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| Titel |
Self-limited uptake of α-pinene oxide to acidic aerosol: the effects of liquid–liquid phase separation and implications for the formation of secondary organic aerosol and organosulfates from epoxides |
| VerfasserIn |
G. T. Drozd, J. L. Woo, V. F. McNeill |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 16 ; Nr. 13, no. 16 (2013-08-22), S.8255-8263 |
| Datensatznummer |
250085640
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| Publikation (Nr.) |
 copernicus.org/acp-13-8255-2013.pdf |
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| Zusammenfassung |
| The reactive uptake of α-pinene oxide (αPO) to acidic sulfate
aerosol was studied under humid conditions in order to gain insight into the
effects of liquid–liquid phase separation on aerosol heterogeneous chemistry
and to elucidate further the formation of secondary organic aerosol and
organosulfates from epoxides. A continuous flow environmental chamber was
used to monitor changes in diameter of monodisperse, deliquesced, acidic
sulfate particles exposed to αPO at 25% and 50% RH (relative humidity). In order
to induce phase separation and probe potential limits to particle growth from
acidic uptake, αPO was introduced over a wide range of concentrations,
from 200 ppb to 5 ppm. Uptake was observed to be highly
dependent on initial aerosol pH. Significant uptake of αPO to aerosol
was observed with initial pH < 0. When exposed to 200 ppb αPO, aerosol with pH = -0.5 showed 23% growth, and 6%
volume growth was observed at pH = 0. Aerosol with pH = 1 showed no
growth. The extreme acidity required for efficient αPO uptake suggests
that this chemistry is typically not a major route to formation of aerosol
mass or organosulfates in the atmosphere. Effective partition coefficients
(Kp, eff) were in the range of (0.1–2) x 10-4 m3μg-1 and were correlated to initial particle acidity and particle organic
content; particles with higher organic content had lower partition
coefficients. Effective uptake coefficients (γeff) ranged
from 0.1 to 1.1 x 10-4 and are much lower than recently reported for
uptake to bulk solutions. In experiments in which αPO was added to
bulk H2SO4 solutions, phase separation was observed for mass
loadings similar to those observed with particles, and product distributions
were dependent on acid concentration. Liquid–liquid phase separation in bulk
experiments, along with our observations of decreased uptake to particles
with the largest growth factors, suggests an organic coating forms upon
uptake to particles, limiting reactive uptake. |
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