10:45 AM - 11:10 AM
[AHW30-05] Mechanisms of Water Quality Formation and the Influence of Volcanic Fluids on River Water, Lake Water, and Hot Spring Water in Shiretokoiozan Volcano and its surrounding area
★Invited Papers
Keywords:Shiretokoiozan Volcano, Hydrogen and Oxygen Isotopes, Hot Spring Water, Lake Water, River and Creek Water, Andesitic Water, Mixing, Sulfur Generation
1. Introduction
We have studied the mechanism of molten sulfur eruption at Shiretokoiozan Volcano at Hokkaido Japan. In this study, to clarify the supply and circulation state of water and substances in the aquifer where sulfur is considered to be generated and its surrounding area, samples of hot springs, creeks, lake water and condensate from a fumarole were collected from the vicinity of the volcano. The hydrogen and oxygen isotope ratios and the concentrations of major ions were analyzed. Based on the results, the origins and circulation states of these waters and the substances contained within them were examined, with a particular focus on the influence of volcanic fluids on water quality formation.
2. Methods
Water samples were collected in 100 ml bottles. Prior to collection, water temperature, pH, electrical conductivity, oxidation-reduction potential, and dissolved oxygen concentration were measured. Additionally, condensate from fumarolic gas at Crater I was collected by inserting a tube into a fumarole to extract volcanic gas. Hydrogen and oxygen isotope ratios were measured using a cavity ring-down spectrometer (Picarro L2130-i). Major ion concentrations (Na+, K+, Mg2+, Ca2+, F-, Cl-, SO42-, etc.) were analyzed using an ion chromatograph (Shimadzu PROMINENCE).
3. Results and Discussion
The regression line of hydrogen and oxygen isotope ratios for creek water on a δ-diagram was determined as δD = 6.88δ18O + 4.54 (R2 = 0.976), which was regarded as the local meteoric water line. Meanwhile, the regression line obtained from data for the hot spring waters at the Kamuiwakka Hot Springs were δD = 2.85δ18O - 46.7 (R2 = 0.966), suggesting that these hot springs were formed by the mixing of meteoric water and andesitic water.
On the δ-diagram, the lake water of Shiretoko Five Lakes was plotted to the right of the local meteoric water line derived from creek water. When the regression line was extended downward, it intersected the region where the isotope ratios of hot spring water were plotted. This suggests that hot spring water upwelling from the lake bottom mixed with meteoric water, followed by evaporation. Additionally, the chloride concentration in the lake water of Shiretoko Five Lakes tended to be higher than that of creek water. The isotope ratios of Lake One and Lake Five were heavier than those of the other lakes due to higher evaporation rates.
The condensate obtained from fumarolic emissions at Crater I showed the lightest isotope ratios among the analyzed samples and was plotted near the local meteoric water line, indicating that it was also of meteoric origin. In several creeks, the isotope ratios were slightly heavier than the local meteoric water line. They exhibited low pH values and higher SO42- and Cl- concentrations compared to typical river water, suggesting the influence of volcanic fluids. The isotope ratios of Iwaobetsu and Akazawa Hot Spring were plotted on the regression line for Kamuiwakka hot spring water, indicating the presence of andesitic water. The pH values of these hot springs ranged from 5.74 to 6.83, showing weak acidity.
Previous studies have revealed that the hot spring water of Shiretokoiozan Volcano contains 11–12% andesitic water. This study confirmed that surrounding hot springs and lake waters also contain andesitic water. E.g. based on the intersection of the regression line for Shiretoko Five Lakes with that of Kamuiwakka hot spring water, the lake water is estimated to contain a similar proportion of andesitic water. Ion concentration analyses revealed that the concentrations of SO42- and Cl- were much lower in surrounding waters compared to the hot spring water of the volcano. The SO42-/Cl- ratio in the hot spring water of the volcano was higher than other samples, and the concentrations of SO2 and H2S were also higher. These findings confirm that a greater amount of sulfur is supplied as a volcanic fluid in Shiretokoiozan Volcano compared to its surrounding areas and volcanic fluids influence for the water quality in this area.
We have studied the mechanism of molten sulfur eruption at Shiretokoiozan Volcano at Hokkaido Japan. In this study, to clarify the supply and circulation state of water and substances in the aquifer where sulfur is considered to be generated and its surrounding area, samples of hot springs, creeks, lake water and condensate from a fumarole were collected from the vicinity of the volcano. The hydrogen and oxygen isotope ratios and the concentrations of major ions were analyzed. Based on the results, the origins and circulation states of these waters and the substances contained within them were examined, with a particular focus on the influence of volcanic fluids on water quality formation.
2. Methods
Water samples were collected in 100 ml bottles. Prior to collection, water temperature, pH, electrical conductivity, oxidation-reduction potential, and dissolved oxygen concentration were measured. Additionally, condensate from fumarolic gas at Crater I was collected by inserting a tube into a fumarole to extract volcanic gas. Hydrogen and oxygen isotope ratios were measured using a cavity ring-down spectrometer (Picarro L2130-i). Major ion concentrations (Na+, K+, Mg2+, Ca2+, F-, Cl-, SO42-, etc.) were analyzed using an ion chromatograph (Shimadzu PROMINENCE).
3. Results and Discussion
The regression line of hydrogen and oxygen isotope ratios for creek water on a δ-diagram was determined as δD = 6.88δ18O + 4.54 (R2 = 0.976), which was regarded as the local meteoric water line. Meanwhile, the regression line obtained from data for the hot spring waters at the Kamuiwakka Hot Springs were δD = 2.85δ18O - 46.7 (R2 = 0.966), suggesting that these hot springs were formed by the mixing of meteoric water and andesitic water.
On the δ-diagram, the lake water of Shiretoko Five Lakes was plotted to the right of the local meteoric water line derived from creek water. When the regression line was extended downward, it intersected the region where the isotope ratios of hot spring water were plotted. This suggests that hot spring water upwelling from the lake bottom mixed with meteoric water, followed by evaporation. Additionally, the chloride concentration in the lake water of Shiretoko Five Lakes tended to be higher than that of creek water. The isotope ratios of Lake One and Lake Five were heavier than those of the other lakes due to higher evaporation rates.
The condensate obtained from fumarolic emissions at Crater I showed the lightest isotope ratios among the analyzed samples and was plotted near the local meteoric water line, indicating that it was also of meteoric origin. In several creeks, the isotope ratios were slightly heavier than the local meteoric water line. They exhibited low pH values and higher SO42- and Cl- concentrations compared to typical river water, suggesting the influence of volcanic fluids. The isotope ratios of Iwaobetsu and Akazawa Hot Spring were plotted on the regression line for Kamuiwakka hot spring water, indicating the presence of andesitic water. The pH values of these hot springs ranged from 5.74 to 6.83, showing weak acidity.
Previous studies have revealed that the hot spring water of Shiretokoiozan Volcano contains 11–12% andesitic water. This study confirmed that surrounding hot springs and lake waters also contain andesitic water. E.g. based on the intersection of the regression line for Shiretoko Five Lakes with that of Kamuiwakka hot spring water, the lake water is estimated to contain a similar proportion of andesitic water. Ion concentration analyses revealed that the concentrations of SO42- and Cl- were much lower in surrounding waters compared to the hot spring water of the volcano. The SO42-/Cl- ratio in the hot spring water of the volcano was higher than other samples, and the concentrations of SO2 and H2S were also higher. These findings confirm that a greater amount of sulfur is supplied as a volcanic fluid in Shiretokoiozan Volcano compared to its surrounding areas and volcanic fluids influence for the water quality in this area.