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| Titel |
Atmospheric organic matter in clouds: exact masses and molecular formula identification using ultrahigh-resolution FT-ICR mass spectrometry |
| VerfasserIn |
Y. Zhao, A. G. Hallar, L. R. Mazzoleni |
| 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 ; 13, no. 24 ; Nr. 13, no. 24 (2013-12-18), S.12343-12362 |
| Datensatznummer |
250085890
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| Publikation (Nr.) |
 copernicus.org/acp-13-12343-2013.pdf |
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| Zusammenfassung |
| Clouds alter the composition of atmospheric aerosol by acting as a medium
for interactions between gas- and particulate-phase substances. To determine
the cloud water atmospheric organic matter (AOM) composition and study the
cloud processing of aerosols, two samples of supercooled clouds were
collected at the Storm Peak Laboratory near Steamboat Springs, Colorado (3220 m a.s.l.).
Approximately 3000 molecular formulas were assigned to ultrahigh-resolution mass spectra of the samples after using a reversed-phase
extraction procedure to isolate the AOM components from the cloud water.
Nitrogen-containing compounds (CHNO compounds), sulfur-containing compounds
(CHOS and CHNOS compounds) and other oxygen-containing compounds (CHO
compounds) with molecular weights up to 700 Da were observed. Average
oxygen-to-carbon ratios of ∼0.6 indicate a slightly more
oxidized composition than most water-soluble organic carbon identified in
aerosol studies, which may result from aqueous oxidation in the clouds. The
AOM composition indicates significant influences from biogenic secondary
organic aerosol (SOA) and residential wood combustion. We observed 60% of
the cloud water CHO molecular formulas to be identical to SOA samples of
α-pinene, β-pinene, d-limonene, and β-caryophyllene
ozonolysis. CHNO compounds had the highest number frequency and relative
abundances and are associated with residential wood combustion and NOx
oxidation. Multiple nitrogen atoms in the assigned molecular formulas for
the nighttime cloud sample composite were observed, indicating the
significance of nitrate radical reactions on the AOM composition. Several
CHOS and CHNOS compounds with reduced sulfur (in addition to the commonly
observed oxidized sulfur-containing compounds) were also observed; however
further investigation is needed to determine the origin of the reduced
sulfur-containing compounds. Overall, the molecular composition determined
using ultrahigh-resolution Fourier-transform ion cyclotron resonance
(FT-ICR) mass spectrometry provides an unambiguous identification of the
cloud water organic anion composition in the Rocky Mountain area that could
help to improve the understanding of aqueous-phase processes. |
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