Seminar

Abstract

The hydroxyl (OH) radical is well-known to be one of the most important species for tropospheric chemistry. Due to its high reactivity, OH reacts withalmost alltrace species except for CFCs, N2O, and CO2 to form peroxy radicals (HO2 or RO2). To understand the mechanism of ozone production in the troposphere, individual research on OH loss and production processes is essential. However, a complete understanding of the OH loss process seems difficult to achieve. To overcome this difficulty, a direct measurement of OH reactivity is required.

We have previously developed a measurement system for total OH reactivity using a laser pump-probe technique. Measurements of OH reactivity were carried out in urban and suburban areas of Tokyo. We demonstrated that there is a significant missing sink for OH even though we considered the OH reactivity of more than 100 chemical species. Secondary generated VOCs in the atmosphere, such as aldehydes and ketones, are candidates for this missing sink as well as unmeasured primary emitted VOCs. Since current knowledge of VOC emissions is limited, it is necessary to identify the unknown species and specify the emission source. Therefore, we designed a couple of experiments such as emission studies of exhaust gas of gasoline vehicles and single plant.