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| Titel |
Semi-continuous gas and inorganic aerosol measurements at a Finnish urban site: comparisons with filters, nitrogen in aerosol and gas phases, and aerosol acidity |
| VerfasserIn |
U. Makkonen, A. Virkkula, J. Mäntykenttä, H. Hakola, P. Keronen, V. Vakkari, P. P. Aalto |
| 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 ; 12, no. 12 ; Nr. 12, no. 12 (2012-06-28), S.5617-5631 |
| Datensatznummer |
250011288
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| Publikation (Nr.) |
 copernicus.org/acp-12-5617-2012.pdf |
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| Zusammenfassung |
| Concentrations of 5 gases (HCl, HNO3, HONO, NH3, SO2) and 8
major inorganic ions in particles (Cl−, NO3−,
SO42−, NH4+, Na+, K+, Mg2+, Ca2+)
were measured with an online monitor MARGA 2S in two size ranges, Dp
<2.5 μm and Dp < 10 μm, in Helsinki,
Finland from November 2009 to May 2010. The results were compared with
filter sampling, mass concentrations obtained from particle number size
distributions, and a conventional SO2 monitor. The MARGA yielded lower
concentrations than those analyzed from the filter samples for most ions.
Linear regression yielded the following MARGA vs. filter slopes: 0.72 for
Cl−, 0.90 for NO3−, 0.85 for SO42−, 0.91 for
NH4+ , 0.49 for Na+, 3.0 for Mg2+, and 3.0 for Ca2+
and 0.90 for the MARGA vs. SO2 monitor. For K+ there were not
enough data points to calculate a statistically significant linear
regression. There were clear seasonal cycles in the concentrations of the
nitrogen-containing gases: the median concentrations of HNO3, HONO, and
NH3 were 0.09 ppb, 0.37 ppb, and 0.01 ppb in winter, respectively, and
0.15, 0.15, and 0.14 in spring, respectively. The gas-phase fraction of
nitrogen decreased roughly with decreasing temperature, so that in the
coldest period from January to February the median contribution was 28%
but in April to May was 53%. There were also large fractionation variations
that temperature alone cannot explain. HONO correlated well with NOx
but a large fraction of the HONO-to-NOx ratios were larger than
published ratios in a road traffic tunnel, suggesting that a large amount of
HONO had other sources than vehicle exhaust. Aerosol acidity was estimated
by calculating ion equivalent ratios. The sources of acidic aerosols were
studied with trajectory statistics that showed that continental aerosol is
mainly neutralized and marine aerosol acidic. |
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