 |
| Titel |
Aging of secondary organic aerosol generated from the ozonolysis of α-pinene: effects of ozone, light and temperature |
| VerfasserIn |
C. Denjean, P. Formenti, B. Picquet-Varrault, M. Camredon, E. Pangui, P. Zapf, Y. Katrib, C. Giorio, A. Tapparo, B. Temime-Roussel, A. Monod, B. Aumont, J. F. Doussin |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 2 ; Nr. 15, no. 2 (2015-01-26), S.883-897 |
| Datensatznummer |
250119345
|
| Publikation (Nr.) |
 copernicus.org/acp-15-883-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
A series of experiments was conducted in the CESAM (French acronym for
Experimental Multiphasic Atmospheric Simulation Chamber) simulation chamber to
investigate the evolution of the physical and chemical properties of
secondary organic aerosols (SOAs) during different forcings. The present
experiments represent a first attempt to comprehensively investigate the
influence of oxidative processing, photochemistry, and diurnal temperature
cycling upon SOA properties. SOAs generated from the ozonolysis of α-pinene were exposed under dry conditions (< 1% relative
humidity) to (1) elevated ozone concentrations, (2) light (under controlled
temperature conditions) or (3) light and heat (6 °C light-induced
temperature increase), and the resultant changes in SOA optical properties
(i.e. absorption and scattering), hygroscopicity and chemical composition
were measured using a suite of instrumentation interfaced to the CESAM
chamber. The complex refractive index (CRI) was derived from integrated
nephelometer measurements of 525 nm wavelength, using Mie scattering
calculations and measured number size distributions. The particle size
growth factor (GF) was measured with a hygroscopic tandem differential
mobility analyzer (H-TDMA). An aerosol mass spectrometer (AMS) was used for
the determination of the f44 / f43 and O : C ratio of the particles
bulk.
No change in SOA size or chemical composition was observed during O3
and light exposure at constant temperature; in addition, GF and CRI of the
SOA remained constant with forcing. On the contrary, illumination of SOAs in
the absence of temperature control led to an increase in the real part of
the CRI from 1.35 (±0.03) to 1.49 (±0.03), an increase of the
GF from 1.04 (±0.02) to 1.14 (±0.02) and an increase of the
f44 / f43 ratio from 1.73 (±0.03) to 2.23 (±0.03). The
simulation of the experiments using the master chemical mechanism (MCM) and
the Generator for Explicit Chemistry and Kinetics of Organics in the
Atmosphere (GECKO-A) shows that these changes resulted from the evaporation
of semi-volatile and less oxidized SOA species induced by the relatively
minor increases in temperature (~ 6 °C). These
surprising results suggest that α-pinene–O3 SOA properties may
be governed more by local temperature fluctuations than by oxidative
processing and photochemistry. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|