[Chemical Composition of Alkanes and Organic Acids in Vehicle Exhaust]

The soot of 11 diesel buses and 20 gasoline cars was sampled by direct sampling, and the main organic compounds of the samples were separated and qualitatively analyzed by GC-MS. The results showed that the mass fraction of n-alkanes was 1.31-149.08 μg·g^-1 and 15.35-556.03 μg·g^-1. The main carbon number of n-alkanes in diesel buses and gasoline cars soot was 20 and 29, respectively, and gasoline cars generated more long chain alkanes with high boiling point. The total mass fraction of pristane and phytane in diesel buses was 15.24 μg·g^-1 and 21.79 μg·g^-1, respectively, while the two values in gasoline cars were 2.31 μg·g^-1 and 2.69 μg·g^-1, respectively. The ratios of pristane and phytane were 0.6994 and 0.8587, and the ratios of phytane and octadecane were 0.3565 and 0.7472. The changes of the relative mass of fatty acids were relatively large, the change ranges in buses and cars were 0.01-40.87 μg·g^-1 and 3.8-113.7 μg·g^-1, respectively, and the organic acid with the highest content in the buses was 3- hydroxybutyric acid.The maximal ratio of hexadecanoic acid and butanedioic acid (C₃/C₄) was 5.93. The most abundant n-alkanes in gasoline cars soot was C₁₆, and the mass fraction of aromatic acids was 5.05-31.70 μg·g^-1 and 0.1-228.38 μg·g^-1, respectively.