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| Titel |
Chemical composition, sources, and processes of urban aerosols during summertime in northwest China: insights from high-resolution aerosol mass spectrometry |
| VerfasserIn |
J. Xu, Q. Zhang, M. Chen, X. Ge, J. Ren, D. Qin |
| 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. 23 ; Nr. 14, no. 23 (2014-12-01), S.12593-12611 |
| Datensatznummer |
250119198
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| Publikation (Nr.) |
 copernicus.org/acp-14-12593-2014.pdf |
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| Zusammenfassung |
| An Aerodyne high-resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) was deployed along with a scanning mobility particle sizer
(SMPS) and a multi-angle absorption photometer (MAAP) to measure the
temporal variations of the mass loading, chemical composition, and size
distribution of submicron particulate matter (PM1) in Lanzhou,
northwest China, during 11 July–7 August 2012. The average
(PM1 mass concentration including non-refractory (PM1 (NR-(PM1)
measured by HR-ToF-AMS and black carbon (BC) measured by MAAP during this
study was 24.5 μg m−3 (ranging from 0.86 to
105 μg m−3), with a mean composition consisting of 47% organics, 16%
sulfate, 12% BC, 11% ammonium, 10% nitrate, and 4% chloride.
Organic aerosol (OA) on average consisted of 70% carbon, 21% oxygen,
8% hydrogen, and 1% nitrogen, with the average oxygen-to-carbon ratio
(O / C) of 0.33 and organic mass-to-carbon ratio (OM / OC) of 1.58. Positive
matrix factorization (PMF) of the high-resolution organic mass spectra
identified four distinct factors which represent, respectively, two primary
OA (POA) emission sources (traffic and food cooking) and two secondary OA
(SOA) types – a fresher, semi-volatile oxygenated OA (SV-OOA) and a more
aged, low-volatility oxygenated OA (LV-OOA). Traffic-related
hydrocarbon-like OA (HOA) and BC displayed distinct diurnal patterns, both
with peak at ~ 07:00–11:00 (BJT: UTC +8), corresponding to
the morning rush hours, while cooking-emission related OA (COA) peaked during three meal
periods. The diurnal profiles of sulfate and LV-OOA displayed a broad peak
between ~ 07:00 and 15:00, while those of nitrate, ammonium, and
SV-OOA showed a narrower peak between ~ 08:00–13:00. The later
morning and early afternoon maximum in the diurnal profiles of secondary
aerosol species was likely caused by downward mixing of pollutants aloft,
which were likely produced in the residual layer decoupled from the boundary
layer during nighttime. The mass spectrum of SV-OOA was similar to that of
coal combustion aerosol and likely influenced by coal combustion activities
in Lanzhou during summer. The sources of BC were estimated by a linear
decomposition algorithm that uses the time series of the NR-PM1 components. Our results indicate that a main source of BC was local traffic
(47%) and that transport of regionally processed air masses also
contributed significantly to BC observed in Lanzhou. Finally, the
concentration and source of polycyclic aromatic hydrocarbons (PAHs) were
evaluated. |
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