2023 Volume 65 Issue 1 Pages 35-52
Temporal atmospheric concentration change (TAC) of sulfur hexafluoride (SF6 ) is essential to estimate groundwater residence time using SF6. This study examined a method to reconstruct a regional TAC of SF6. Groundwater samples were collected in the Kyoto Basin to measure concentrations of tritium and SF6. Groundwater flow and mass transport analyses were conducted using a calibrated hydrogeological model. In the mass transport analysis of SF6, three corrected TAC models were assumed, and the calculated SF6 concentrations in groundwater were compared with the measured SF6 concentrations. The error between the calculated and measured SF6 concentrations was the smallest when the TAC was corrected in accordance with the number of business establishments in Kyoto Prefecture. The difference in apparent residence time estimated from the uncorrected and corrected TAC models ranges from 7 to 10 years. This method contributes to increasing the accuracy of groundwater dating by SF6.
