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| Titel |
Chemical composition, main sources and temporal variability of PM1 aerosols in southern African grassland |
| VerfasserIn |
P. Tiitta, V. Vakkari, P. Croteau, J. P. Beukes, P. G. Van Zyl, M. Josipovic, A. D. Venter, K. Jaars, J. J. Pienaar, N. L. Ng, M. R. Canagaratna, J. T. Jayne, V.-M. Kerminen, H. Kokkola, M. Kulmala  , A. Laaksonen, D. R. Worsnop, L. Laakso |
| 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. 4 ; Nr. 14, no. 4 (2014-02-18), S.1909-1927 |
| Datensatznummer |
250118413
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| Publikation (Nr.) |
 copernicus.org/acp-14-1909-2014.pdf |
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| Zusammenfassung |
Southern Africa is a significant source region of atmospheric pollution, yet
long-term data on pollutant concentrations and properties from this region
are rather limited. A recently established atmospheric measurement station
in South Africa, Welgegund, is strategically situated to capture regional
background concentrations, as well as emissions from the major source
regions in the interior of South Africa. We measured non-refractive
submicron aerosols (NR-PM1) and black carbon over a one year period in
Welgegund, and investigated the seasonal and diurnal patterns of aerosol
concentration levels, chemical composition, acidity and oxidation level.
Based on air mass back trajectories, four distinct source regions were
determined for NR-PM1. Supporting data utilised in our analysis
included particle number size distributions, aerosol absorption, trace gas
concentrations, meteorological variables and the flux of carbon dioxide.
The dominant submicron aerosol constituent during the dry season was organic
aerosol, reflecting high contribution from savannah fires and other
combustion sources. Organic aerosol concentrations were lower during the wet
season, presumably due to wet deposition as well as reduced emissions from
combustion sources. Sulfate concentrations were usually high and exceeded
organic aerosol concentrations when air-masses were transported over regions
containing major point sources. Sulfate and nitrate concentrations peaked
when air masses passed over the industrial Highveld
(iHV) area. In contrast, concentrations were much lower when air masses
passed over the cleaner background (BG) areas. Air masses associated with
the anti-cyclonic recirculation (ACBIC) source region contained largely aged
OA.
Positive Matrix Factorization (PMF) analysis of aerosol mass spectra was
used to characterise the organic aerosol (OA) properties. The factors
identified were oxidized organic aerosols (OOA) and biomass burning organic
aerosols (BBOA) in the dry season and low-volatile (LV-OOA) and
semi-volatile (SV-OOA) organic aerosols in the wet season. The results
highlight the importance of primary BBOA in the dry season, which
represented 33% of the total OA. Aerosol acidity and its potential impact
on the evolution of OOA are also discussed. |
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