Verlag des Forschungszentrums Jülich
JUEL-3812
The average OH-radical concentration in the plume of Berlin was estimated from the decay of reactive hydrocarbons using flight and ground data. The estimated OH concentration from the flight data show a quite good agreement with the direct spectroscopic measurements. The ground stations provide insufficient information on the horizontal expansion of the plume in order to assure the required quasi Lagrangian relationship.
The local ozone production rate P(O3) was determined from the photo stationary state of NOx (PSS) at Pabstthum. Comparison with P(O3) derived from the concentrations of peroxy radicals measured by MIESR and with the ozone budget derived from the airborne measurements shows, that PSS severely overestimates the true ozone production rate by up to a factor of 20. Due to the quality of the measurements the results are highly significant and provide strong evidence for a yet unknown reaction in the atmosphere that oxidizes NO to NO2 without leading to a net O3 production.
The trace gas measurements performed at Pabstthum were used to evaluate the photochemical boxmodel RACM by comparing the simulated OH, HO2 and RO2 concentrations with the measured values. The comparison shows relatively good agreement for NOx mixing ratios > 5 ppb. For lower NOx mixing ratios, however, the model overestimates the measured OH an HO2 concentrations by up to 100 % and 40 %, respectively, similar to findings obtained elsewhere. The model predicts a much stronger dependence of OH on NOx than the measurements. The simulated OH and HO2 radical concentrations can be brought into agreement with the measured values only if a first order loss reaction for OH with kOH ~ 1 s-1 is introduced in the model. Then, additional VOC reactivity of about 100 ppt Limonene is necessary to bring measured and simulated RO2 radicals in accordance.
Konrad, Stephan
Untersuchungen zur Radikalchemie in der Abluftfahne von Berlin
190 S., 2000
The thesis discusses results from ground based and airborne measurements made during the BERLIOZ campaign in summer 1998. During BERLIOZ, measurements of a large variety of atmospheric trace gases including spectroscopic measurements of OH, HO2 and RO2 radicals were performed near Pabstthum, a small village 50 km north-west of Berlin. Hydrocarbons were measured with a commercial automated gas chromatograph (AirmoVoc HC1010) and a custom made GC with cryogenic preconcentration. In preparation for the campaign the HC1010 was coupled with a mass spectrometer in parallel with the flame ionization detector and characterised for its suitability for quasi continuous measurements with a time resolution of 20 min.
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