昭和新山噴気孔ガス凝縮水中の化学成分の連続観測

抄録

The aim of this research is focused on the following two points: 1) To examine whether the constancy of the chemical composition of fumarolic gas is established or not in a short period (10-20 hrs.). 2) To examine the feasibility of chemical forecast of volcanic eruption by knowing the chemical behavior of fumarolic gases in calm periods of a volcano. Sampling of condensed water and measurement of temperature and relative flow rate were made 24 times at the intervals of 1 hr. at a fumarole of Volcano Showa-shinzan on 17th. August, 1958. Chemical components analysed are pH, Cl^-, F^-, NO₃^-, SO₄^-, B, Na⁺, K⁺, Mg⁺⁺, and Ca⁺⁺. The results obtained are: 1) Little time variation of the temperature of fumarolic gas is observed (653±2℃). 2) About ±5% fluctuations are found for the concentration of Cl^-, F^-, and B in the “normal” samples. The Cl:F:B ratio is almost constant in these samples, viz., Cl:F:B = 37:9.3:1 (wt. ratio). 3) “Abnormal” samples are classified into the following three types, (1) KCl contamination (2) KNO₃ contamination (3) dilution with water vapor. (1) and (2) are due to the abrupt feeds of KCl and KNO₃ to the fumarolic gas separatedly. Almost all of the abnormal samples are followed by the increase of SO₄^-- and the decrease of F^-. We cannot explain the ultimate cause of the occurrence of abnormal samples.