[A-HW26] Isotope Hydrology 2022

[AHW26-P07] Temporal change of Excess air component in groundwater

*Kazuyoshi Asai¹, Kazumi Asai¹ (1.Geo Science Laboratory)

Keywords:Excess air, SF6, Groundwater age, Dissolved nitrogen and argon, Ogaki artesian zone

In groundwater dating using sulfur hexafluoride, the evaluation of Excess air is the main factor controlling the reliability of groundwater age. Excess air is a phenomenon in which a gas that exceeds the dissolution equilibrium dissolves in the groundwater during groundwater recharge. Previous studies suggest that most of the groundwater in Japan contains Excess air. However, little is known about the temporal variation and formation process of Excess air. In this study, in order to understand the characteristics of temporal variation in Excess air, the concentrations of dissolved nitrogen and argon in river water, spring water, and groundwater were measured regularly around the Ogaki artesian zone.