Abstract
The measurements of OH reactivity of exhaust gases determined by the laser-induced pump and probe technique were carried out. The tested gasoline vehicles have adopted the regulation standard for 2005 emissions. The concentrations of trace species in the exhaust gases from these gasoline vehicles were found to depend on the condition of the driving cycles, temperature of the catalysts or the load on the engines. For all driving cycles, there were 4 to 60 % differences between the measured and calculated OH reactivities in the vehicles that have adopted the regulation standard for 2005 emissions. These results suggested that unknown trace species exist in the exhaust gases. (Especially, during the JC08C driving mode, the OH reactivity was much higher than that of the other driving modes).Therefore, for improvement of the ambient air quality, it is very important to enhance the performance of the purification system for the exhaust gases (during JC08C driving mode) and to study the relationship between the unknown trace species and OH reactivity. Moreover, we also measured the exhaust gases of vehicles that have adopted the regulation standard for 2000 emissions. These results showed that the OH reactivity was about 30 to 98 times higher than the vehicles that have adopted the regulation standard for 2005 emissions. Since the current use of vehicles adopting the regulation standard for emissions earlier than 2005 are predominant, it is important to take countermeasures against the exhaust gases of these vehicles.
