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| Titel |
Particle number size distributions in urban air before and after volatilisation |
| VerfasserIn |
W. Birmili, K. Heinke, M. Pitz, J. Matschullat, A. Wiedensohler, J. Cyrys, H.-E. Wichmann, A. Peters |
| 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 ; 10, no. 10 ; Nr. 10, no. 10 (2010-05-21), S.4643-4660 |
| Datensatznummer |
250008467
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| Publikation (Nr.) |
 copernicus.org/acp-10-4643-2010.pdf |
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| Zusammenfassung |
Aerosol particle number size distributions (size range
0.003–10 μm) in the urban atmosphere of Augsburg (Germany) were
examined with respect to the governing anthropogenic sources and
meteorological factors. The two-year average particle number concentration
between November 2004 and November 2006 was 12 200 cm−3, i.e. similar
to previous observations in other European cities. A seasonal analysis
yielded twice the total particle number concentrations in winter as compared
to summer as consequence of more frequent inversion situations and enhanced
particulate emissions. The diurnal variations of particle number were shaped
by a remarkable maximum in the morning during the peak traffic hours. After a
mid-day decrease along with the onset of vertical mixing, an evening
concentration maximum could frequently be observed, suggesting a
re-stratification of the urban atmosphere. Overall, the mixed layer height
turned out to be the most influential meteorological parameter on the
particle size distribution. Its influence was even greater than that of the
geographical origin of the prevailing synoptic-scale air mass.
Size distributions below 0.8 μm were also measured downstream of a
thermodenuder (temperature: 300 °C), allowing to retrieve the volume
concentration of non-volatile compounds. The balance of particle number
upstream and downstream of the thermodenuder suggests that practically all
particles >12 nm contain a non-volatile core while additional nucleation
of particles smaller than 6 nm could be observed after the thermodenuder as
an interfering artifact of the method. The good correlation between the
non-volatile volume concentration and an independent measurement of the
aerosol absorption coefficient (R2=0.9) suggests a close correspondence
of the refractory and light-absorbing particle fractions. Using the
"summation method", an average diameter ratio of particles before and after
volatilisation could be determined as a function of particle size. The
results indicated that particles >60 nm contain a significantly higher
fraction of non-volatile compounds, most likely black carbon, than particles
<60 nm. The results are relevant for future health-related studies in that
they explore the size distribution and time-dependent behaviour of the
refractory component of the urban aerosol over an extended time period. |
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