10:45 AM - 11:00 AM
[MIS20-07] Age dating of groundwater using tritium and CFCs in headwater catchments, Fukushima after the Fukushima Dai-ichi Nuclear Power Plant accident
Keywords:tritium, CFCs, groundwater age, headwater catchment
Mean groundwater age in the study areas was estimated to be ranging from 10 to 26 years by combined use of multiple CFCs concentrations. The tritium concentration in groundwater was between 1.3 TU and 6.0 TU, which supported the estimated CFCs-based groundwater age. In addition, the governing groundwater flow system was approximated by a piston flow model; however, a modern water fraction was also suggested based on the relationship between CFC-11 and CFC-12. The estimated water age and isotopic signals among the stream water, spring water, and groundwater suggested an indication of the radionuclide intrusion into the groundwater. This is consistent with the monitored 137Cs concentration in the groundwater (Iwagami et al., 2017). Modern water fractions with relatively high radionuclide concentrations into groundwater possibly cause the prolonged contamination of water resources.