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Titel |
The chemical composition of fine ambient aerosol particles in the Beijing area |
VerfasserIn |
Bettina Nekat, Dominik van Pinxteren, Yoshiteru Iinuma, Thomas Gnauk, Konrad Müller, Hartmut Herrmann |
Konferenz |
EGU General Assembly 2010
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 12 (2010) |
Datensatznummer |
250040277
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Zusammenfassung |
The strong economical growth in China during the last few decades led to heavy air pollution
caused by significantly increased particle emissions. The aerosol particles affect not
only the regional air quality and visibility, but can also influence cloud formation
processes and the radiative balance of the atmosphere by their optical and microphysical
properties.
The ability to act as Cloud Condensation Nuclei (CCN) is related to microphysical
properties like the hygroscopic growth or the cloud droplet activation. The chemical
composition of CCN plays an important role on these properties and varies strongly with the
particle size and the time of day. Hygroscopic or surface active substances can increase the
hygroscopicity and lower the surface tension of the particle liquid phase, respectively. The
presence of such compounds may result in faster cloud droplet activation by faster water
uptake.
The DFG project HaChi (Haze in China) aimed at studying physical and chemical
parameters of urban aerosol particles in the Beijing area in order to associate the chemical
composition of aerosol particles with their ability to act as CCN. To this end, two
measurement campaigns were performed at the Wuqing National Ordinary Meteorological
Observing Station, which is a background site near Beijing. The winter campaign was
realized in March 2009 and the summer campaign took place from mid July 2009 to mid
August 2009. Fine particles with an aerodynamic diameter smaller than or equal 1 μm were
continuously sampled for 24h over the two campaigns using a DIGITEL high volume
sampler (DHA-80).
The present contribution presents and discusses the results of the chemical characterization of
the DIGITEL filters samples. The filters were analyzed for the mass concentration, inorganic
ions and carbon sum parameters like elemental (EC), organic (OC) and water soluble organic
carbon (WSOC). The WSOC fraction was further characterized for hygroscopic
substances like low molecular dicarboxylic acids as well as sugars and sugar related
compounds. Additionally fatty acids were analyzed to investigate surface active
substances.
Usually, the highest PM1 concentrations were observed during periods with prevailing
wind directions from southern areas, while northern wind directions led to significantly
lower concentrations. The main components of the fine particles are inorganic ions
like the secondary formed ammonium nitrate und ammonium sulphate, as well as
carbonaceous material. The organic carbon fraction is mostly dominated by water
soluble organic carbon (80% in average). High concentrations of tracers like the
anhydrosugar levoglucosan (Iinuma et al., 2007) suggest biomass burning emissions as
a dominant source of organic particles in the area. A significant fraction of PM1
remains unidentified and most likely consists of crust material like dust as well as
water.
Iinuma, Y., E. Brüggemann, T. Gnauk, K. Müller, M. O. Andreae, G. Helas, R. Parmar,
and H. Herrmann (2007), Source characterization of biomass burning particles: The
combustion of selected European conifers, African hardwood, savanna grass, and German
and Indonesian peat, J. Geophys. Res. [Atmos.], 112(D8), Doi 10.1029/2006jd007120. |
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