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| Book | PreJuSER-52326 |
; ;
1997
Forschungszentrum, Zentralbibliothek
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/20181
Report No.: Juel-3457
Abstract: Measurements of real-world traffic emissions were performed in three different locations : a highway without speed limit, a highway with a speed limit of 60 km/h and a slight road inelination, and an urban location dose to the City centre of Wuppertal . Special emphasis was placed on the speciation of the emissions with respect to hydrocarbons . To this end, a GC system for the analysis of C 2-C9- hydrocarbons was built up and characterised . The date were analysed with respect to the VGC/NO ratio and the composition of the hydrocarbon mixture. The VOC/N®X ratio differed significantly between weekends and weekdays . It was higher on weekends due to the reduced amount of heavy duty vehicles . The VOC/NOX ratio decreased with increasing speed . The lowest VOCENQX ratio of 0,71 ppbC/ppbV was found on weekdays an the highway without speed limit . The highest VOC/NO x ratio of 7,5 ppbC/ppbV was found an weekends in the urban location. The measured VGC/Nßx ratios were compared with the results of an emission model [INFRAS AG, 1995] . The model always underpredicts the observed VGC/NG X ratios, differentes of up to a factor of two were found. However, the trends predicted by the model with respect to different traffic situation agree with the observed trends. Detailed analysis of individual hydrocarbons showed an increase of the emissions of alkenes with increasing speed, whereas the emissions of aromatics were found to increase substantially at reduced speeds. In addition, the measured date were compared to the emission profiles of individual vehicles obtained by different dynamometer studies. The literature date for the vehicles without catalysts agree reasonably well between the different studies, while 'arger differentes for vehicles equipped with catalysts are found in the literature. The comparison of the literature dato with the measured emissions suggests that the measured emissions are dominated by vehicles without catalysts. The influence of the VOC7NO X ratio on the photochernical formation of GX was studied with a photochemical box model (Euro- M) . lt was found that the VGC/NO X ratio has a dominating influence on the production rate of ®X as well as on the maximum GX concentration. To analyse the influence of the different hydrocarbon mixtures, a four day summer smog episode was simulated . The maximum ®X concentrations obtained with the different hydrocarbon mixtures (using the saure VOC/NO x ratio) span a factor of about 1,5 . No correlation was found between the maximum ®x concentration obtained and the average reactivity of the different mixtures with respect to the reaction with OH . This indicates the importance of secondary pollutants (e .g. carbonyls) for the ozone production dose to the sources and the need to analyse the hydrocarbon mixtures in detail for the successful development of ozone reduction strategies .
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