Zhiliang Yao

Characteristics of Real-World Vehicular Emissions in Chinese Cities

Abstract On-board emission measurements were performed on 49 light-duty gasoline vehicles in seven cities of China. Vehicle-specific power mode distribution and emission characteristics were analyzed based on the data collected. The results of our study show that there were significant differences in different types of roads. The emission factors and fuel consumption rates on arterial roads and residential roads were approximately 1.4–2 times those on freeways. The carbon monoxide, hydrocarbon, and nitrogen oxides emission factors of Euro II vehicles were on average 86.2, 88.2, and 64.5% lower than those of carburetor vehicles, respectively. The new vehicle emission standards implemented in China had played an important role in reducing individual vehicle emissions. More comprehensive measures need to be considered to reduce the total amount of emissions from vehicles.

Modeling vehicle emissions in different types of Chinese cities: importance of vehicle fleet and local features.

We propose a method to simulate vehicle emissions in Chinese cities of different sizes and development stages. Twenty two cities are examined in this study. The target year is 2007. Among the cities, the vehicle emission factors were remarkably different (the highest is 50-90% higher than the lowest) owing to their distinct local features and vehicle technology levels, and the major contributors to total vehicle emissions were also different. A substantial increase in vehicle emissions is foreseeable unless stronger measures are implemented because the benefit of current policies can be quickly offset by the vehicle growth. Major efforts should be focused on all cities, especially developing cities where the requirements are lenient. This work aims a better understanding of vehicle emissions in all types of Chinese cities. The proposed method could benefit national emission inventory studies in improving accuracy and help in designing national and local policies for vehicle emission control.

PM2.5 emissions from light-duty gasoline vehicles in Beijing, China

As stricter standards for diesel vehicles are implemented in China, and the use of diesel trucks is forbidden in urban areas, determining the contribution of light-duty gasoline vehicles (LDGVs) to on-road PM2.5 emissions in cities is important. Additionally, in terms of particle number and size, particulates emitted from LDGVs have a greater health impact than particulates emitted from diesel vehicles. In this work, we measured PM2.5 emissions from 20 LDGVs in Beijing, using an improved combined on-board emission measurement system. We compared these measurements with those reported in previous studies, and estimated the contribution of LDGVs to on-road PM2.5 emissions in Beijing. The results show that the PM2.5 emission factors for LDGVs, complying with European Emission Standards Euro-0 through Euro-4 were: 117.4 ± 142, 24.1 ± 20.4, 4.85 ± 7.86, 0.99 ± 1.32, 0.17 ± 0.15 mg/km, respectively. Our results show a significant decline in emissions with improving vehicle technology. However, this trend is not reflected in recent emission inventory studies. The daytime contributions of LDGVs to PM2.5 emissions on highways, arterials, residential roads, and within urban areas of Beijing were 44%, 62%, 57%, and 57%, respectively. The contribution of LDGVs to PM2.5 emissions varied both for different road types and for different times.

Impacts of temporary traffic control measures on vehicular emissions during the Asian Games in Guangzhou, China

To guarantee good traffic and air quality during the 16th Asian Games in Guangzhou, China, the government carried out two traffic control Drills before the Games and adopted traffic control measures during the Games. Vehicle activities before and during the first and second Drills, and during the Games, were surveyed. Based on the data under investigation, the impacts of control measures on traffic volumes and driving characteristics were analyzed during the first and second Drills, and the Games. The emission reduction of traffic control measures was also evaluated during the three stages using the MOBILE-China model. The results show that there were significant effects of implementing temporary traffic control measures on transportation activity and vehicular emissions. During the first and second Drills, and the Games, the average traffic volumes in monitored roads decreased, and the average speed of vehicles increased significantly. The co-effects of traffic flow reduction, traffic congestion improvement, and the banning of high-emitting vehicles helped to greatly reduce the estimated emissions from motor vehicles in Guangzhou during the first and second Drills, and the Games. Estimated vehicular emissions were reduced by 38∼52% during the first Drill and 28∼36% for the second Drill. During the Asian Games, vehicular emissions of carbon monoxide (CO), hydrocarbon (HC), oxides of nitrogen (NOx), and particulate matter with an aerodynamic diameter <10 μm (PM10) reduced by an estimated 42%, 46%, 26%, and 30%, respectively, compared with those before the Games. Both the banning of high-emitting vehicles and the travel restrictions imposed by use of odd-even licenses had significant effects on the reduction of vehicular emissions of CO, HC, NOx, and PM10. Implications: Motor vehicles have become the most prevalent source of emissions and subsequently air pollution within Chinese cities. Understanding the impacts that different control measures have on vehicular emissions is very important in order to be able to control vehicle emissions. The results of this study will be very helpful for the further control of vehicle emissions in Guangzhou in the future. In addition, the effects of temporary transportation control measures will provide important awareness to other cities that will be hosting large-scale activities similar to the Asian Games.

Characterization of the chemical composition of PM2.5 emitted from on-road China III and China IV diesel trucks in Beijing, China.

The composition of diesel exhaust fine particulate matter (PM2.5) is of growing interest because of its impacts on health and climatic factors and its application in source apportionment and aerosol modeling. We characterized the detailed chemical composition of the PM2.5, including the organic carbon (OC), elemental carbon (EC), water-soluble ions (WSIs), and elemental contents, emitted from China III and China IV diesel trucks (nine each) based on real-world measurements in Beijing using a portable emissions measurement system (PEMS). Carbonaceous compounds were the dominant components (totaling approximately 87%) of the PM2.5, similar to the results (greater than 80% of the PM2.5) of our previous study of on-road China III diesel trucks. In general, the amounts of individual component groups (carbonaceous compounds, WSIs, and elements) and PM2.5 emissions for China IV diesel trucks were lower than those of China III diesel trucks of the same size, except for the WSIs and elements for the light- and medium-duty diesel trucks. The EC/OC mass ratios were strongly dependent on the emission standards, and the ratios of China IV diesel trucks were higher than those of China III diesel trucks of the same size. The chemical species in the PM2.5 were significantly affected by the driving conditions. Overall, the emission factors (EFs) of the PM2.5 and OC under non-highway (NHW) driving conditions were higher than those under highway (HW) driving conditions, and the EC/OC mass ratios presented an increasing trend, with decreasing OC/PM2.5 and increasing EC/PM2.5 from NHW to HW driving conditions; similar trends were reported in our previous study. In addition, Pearsons correlation coefficients among the PM2.5 species were analyzed to determine the relationships among the various chemical components.

Development of database of real-world diesel vehicle emission factors for China.

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT (Computer Programmer to calculate Emissions from Road Transport) and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5 (Highway Vehicle Particulate Emission Modeling Software) models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent, which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.

Characterization and carcinogenic risk assessment of polycyclic aromatic and nitro-polycyclic aromatic hydrocarbons in exhaust emission from gasoline passenger cars using on-road measurements in Beijing, China

The polycyclic aromatic hydrocarbon (PAH) and nitro-polycyclic aromatic hydrocarbon (NPAH) emissions from 16 gasoline passenger cars, encompassing five emission standards and two driving conditions, were tested using a portable emission measurement system (PEMS) in Beijing under on-road conditions. In total, 16 PAHs and 9 NPAHs were quantified in both the gaseous and particulate phases by high-performance liquid chromatography (HPLC). The results indicated that lower PAH and NPAH emissions were observed with improved emission standards, especially for China 3 to China 5 vehicles (P < 0.05). Higher emission factors (EFs) were detected on nonhighway roads than on highway roads due to incomplete combustion. Although most PAHs and NPAHs were in the gas-phase, the TEQBaP of the particulate-phase PAHs was 4.2 times higher than that of the gas-phase PAHs, whereas the opposite pattern was observed for NPAHs. The TEQBaP EFs on nonhighway roads were 1.0-2.3 times higher than those on highway roads. The results of this study will be valuable for estimating the emissions and performing carcinogenic risk assessment of PAHs and NPAHs from urban gasoline passenger cars on roads. Formulating more stringent regulations and emission control technologies for PAHs and NPAHs is important.