Effect of ions on the measurement of sulphuric acid in the CLOUD experiment at CERN

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., with and w
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., with and without the presence of ions, were carried out under precisely controlled conditions. The sulphuric acid concentration was measured with a Chemical Ionization 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 sulphuric 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 (GCR) or the proton synchrotron (PS) pion beam for the ion generation, respectively. The ion effect typically involved an increase in the apparent sulphuric acid concentration by a factor of ~2 to 3 and was qualitatively verified by the ion measurements by 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 one second. In order to exclude the ion effect and to provide corrected sulphuric acid concentrations during the GCR and PS beam nucleation experiments, a parameterisation was derived that utilizes the trace gas concentrations and the UV light intensity as input parameters. Atmospheric sulphuric acid measurements with a CIMS showed an insignificant ion effect.
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Author:Linda Rondo, Andreas Kürten, Sebastian Ehrhart, Siegfried Schobesberger, Alessandro Franchin, Heikki Junninen, Tuukka Petäjä, Mikko Sipilä, Douglas R. Worsnop, Joachim Curtius
URN:urn:nbn:de:hebis:30:3-372334
DOI:http://dx.doi.org/10.5194/amtd-7-6595-2014
ISSN:1867-8610
Parent Title (English):Atmospheric measurement techniques discussions
Publisher:European Geosciences Union
Place of publication:Katlenburg-Lindau
Document Type:Article
Language:English
Date of Publication (online):2014/07/03
Date of first Publication:2014/07/03
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2015/04/22
Volume:7
Pagenumber:30
First Page:6595
Last Page:6624
Note:
© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License.
HeBIS PPN:368994694
Institutes:Geowissenschaften
Dewey Decimal Classification:550 Geowissenschaften
Sammlungen:Universitätspublikationen
Licence (German):License LogoCreative Commons - Namensnennung 3.0

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