This research investigated the polycyclic aromatic hydrocarbons (PAHs) concentrations and emissions in the particulate matter of diesel engine exhausts on a dynamometer. Four buses under good routine maintenance were chosen and operated at various driving modes, such as idling, accelerating, constant speeds of 20 km/hr (V20), 40 km/hr(V40) on a dynamometer in the Taoyuan County diesel vehicle test center. Particulate samples in diesel bus engine exhaust at different driving modes were collected and 16 target PAHs were thereafter analyzed. The particle-bound PAH concentrations in diesel bus exhaust revealed that the buses under idling conditions emit a minimal PAHs of 1.38 ug/Nm3 while accelerating, V20 and V40 produced about 20.3, 5.3 and 9.3 ug/Nm3, respectively. The bus emission in both idling and accelerating modes contained significant amounts of high molecular weight carcinogenic PAHs, the health effect to the general public contributed by diesel vehicle should be notified. By using engine speed information under the above driving conditions for the testing buses, PAH emission factors can be calculated and compared.

PAH,Diesel Engine Particulate Exhaust,Emissions