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| Titel |
Parameterising secondary organic aerosol from α-pinene using a detailed oxidation and aerosol formation model |
| VerfasserIn |
K. Ceulemans, S. Compernolle, J.-F. Müller |
| 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 ; 12, no. 12 ; Nr. 12, no. 12 (2012-06-19), S.5343-5366 |
| Datensatznummer |
250011273
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| Publikation (Nr.) |
 copernicus.org/acp-12-5343-2012.pdf |
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| Zusammenfassung |
| A new parameter model for α-pinene secondary organic aerosol (SOA) is
presented, based on simulations with the detailed model BOREAM (Biogenic
hydrocarbon Oxidation and Related Aerosol formation Model). The
parameterisation takes into account the influence of temperature, type of
oxidant, NOx-regime, photochemical ageing and water uptake, and
is suitable for use in global chemistry transport models. BOREAM is validated
against recent photooxidation smog chamber experiments, for which it
reproduces SOA yields to within a factor of 2 in most cases. In the simple
chemical mechanism of the parameter model, oxidation of α-pinene
generates peroxy radicals, which, upon reaction with NO or HO2, yield
products corresponding to high or low-NOx conditions,
respectively. The model parameters – i.e. the temperature-dependent
stoichiometric coefficients and partitioning coefficients of 10 semi-volatile
products – are obtained from simulations with BOREAM, including a prescribed
diurnal cycle for the radiation, oxidant and emission levels, as well as a
deposition sink for the particulate and gaseous products. The effects of
photooxidative ageing are implicitly included in the parameterisation, since
it is based on near-equilibrium SOA concentrations, obtained through
simulations of a two-week period. In order to mimic the full BOREAM model
results both during SOA build-up and when SOA has reached an equilibrium
concentration, the revolatilisation of condensable products due to
photochemical processes is taken into account through a fitted
pseudo-photolysis reaction of the lumped semi-volatile products. Modelled SOA
mass yields are about ten times higher in low-NOx than in
high-NOx conditions, with yields of more than 50% in the
low-NOx OH-initiated oxidation of α-pinene, considerably
more than in previous parameterisations based on smog chamber experiments.
Sensitivity calculations indicate that discrepancies between the full model
and the parameterisation due to variations in assumed oxidant levels are
limited, but that changes in the radiation levels can lead to larger
deviations. Photolysis of species in the particulate phase is found to
strongly reduce SOA yields in the full model. Simulations of ambient
conditions at 17 different sites (using oxidant, radiation and meteorological
data from a global chemistry-transport model) show that overall, the
parameterisation displays only little bias (2%) compared with the full
model, whereas averaged relative deviations amount to about 11%. Water
uptake is parameterised using fitted activity coefficients, resulting in a
good agreement with the full model. |
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