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| Titel |
Ambient aromatic hydrocarbon measurements at Welgegund, South Africa |
| VerfasserIn |
K. Jaars, J. P. Beukes, P. G. Van Zyl, A. D. Venter, M. Josipovic, J. J. Pienaar, V. Vakkari, H. Aaltonen, H. Laakso  , M. Kulmala , P. Tiitta, A. Guenther, H. Hellén, L. Laakso, H. Hakola |
| 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. 13 ; Nr. 14, no. 13 (2014-07-11), S.7075-7089 |
| Datensatznummer |
250118881
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| Publikation (Nr.) |
 copernicus.org/acp-14-7075-2014.pdf |
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| Zusammenfassung |
| Aromatic hydrocarbons are associated with direct adverse human health
effects and can have negative impacts on ecosystems due to their toxicity,
as well as indirect negative effects through the formation of tropospheric
ozone and secondary organic aerosol, which affect human health, crop
production and regional climate. Measurements of aromatic hydrocarbons were
conducted at the Welgegund measurement station (South Africa), which is
considered to be a regionally representative background site. However, the
site is occasionally impacted by plumes from major anthropogenic source
regions in the interior of South Africa, which include the western Bushveld
Igneous Complex (e.g. platinum, base metal and ferrochrome smelters), the
eastern Bushveld Igneous Complex (platinum and ferrochrome smelters), the
Johannesburg–Pretoria metropolitan conurbation (> 10 million
people), the Vaal Triangle (e.g. petrochemical and pyrometallurgical
industries), the Mpumalanga Highveld (e.g. coal-fired power plants and
petrochemical industry) and also a region of anticyclonic recirculation of
air mass over the interior of South Africa. The aromatic hydrocarbon
measurements were conducted with an automated sampler on Tenax-TA and
Carbopack-B adsorbent tubes with heated inlet for 1 year. Samples were
collected twice a week for 2 h during daytime and 2 h during
night-time. A thermal desorption unit, connected to a gas chromatograph and
a mass selective detector was used for sample preparation and analysis.
Results indicated that the monthly median (mean) total aromatic hydrocarbon
concentrations ranged between 0.01 (0.011) and 3.1 (3.2) ppb. Benzene levels
did not exceed the local air quality standard limit, i.e. annual mean of
1.6 ppb. Toluene was the most abundant compound, with an annual median
(mean) concentration of 0.63 (0.89) ppb. No statistically significant
differences in the concentrations measured during daytime and night-time
were found, and no distinct seasonal patterns were observed. Air mass back
trajectory analysis indicated that the lack of seasonal cycles could be
attributed to patterns determining the origin of the air masses sampled.
Aromatic hydrocarbon concentrations were in general significantly higher in
air masses that passed over anthropogenically impacted regions.
Inter-compound correlations and ratios gave some indications of the possible
sources of the different aromatic hydrocarbons in the source regions
defined in the paper. The highest contribution of aromatic hydrocarbon
concentrations to ozone formation potential was also observed in plumes
passing over anthropogenically impacted regions. |
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