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| Titel |
Detailed heterogeneous oxidation of soot surfaces in a particle-resolved aerosol model |
| VerfasserIn |
J. C. Kaiser, N. Riemer, D. A. Knopf |
| 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 ; 11, no. 9 ; Nr. 11, no. 9 (2011-05-12), S.4505-4520 |
| Datensatznummer |
250009716
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| Publikation (Nr.) |
 copernicus.org/acp-11-4505-2011.pdf |
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| Zusammenfassung |
| Using the particle-resolved aerosol model PartMC-MOSAIC, we simulate the
heterogeneous oxidation of a monolayer of polycyclic aromatic
hydrocarbons (PAHs) on soot particles in an urban atmosphere. We
focus on the interaction of the major atmospheric oxidants (O3,
NO2, OH, and NO3) with PAHs and include competitive
co-adsorption of water vapour for a range of atmospheric conditions. For
the first time detailed heterogeneous chemistry based on the
Pöschl-Rudich-Ammann (PRA) framework is modelled on soot particles
with a realistic size distribution and a continuous range of chemical
ages. We find PAHs half-lives, τ1/2, on the order of seconds
during the night, when the PAHs are rapidly oxidised by the
gas-surface reaction with NO3. During the day, τ1/2 is
on the order of minutes and determined mostly by the surface layer
reaction of PAHs with adsorbed O3. Such short half-lives of
surface-bound PAHs may lead to efficient conversion of hydrophobic
soot into more hygroscopic particles, thus increasing the particles'
aerosol-cloud interaction potential. Despite its high reactivity OH
appears to have a negligible effect on PAH degradation which can be
explained by its very low concentration in the atmosphere. An increase
of relative humidity (RH) from 30 % to 80 % increases
PAH half-lives by up to 50 % for daytime degradation and
by up to 100 % or more for nighttime degradation. Uptake
coefficients, averaged over the particle population, are found to be
relatively constant over time for O3 (∼2 × 10−7 to
∼2 × 10−6) and NO2 (∼5 × 10−6 to
∼10−5) at the different levels of NOx emissions and RH
considered in this study. In contrast, those for OH and NO3
depend strongly on the surface concentration of PAHs. We do not
find a significant influence of heterogeneous reactions on soot
particles on the gas phase composition. The derived half-lives of surface-bound PAHs and the time and particle population averaged
uptake coefficients for O3 and NO2 presented in this paper can be used as parameterisations for the
treatment of heterogeneous chemistry in large-scale atmospheric chemistry models. |
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