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| Home > Publications database > Messungen von Peroxiradikalen am Schauinsland über chemische Verstärkung |
| Book/Report | FZJ-2019-00507 |
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1995
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21295
Report No.: Juel-3047
Abstract: For measurements of atmospheric peroxy radical concentrations, a chemical amplifier and a calibration source were built. The calibration source uses photolysis of H$_{2}$O at 185 nm to produce HO$_{2}$ radicals and photolysis of O$_{2}$ at the same wavelength to produce a reference ozone concentration. It was characterised by using Matrix-Isolation with subsequent electron spin resonance (MIESR). The regression of observed versus predicted values yielded a slope of 0.5. The chemical amplifier was used in Winter 1993 to measure peroxy radicals at Schauinsland. An interesting observation was the presence of up to 10 ppt of radicals in very polluted air masses (i.e. about 40 ppb of NO$_{x}$). This is in contrast to current theories of radical chemistry. A chemical box model was used to calculate the RO$_{2}$ concentrations from the measured concentrations of NO$_{x}$ O$_{3}$, CO, and C$_{2}$-C$_{6}$-Hydrocarbons. Even after accounting for the deacy of HO$_{2}$NO$_{2}$, which was found to be an important interference under these conditions, the measured RO$_{2}$ concentrations could be reproduced with the model only by introducing a strong radical source, represented by 100 ppb of Formaldehyde or 10 of ppb nitric acid, for example. Another possible explanation would be a significantly longer lifetime of organic peroxy radicals with respect to the reaction with NO (by a factor of 2300 or more), which seems highly improbable.
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