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| Titel |
Impact of relative humidity and particles number size distribution on aerosol light extinction in the urban area of Guangzhou |
| VerfasserIn |
Z. J. Lin, J. Tao, F. H. Chai, S. J. Fan, J. H. Yue, L. H. Zhu, K. F. Ho, R. J. Zhang |
| 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 ; 13, no. 3 ; Nr. 13, no. 3 (2013-02-01), S.1115-1128 |
| Datensatznummer |
250017619
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| Publikation (Nr.) |
 copernicus.org/acp-13-1115-2013.pdf |
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| Zusammenfassung |
| In the urban area of Guangzhou, observations on aerosol light extinction
effect were conducted at a monitoring site of the South China Institute of
Environmental Sciences (SCIES) during April 2009, July 2009, October 2009
and January 2010. The main goal of these observations is to recognise the
impact of relative humidity (RH) and particles number distribution on aerosol
light extinction. PM2.5 was sampled by Model PQ200 air sampler; ions
and OC/EC in PM2.5 were identified by the Dionex ion chromatography and
the DRI model 2001 carbon analyser, respectively; particles number size
distribution was measured by TSI 3321 APS, while total light scattering
coefficient was measured by TSI 3563 Nephelometer. Chemical composition of
PM2.5 was reconstructed by the model ISORROPIA II. As a result,
possible major components in PM2.5 were
(NH4)2SO4, Na2SO4, K2SO4,
NH4NO3, HNO3, water, POM and EC. Regarding ambient RH, mass
concentration of PM2.5 ranged from 26.1 to 279.1 μg m−3 and had
an average of 94.8, 44.6, 95.4 and 130.8 μg m−3 in April, July,
October and January, respectively. With regard to the total mass of
PM2.5, inorganic species, water, POM, EC and the Residual accounted for
34–47%, 19–31%, 14–20%, 6–8% and 8–17%, respectively.
Under the assumption of "internal mixture", optical properties of
PM0.5–20 were estimated following the Mie Model. Optical refractive
index, hygroscopic growth factor and the dry aerosol density required by the
Mie Model were determined with an understanding of chemical composition of
PM2.5. With these three parameters and the validated particles number
size distribution of PM0.5–20, the temporal variation trend of optical
property of PM0.5–20 was estimated with good accuracy. The
highest average of bep,pm0.5–20 was 300 Mm−1 in April while the
lowest one was 78.6 Mm−1 in July. Regarding size distribution of
bep,pm0.5–20, peak value was almost located in the diameter range
between 0.5 and 1.0 μm. Furthermore, hygroscopic growth of optical
properties of PM0.5–20 largely depended on RH. As RH increased,
bep,pm0.5–20 grew and favoured a more rapid growth when aerosol had a
high content of inorganic water-soluble salts. Averagely,
fbep,pm0.5–20 enlarged 1.76 times when RH increased from 20% to
90%. With regard to the temporal variation of ambient RH,
fbep,pm0.5–20 was 1.29, 1.23, 1.14 and 1.26 on average in April, July,
October and January, respectively. |
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