A simple weak-radon spring rising in a residential pocket of Morioka. Strongly alkaline at pH 9.9, it has the slippery feel of the Japanese beauty-water family. Light overall mineralization (234 mg/kg dissolved solids) is offset by a notable radon load — 121 Bq/kg, well into the hormesis-tradition range. The wellhead runs at 31 C, so the bath is reheated for soaking.
Good for
Aches & joints
Warmth eases stiffness and raises the pain threshold. Radon and sulfate springs show the strongest evidence for joint and muscle pain.
stiff shoulders
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺78.6mgP24 national96%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺1.8mgP7 national3%
- FeTotalFe0.70mgP67 national0.8%
- PotassiumK⁺0.60mgP7 national0.6%
- Aluminumshows up in acidic volcanic waterAl³⁺0.0000mg
- Hydrogenmakes the water acidic — sharp and bactericidalH⁺0.0000mg
- Magnesiummild; a laxative if you drink itMg²⁺0.0000mg
- Manganesetrace; companion to iron springsMn²⁺0.0000mg
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻56.8mgP29 national45%
- Carbonatestrongly alkaline; slippery feelCO₃²⁻38.2mgP87 national35%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻15.2mgP27 national9%
- HydroxideOH⁻5.5mgP99 national9%
- ThiosulfateS₂O₃²⁻1.6mgP79 national0.8%
- Fluoridetrace; drinking limits applyF⁻0.0000mg
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻0.0000mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻0.0000mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃27.6mgP10 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂7.5mgP48 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs< —mg
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
- Radonfaint radon — studied for joint pain (hormesis)Rn—mg
Measured at the source
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Donaubauer AJ et al. Serial radon spa therapy on pain in musculoskeletal disorders. Frontiers in Immunology, 2024.
- Verhagen AP et al. Balneotherapy for rheumatoid arthritis. Cochrane Database of Systematic Reviews CD000518, 2015.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.