Concentrations of halide ions in river waters in the Kusatsu-Shirane volcano area, Gunma, were measured by ion chromatography. The decreasing order of concentration among halide ions at various sampling locations is in general: chloride ion>fluoride ion>bromide ion>iodide ion. A strong correlation was observed between the concentrations of the chloride and bromide ions. High halide ion concentrations were observed in river waters indicating that the volcanic activity of Mt. Kusatsu-Shirane is the major source of halide ions in river waters of the area. Measurements of halide ion concentrations along the downward streams of selected rivers revealed that concentration ratios among halide ions did not vary substantially in the absence of any circumstantial change. The amounts of halide ions transported from the Kusatsu-Shirane volcano area by rivers per year were estimated to be 1.4 x 10⁷ mol for the fluoride ion, 3.8 x 10⁸ mol for the chloride ion, 4.1 x 10⁵ mol for the bromide ion and 1.0 x 10⁵ mol for the iodide ion.

Key words: Halide ions; Japan; River waters; Volcano.

Reprints: M Yamano, Sophia University, Department of Chemistry, Faculty of Science and Technology, Chiyoda Ku, 7-1 Kioicho, Tokyo 102, Japan.

FLUORIDE 30 (3)  1997, p. 188	International Society for Fluoride Research
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