Measurement of volatile organic compounds in the urban atmosphere of Yokohama, Japan, by an automated gas chromatographic system

Urban air concentrations of six selected volatile aromatic and five selected volatile chlorinated compounds were measured at Hiyoshi in Yokohama, Japan, from November 1994 to October 1997 using an automated gas chromatographic (GC) system. Continuous measurements were made with 1 h cycles over a 1- or 2-day period. The data from these studies were analyzed and interpreted with respect to variabilities in the urban air concentrations and the diurnal changes in relation to prevailing sources. The mean concentrations of aromatic hydrocarbons were in the range of 0.38–1.13 ppb benzene, 1.23–8.95 ppb toluene, 0.12–0.88 ppb ethylbenzene, 0.03–0.18 ppb m-, p-xylene, 0.23–0.46 ppb o-xylene and 0.24–0.38 ppb 1.2.4-trimethylbenzene. Although variations exist in the measurements, the mean distributions in the aromatic hydrocarbons were 10.4% benzene, 69.7% toluene, 7.7% ethylbenzene, 5.4% m-, p-xylene, 1.6% o-xylene and 5.3% 2.4-trimethybenzene. Diurnal variations in the aromatic hydrocarbons were found to be very similar to each other and positively correlated with traffic activities. On the other hand, the mean concentrations of 1,1-dichloroethene, 1,1,1-trichloroethane, trichloroethene, tetrachloroethene and 1,4-dichlorobenzene were 0.08–0.86, 0.08–0.93, 0.24–0.79, 0.03–0.24 and 0.07–0.42 ppb, respectively. The concentrations of these chlorinated hydrocarbons were always lower and less variable than those of the aromatic hydrocarbons.