| Title | Effects of Volcanic Gases on Rain and Soil Chemistries at Kuju, Japan |
|---|---|
| Authors | Rie Unoki, Ryuichi Itoi |
| Year | 2005 |
| Conference | World Geothermal Congress |
| Keywords | Kuju volcano, volcanic gas, rainwater chemistry, Soil pH, clay mineral |
| Abstract | Rainwater was collected near the fumarolic area at Kuju volcano, Japan from 1992 to 2003 to examine the effects of volcanic gases on regional rainwater chemistry. During this monitoring period, a phreatic eruption occurred in 1995 and formed new craters which have been discharging volcanic gases until now. The rain samples were collected with bulk samplers every two weeks from April to November every year, and then chemically analyzed. Additionally, soil samples down to about 2 m were collected in 1993 and 2004 at a point of 1 km distant from the fumarolic area. Soil pH, adsorbed amount of SO42?, exchangeable Al3+ and cations were measured. Extracted soil water from the samples were also chemically analyzed. The results indicated that concentrations of Cl? and F? in rainwater quickly decreased with distance from the main fumarolic area whereas that of SO42? gradually decreased. This implies that HCl and HF preferentially dissolve into rainwater and deposit in the vicinity of the fumarolic area. Vertical profiles of adsorbed SO42? showed high values where soil contains clay minerals rich in hydroxide base. High values of soil water pH and soil pH were also obtained. The profile of Cl? in soil water represents a constant concentration irrelative to the depth. This is attributed to poor adsorption capacity of soil with respect to Cl? among anions in soil water. SO42? concentrations of soil water show higher values at deeper layers. |