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| Titel |
Technical Note: Quantitative long-term measurements of VOC concentrations by PTR-MS – measurement, calibration, and volume mixing ratio calculation methods |
| VerfasserIn |
R. Taipale, T. M. Ruuskanen, J. Rinne, M. K. Kajos, H. Hakola, T. Pohja, M. Kulmala  |
| 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 ; 8, no. 22 ; Nr. 8, no. 22 (2008-11-19), S.6681-6698 |
| Datensatznummer |
250006457
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| Publikation (Nr.) |
 copernicus.org/acp-8-6681-2008.pdf |
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| Zusammenfassung |
| Proton transfer reaction mass spectrometry (PTR-MS) is a technique for
online measurements of atmospheric concentrations, or volume mixing ratios,
of volatile organic compounds (VOCs). This paper gives a detailed
description of our measurement, calibration, and volume mixing ratio
calculation methods, which have been designed for long-term stand-alone
field measurements by PTR-MS. The PTR-MS instrument has to be calibrated
regularly with a gas standard to ensure the accuracy needed in atmospheric
VOC measurements. We introduce a novel method for determining an instrument
specific relative transmission curve using information obtained from a
calibration. This curve enables consistent mixing ratio calculation for
VOCs not present in a calibration gas standard. Our method proved to be
practical, systematic, and sensitive enough to capture changes in the
transmission over time. We also propose a new approach to considering the
abundance of H3O+H2O ions in mixing ratio calculation. The
approach takes into account the difference in the transmission efficiencies
for H3O+ and H3O+H2O ions. To illustrate the
functionality of our measurement, calibration, and calculation methods, we
present a one-month period of ambient mixing ratio data measured in a
boreal forest ecosystem at the SMEAR II station in southern Finland. During
the measurement period 27 March–26 April 2007, the hourly averages of the
mixing ratios were 0.051–0.57 ppbv for formaldehyde, 0.19–3.1 ppbv for
methanol, 0.038–0.39 ppbv for benzene, and 0.020–1.3 ppbv for
monoterpenes. The detection limits for the hourly averages were 0.020,
0.060, 0.0036, and 0.0092 ppbv, respectively. |
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