More than 70 years observation of the SO₄²⁻/Cl⁻ molar ratios of water from the Obuki hot spring in the vicinity of Mt. Akita-Yakeyama volcano indicated that the ratio started increasing rapidly from 1973, peaked in 1980 (SO₄²⁻/Cl⁻ = 0.34), remained at high values for about 18 years, then gradually decreased and returned to a normal baseline value (0.14) in 1991. The volcano erupted near the summit in 1948–1957 and again in 1997. The 1980 peak of SO₄²⁻/Cl⁻ ratios may reflect the 1948 phreatic eruption of the volcano. Similarly, high SO₄²⁻/Cl⁻ ratios were also observed in 2013 lasting for two years. The SO₄²⁻/Cl⁻ peak in 2013 appeared 16 years after the 1997 phreatic explosion. The delayed appearance of the SO₄²⁻/Cl⁻ peaks may represent slow upward movement of reservoir water to the surface after input of magmatic SO₂ into the fluid reservoir which produced HSO₄⁻ through disproportionation reaction. The slow movement of water is supported by a long subsurface residence time (13–25 years) of reservoir fluid estimated from tritium measurement of the Obuki hot spring water. One-dimensional channel model was applied to analyze the effect of volcanic activity on SO₄²⁻/Cl⁻ ratios of the Obuki hot spring water. The model supported the long travel time of the fluid implying that the effects of the 1997 eruption may appear in the spring water chemistry after about 29 years later, i.e., around 2026.

所述SO的超过70年的观察₄ ^2- /氯^-从在山的周围的Obuki温泉水的摩尔比 秋田Yakeyama火山表明比开始从1973迅速增加，在1980年达到高峰（SO ₄ ^{2- /}氯^- = 0.34），仍保持在高的值约18年，然后逐渐下降，并返回到正常基线值（0.14 ）于1991年在火山爆发1948-1957山顶附近，并再次在1997年SO的1980峰₄ ^2- /氯^-比率可能反映了火山1948潜水喷发。类似地，高的SO ₄ ^2- /氯^-2013年的比率也持续了两年。该SO ₄ ^2- /氯^-在2013年的峰值1997年的蒸汽爆炸后出现的16年。所述SO的延迟外观₄ ^2- /氯^-峰可岩浆SO的输入后表示于表面水库水的缓慢向上移动₂到其中产生HSO流体贮存器₄ ^-通过歧化反应。根据Obuki温泉水的tri测量估计，储层流体的地下停留时间长（13–25年），从而支持水的缓慢运动。应用一维通道模型分析火山活动对SO _4的影响^2- /氯^-所述Obuki温泉水的比率。该模型支持流体的长途传播时间，这意味着在大约29年后（即2026年左右），泉水化学中可能会出现1997年喷发的影响。