Abstract
The concentrations of representative five volatile chlorocarbons, namely 1, 1, 1-trichloroethane (methylchlorof orm), trichloroethylene, tetrachloroethylene, chloroform and carbon tetrachloride, in ambient air at residential area in Musashino City andNerima Ward in Tokyo were measured by GC/MS using negative ion chemical ionization at hourly intervals, during three days (Wednesday, Thursday and Friday) in alternate months from October 1989 to August 1990 in the former and every Thursdays at January and February 1989 in the latter. The obtained results were summarized as follows. 1) Their hourly concentrations were 0.31-15.3, <0.1-6.4, 0.07-3.8, <0.1-6.6 and <0.01-2.7 ppb in Musashino City and 2.0-25.0, 0.30-16.8, 0.30-9.8, 0.18-1.8 and 0.15-0.85 ppb in Nerima Ward, respectively. The variation was fairly large and irregular. 2) In winter, relatively high concentrations were appeared because of increase of the use in dry-cleaning. Particulary, increase of 1, 1, 1-trichloroethane concentration was often observed from midnight to daybreak and correlated with NO concentration. It was considered that this fact was responsible for appearance of inversion layer. 3) Correlation between concentrations of 1, 1, 1-trichloroethane, trichloroethylene and tetrachloroethylene were found. They may begenerated from the same emission sources. 4) Correlations between chlorocarbon concentrations and several weather conditions such as temperature, humidity and direction of wind were poor, but the wind speed was correlated inversely to the concentrations.
