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| Titel |
Measurements of the aerosol chemical composition and mixing state in the Po Valley using multiple spectroscopic techniques |
| VerfasserIn |
S. Decesari, J. Allan, C. Plass-Duelmer, B. J. Williams, M. Paglione, M. C. Facchini, C. O'Dowd, R. M. Harrison, J. K. Gietl, H. Coe, L. Giulianelli, G. P. Gobbi, C. Lanconelli, C. Carbone, D. Worsnop, A. T. Lambe, A. T. Ahern, F. Moretti, E. Tagliavini, T. Elste, S. Gilge, Y. Zhang, M. Dall'Osto |
| 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. 22 ; Nr. 14, no. 22 (2014-11-18), S.12109-12132 |
| Datensatznummer |
250119168
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| Publikation (Nr.) |
 copernicus.org/acp-14-12109-2014.pdf |
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| Zusammenfassung |
| The use of co-located multiple spectroscopic techniques can provide detailed
information on the atmospheric processes regulating aerosol chemical
composition and mixing state. So far, field campaigns heavily equipped with
aerosol mass spectrometers have been carried out mainly in large
conurbations and in areas directly affected by their outflow, whereas lesser
efforts have been dedicated to continental areas characterised by a less
dense urbanisation. We present here the results obtained at a background
site in the Po Valley, Italy, in summer 2009. For the first time in Europe,
six state-of-the-art spectrometric techniques were used in parallel: aerosol
time-of-flight mass spectrometer (ATOFMS), two aerosol mass spectrometers
(high-resolution time-of-flight aerosol mass spectrometer – HR-ToF-AMS and soot particle aerosol mass spectrometer – SP-AMS), thermal desorption aerosol gas chromatography
(TAG), chemical ionisation mass spectrometry (CIMS) and (offline) proton
nuclear magnetic resonance (1H-NMR) spectroscopy. The results indicate that,
under high-pressure conditions, atmospheric stratification at night and
early morning hours led to the accumulation of aerosols produced by
anthropogenic sources distributed over the Po Valley plain. Such aerosols
include primary components such as black carbon (BC), secondary semivolatile
compounds such as ammonium nitrate and amines and a class of monocarboxylic
acids which correspond to the AMS cooking organic aerosol (COA) already
identified in urban areas. In daytime, the entrainment of aged air masses in
the mixing layer is responsible for the accumulation of low-volatility
oxygenated organic aerosol (LV-OOA) and also for the recycling of
non-volatile primary species such as black carbon. According to organic
aerosol source apportionment, anthropogenic aerosols accumulating in the
lower layers overnight accounted for 38% of organic aerosol mass on
average, another 21% was accounted for by aerosols recirculated in
residual layers but still originating in northern Italy, while a substantial
fraction (41%) was due to the most aged aerosols imported from
transalpine areas. The different meteorological regimes also affected the BC
mixing state: in periods of enhanced stagnation and recirculation of
pollutants, the number fraction of the BC-containing particles determined by
ATOFMS was 75% of the total, while in the days of enhanced ventilation of
the planetary boundary layer (PBL), such fraction was significantly lower (50%) because of the
relative greater influence of non-BC-containing aerosol local sources in the
Po Valley. Overall, a full internal mixing between BC and the non-refractory
aerosol chemical components was not observed during the experiment in this
environment. |
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