 |
| Titel |
Effect of oxidant concentration, exposure time, and seed particles on secondary organic aerosol chemical composition and yield |
| VerfasserIn |
A. T. Lambe, P. S. Chhabra, T. B. Onasch, W. H. Brune, J. F. Hunter, J. H. Kroll, M. J. Cummings, J. F. Brogan, Y. Parmar, D. R. Worsnop, C. E. Kolb, P. Davidovits |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 6 ; Nr. 15, no. 6 (2015-03-18), S.3063-3075 |
| Datensatznummer |
250119558
|
| Publikation (Nr.) |
 copernicus.org/acp-15-3063-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| We performed a systematic intercomparison study of the chemistry and
yields of secondary organic aerosol (SOA) generated from OH oxidation of a common set of
gas-phase precursors in a Potential Aerosol Mass (PAM) continuous
flow reactor and several environmental chambers. In the flow
reactor, SOA precursors were oxidized using OH concentrations
ranging from 2.0 × 108 to
2.2 × 1010 molec cm−3 over exposure times of
100 s. In the environmental chambers, precursors were oxidized
using OH concentrations ranging from 2 × 106 to
2 × 107 molec cm−3 over exposure times of several
hours. The OH concentration in the chamber experiments is close to
that found in the atmosphere, but the integrated OH exposure in the
flow reactor can simulate atmospheric exposure times of multiple
days compared to chamber exposure times of only a day or so.
In most cases, for a specific SOA type the most-oxidized chamber SOA and the
least-oxidized flow reactor SOA have similar mass spectra, oxygen-to-carbon and
hydrogen-to-carbon ratios, and carbon oxidation states at integrated OH exposures
between approximately 1 × 1011 and 2 × 1011 molec cm−3 s,
or about 1–2 days of equivalent atmospheric oxidation. This observation suggests that
in the range of available OH exposure overlap for the flow reactor and chambers, SOA
elemental composition as measured by an aerosol mass spectrometer is similar whether
the precursor is exposed to low OH concentrations over long exposure times or high OH
concentrations over short exposure times.
This similarity in turn suggests
that both in the flow reactor and in chambers, SOA chemical
composition at low OH exposure is governed primarily by gas-phase OH
oxidation of the precursors rather than heterogeneous oxidation of
the condensed particles. In general, SOA yields measured in the
flow reactor are lower than measured in chambers for the range of
equivalent OH exposures that can be measured in both the flow
reactor and chambers. The influence of sulfate seed particles on
isoprene SOA yield measurements was examined in the flow reactor.
The studies show that seed particles increase the yield of SOA
produced in flow reactors by a factor of 3 to 5 and may also account
in part for higher SOA yields obtained in the chambers, where seed
particles are routinely used. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|