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| Titel |
Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multilayer model ADCHAM |
| VerfasserIn |
P. Roldin, A. C. Eriksson, E. Z. Nordin, E. Hermansson, D. Mogensen, A. Rusanen, M. Boy, E. Swietlicki, B. Svenningsson, A. Zelenyuk, J. Pagels |
| 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 ; 14, no. 15 ; Nr. 14, no. 15 (2014-08-11), S.7953-7993 |
| Datensatznummer |
250118935
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| Publikation (Nr.) |
 copernicus.org/acp-14-7953-2014.pdf |
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| Zusammenfassung |
We have developed the novel Aerosol Dynamics, gas- and particle-phase
chemistry model for laboratory CHAMber studies (ADCHAM). The model combines
the detailed gas-phase Master Chemical Mechanism version 3.2 (MCMv3.2), an aerosol
dynamics and particle-phase chemistry module (which considers acid-catalysed
oligomerization, heterogeneous oxidation reactions in the particle phase and
non-ideal interactions between organic compounds, water and inorganic ions)
and a kinetic multilayer module for diffusion-limited transport of compounds
between the gas phase, particle surface and particle bulk phase. In this
article we describe and use ADCHAM to study (1) the evaporation of liquid
dioctyl phthalate (DOP) particles, (2) the slow and almost particle-size-independent evaporation of α-pinene ozonolysis secondary organic
aerosol (SOA) particles, (3) the mass-transfer-limited uptake of ammonia
(NH3) and formation of organic salts between ammonium (NH4+)
and carboxylic acids (RCOOH), and (4) the influence of chamber wall effects
on the observed SOA formation in smog chambers.
ADCHAM is able to capture the observed α-pinene SOA mass increase in
the presence of NH3(g). Organic salts of ammonium and carboxylic acids
predominantly form during the early stage of SOA formation. In the
smog chamber experiments, these salts contribute substantially to the
initial growth of the homogeneously nucleated particles.
The model simulations of evaporating α-pinene SOA particles support
the recent experimental findings that these particles have a semi-solid tar-like amorphous-phase state. ADCHAM is able to reproduce the main features of
the observed slow evaporation rates if the concentration of low-volatility
and viscous oligomerized SOA material at the particle surface increases upon
evaporation. The evaporation rate is mainly governed by the reversible
decomposition of oligomers back to monomers.
Finally, we demonstrate that the mass-transfer-limited uptake of condensable
organic compounds onto wall-deposited particles or directly onto the Teflon
chamber walls of smog chambers can have a profound influence on the observed
SOA formation. During the early stage of the SOA formation the wall-deposited particles and walls themselves serve as an SOA sink from the air to
the walls. However, at the end of smog chamber experiments the semi-volatile
SOA material may start to evaporate from the chamber walls.
With these four model applications, we demonstrate that several poorly
quantified processes (i.e. mass transport limitations within the particle
phase, oligomerization, heterogeneous oxidation, organic salt formation, and
chamber wall effects) can have a substantial influence on the SOA formation,
lifetime, chemical and physical particle properties, and their evolution. In
order to constrain the uncertainties related to these processes, future
experiments are needed in which as many of the influential variables as
possible are varied. ADCHAM can be a valuable model tool in the design and
analysis of such experiments. |
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