Observation of Variation of Atmospheric Concentrations of Volatile Organic Compounds (VOCs) at the Central Tokyo and Analysis of Their Behaviors Based on the Correlation with Their Sources

Takao MIYOSHI and Yoshihiro MAKIDE*

Radioisotope Center, The University of Tokyo; Yayoi, Bunkyo-ku, Tokyo 113-0032 Japan

The influences to the global atmospheric environment by anthropogenic trace gases emitted by human activities are seriously concerned. Tokyo is one of the largest cities in the world, and includes all kind human activities: i.e., industries, automobiles, facilities, etc. Therefore, all kinds of anthropogenic emissions are expected in the Tokyo area. Radioisotope Center of the University of Tokyo is located at the center of Tokyo area, and air samples were continuously drawn from the top of the building into the laboratory, cryogenically preconcentrated, and analyzed with a GC-MS system. The atmospheric concentrations of 21 volatile organic compounds (VOCs; hydrocarbons and halocarbons including CFC substitutes) were measured every 3 hours for 100 days, and their variations were analyzed using correlation with meteorological conditions and human activities. Parameters used for the analysis are (1) atmospheric averaged concentration ratios of the weekdays (from Monday to Friday) to Sunday's, (2) distribution patterns of concentration variations, (3) ratios of the weekday's averaged concentrations observed at the center of Tokyo area to the background concentrations obtained from Hokkaido samples, (4) diurnal variations, (5) influence of wind direction, etc. As a result, it was shown that such parameters exactly reflected recent emission of each compound in the Tokyo area. Therefore, precise monitoring of atmospheric trace gases in urban areas will be useful for the understanding of the situation of their emissions by human activities (specially, industries and automobiles). Since the CFC substitutes such as hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) are emitted largely in urban areas and their global concentrations increase slowly, the future changes of global atmospheric conditions will be anticipated from their trends in urban areas.

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