CONTENTS OF HALIDE-IONS OF HOT-SPRING WATERS IN THE KUSATSU-SHIRANE VOLCANO AREA

Contents of halide ions (F-, Cl-, Br- and I-) of twelve hot spring wat ers in the Kusatsu-Shirane volcano area were determined using ion chro matography. High correlations were observed among those ions, which in dicated that they were of the same origin, that is, they were all deri ved by the volcanic activity of Mt. Kusatsu-Shirane. Secular changes i n F-, Cl- and Br- contents of Kusatsu-Yubatake and Bandaiko hot spring waters and Yugama lake water since around 1970 were presented. Increa ses in most of those contents are observed in recent years.