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| Titel |
Influence of aqueous chemistry on the chemical composition of fog water and interstitial aerosol in Fresno |
| VerfasserIn |
Hwajin Kim, Xinlei Ge, Sonya Collier, Jianzhong Xu, Yele Sun, Youliang Wang, Pierre Herckes, Qi Zhang |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250103660
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| Publikation (Nr.) |
 EGU/EGU2015-3075.pdf |
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| Zusammenfassung |
| A measurement study was conducted in the Central Valley (Fresno) of California in January
2010, during which radiation fog events were frequently observed. Fog plays important roles
in atmospheric chemistry by scavenging aerosol particles and trace gases and serving as a
medium for various aqueous-phase reactions. Understanding the effects of fog on the
microphysical and chemical processing of aerosol particles requires detailed information on
their chemical composition. In this study, we characterized the chemical composition of
fog water and interstitial aerosol particles to study the effects of fog processing
on aerosol properties. Fog water samples were collected during the 2010 Fresno
campaigns with a Caltech Active Strand Cloud water Collector (CASCC) while
interstitial submicron aerosols were characterized in real time with an Aerodyne
High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) and a scanning
Mobility Particle Sizer (SMPS). The fog water samples were later analyzed using the
HR-ToF-AMS, ion chromatography, and a total carbon analyzer. The chemical
composition and characteristics of interstitial particles during the fog events were
compared to those of dissolved inorganic and organic matter in fog waters. Compared
to interstitial aerosols, fog water is composed of a higher fraction of ammonium
nitrate and oxygenated organics, due to aqueous formation of secondary aerosol
species as well as enhanced gas-to-particle partitioning of water soluble species under
water rich conditions. Sulfate is formed most efficiently in fog water although its
contribution to total dissolved mass is relatively low. The HR-ToF-AMS mass spectra of
organic matter in fog water (FOM) are very similar to that of oxygenated organic
aerosols (OOA) derived from positive matrix factorization (PMF) of the HR-ToF-AMS
spectra of ambient aerosol (r2 = 0.96), but FOM appears to contain a large fraction
of acidic functional groups than OOA. FOM is also enriched of organic nitrogen
compounds, with an average N/C ratio ~3.8 times that of OOA. Most strikingly
is the enhancement of the CxHyN2+ family ions in FOM spectra, indicating the
presence of imidazole compounds, which commonly result from the aqueous phase
reactions of tropospheric aldehyde such as glyoxal, formaldehyde or acetaldehyde
with amino compounds. The results of this study demonstrate that aqueous phase
reactions in fog water lead to the formation of some oxidized and nitrogen-containing
compounds. Details and the environmental implications of results will be discussed. |
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