[M-ZZ48] Renewable energy and earth science

[MZZ48-P04] Cold surface water chemistry in the western area of Iwodake, North Hakkoda volcanoes

*Seiichiro Ioka¹, Yui Inaba², Sachi Wakasa¹ (1.Institute of Regional Innovation, Hirosaki University, 2.Hirosaki University)

Keywords:surface water, geothermal area, North Hakkoda volcanoes

Understanding the chemical evolution of thermal surface water (25 °C or higher) during passage from the geothermal reservoir to the surface in a geothermal area is important for assessing subsurface conditions from surface water composition and for evaluating the potential for geothermal utilization. Many studies have assessed the chemistry of thermal surface water in geothermal areas. However, little research has been done on the chemical properties of cold surface water (less than 25 °C) in geothermal areas, even when the cold surface water has a hydrogen sulfide odor. Thus, the importance of understanding the chemical evolution of cold surface water in geothermal areas for assessing subsurface conditions from surface water composition and evaluating the potential for geothermal utilization remains unclear. Therefore, we aimed to understand the chemical evolution of cold surface water with a hydrogen sulfide odor in a geothermal area, the western area of Iwodake, North Hakkoda volcanoes.
We performed on-site measurements of pH, electrical conductivity, oxidation–reduction potential, temperature, dissolved oxygen, and Fe²⁺ and S^2– concentrations of the cold surface water with a hydrogen sulfide odor. Sampled water was analyzed in a laboratory for Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, CH₃COO^–, HCOO^–, F^–, Cl^–, Br^–, NO₃^–, SO₄^2–, Fe, Mn, B, Si, dissolved organic carbon (DOC), δ¹⁸O, and δ²H. The results suggested that the cold surface water may be affected by HCl volcanic gas as it has high Cl^– and SO₄^2– concentrations. Ongoing work is focused on analysis using PHREEQC and calculation of the effective energy of microorganisms.