Measurement of tritium in tree rings

All of the combustion water samples extracted from cellulose in pine tree rings corresponding to the 1983-1987 period showed elevated tritium concentrations of approximately 65 pCi/dm3, which were 30 to 35 pCi/dm3 higher than those for precipitation and atmospheric vapor in recent years. In addition, other environmental samples, viz. the tissue-free water in tree rings, and of combustion and tissue-free water in pine needles and spring water near the pine tree site also showed concentrations similar to the combustion water of cellulose. These findings suggest that most of the tritium in tree rings was supplied from underground water containing a high tritium concentration in the root zone of the pine tree. (author) 14 refs.; 2 figs