Statistical analysis of non-methane hydrocarbon variability at a European background location (Jungfraujoch, Switzerland)
1Empa, Swiss Federal Laboratories for Materials Testing and Research, Laboratory for Air Pollution and Environmental Technology, 8600 Duebendorf, Switzerland
2Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
*now at: PSI (Paul Scherrer Institute) Laboratory for Atmospheric Chemistry, 5232 Villingen PSI, Switzerland
Abstract. In-situ measurements of volatile hydrocarbons, CxHy, and chlorinated organic compounds, CxHyClz, were performed at Jungfraujoch (Switzerland) during eight years (2000–2007). The analysis of 4-hourly resolved non-methane hydrocarbons (NMHCs) was achieved by using gas-chromatography coupled with mass spectrometry (GC-MS). Variabilities in the NMHC series were modeled by factor analysis. Four factors defined the solution space and could be related to hydrocarbon sources. In order to facilitate factor interpretations the retrieved contributions were compared with independent measurements, such as trace gases (NOx, CO, and CH4) and meteorological data (back trajectories). The most dominant factor (accounting on average for 42% of the total mixing ratio of the considered NMHCs) was found to be most active in winter, co-varying with CO and could be related to combustion sources. The other three factors represent both industrial and evaporative sources. Trajectory statistics suggest that the most influential anthropogenic NMHCs sources for Jungfraujoch are located in Eastern Europe, but the Po Valley has been identified as a potential source region for specific industrial sources as well. Aging of the arriving NMHCs, the derived factors as well as limitations of the methods are discussed.