Chemical Composition Of Organic Matter From Vehicle Soot

The soot of 24 diesel buses and 20 gasoline cars were sampled by direct sampling, and the main organic compounds （alkanes, organic acids, polycyclic aromatic hydrocarbons, phenols and aromatic ketones） of the samples were separated and qualitatively analyzed by GC-MS. The results indicated that:The content range of n-alkanes were 1.31-149.08 μg·g-1 and 15.35-556.03μg·-1 in diesel buses and gasoline cars.The main carbon number of n-alkanes in diesel buses and gasoline cars soot were 20 and 29, and gasoline cars generate more long chain alkanes.The highest concentration of fatty acids in the buses was 3-hydroxybutyric acid, but hexadecanoic acid (C₁₆) was the most abundant normal alkyl acids in gasoline cars soot. In two kinds of vehicle, the most abundant aromatic organic acid was benzoic acid. However, the types and content of aromatic acids in gasoline cars are much more than those in diesel vehicles.21 kinds of polycyclic aromatic hydrocarbons （PAHs） were detected in the gasoline cars, the content of pyrene is the highest, while PAHs in the samples of buses soot only three, respectively for phenanthrene, fluoranthene and pyrene, phenanthrene content was the highest.The distribution rule of PAHs rings in cars was ring 4> ring （2-3）> ring （5-6）. There was a good linear relationship of fluoranthene and pyrene in the soot of cars and buses, and there was also a good correlation between benzo[a]pyrene （BaP） and the total PAHs content in the gasoline cars soot.Only 2,6-dimethoxyphenol was quantified in 24 diesel buses soot, the phenolic species in gasoline cars soot were far greater than the buses, in addition to the 2,6-dimethoxyphenol, and seven kinds of phenolic compounds.Particle phase of aromatic ketones in the gasoline cars soot can quantitatively with three, respectively for benzophenone,3-methylbenzophenone and 4-methyl diphenyl ethanedione, the content of benzophenone in the soot of gasoline cars was the highest,while we did not detect the aromatic ketones in 24 buses soot.The contents of organic matter in the exhaust pipe wall of the gasoline cars have a great relationship with vehicle brands and the aging of engine. The n-alkanes and aromatic acid contents of Harvard CUV and Santana 2000 soot were a few times higher than other brands of gasoline cars. And in the study of PAHs, the content of PAHs in Chery QQ and Santana 2000 soot were higher than the rest, the big reason is due to the aging lead to inadequate fuel engine and exhaust pipe carbonization coking seriously.