, as particles were smaller than the optimal AMS transmission
range. The higher supersaturation in the flow reactors resulted in more
nucleation than in the SC. For the wood-combustion system, emission factors
measured from the MSC were typically lower than those measured from the SC.
Lower emission factors in the MSC may have been due to considerable
nucleation mode particles formed in the MSC which were not detected by the
AMS or due to condensational loss of gases to the walls inside or after the
MSC. More comprehensive coverage of the potential particle size range is
needed in future SOA measurements to improve our understanding of the
differences in yields when comparing the MSC to the SC. The PAM and the SC
agreed within measurement uncertainties in terms of yields and
composition for the systems and conditions studied here and this agreement
supports the continued use of the PAM to study atmospheric aging. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|