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Titel |
Characteristics of Submicron Aerosols in 2013 summer of Beijing |
VerfasserIn |
Song Guo, Min Hu, Dongjie Shang, Jing Zheng, Zhuofei Du, Yusheng Wu, Sihua Lu, Limin Zeng, Renyi Zhang |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250123849
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Publikation (Nr.) |
EGU/EGU2016-3169.pdf |
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Zusammenfassung |
To characterize the air pollution of North China Plain of China, CAREBEIJING-2013 field
campaign (Campaigns of Air quality REsearch in BEIJING and surrounding region) was
conducted in summer of 2013. Submicron aerosols were measured at an urban site PKU
(Peking University, 39˚ 59’21”N, 116˚ 18’25”E) from July 28th to September 31st 2013. A
suite of integrated instruments was used to measure the size distribution, effective density and
hygroscopicity of ambient particles. The chemical composition of submicron particles were
measured by using an Aerodyne High-Resolution Time-of-Flight Aerosol Mass
Spectrometer (HR-ToF-AMS) (Billerica, MA, USA). The average PM2.5 concentration was
73.0±70.7 μg m−3 during the measurement. The particulate pollution showed distinct
4-7 days cycles controlled by the meteorological conditions. Each cycle started
with low PM2.5 mass concentrations (<20 μg m−3), since the air mass was from
relatively clean mountainous area. The particle number concentrations were high, but
and the sizes were small (<30 nm) at this stage, which can be explained by the
new particle formation. In the succeeding days, both the particle mass and size
continuously increased. The PM2.5concentration increased rapidly by >60 μg day−1,
and the particle mean diameter grew to >100 nm. It is interesting to note that the
mean diameters showed similar trend to PM2.5 mass concentrations, indicating
the particle pollution attributed to the growth of the newly formed small particles.
During the measurement, the average particle densities are between 1.3-1.5 g cm−3,
indicating organics and sulfate were dominant in the particles. The densities of smaller
particles, i.e. 46 nm, 81nm, showed single peak at 1.3-1.5 g cm−3, indicating the
particles are internal mixed sulfate and organics. While the 150nm and 240 nm
particle densities exhibited bimodal distribution with an additional small peak at
∼1.1 g cm−3, which is considered as external mixed organic particles or aged soot
particles. The particle hygroscopic growth factor for all the measured sizes at RH
of 90% showed bimodal distribution, attributing to external mixed organics (or
aged soot) and internal mixed organics and sulfate. Both the density and HGF were
higher than Tijuana, but similar to Houston. PMF (Positive Matrix Factorization)
model was deployed to quantify the contributions of different mixing state particles.
Internal mixed organics and sulfate were dominant in the ambient particles in Beijing. |
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