Local distribution of chlorinated hydrocarbons in the ambient air in Tokyo

Abstract

The measurements of four chlorinated hydrocarbons were made in Tokyo air from May 1974 to April 1975. The annual average concentrations were 0.8 ppb(10 −9), 1.4 ppb, 1.2 ppb, and 1.2 ppb, for 1,1,1-trichloroethane, carbontetrachloride, trichloroethylene and perchloroethylene respectively. The correlations between the levels of these chemicals and the meteorological data were discussed and these results demonstrated that rain, the eastwind (seabreeze) for Tokyo and strong winds (the maximum velocity of the wind in a day is 10–15 m s −1) contributed to remove these chemicals from air, on the other hand, the cloudiness and the weaker wind contributed to keep these levels high and the southwind contributed to increase them. The distributions peaks of trichloroethylene and 1,1,1-trichloroethane coincided with locations of machine or metal products plants which are the major user of both solvents, and furthermore the distribution of carbontetrachloride showed a good relation with that of chemical factories. However perchloroethylene was distributed rather evenly. The concentration of carbontetrachloride was much larger than the expected value from the annual production compared with that of 1,1,1-trichloroethane, trichloroethylene and perchloroethylene, the reason for this is not clearly understood at present.