Development and preliminary evaluation of a particulate matter emission factor model for European motor vehicles

Although modeling of gaseous emissions from motor vehicles is now quite adv anced, prediction of particulate emissions is still at an unsophisticated s tage. Emission factors for gasoline vehicles are not reliably available, si nce gasoline vehicles are not included in the European Union (EU) emission test procedure. Regarding diesel vehicles, emission factors are available f or different driving cycles but give little information about change of emi ssions with speed or engine load. We have developed size-specific speed-dep endent emission factors for gasoline and diesel vehicles. Other vehicle-gen erated emission factors are also considered and the empirical equation for re-entrained road dust is modified to include humidity effects. A methodolo gy is proposed to calculate modal (accelerating, cruising, or idling) emiss ion factors. The emission factors cover particle size ranges up to 10 mum, either from published data or from user-defined size distributions. A particulate matter emission factor model (PMFAC), which incorporates virt ually all the available information on particulate emissions for European m otor vehicles, has been developed. PMFAC calculates the emission factors fo r five particle size ranges [i.e., total suspended particulates (TSP), PM10 , PM5, PM2.5, and PM1] from both vehicle exhaust and nonexhaust emissions, such as tire wear, brake wear, and re-entrained road dust. The model can be used for an unlimited number of roads and lanes, and to calculate emission factors near an intersection in user-defined elements of the lane. PMFAC c an be used for a variety of fleet structures. Hot emission factors at the u ser-defined speed can be calculated for individual vehicles, along with rel ative cold-to-hot emission factors. The model accounts for the proportions of distance driven with cold engines as a function of ambient temperature a nd road type (i.e., urban, rural, or motorway). A preliminary evaluation of PMFAC with an available dispersion model to pre dict the airborne concentration in the urban environment is presented. The trial was on the A6 trunk road where it passes through Loughborough, a medi um-size town in the English East Midlands. This evaluation for TSP and PM(1 0)was carried out for a range of traffic fleet compositions, speeds, and me teorological conditions. Given the limited basis of the evaluation, encoura ging agreement was shown between predicted and measured concentrations.