Extensive trace gas measurement campaigns were performed in 2005 at the Swiss high‐altitude station Jungfraujoch, including measurements of ozone (O3), carbon monoxide (CO), nitrogen oxides (NOx = NO + NO2), the sum of reactive nitrogen species (NOy), peroxyacetylnitrate (PAN), formaldehyde (HCHO), oxygenated volatile organic compounds (OVOCs), volatile hydrocarbons (HCs), methane (CH4), and nitrous oxide (N2O). The air masses arriving at Jungfraujoch experience particular transport pathways and therefore are expected to have characteristic chemical signatures. These characteristics are often masked by mixing with European planetary boundary layer air. In order to address the influence of European emissions, a method to retrieve “background concentrations” based on backward trajectories and statistics was developed and applied to the trace gas observations at Jungfraujoch. This procedure is important to determine baseline values for subsequent assessment of surface air quality targets. Cluster analysis of backward trajectories for “background conditions” shows that the influence of long‐range transport is discernible in most of the clusters. Air masses tend to have lower background concentrations whenever transport conditions favor a higher amount of photochemical degradation (e.g., low latitude or no recent contact to emissions). The results of this study represent an alternative to aircraft measurements which are typically used to determine free tropospheric background conditions. They are valuable for comparison with numerical simulations and for policy making, and provide additional information about free tropospheric chemistry.

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[1] This paper presents results from the first large-scale in situ intercomparison of oxygenated volatile organic compound (OVOC) measurements. The intercomparison was conducted blind at the large (270 m 3 ) simulation chamber, Simulation of Atmospheric Photochemistry in a Large Reaction Chamber (SAPHIR), in Jülich, Germany. Fifteen analytical instruments, representing a wide range of techniques, were challenged with measuring atmospherically relevant OVOC species and toluene (14 species, C 1 to C 7 ) in the approximate range of 0.5-10 ppbv under three different conditions: (1) OVOCs with no humidity or ozone, (2) OVOCs with humidity added (r.h. % 50%), and (3) OVOCs with ozone (%60 ppbv) and humidity (r.h. % 50%). The SAPHIR chamber proved to be an excellent facility for conducting this experiment. Measurements from individual instruments were compared to mixing ratios calculated from the chamber volume and the known amount of OVOC injected into the chamber. Benzaldehyde and 1-butanol, compounds with the lowest vapor pressure of those studied, presented the most overall difficulty because of a less than quantitative transfer through some of the participants' analytical systems. The performance of each individual instrument is evaluated with respect to reference values in terms of time series and correlation plots for each compound under the three measurement conditions. A few of the instruments performed very well, closely matching the reference values, and all techniques demonstrated the potential for quantitative OVOC measurements. However, this study showed that nonzero offsets are present for specific compounds in a number of instruments and overall improvements are necessary for the majority of the techniques evaluated here.Citation: Apel, E. C., et al. (2008), Intercomparison of oxygenated volatile organic compound measurements at the SAPHIR atmosphere simulation chamber,

Eighteen oxygenated volatile organic compounds (OVOCs) and eight nonmethane hydrocarbons (NMHCs) were measured continuously during a two-week campaign in 2004 in the Gubrist highway tunnel (Switzerland). The study aimed to estimate selected OVOC and NMHC emissions of the current vehicle fleet under highway conditions. For the measured OVOCs the highest EFs were found for ethanol (9.7 mg/km), isopropanol (3.2 mg/km), and acetaldehyde (2.5 mg/km), followed by acetone, benzaldehyde, and acrolein. Formaldehyde, the most abundant OVOC measured in other studies, was not measured by the method applied. Relative emissions of the measured OVOCs were estimated to contribute approximately 6 and 4% to the total road traffic VOC emissions from Switzerland and Europe, respectively. Results are compared with those from previous studies from the same tunnel performed in 1993 and 2002, and from campaigns in other tunnels. A continuous reduction in the emission factors (EFs) was determined for all measured compounds from 1993 until 2004. The relative contributions of light-duty vehicles (LDV) and heavy-duty vehicles (HDV) to the total emissions indicated that OVOCs were mainly produced by the HDVs, whereas LDVs dominated the production of the NMHCs.