Abstract
Abstract. Diesel trucks are major contributors of nitrogen oxides (NOx) and primary particulate matter smaller than 2.5 μm (PM2.5) in the transportation sector. However, there are more obstacles to existing estimations of diesel-truck emissions compared with those of cars. The obstacles include both inappropriate methodology and missing basic data in China. According to our research, a large number of trucks are conducting long-distance intercity or interprovincial transportation. Thus, the method used by most existing inventories, based on local registration number, is inappropriate. A road emission intensity-based (REIB) approach is introduced in this research instead of registration-population-based approach. To provide efficient data for the REIB approach, 1060 questionnaire responses and approximately 1.7 million valid seconds of onboard GPS monitoring data were collected in China. The estimated NOx and PM2.5 emissions from diesel freight trucks in China were 5.0 (4.8–7.2) million tonnes and 0.20 (0.17–0.22) million tonnes, respectively, in 2011. The province-based emission inventory is also established using the REIB approach. It was found that the driving conditions on different types of road have significant impacts on the emission levels of freight trucks. The largest differences among the emission factors (in g km−1) on different roads exceed 70 and 50% for NOx and PM2.5, respectively. A region with more intercity freeways or national roads tends to have more NOx emissions, while urban streets play a more important role in primary PM2.5 emissions from freight trucks. Compared with the inventory of the Ministry of Environment Protection, which allocates emissions according to local truck registration number and neglects interregional long-distance transport trips, the differences for NOx and PM2.5 are +28 and −57%, respectively. The REIB approach matches better with traffic statistical data on a provincial level. Furthermore, the different driving conditions on the different roads types are no longer overlooked with this approach.
Highlights
China has been facing severe air-quality challenges in the past several years
Li where ρi is the emission density of i type road, g km−1 yr−1; VKTj,k is the average vehicle kilometers traveled (VKT) per vehicle, km year−1; NVcurrent_year − k, j is the new vehicle population of type j k years ago; SRj,k is the survival rate of a k-year-old type j vehicle; DPi,j is the distance portion for type j truck running on type i road; and Li is the total length of type i road in China, km
This significant variation is caused by the diversity of functions of different trucks, which makes the investigation of truck activity a difficult task
Summary
China has been facing severe air-quality challenges in the past several years. Air pollution in China endangers the health of billions of people and creates a substantial burden on the economy (Matus et al, 2012). According to the MEP, diesel vehicles, mainly consisting of freight trucks, contributed 70 % of NOx and 90 % of PM of the total vehicular emissions in 2012 (MEP, 2012a). Yang et al.: Characterization of road freight transportation in China current emission inventory and reducing the uncertainty is of great necessity. Another major impediment to developing a new approach to estimate freight-truck emissions is that most inventories were based on the local registration numbers, which means there is an assumption that trucks are running within the province or city where they registered (Zheng et al, 2013). This research serves to (1) provide more accurate activity-level data for freight trucks, including mileage traveled versus age, activity regions and driving conditions; (2) identify the different emission rates caused by different driving conditions on each type of road; and (3) provide a national emissions inventory that considers the road freight system as whole instead of separating it into different pieces according to the provincial divisions
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