日本質量分析学会 第67回質量分析総合討論会

Abstract

Poster Presentations

Day 3, May 17(Fri.)  Room P (Multi-purpose Hall)

Development of 3H-3He Groundwater Dating Method

(Univ. Tokyo)
oNaoki Nomata, Hirochika Sumino

Residence time of groundwater is an important parameter to elucidate groundwater flow system. We are developing a 3H-3He dating method, which is one of the methods to estimate groundwater residence time. An advantage of this method is that it is applicable to accurately determine an age of young water compared to other methods, because initial 3H concentration is directly determined as the sum of 3He and 3H in the water at present, if the groundwater flow system has been a closed system for 3He and 3H until its discharge. In this method, 3He concentration in a sample is measured first, and after a few months' storage, 3He produced from decay of 3H in the sample is measured to determine 3H concentration. Thus how the water sample is well degassed during the first analysis and how leaking of ambient helium into the degassed water is suppressed are crucial to determine small amount of 3H. We analyzed standard water samples provided by IAEA with known 3H concentrations to evaluate accuracy and precision of our method. But we failed to measure 3H concentrations correctly in some samples. This presentation will discuss the reason of failure and future plans for developing this method.