Abstract
The high ozone concentration in urban atmospheres including Tokyo is still one of the important environmental issues. One of the possible causes is ozone formation by unconsidered VOC. In this study, we performed chamber experiments to understand the importance of biogenic VOCs emitted from urban green flora. Isoprene and α-pinene were added to ambient air and irradiated by UV. The ozone and formaldehyde concentrations were measured to compare the ozone formation potential with the control. The ozone formation potential of isoprene was also compared to that of toluene. Considering the typical emission rates of isoprene and α-pinene, 10 and 0.7 ppbv of these VOCs were separately added to the ambient air in the chamber. Both isoprene and α-pinene showed approximately 30% higher ozone concentrations compared to the control after 6 h of UV irradiation. On the other hand, isoprene showed a 33% higher ozone concentration than toluene for a 10 ppbv addition to the ambient air after 6 h of reaction. This means that the ozone formation by biogenic VOC is important as well as that of anthropogenic VOCs, such as toluene, which is a typical anthropogenic VOC. The possibility that biogenic VOCs emitted from green areas and street trees are important for ozone formation has been suggested by this study.
