摘要：Concentrations of six volatile aromatic hydrocarbons (VAHs), i.e. benzene, toluene, ethylbenzene and three kinds of xylene, in the ambient air at the rural, suburban and urban sites were monitored. Twenty-four h measurements of VAHs were carried out during 8 consecutive days in June, August, October and December, 1991, and in February and April, 1992. Mean concentrations at all sites of benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene were 1.7 ppb, 2.3 ppb, 0.39 ppb, 0.29 ppb, 0.70 ppb and 0.29 ppb, respectively. Concentrations of all VAHs were most elevated at the urban site compared with those at the rural and suburban sites. The VAH concentrations decreased on Sunday ; the relative ratios of VAH to benzene in air at the investigated sites were similar to those in exhaust gas from vehicles and to those in air from automobile tunnels. These facts suggest that the VAHs in these sites are mainly originated from vehicle emissions and also suggest that the VAH concentrations reflect traffic of each area. An excursion in toluene measured at the suburban site was related to the usage of solvent for painting. All the VAH concentrations were higher in winter season than in summer season. This seems to be caused by meteorological factors. Cancer risk calculations for inhalation of benzene in the ambient air were from 30×10-6 (rural) to 70×10-6 (urban).
