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| Titel |
One-year observations of size distribution characteristics of major aerosol constituents at a coastal receptor site in Hong Kong – Part 1: Inorganic ions and oxalate |
| VerfasserIn |
Q. Bian, X. H. H. Huang, J. Z. Yu |
| 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 ; 14, no. 17 ; Nr. 14, no. 17 (2014-09-02), S.9013-9027 |
| Datensatznummer |
250118997
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| Publikation (Nr.) |
 copernicus.org/acp-14-9013-2014.pdf |
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| Zusammenfassung |
Size distribution data of major aerosol constituents are essential in source
apportioning of visibility degradation, testing and verification of air
quality models incorporating aerosols. We report here 1-year observations
of mass size distributions of major inorganic ions (sulfate, nitrate,
chloride, ammonium, sodium, potassium, magnesium and calcium) and oxalate at
a coastal suburban receptor site in Hong Kong, China. A total of 43 sets of
size-segregated samples in the size range of 0.056–18 μm were
collected from March 2011 to February 2012. The size distributions of
sulfate, ammonium, potassium and oxalate were characterized by a dominant
droplet mode with a mass mean aerodynamic diameter (MMAD) in the range of
~ 0.7–0.9 μm. Oxalate had a slightly larger MMAD than
sulfate on days with temperatures above 22 °C as a result of the
process of volatilization and repartitioning. Nitrate was mostly dominated by
the coarse mode but enhanced presence in fine mode was detected on winter
days with lower temperature and lower concentrations of sea salt and soil
particles. This data set reveals an inversely proportional relationship
between the fraction of nitrate in the fine mode and product of the sum of
sodium and calcium in equivalent concentrations and the dissociation constant
of ammonium nitrate (i.e.,
(1/([Na+] + 2[Ca2+]) × (1/Ke')) when
Pn_fine is significant (> 10%). The
seasonal variation observed for sea salt aerosol abundance, with lower values
in summer and winter, is possibly linked with the lower marine salinities in
these two seasons.
Positive matrix factorization was applied to estimate the relative
contributions of local formation and transport to the observed ambient
sulfate level through the use of the combined data sets of size-segregated
sulfate and select gaseous air pollutants. On average, the
regional/super-regional transport of air pollutants was the dominant source
at this receptor site, especially on high-sulfate days while local formation
processes contributed approximately 30% of the total sulfate. This work
provides field-measurement-based evidence important for understanding
both local photochemistry and regional/super-regional transport in order to
properly simulate sulfate aerosols in air quality models. |
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