Characterization of Benzene, Toluene, Ethylbenzene, and Xylene Concentrations in the Ambient Atmosphere of Tokyo, Japan

Extensive volatile organic carbons (VOCs) data for a 12-month measurement period, which were collected by the Bureau of the Environment, Tokyo Metropolitan Government, are examined in this study. Behavior of benzene, toluene, ethylbenzene, and xylene was discussed, which were monitored at two specified sampling locations, roadside (Hachimanyama) and residential area (Shirogane) in 2001. The monthly variations of these compounds showed two peaks in June and November. The high concentrations in June were considered to be derived from the unburned and evaporated components of fuel due to raised ambient temperature. On the other hand, atmospheric conditions in Tokyo are generally very stable in November. These conditions would result in the peak in November in monthly variations. The concentrations of benzene and xylene were higher at the roadside than that at residential site. These readings were considered to be strongly influenced by vehicle emissions. The difference between concentrations at the both sites was small with respect to toluene and ethylbenzene. Their sources may be not only vehicles but also some stationary sources. The ratios between m,p-xylene to o-xylene were observed to be constant throughout the year with the exception of June, July, and August only at the residential site.