VOC AIR-POLLUTANTS IN COPENHAGEN

Measurements of non-methane hydrocarbons (VOCs) were initiated in Cope nhagen in 1993 as part of a project on air pollution from traffic unde r a national Strategic Environmental Research Programme (SMP). Two mea suring stations were established in central Copenhagen, one at street level and another some 20 m higher (roof level) for background monitor ing. An analytical method was set up to determine eleven VOCs from eth ane to toluene at the ppbv level by gas chromatography. Sampling was p erformed on weekdays during morning and afternoon rush hours simultane ously at both stations during five 2- to 3-week campaigns throughout 1 994 up to the present. The measured concentrations of VOCs were typica lly three to five times higher at street level than at the background station due to proximity to emission sources; background concentration s were probably lowered by dispersive dilution and mixing and photoche mical reactions. Small seasonal variations were also observed with the concentration of most VOCs at street level being higher in winter tha n in summer. Finally, strong correlations were observed between measur ed street level VOC and CO concentrations and traffic density, indicat ing that motor vehicles are the major source of VOC air pollution in c entral Copenhagen.