| Summary: | 碩士 === 國立成功大學 === 環境工程學系 === 87 === The characteristics of twenty-one polycyclic aromatic hydrocarbons (PAHs) in the exhaust of 111 diesel-engine vehicles, including concentration, composition and emission rate of twenty-one individual PAHs were investigated. The diesel-engine exhaust samples were collected with a PAHs sampling system and analyzed by using a Hewlett Packard GC/MS.
The results of this study indicate that the total PAHs concentration in the exhaust of diesel-engine vehicles was in decreasing sequence as follows：Light-duty trucks, engineering trucks, military trucks, garbage trucks, buses and heavy-duty trucks. The concentration summation of three highest carcinogenic PAHs (BbF+BaP+DBA) in diesel engine exhausts was in decreasing sequence as follows：Light-duty trucks, heavy-duty trucks, garbage trucks, military trucks, engineering trucks and buses.
Two- and three-ring PAH homologues were dominant in the exhaust of diesel-engine vehicles. The summation concentration of two- and three-ring PAH homologues counted for 95% of total-PAH concentration. Therefore, the characteristics of exhaust of in diesel-engine vehicle were predominant in low molecular weight PAHs. More than 90% of total-PAH mass were in the gas phase. This result also indicated that lower molecular weight PAHs are mainly in gas phase, while higher molecular weight PAHs are primarily associated with particulate. Total-PAH concentration increased by a higher vehicle milage and exhaust opacity.
The particle-bound total-PAH composition in the exhaust of diesel engine vehicles was in decreasing sequence as follows：Engineering trucks, light-duty trucks, buses, garbage trucks, military trucks and heavy-duty trucks. The summation of particle-bound total-PAH composition for the three highest carcinogenic PAHs (BbF+BaP+DBA) in diesel engine exhausts was in decreasing sequence as follows：Engineering trucks, light-duty trucks, garbage trucks, heavy-duty trucks, military trucks and buses. The summation particle-bound composition of 4-~7-ring PAH homologues counted for more than 50% of total-PAH composition.
The emission rate of six types of diesel engine vehicles in decreasing sequence were buses (27.2 mg/min), light-duty trucks (18.3 mg/min), heavy-duty trucks (14.6 mg/min), engineering trucks (7.31 mg/min), garbage trucks (2.41 mg/min), and military trucks (1.89 mg/min). The amount of the total PAHs were estimated as 38.4 ton/yr, 11.1 ton/yr, 3.99 ton/yr, 2.68 ton/yr, 0.04 ton/yr, respectively.
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