FWT and OBT concentrations in pine needle samples collected at Toki, Japan (1998-2012)

Area of Science:

• Environmental Science
• Radiochemistry
• Isotope Hydrology

Background:

• Tritium (hydrogen-3) is a radioactive isotope of hydrogen.
• Understanding regional tritium distribution is crucial for environmental monitoring.
• Pine needles serve as effective bioindicators for atmospheric tritium levels.

Purpose of the Study:

• To determine regional background tritium concentrations in Toki City.
• To investigate Free Water Tritium (FWT) and Organically Bound Tritium (OBT) levels.
• To assess temporal trends and half-lives of tritium in pine needles.

Main Methods:

• Regular collection of pine needle samples from two distinct sites in Toki City (1998-2012).
• Measurement of Free Water Tritium (FWT) and Organically Bound Tritium (OBT) concentrations.
• Analysis of concentration data to determine trends, ratios, and apparent half-lives.

Main Results:

• FWT concentrations ranged from 0.32 to 0.92 Bq l(-1) and OBT from 0.33 to 1.10 Bq l(-1).
• Tritium levels in Toki City were comparable to Japan's average background concentration.
• Apparent half-lives for FWT (approx. 10 years) and OBT (approx. 12 years) closely matched physical half-lives.

Conclusions:

• Pine needles effectively reflect regional background tritium levels in Toki City.
• Observed tritium concentrations are consistent with natural background levels.
• The gradual decrease and estimated half-lives suggest minimal anthropogenic tritium input during the study period.