Fixation of tritium gas by a pine tree and its surroundings

The fixation (oxidation) of atmospheric tritium gas (HT) in vegetation in in vitro experiments was determined for pine needles, pine bark, lichen attached to pine trees, taken from a coastal pine forest, and compared with that in soil. HT oxidation in pine needles was extremely low and about 1/40000 that in the surface soil, whereas its oxidation in pine bark with a lichen was almost 1000-7000 times that in pine needles. In vivo laboratory experiments on HT fixation in pine trees were conducted using one-way circuit inhalation apparatus and potted dwarf pine trees. After 2 hours of exposure to HT, tritium distribution and its specific activity in pine needles, branches, trunk, roots and soil were measured. Tritium distribution in the pine needles was 0.30% that in the soil. However, HT oxidation in the pine needles was only about 0.003% that in the soil. (author)