Variation of tritium concentration in the course of the degradation of fresh pine needles on a forest floor

Variation of tritium concentration was examined for 100 days in the course of degradation of fresh pine needles, which were left on a pine forest floo r. No difference was observed on free water tritium (FWT) and organically b ound tritium (OBT) concentrations of sterilized samples by gamma-ray irradi ation or fumigation and control samples, attributable to incomplete sterili zation. The OBT concentrations did not increase within the experimental per iod as the level of humus collected from the forest floor. The results sugg est that a longer degradation time, more than 100 days, is necessary to ele vate OBT up to the level, which is observed in the general environment.