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| Titel |
Effect of ions on the measurement of sulfuric acid in the CLOUD experiment at CERN |
| VerfasserIn |
L. Rondo, A. Kürten, S. Ehrhart, S. Schobesberger, A. Franchin, H. Junninen, T. Petäjä, M. Sipilä, D. R. Worsnop, J. Curtius |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 11 ; Nr. 7, no. 11 (2014-11-19), S.3849-3859 |
| Datensatznummer |
250115956
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| Publikation (Nr.) |
 copernicus.org/amt-7-3849-2014.pdf |
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| Zusammenfassung |
| Ternary aerosol nucleation experiments were conducted in the CLOUD chamber
at CERN in order to investigate the influence of ions on new particle
formation. Neutral and ion-induced nucleation experiments, i.e. without and
with the presence of ions, respectively, were carried out under precisely
controlled conditions. The sulfuric acid concentration was measured with a
chemical ionisation mass spectrometer (CIMS) during the new particle
formation experiments. The added ternary trace gases were ammonia
(NH3), dimethylamine (DMA, C2H7N) or oxidised products of
pinanediol (PD, C10H18O2). When pinanediol was introduced
into the chamber, an increase in the mass spectrometric signal used to
determine the sulfuric acid concentration (m/z 97, i.e. HSO4−)
was observed due to ions from the CLOUD chamber. The enhancement was only
observed during ion-induced nucleation measurements by using either galactic
cosmic rays (GCRs) or the proton synchrotron (PS) pion beam for the ion
generation, respectively. The ion effect typically involved an increase in
the apparent sulfuric acid concentration by a factor of ~ 2
to 3 and was qualitatively verified by the ion measurements with an
atmospheric-pressure interface-time of flight (APi-TOF) mass spectrometer.
By applying a high-voltage (HV) clearing field inside the CLOUD chamber, the
ion effect on the CIMS measurement was completely eliminated since, under
these conditions, small ions are swept from the chamber in about 1 s.
In order to exclude the ion effect and to provide corrected sulfuric acid
concentrations during the GCR and PS beam nucleation experiments, a
parameterisation was derived that utilises the trace gas concentrations and
the UV light intensity as input parameters. Atmospheric sulfuric acid
measurements with a CIMS showed an insignificant ion effect. |
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