Spatial concentration profiles of C₂-C₆ hydrocarbons in the atmosphere of Taipei metropolitan area

The spatial concentration profiles of non-methane hydrocarbons in the atmosphere of the Taipei metropolitan area are reported to show their area dependence. Twenty C₂-C₆ hydrocarbons have been identified and quantified in 50 air samples using canisters and a GC/FID system. Statistical analysis indicates that a Weibull distribution was adequated to describe the probability distribution of most measured hydrocarbons. The average concentrations were estimated by the method of maximum likelihood. Relatively high concentrations of ethene (14.1 ppbv), ethyne (15.1 ppbv) and 2-methylbutane (12.8 ppbv) were observed. Comparison of NMHC concentration profiles with other cities and the high correlation coefficients among the measured C₂-C₆ hydrocarbons suggest that gasoline-fueled car and motorcycle emissions are the two major sources of NMHC in Taipei. However, lower correlation coefficients of ethane, propane, iso-butane and n-butane suggest additional sources of these gases.