Non-methane hydrocarbons (NMHC) play a key role in the formation of ozone. Traffic is one of the main emission sources of such pollutants being composed of tail pipe exhaust and of evaporated gases from cars or fuel stations. Over the last six years, airborne measurements of non-methane hydrocarbons have been performed with an online gaschromatograph in several national and international projects. The measurements included large cities like Vienna and Milano, the polluted Lombardy region, moderately polluted regions like the Swiss Plateau and alpine areas. This set of data has been analysed with respect to pollution level, composition, reactivity and contribution of emission sources in the different areas. The measured hydrocarbon concentrations coincide with the emission strengths given by the emission inventories of the respective regions. The alpine Mesolcina valley south of the Alps is strongly influenced by advected air polluted with hydrocarbons. The relative concentration of individual species to the sum of the measured hydrocarbons is similar in all regions, but show a few peculiarities specific to some regions, e.g. a low benzene fraction in Milano and high o-xylene concentrations in Vienna. (A)
Abstract