机动车尾气碳质气溶胶排放因子及其稳定碳同位素特征

机动车尾气是大气碳质气溶胶的重要人为来源，其排放因子与稳定碳同位素组成是重要的基础数据.选取多辆不同类型在用机动车，进行多种工况、冷/热条件下启动的台架试验，收集各测试阶段尾气分析其碳质组分含量与稳定碳同位素比值，并探讨其影响因素.结果表明，总碳排放因子大小为：重型柴油车>轻型柴油车>轻型汽油车，轻型天然气车虽然在低速与中速阶段排放因子极低，但高速行驶阶段可达到重型柴油车的排放水平.各型车冷启动的排放因子均高于热启动，NEDC工况的排放因子整体低于WLTC工况，应与其测试车速有关.汽油车和天然气车各测试阶段排放有机碳(OC)均远高于元素碳(EC),柴油车OC与EC排放因子相近，各类车辆OC/EC都随测试车速的提高而上升.稳定碳同位素EC重于OC,同位素比值大小关系均呈现：汽油车<天然气车<轻型柴油车<重型柴油车，现有源解析的稳定碳同位素源谱较难反映汽油车与天然气车特征.在排放治理与源解析工作中，应注意替代燃料的使用与机动车老化过程所造成的排放因子与同位素特征值的变化影响.

Emission Factors of Carbonaceous Aerosol and Stable Carbon Isotope for In-use Vehicles

Vehicle exhaust is an important anthropogenic source of atmospheric carbonaceous aerosols; of which, the emission factors and stable carbon isotope composition are important basic data. In-use motor vehicles of different types were selected to conduct dynamometer tests using different test cycles and under cold/hot start conditions. The exhaust of each test stage was collected to analyze the carbonaceous components and stable carbon isotopes and to discuss the influencing factors. The total carbon emission factors follow the order:heavy-duty diesel vehicles>light-duty diesel vehicles>light-duty gasoline vehicles. Although the emission factors of light-duty natural gas vehicles were very low at the low- and medium-speed stages, they were similar to those of heavy-duty diesel vehicles at the high-speed stage. The emission factors of cold start were higher than those of hot start, and the emission factors of the NEDC test cycle were lower than those of WLTC (which should be related to the driving speed). The emission factors of organic carbon (OC) of gasoline and natural gas vehicles were much higher than those of elemental carbon (EC) in every test stage. The emission factors of OC and EC of diesel vehicles were similar. The OC/EC of all types of vehicles increased with the increase in driving speed. Stable carbon isotopes in EC were higher than those in OC. The stable carbon isotope in different vehicles follow the order:light-duty gasoline vehicles