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| Titel |
Seasonal characteristics of fine particulate matter (PM) based on high-resolution time-of-flight aerosol mass spectrometric (HR-ToF-AMS) measurements at the HKUST Supersite in Hong Kong |
| VerfasserIn |
Y. J. Li, B. P. Lee, L. Su, J. C. H. Fung, C. K. Chan |
| 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. 1 ; Nr. 15, no. 1 (2015-01-07), S.37-53 |
| Datensatznummer |
250119285
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| Publikation (Nr.) |
 copernicus.org/acp-15-37-2015.pdf |
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| Zusammenfassung |
| Atmospheric particulate matter (PM) remains poorly understood due to the
lack of comprehensive measurements at high time resolution for tracking its
dynamic features and the lack of long-term observation for tracking its
seasonal variability. Here, we present highly time-resolved and seasonal
compositions and characteristics of non-refractory components in PM with a
diameter less than 1 μm (NR-PM1) at a suburban site in Hong
Kong. The measurements were made with an Aerodyne high-resolution
time-of-flight aerosol mass spectrometer (HR-ToF-AMS) at the Hong Kong
University of Science and Technology (HKUST) Air Quality Research Supersite
for 4 months, with one in each season of the year. The average
NR-PM1 concentration of ~ 15 μg m−3 is higher
than those AMS measurements made in South Korea and Japan, but lower than
those in North China, the Yangtze River Delta and the nearby Pearl River
Delta. The seasonal dependence of the total NR-PM1 monthly averaged
concentrations was small, but that of the fractions of the species in
NR-PM1 was significant. Site characteristic plays an important role in
the relative fractions of species in NR-PM1 and our results are
generally consistent with measurements at other non-urban sites in this
regard. Detailed analyses were conducted on the AMS data in the aspects of
(1) species concentrations, (2) size distributions, (3) degree of
oxygenation of organics, and (4) positive matrix factorization
(PMF)-resolved organic factors in a seasonal context, as well as with air
mass origin from back-trajectory analysis. Sulfate had the highest fraction
in NR-PM1 (> 40%), and the surrogates of secondary organic
species – semi-volatile oxygenated organic aerosol (SVOOA) and low-volatility
oxygenated organic aerosol (LVOOA) – prevailed (~ 80%) in
the organic portion of NR-PM1. Local contributions to the organic
portion of NR-PM1 at this suburban site was strongly dependent on
season. The hydrocarbon-like organic aerosol (HOA) factor related to local
traffic emissions contributed > 10% to organic aerosols in
spring and summer but only 6–7% in autumn and winter. The cooking
organic aerosol (COA) factor contributed > 10% to organic
aerosols in winter. With the aid of highly time-resolved data, diurnal
patterns of the degree of oxygenation of organic aerosols were used to
determine the sources and formation processes of the least understood
organic portion of PM. The oxygen-to-carbon atomic ratio (O : C) and average
carbon oxidation state OS C) showed little variation in autumn
and winter, when the long-range transport of oxidized organics dominated,
whereas they peaked in the afternoon in spring and summer, when locally
produced secondary organic aerosol prevailed. Air mass origin, in contrast,
had a strong influence on both NR-PM1 concentrations and the fractions
of species in NR-PM1. The findings of the current study provide a
better understanding of the role of air mass origin in the seasonal
characteristics of the PM composition and the relative importance of local
vs. transported organic aerosols in this region. |
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