炭酸泉源Tansan Springhead
A carbonated, iron-bearing simple cold-mineral spring. With 1,010 mg/kg of free CO2 it counts as a rare carbonated source, and fine bubbles cling to the skin on entry. Iron runs high at about 40 mg/kg, so the water oxidizes reddish-brown on contact with air. It is weakly acidic, faintly tangy on the skin, and as a cold-mineral source below 25 °C it is heated before bathing.
Good for
Circulation
Skin-absorbed CO₂ and hydrogen sulfide relax the vessel walls; carbon-dioxide springs can raise peripheral blood flow several-fold.
tired legs
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.
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺31.0mgP46 national35%
- Iron (II)rusts brown in air; iron for anemia when drinkableFe²⁺40.6mgP97 national32%
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺17.0mgP4 national17%
- Aluminumshows up in acidic volcanic waterAl³⁺3.5mgP82 national9%
- Magnesiummild; a laxative if you drink itMg²⁺1.5mgP29 national3%
- ZincZn²⁺3.4mgP99 national2%
- Potassiumminor; matters for drinking limitsK⁺3.6mgP30 national2%
- ManganeseMn²⁺0.70mgP72 national0.7%
- AmmoniumNH₄⁺0.40mgP43 national0.2%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻182mgP63 national88%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻8.2mgP11 national5%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻12.6mgP8 national5%
- Fluoridetrace; drinking limits applyF⁻2.1mgP59 national3%
- Bromidetrace, sea-originBr⁻< —mg
- Hydrogen sulfidesulfur character — antibacterialHS⁻< —mg
- Iodideyellows in air; helps blood lipidsI⁻< —mg
- Thiosulfateoxidized sulfurS₂O₃²⁻< —mg
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃81.2mgP48 national
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂1.6mgP16 national
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂1,010mgP99 national
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S< —mg
- LeadPb0.09mgP95 national
- ArsenicAs0.04mgP45 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —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.
- Tei C, Kihara T. Waon Therapy for Chronic Heart Failure. J. Cardiology 53(2):214–218, 2009.
- Coavoy-Sánchez SA et al. Hydrogen sulfide and dermatological diseases. Int. J. Dermatology, 2019.
- Toriyama T et al. Carbon dioxide foot bathing on critical limb ischemia. International Angiology 21(4):367–373, 2002.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.