ENVIRONMENTAL EFFECTS OF VOLCANIC GASES ON REGIONAL RAINWATER CHEMISTRY AT KUJU, JAPAN

摘要

Sampling and chemical analysis of rainwater at Kuju volcano were made for ten years from 1992 to examine the effects of volcanic gases on acidification of rainwater and the relationship with volcanic activity. Rainwaters in the near vicinity of the fumarolic area were acidified by HC1, H_2SO_4 and HF. Concentration of Cl~- quickly decreases with distance whereas that of SO_4~(2-) gradually decreases in spite of larger discharge rate of SO_2 relative to HC1 from the fumaroles. This implies that HCl preferentially dissolves into rainwater and deposits in the vicinity of the fumarole. Eruptive activity accompanying increase in discharge rates of acidic gases resulted in lowering pH of rainwater only in the near vicinity of fumarolic area. No appreciable effect was detected at distant places.