| In recent decades, the Pearl River Delta (PRD) region located in south China is experiencing serious primary and secondary (high concentrations in NO2, PM10, O3 and PM2.5) air pollutions, arising from the rapid increases in motor vehicles. How to identify the characteristics of vehicular emissions, and make reasonable and operational policies for controlling motor vehicle emissions in the region has become a challenging issue for both academic researchers and policy-makers.In this study, a methodological framework for systematically assesing motor vehicle control strategies for the PRD region was established. The framework includes the methods for developing motor vehicle emission inventory, temporally and spatially allocating emissions, design control strategies, and assessing their effects on air quality using air quality models. This framework can be applied to the analysis of dynamic vehicular emission characteristics and the optimization study of emission control strategies from vehicular pollution in this region.First, an emission factor model named as MOBILE 6.2 was employed to develop the emission inventory from motor vehicles in the PRD. In 2006, the total emissions of NOx, VOC, PM10, PM2.5 and SO2 from vehicles were 314 kt, 475kt, 83kt, 67kt and 36ke, respectively. The emission characteristics varied dramatically among different types of motor vehicles, gasoline vehicles had significant contributions to the VOC emissions, while diesel vehicles were the major contributors to NOx and PM10 emissions.Second, a new approach was proposed to help the spatial and temporal allocations of mobile source emissions in the PRD by utilizing the GIS-based road network information and road types-based traffic flow data. The results showed that most NOx and VOC emissions from mobile sources were spatially distributed over the economically developed cities in the PRD region such as Guangzhou, Foshan, Dongguan and Shenzhen where vehicle population and traffic flows were higher, as expected. There were obvious differences in diurnal variations of mobile spurce emissions from different road typesThird, on the basis of reviewing existing motor vehicle control practices in the PRD, five possible motor vehicle emission control strategies, including motorcycle forbidden in the urban areas, implementation of Euro IV emission standard, early retirement of old/high emit vehicles, encouragement of public transportation, and wider use of Hybrid Electric Vehicles (HEVs), were proposed.Finally, the emission reduction potentials from the five strategies were evaluated and their influences on air quality in the PRD region were investigated with the aid of Model-3/CMAQ (Community Multi-scale Air Quality) model, as the target year of 2015. The results show that (1) the implementation of Euroâ…£is the most effective measure in NOx, VOC, and PM emission reductions, which can reduce the emissions from vehicles by 50% on average; motorcycle restriction in urban area can largely reduce VOC emissions (about 100 kiloton reduction per year), but contributes little to NOx and PM10 emission reductions; other measures have potentials in reducing NOx,VOC and other pollutant emissions from 4%-12%; (2) an overall decrease in SO2,NO2 and PM10 concentrations was found in most parts of the PRD region, but increased O3 concentrations may occur especially in the urban areas of the PRD region after implementing these control measures, except that a slight decrease in O3 concentration was observed for the motorcycle restriction and wider use of HEVs. These results suggest that solely controlling motor vehicle emissions is not sufficient to control O3 pollution in the region though it may be effective in reducing primary pollutant concentrations; more stringent control measures for other emission sources, especially for VOC-related emission sources, and further researches for the design of regional ozone control strategies, are needed.
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