中文摘要：

单颗粒分析技术能够提供PM_（2.5）的形貌、化学组成、内部结构、混合特性和表面物理化学特性。选取了中国市场上常见的GDI汽车和PFI汽车,在整车转鼓试验台上,采样透射电镜分析了机动车在北京驾驶循环上排放单颗粒的物理化学特征。结果表明,汽油机动车排放的颗粒物可分成6种类型：碳烟（soot）颗粒、球形有机颗粒、富Ca颗粒、富S颗粒、富Fe颗粒和富Mn颗粒,其中以碳烟颗粒、球形有机颗粒和富Ca颗粒为主。不同的机动车在不同的运行条件下（冷启动阶段和稳速阶段）,排放碳烟（soot）颗粒和球形有机颗粒的相对含量不同。GDI机动车不同阶段所排放的PM_（2.5）中,冷启动阶段和稳速阶段相比,前者排放碳烟颗粒相对含量明显偏高,而球形有机颗粒相对含量明显偏低。GDI机动车与PFI机动车相比,在稳速阶段和冷起动阶段所排放的PM_（2.5）中,前者碳烟颗粒相对含量都明显偏高,而球形有机颗粒相对含量都明显偏低。

英文摘要：

Individual particle analysis was developed to study the morphology, internal structure, mixing state and surface properties of PM_（2.5）. Individual particles of the PM_（2.5） emitted by gasoline vehicles on the chassis dynamometer using the Beijing driving cycle were characterized by transmission electron microscopy coupled with energy-dispersive X-ray spectrometry. The different vehicles types, powered by gasoline direct injection（GDI） engine and port fuel injection（PFI） engine, were tested in order to understand how the different driving conditions affect particulate emissions. As a result, a total of six types of individual particles are classified, including soot, spherical organic particles, Ca-rich particles, S-rich particles, Mn-rich particles, and Fe-rich particles, with the spherical organic particles, soot, and Ca-rich particles to be the predominant types. The emission characteristics are different under different vehicle driving conditions, i.e., the cold start phase and the steady speed phase. For the GDI gasoline vehicles, the particles emitted in the cold start phase has a higher relative percentage of soot and a lower relative percentage of spherical organic particles than those in the steady speed phase. For both the steady speed phase and the cold start phase, the relative percentage of soot particles is higher, the relative percentage of the spherical organic particles is lower in the PM_（2.5） emitted by GDI vehicles than those emitted by PFI vehicles.