Determination of anthropogenic emission ratios in the Augsburg area from concentration ratios: results from long-term measurements

As part of a joint coordinated effort of several institutions to experimentally assess the uncertainty of highly resolved CO, NOx and VOC emission inventories, this paper presents the emission ratios derived from the concentrations measured at a receptor site. For this purpose, representative data sets on concentrations in the plume of Augsburg were obtained during two 4-week long campaigns in March and October 1998. Characteristic emission ratios and their experimental uncertainties have been determined for pure non-methane-hydrocarbons (NMHC/NOx-ratios, NMHC/CO-ratios) and for formaldehyde (HCHO/NOx-ratios, HCHO/CO-ratios) by means of correlation analyses. Special emphasis is also placed on the detailed hydrocarbon composition profile, the mean diurnal behavior of the emissions and the characterization of differences between weekdays and weekends as well as between seasons. The emission ratios at the receptor ground site were generally found to be in reasonable agreement with the emission ratios determined from the concurrent measurements onboard an aircraft. This agreement is remarkable in view of the difference between the aircraft and ground measurements. Circling around the city as is performed by air-borne measurements yields a good spatial average of the emissions released from the city, but the small number of measurement days limits their statistical representativity. Receptor ground-based measurements downwind of the city, on the other hand, cover many days during the long-term investigation, but may not be representative for the emissions of the whole city. Thus, the observed agreement between ground-based and air-borne studies strongly supports the assumption of spatial representativity for the long-term data set. Comparisons of mean hydrocarbon emission profiles measured in Augsburg with those measured over Berlin, in streets of Berlin and Munich as well as with the mean German urban hydrocarbon composition show that Augsburg is a typical German city with respect to its NMHC emission profiles and that these profiles, at least for the measured NMHC compounds, are dominated by traffic related NMHC emissions.