Study of radial distribution of fallout nuclides and trace elements in tree rings as a method of determining environmental contamination over time.

测定<90><137>了长崎和和歌山的柳杉（Cryptomeria japonica D.Don）年轮中~（13）Sr与稳定态Sr的比值和~（13）Cs与K的比值。长崎市西山区遭受了1945年原子弹轰炸造成的“黑雨”。和歌山没有受到原子弹的影响。每<90>棵雪松的Sr/Sr比值沿径向沿着由形成层向内侧逐渐减小。在1924-1925年的长崎雪松年轮中观察到一个明显的峰值，推测这是由于长崎原子弹爆炸产生的黑雨造成的<137>。没有发现长崎原子弹的影响。在日本和歌山的雪松中，Sr/Sr的比值与此相似，但变化范围较大。<90>来自广岛的辐射。从形成层到髓心，这一比例逐渐增大。用中子活化分析和PIXE方法测定了未受原子弹辐射影响的京都柿茎中19种微量元素沿着径向的浓度分布。

The ratios of ^<90>Sr to stable strontium and ^<137>Cs to potassium in the tree rings of two Japanese cedars (Cryptomeria japonica D.Don), one from Nagasaki and the other from Wakayama, were determined. The Nishiyama district of Nagasaki city was exposed to heavy "black rain" caused by the atomic bomb which was dropped there in 1945. Wakayama was not affected by the fallout from atomic bombs. The ratio of ^<90>Sr/Sr along a radial direction in each cedar decreased from the cambium to the inside. A clear peak in the ratio presumed due to the black rain from the Nagasaki atomic bomb was observed in the 1924-1925 rings of the cedar from Nagasaki.The ^<137>Cs/K ratios in the cedar from Nagasaki have almost the same value in every ring. No effect from the Nagasaki atomic bomb could be detected. The ratios in the cedar from Wakayama are similar but with a rather wider variation.The ratios of ^<90>Sr/Sr along a radial direction in the tree rings of a kaki (Diospros kaki Thunb.) from Hiroshima were determined. The ratios gradually increased from the cambium to the pith. No effect from the fallout from atomic bomb could be detected.The concentration profiles of 19 trace elements along radial direction in the stem of a kaki from Kyoto (which was not affected by the fallout from atomic bombs) were also determined by neutron activation analysis and/or the PIXE method.