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| Titel |
Formation of secondary organic aerosol in the Paris pollution plume and its impact on surrounding regions |
| VerfasserIn |
Q. J. Zhang, M. Beekmann, E. Freney, K. Sellegri, J. M. Pichon, A. Schwarzenboeck, A. Colomb, T. Bourrianne, V. Michoud, A. Borbon |
| 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 ; 15, no. 24 ; Nr. 15, no. 24 (2015-12-18), S.13973-13992 |
| Datensatznummer |
250120234
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| Publikation (Nr.) |
 copernicus.org/acp-15-13973-2015.pdf |
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| Zusammenfassung |
| Secondary pollutants such as ozone, secondary inorganic aerosol,
and secondary organic aerosol formed in the plumes of megacities can affect
regional air quality. In the framework of the FP7/EU MEGAPOLI (Megacities: Emissions, urban, regional and Global
Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation) project, an
intensive campaign was launched in the greater Paris region in July 2009.
The major objective was to quantify different sources of organic aerosol
(OA) within a megacity and in its plume. In this study, we use airborne
measurements aboard the French ATR-42 aircraft to evaluate the regional
chemistry-transport model CHIMERE within and downwind of the Paris region. Two
mechanisms of secondary OA (SOA) formation are used, both including SOA
formation from oxidation and chemical aging of primary semivolatile and
intermediate volatility organic compounds (SI-SOA) in the volatility basis set (VBS) framework.
As for SOA formed from traditional VOC (volatile organic compound) precursors (traditional SOA), one
applies chemical aging in the VBS framework adopting different SOA yields
for high- and low-NOx environments, while another applies a single-step
oxidation scheme without chemical aging. Two emission inventories are used
for discussion of emission uncertainties. The slopes of the airborne OA levels
versus Ox (i.e., O3 + NO2) show SOA formation normalized with
respect to photochemical activity and are used for specific evaluation of
the OA scheme in the model. The simulated slopes were overestimated slightly
by factors of 1.1, 1.7 and 1.3 with respect to those observed for the three
airborne measurements, when the most realistic "high-NOx" yields for
traditional SOA formation in the VBS scheme are used in the model. In
addition, these slopes are relatively stable from one day to another, which
suggests that they are characteristic for the given megacity plume
environment. The configuration with increased primary organic
aerosol (POA) emissions and with a
single-step oxidation scheme of traditional SOA also agrees with
the OA / Ox slopes (about ± 50 % with respect to the observed
ones); however, it underestimates the background. Both configurations are coherent
with observed OA plume buildup, but they show very different SI-SOA and
traditional anthropogenic SOA (ASOA) contributions. It is hence concluded
that available theoretical knowledge and available data in this study are
not sufficient to discern the relative contributions of different types of
anthropogenic SOA in the Paris pollution plume, while its sum is correctly
simulated. Based on these simulations, for specific plumes, the
anthropogenic OA buildup can reach between 8 and 10μg m−3. For
the average of the month of July 2009, maximum OA increases due to emissions
from the Paris agglomeration are noticed close to the agglomeration at
various length scales: several tens (for primary OA) to hundreds (for SI-SOA
and ASOA) of kilometers from the Paris agglomeration. In addition, BSOA
(SOA formed from biogenic VOC precursors) is an important contributor to
regional OA levels (inside and outside the Paris plume). |
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