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

Monitoring measurements of single very volatile organic compounds (volatility range ranges up to toluene) and inorganic compounds are available from one year at the city centre of Zurich (Switzerland) and from another year from 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 to extend the analytical window to less volatile VOCs including more aromatics and chlorinated VOCs. The concentration of the class of oxygenated compounds was estimates using t-NMVOC measurements from a FID instrument operated at the city centre of Zurich (difference of the measurements of the single compounds from t-NMVOC measurements). From their analysis the authors 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%). (A)