OH-initiated degradation of several hydrocarbons in the atmosphere simulation chamber SAPHIR |
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Authors: | D Poppe T Brauers H -P Dorn M Karl T Mentel E Schlosser R Tillmann R Wegener A Wahner |
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Institution: | 1.Institut für Chemie und Dynamik der Geosph?re II: Troposph?re, Forschungszentrum Jülich,Jülich,Germany |
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Abstract: | Degradation of isoprene, m-xylene, n-octane, propene, and methacrolein by hydroxyl radicals has been studied in the simulation chamber SAPHIR under burden of
trace gases as they are typical for the moderately polluted planetary boundary layer. Measured time series of the hydrocarbon
mixing ratios and the OH concentrations were used to determine the rate constants. The hydrocarbons were measured with gas
chromatography and proton transfer reaction mass spectrometry. OH was measured with the Jülich DOAS (differential optical
absorption spectroscopy) instrument. In all cases except methacrolein good agreement was found with the reference rate constants
taken from the Master Chemical Mechanism (MCM3.1). The data for methacrolein are consistent with the results of Karl et al.
(J. Atmos. Chem 55, 2006, doi:) who reported a 12% smaller value. The degradation of hydrocarbons provides an independent method to analyse precision and
accuracy of the OH measurements. A precision of better than 4% over a period of nearly 4 months was found. The accuracy is
within the limitations given by the light absorption cross section of OH. Both results are consistent with earlier results
by Hausmann et al. (J. Geophys. Res. 102:16011–16022, 1997). |
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Keywords: | Atmospheric degradation of hydrocarbons Hydroxyl radicals Tropospheric ozone n-Octane: propene m-Xylene Isoprene Methacrolein Simulation chamber Measurement of atmospheric OH concentrations |
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