幕岩源泉
Makuiwa Spring黄
Sulfur
A simple sulfur spring at Shiga Kogen's Makuiwa Onsen. The source emerges at 71 °C — among Japan's hottest natural sources — with near-neutral pH 6.47 and hypotonic mineralization. Free H₂S of 8.3 mg/kg classifies it as a sulfur spring and carries the characteristic rotten-egg note. Mineralization is light overall, but the sulfur signature and the heat give the water real presence.
Source temperature
71.2°C
Hot
Tonicity
Hypotonic
Free CO₂
53mg/kg
Low
Free H₂S
8.30mg/kg
Very high
Highlights
- Sulfur-rich
- Top-decile hot
Analyzed Dec 22, 1994·長野県衛生公害研究所