Verkehrsemissionen und Sommersmog : Umweltpotentiale neuer Energieträger und Antriebe - insbesondere für den Strassenverkehr

Die wiederkehrenden hohen sommerlichen Ozonwerte in den vergangenen Jahren haben auch in Deutschland zu einer verstärkten Diskussion über die Entstehung von Sommersmog und seine möglichen negativen Auswirkungen auf Menschen, Tiere und Pflanzen geführt. Im Forschungszentrums Jülich wurden dadurch interdisziplinäre Fachdiskussionen ausgelöst, die zu neuen Forschungsansätzen bezüglich der Bedeutung von Spurengasemissionen des Verkehrs für die Bildung von Sommersmog führte. Grundlagen für diese Fachdiskussionen waren dadurch gegeben, daß Fragestellungen aus den Bereichen Energie und Umwelt schon lange Schwerpunkte im Forschungs und Entwicklungsprogramm des Jülicher Zentrums bildeten. An diesen Diskussionen beteiligt waren und sind Wissenschaftler aus den Disziplinen Luftchemie, Biologie, Energie und Verfahrenstechnik sowie Systemanalyse. Durch das Zusammenführen der Ergebnisse laufender Forschungsvorhaben soll herausgefunden werden, welche wissenschaftlichen Untersuchungen zur Beantwortung noch offener Fragestellungen notwendig sind und in Angriff genommen werden müssen. Ziel dieser Arbeiten ist letztlich die Erarbeitung von Empfehlungen zur Verminderung jenes Anteils des Sommersmogs durch technische und/oder gesetzgeberische Maßnahmen, der durch Verkehrsemissionen verursacht wird. Die vorliegende Monographie gibt einen Überblick über den derzeitigen Stand der wissenschaftlichen Erkenntnisse, der laufenden Arbeiten und der Gesetzgebung und zeigt mögliche Beiträge Jülicher Wissenschaftler zur Beantwortung der offenen Fragestellungen auf. Sie aktualisiert, ergänzt und vertieft damit zwei frühere Monographien des Forschungszentrums Jülich: Ozon in Deutschland(Nr. 2/1990) und Neue Energieträger für den Verkehr(Nr.5/1991)

Messungen von Wasserstoffperoxid und organischen Hydroperoxiden am Schauinsland im Schwarzwald: ein Beitrag zur Charakterisierung der limitierenden Faktoren bei der Ozonproduktion

Continuous measurements ofH202and organic hydroperoxides were performed at the field station Schauinsland between January 1989 and June 1991 using an ezyme catalysed fluorescence instrument. The mixing ratios were in the range of the detection limit (20 ppt) up to 4.4 ppb for ~Oz and 1.7 ppb for ROOR. Both Hz02 and ROOH show a strong seasonal variation with maximum concentrations in summer. The observed seasonal trend is in line with the photochemical formation mechanism on the one hand and the main atmospheric loss processes on the other hand. The mixing ratios ofHz02 and ROOH are strongly influenced by wet deposition. For interpretation ofthe behavior ofthese substances in gas phase, this influence has to be eliminated. This was achieved by selecting sunny periods from the whole data set. In addition, periods were selected, where production exeeds chemical losses, because then, the measured concentrations of photochemically produced species, in first approximation, should reflect their production rates. This is the case when air masses arrive at Schauinsland from the nearby city of Freiburg and Rhine valley during summer and daytime. Comparison of results of smog chamber experiments performed by Hess et al. (1992 a.b,c) with chemical box model calculations using the EURORADM mechanism (Stockwell and Kley, 1994) showed, that a positive slope in the H20/Ox ratio with increasing photochemical age is an indicator for NOx limitation of photochemical ozone production. The box model was initialized using typical NOx start concentrations and VOCINOx ratios for the Schauinsland site. Analysis ofthe measured concentration ratios ofH202 and Ox versus the photochemical age of the air masses gave the result, that a large fraction of these measurements already fall into thecategory where theozone production isNOx limited. For this analysis only data were used, where the station was influenced by fresh anthropogenic emissions from Freiburg and the Rhine Valley, i.e. the analysed air masses were exposed to anthropogenic emissions later than four hours before arrival at the site. Since the advected air mass from other wind sectors are photochemically further processed, because anthropogenic sources are more distant, it C3Jl be coneluded that at Schauinsland the photochemical ozone production is in most cases limited by the availibility ofNOx' Since Schauinsland is relative dose to a large anthropogenic pollution source, this conclusion shoud be also valid for most rural areas in Europe

Messungen von Peroxiradikalen am Schauinsland über chemische Verstärkung

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