Variation in the concentrations of some chemical constituents in precipitation was studied from January, 1967 through October, 1971 at Kichijoji, Tokyo. (1) Annual variation of Cl
- and SO
42- concentrations. The Cl
- concentration shows the maximum in December and the minimum in April. The SO
42- concentration reaches the maximum in December-January and the minimum in June. (2) Secular variation of Cl
- and SO
42- concentrations. There is a steadily increasing tendency from year to year, with a single exception of 1967-70 when SO
42- concentration remains the same. (3) Chemical constituents concentrations in precipitation and air mass trajectories. Concentrations of constituents in precipitation depends on the trajectories of air masses from which precipitation is supposed to be derived. Precipitation derived from the air mass which has passed through the industrial area contains higher amount of Zn
2+, Cl
-, SO
42- and Ca
2+.
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