Details

Autor(en) / Beteiligte

• Ehlers, Christian
• Klemp, Dieter
• Rohrer, Franz
• Mihelcic, Djuro
• Wegener, Robert
• Kiendler-Scharr, Astrid
• Wahner, Andreas

Titel

Twenty years of ambient observations of nitrogen oxides and specified hydrocarbons in air masses dominated by traffic emissions in Germany

Ist Teil von

• Faraday discussions, 2016-01, Vol.189, p.47-437

Ort / Verlag

England

Erscheinungsjahr

2016

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The analysis of the individual composition of hydrocarbon (VOC) mixtures enables us to transform observed VOC-concentrations into their respective total VOC-reactivity versus OH radicals ( R VOC = Σ( k OH+VOC i × [VOC i ])). This is particularly useful because local ozone production essentially depends on this single parameter rather than on the details of the underlying hydrocarbon mixture (Klemp et al. , Schriften des Forschungszentrums Jülich , Energy & Environment , 2012, 21 ). The VOC composition also enables us to pin down the major emission source of hydrocarbons in urban areas to be petrol cars with temporarily reduced catalyst efficiency (the so-called cold-start situation) whereas the source of nitrogen oxides (NO x = NO + NO 2 ) is expected to be nowadays dominated by diesel cars. The observations in the vicinity of main roads in German cities show a decrease in the ratio of OH reactivities of VOC and NO 2 ( R VOC / R NO 2 ) by a factor of 7.5 over the time period 1994-2014. This is larger than the expected decrease of a factor of 2.9 taking estimated trends of VOC and NO x traffic emissions in Germany (Umweltbundesamt Deutschland, National Trend Tables for the German Atmospheric Emission Reporting , 2015), during this time period. The observed reduction in the R VOC / R NO 2 ratio leads to a drastic decrease in local ozone production driven by the reduction in hydrocarbons. The analysis reveals that the overall reduction of ozone production benefits from the low decrease of NO x emissions from road traffic which is a consequence of the eventual absence of catalytic converters for nitrogen oxide removal in diesel cars up to now.