11:25 〜 11:50
[AHW30-07] Dissolved (Noble) Gas Analyses as a Complement to Stable Water Isotopes for Snow and Ice Melt Identification in Groundwater
★Invited Papers
キーワード：dissolved noble gases, snowmelt, nitrogen fixation, greenhouse gases, cryosphere, groundwater
Stable water isotopes are currently considered the principal tracer method to quantify the contributions of snowmelt and ice melt to groundwater recharge. However, while stable water isotopes can be measured at a very high precision, due to a very large variation and significant overlap of the stable water isotopic compositions of snowfall, ice and rain, and the difficulty to identify a sufficiently distinct and representative stable water isotope signal for snow or ice melt, the method bears a lot of risk for bias. Due to this representation error, scientists have long tried to identify a complementary method for snowmelt recharge quantification (e.g., Beria et al., 2018, doi: 10.1002/wat2.1311; Kendall & McDonnell, 1998, doi: 10.1016/C2009-0-10239-8).
Here, we present a new method that employs continuous measurement of dissolved noble gases in the field as tracer for the quantification of snowmelt recharge. Based on dissolved gas concentrations and noble gas thermometry, (i) snowmelt recharge, (ii) temporal recharge dynamics, and (iii) primary recharge pathways can be identified (Schilling et al., 2021, doi: 10.1029/2020WR028479). In contrast to the stable water isotope method, which was employed alongside the new approach, dissolved noble gases produced more consistent estimates of snowmelt recharge, even though the exact temperature of snowmelt during recharge was not precisely known. As the concentrations of dissolved noble gases are not controlled by the same processes as stable water isotopes, dissolved noble gases represent an ideal complement to stable water isotopes for the quantification of snowmelt recharge dynamics in snow-dominated regions.
Moreover, the new method, which uses a portable gas equilibrium-membrane inlet mass spectrometer, also allows detecting and quantifying other critical biogeochemical processes, such as the build up and release of greenhouse gases in peatlands during the winter and after snowmelt, or the assimilation of atmospheric nitrogen in boreal systems.
In this talk, we present the methods as well as exciting new data from two long-term field experiments.
Here, we present a new method that employs continuous measurement of dissolved noble gases in the field as tracer for the quantification of snowmelt recharge. Based on dissolved gas concentrations and noble gas thermometry, (i) snowmelt recharge, (ii) temporal recharge dynamics, and (iii) primary recharge pathways can be identified (Schilling et al., 2021, doi: 10.1029/2020WR028479). In contrast to the stable water isotope method, which was employed alongside the new approach, dissolved noble gases produced more consistent estimates of snowmelt recharge, even though the exact temperature of snowmelt during recharge was not precisely known. As the concentrations of dissolved noble gases are not controlled by the same processes as stable water isotopes, dissolved noble gases represent an ideal complement to stable water isotopes for the quantification of snowmelt recharge dynamics in snow-dominated regions.
Moreover, the new method, which uses a portable gas equilibrium-membrane inlet mass spectrometer, also allows detecting and quantifying other critical biogeochemical processes, such as the build up and release of greenhouse gases in peatlands during the winter and after snowmelt, or the assimilation of atmospheric nitrogen in boreal systems.
In this talk, we present the methods as well as exciting new data from two long-term field experiments.