ISOTOPIC CHARACTERIZATION OF NATURAL WATERS AT MT. RAINIER
In the August 2017 campaign, both authors collected samples from a suite of thermal springs, talus springs, end-glacial streams, fumaroles, drip waters, and glacial ice for geochemical and isotopic analysis. From all sample sites, the isotopic ratios of δ2H and δ18O were analyzed and compared to data from earlier studies. The δ2H and δ18O values of talus springs largely align with recharge originating from localized flow systems. Thermal springs and end-glacial streams are more depleted than their elevation would predict; a portion of their recharge originates from higher elevations. In the crater, fumarole moisture and drip waters in the glacial caves overlap and are narrower in range than glacial ice; in other words, from locally recycled moisture.
Three thermal springs (Paradise 1 & 2, Longmire) and one end-glacial stream (Winthrop) were additionally analyzed for dissolved ions, δ34S, and 36Cl/Cl and 129I/I. The Paradise thermal springs (7-70 mg/L Cl; 18-200 mg/L SO4) and the end-glacial stream (3 mg/L Cl; 13 mg/L SO4) returned similar δ34S values of +4‰, compared to the ~0.5‰ in summit fumaroles and the +15‰ from Longmire hot spring (200 mg/L Cl; 18 mg/L SO4). Ratios of 129I/I follow the same trend as δ34S, suggesting older waters contribute more to the thermal springs at Paradise. The 36Cl/Cl data are the inverse of 129I/I. This may seem contradictory, but it is important to note that, unlike 129I/I, modern 36Cl/Cl is lower today than during peak nuclear testing.