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| Titel |
Laboratory photochemical processing of aqueous aerosols: formation and degradation of dicarboxylic acids, oxocarboxylic acids and α-dicarbonyls |
| VerfasserIn |
C. M. Pavuluri, K. Kawamura, N. Mihalopoulos, T. Swaminathan |
| 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. 14 ; Nr. 15, no. 14 (2015-07-20), S.7999-8012 |
| Datensatznummer |
250119914
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| Publikation (Nr.) |
 copernicus.org/acp-15-7999-2015.pdf |
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| Zusammenfassung |
| To better understand the photochemical processing of
dicarboxylic acids and related polar compounds, we conducted batch UV
irradiation experiments on two types of aerosol samples collected from
India, which represent anthropogenic (AA) and biogenic (BA) aerosols, for
time periods of 0.5 to 120 h. The irradiated samples were analyzed for
molecular compositions of diacids, oxoacids and α-dicarbonyls. The
results show that photochemical degradation of oxalic (C2), malonic
(C3) and other C8–C12 diacids overwhelmed their production in
aqueous aerosols, whereas succinic acid (C4) and C5–C7 diacids
showed a significant increase (ca. 10 times) during the course of
irradiation experiments. The photochemical formation of oxoacids and α-dicarbonyls overwhelmed their degradation during the early stages of
experiment except for ω-oxooctanoic acid (ωC8), which
showed a similar pattern to that of C4. We also found a gradual
decrease in the relative abundance of C2 to total diacids and an
increase in the relative abundance of C4 during prolonged experiment.
Based on the changes in concentrations and mass ratios of selected species
with the irradiation time, we hypothesize that iron-catalyzed photolysis of
C2 and C3 diacids controls their concentrations in Fe-rich
atmospheric waters, whereas photochemical formation of C4 diacid (via
ωC8) is enhanced with photochemical processing of aqueous
aerosols in the atmosphere. This study demonstrates that the ambient
aerosols contain abundant precursors that produce diacids, oxoacids and
α-dicarbonyls, although some species such as oxalic acid decompose
extensively during an early stage of photochemical processing. |
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