DISTRIBUTION OF SR-90 AND CS-137 IN ANNUAL TREE RINGS OF JAPANESE CEDAR, CRYPTOMERIA-JAPONICA D DON

The contents of 90Sr and 137Cs in two samples of Japanese cedar from Takao and Tsukui districts were determined in tree rings cut into segments representing steps of 5 years of growth. 90Sr in both cedar samples and 137Cs in the Tsukui cedar sample were determined after ashing and chemical isolation, while 137Cs in the Takao sample was directly determined from the sample ash. The distribution of 90Sr fallout in tree rings suggests that 90Sr had given a rather direct effect and showed no significant translocation from sapwood to heartwood, whereas 137Cs tends to concentrate in heartwood irrespective of the effect of the fallout. Average contents of 90Sr and 137Cs were 22 and 9.4 pCi/kg in the Takao sample (9.61 kg air dried) and were 23 and 12 in the Tsukui (4.71 kg air dried) in 1982. Copyright © 1988 Japan Radiation Research Society.