On-road diesel vehicle emission factors for nitrogen oxides and black carbon in two Chinese cities

摘要

Nitrogen oxides (NO_X) and black carbon (BC) emission factors (EF) of 440 on-road diesel trucks were determined by conducting on-road chasing studies in Beijing and Chongqing, China, in the winter 2010. NO_X and BC EF distributions are reported. The median NO_X EFs for trucks sampled on level roads in Chongqing and Beijing are 40.0 and 47.4 g kg-fuel~(-1), respectively. The median BC EFs are 1.1 and 0.4 g kgfuel~(-1) in Chongqing and Beijing, respectively. In addition, a clear downward trend of BC EFs of on-road diesel trucks sampled in Beijing since 2008 is observed. Moreover, Beijing-registered trucks had the lowest BC EFs among the entire sample. These observations appear to reflect the effectiveness of emission standard and fuel quality standard implemented in Beijing (China d Ⅳ) and nationwide (China Ⅲ) in reducing BC (and likely overall paniculate matter) emission. However, NO_X EFs for Beijing-registered trucks did not show lower value than those from other regions. Unlike black carbon, there is no clear correlation between emission controls and NO_X emissions from the sampled on-road trucks. Further analysis shows that trucks with high BC EFs do not usually have high NO_x EFs, and vice versa, indicating that the current emission standards implemented in Beijing and nationwide have only limited impact on NO_X emissions control. Therefore, effective multi-pollutant control strategies and in-use compliance programs are imperative to reduce the overall emissions from the transportation sector.