Contribution of road traffic emissions to ambient air concentrations of hydrocarbons: the interpretation of monitoring measurements in Switzerland by Principal Component Analysis and road tunnel measurements

Abstract

Monitoring measurements of single very volatile organic compounds (volatility range ranges up to toluene) and inorganic compounds are available for one year at the city centre of Zurich (Switzerland) and for another year for a suburban site close to Zurich. A novel approach of Principal Component Analysis with visual analysis is used to determine the proportion of motor traffic emission to the ambient air concentrations of these compounds. Passive sampler measurements allowed the extension of the analytical window to less volatile VOCs including more aromatics and chlorinated VOCs. The concentration of the class of oxygenated compounds was estimated using t-NMVOC measurements from a FID instrument operated at Zurich city centre. From our analysis we conclude that the proportion of VOCs of motor traffic including gasoline vaporisation amounts to 48-67% whereas the Swiss emission inventory (basis year 1990) gives lower values (33-48%#37;).