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| Titel |
In-cloud oxalate formation in the global troposphere: a 3-D modeling study |
| VerfasserIn |
S. Myriokefalitakis, K. Tsigaridis, N. Mihalopoulos, J. Sciare, A. Nenes, K. Kawamura, A. Segers, M. Kanakidou |
| 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. 12 ; Nr. 11, no. 12 (2011-06-22), S.5761-5782 |
| Datensatznummer |
250009857
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| Publikation (Nr.) |
 copernicus.org/acp-11-5761-2011.pdf |
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| Zusammenfassung |
| Organic acids attract increasing attention as contributors to atmospheric
acidity, secondary organic aerosol mass and aerosol hygroscopicity. Oxalic
acid is globally the most abundant dicarboxylic acid, formed via chemical
oxidation of gas-phase precursors in the aqueous phase of aerosols and
droplets. Its lifecycle and atmospheric global distribution remain highly
uncertain and are the focus of this study. The first global spatial and
temporal distribution of oxalate, simulated using a state-of-the-art
aqueous-phase chemical scheme embedded within the global 3-dimensional
chemistry/transport model TM4-ECPL, is here presented. The model accounts
for comprehensive gas-phase chemistry and its coupling with major aerosol
constituents (including secondary organic aerosol). Model results are
consistent with ambient observations of oxalate at rural and remote
locations (slope = 1.16 ± 0.14, r2 = 0.36, N = 114) and suggest that
aqueous-phase chemistry contributes significantly to the global atmospheric
burden of secondary organic aerosol. In TM4-ECPL most oxalate is formed
in-cloud and less than 5 % is produced in aerosol water. About 62 % of
the oxalate is removed via wet deposition, 30 % by in-cloud reaction with
hydroxyl radical, 4 % by in-cloud reaction with nitrate radical and 4 %
by dry deposition. The in-cloud global oxalate net chemical production is
calculated to be about 21–37 Tg yr−1 with almost 79 % originating
from biogenic hydrocarbons, mainly isoprene. This condensed phase net source
of oxalate in conjunction with a global mean turnover time against
deposition of about 5 days, maintain oxalate's global tropospheric burden of
0.2–0.3 Tg, i.e. 0.05–0.1 Tg-C that is about 5–9 % of model-calculated
water soluble organic carbon burden. |
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