VOC air pollutants in Copenhagen

Measurements of non-methane hydrocarbons (VOCs) were initiated in Copenhagen in 1993 as part of a project on air pollution from traffic under a national Strategic Environmental Research Programme (SMP). Two measuring stations were established in central Copenhagen, one at street level and another some 20 m higher (roof level) for background monitoring. An analytical method was set up to determine eleven VOCs from ethane to toluene at the ppbv level by gas chromatography. Sampling was performed on weekdays during morning and afternoon rush hours simultaneously at both stations during five 2- to 3-week campaigns throughout 1994 up to the present. The measured concentrations of VOCs were typically three to five times higher at street level than at the background station due to proximity to emission sources; background concentrations were probably lowered by dispersive dilution and mixing and photochemical reactions. Small seasonal variations were also observed with the concentration of most VOCs at street level being higher in winter than in summer. Finally, strong correlations were observed between measured street level VOC and CO concentrations and traffic density, indicating that motor vehicles are the major source of VOC air pollution in central Copenhagen.