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Fig. 3 – Spatial distribution of vehicular HC emissions for Beijing urban area in 2005.
(2007) developed the vehicle emission inventories for Beijing in his thesis using this approach. The total stabilized running emissions for the Beijing urban area based on the two different methods are presented in Fig. 6. It should be noted that the macro-scale emission inventory was developed for the whole area of Beijing (including the suburban area) in 2005. Accord- ing to a study, vehicle emissions in the urban area made up 75% (DESE, 2005) of the total air emissions in Beijing in 2002 for vehicle-related pollutants. Considering the suburbanization of Beijing in recent years, the vehicle activity in the suburban area likely increased. The study estimated that the vehicle- related emissions in the suburbs were 70% of the total.
Fig. 6 shows that compared with grid-based (micro-scale) emission inventory macro-scale methodologies may under- estimate emissions in Beijing by 18.7% and 6.1% of HC and CO emissions, respectively. There may be two reasons for this underestimation:
(1) The vehicle activity data used in the macro-scale method are usually from statistical material, which reflect the static level of average vehicle activity throughout the city. There may exist significant differ- ences between these data and the actual vehicle activity level on the roads (Wang et al., 2008). The TDM model
Fig. 4 – Spatial distribution of vehicular CO emissions for Beijing urban area in 2005.
Please cite this article as: Wang H, et al, A bottom-up methodology to estimate vehicle emissions for the Beijing urban area, Sci Total Environ (2008), doi:10.1016/j.scitotenv.2008.11.008