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| Titel |
Aerosol hygroscopicity derived from size-segregated chemical composition and its parameterization in the North China Plain |
| VerfasserIn |
H. J. Liu, C. S. Zhao, B. Nekat, N. Ma, A. Wiedensohler, D. van Pinxteren, G. Spindler, K. Müller, H. Herrmann |
| 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. 5 ; Nr. 14, no. 5 (2014-03-12), S.2525-2539 |
| Datensatznummer |
250118475
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| Publikation (Nr.) |
 copernicus.org/acp-14-2525-2014.pdf |
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| Zusammenfassung |
| Hygroscopic growth of aerosol particles is of significant importance in
quantifying the aerosol radiative effect in the atmosphere. In this study,
hygroscopic properties of ambient particles are investigated based on
particle chemical composition at a suburban site in the North China Plain
during the HaChi campaign (Haze in China) in summer 2009. The
size-segregated aerosol particulate mass concentration as well as the
particle components such as inorganic ions, organic carbon and water-soluble
organic carbon (WSOC) are identified from aerosol particle samples collected
with a ten-stage impactor. An iterative algorithm is developed to evaluate
the hygroscopicity parameter κ from the measured chemical
composition of particles. During the HaChi summer campaign, almost half of the mass
concentration of particles between 150 nm and 1 μm is contributed by
inorganic species. Organic matter (OM) is abundant in ultrafine particles,
and 77% of the particulate mass with diameter (Dp) of around 30 nm is
composed of OM. A large fraction of coarse particle mass is undetermined and
is assumed to be insoluble mineral dust and liquid water. The campaign's
average size distribution of κ values shows three distinct modes: a
less hygroscopic mode (Dp < 150 nm) with κ slightly above
0.2, a highly hygroscopic mode (150 nm < Dp < 1 μm)
with κ greater than 0.3 and a nearly hydrophobic mode
(Dp > 1 μm) with κ of about 0.1. The peak of the
κ curve appears around 450 nm with a maximum value of 0.35. The
derived κ values are consistent with results measured with a high
humidity tandem differential mobility analyzer within the size range of 50–250 nm. Inorganics are the predominant species contributing to particle
hygroscopicity, especially for particles between 150 nm and 1 μm. For
example, NH4NO3, H2SO4, NH4HSO4 and
(NH4)2SO4 account for nearly 90% of κ for particles
of around 900 nm. For ultrafine particles, WSOC plays a critical role in
particle hygroscopicity due to the predominant mass fraction of OM in
ultrafine particles. WSOC for particles
of around 30 nm contribute 52% of κ. Aerosol hygroscopicity is related to synoptic transport
patterns. When southerly wind dominates, particles are more hygroscopic;
when northerly wind dominates, particles are less hygroscopic. Aerosol
hygroscopicity also has a diurnal variation, which can be explained by the
diurnal evolution of planetary boundary layer, photochemical aging processes
during daytime and enhanced black carbon emission at night. κ is
highly correlated with mass fractions of SO42−, NO3− and
NH4+ for all sampled particles as well as with the mass fraction
of WSOC for particles of less than 100 nm. A parameterization scheme for
κ is developed using mass fractions of SO42−,
NO3−, NH4+ and WSOC due to their high correlations with
κ, and κ calculated from the parameterization agrees well
with κ derived from the particle's chemical composition. Further
analysis shows that the parameterization scheme is applicable to other
aerosol studies in China. |
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