Evaluation of environmental pollution with measurement of radioactivity and heavy metals in tree rings

为了弄清过去放射性物质对环境的污染，对树木年轮进行了放射性测量。测定了长崎和广岛两种生长在原子弹黑雨区的杉树茎中^<90>Sr和^<137>Cs的浓度分布。通过分析从长崎sugi获得的^<90>Sr/Sr比率剖面，并经过适当修正，长崎原子弹对当地土壤环境的沉降物可以与广泛的核武器试验区分开来。采用中子活化分析和ICP-MS法测定了樱花和梅花健康树和生长缺陷树茎中22种元素沿径向的浓度分布。由于元素浓度不高，抑制了树木的生长。在1987年左右形成的年轮中，在一些树木中发现了锰、镍和锌等元素分布谱中的小峰。这为在年轮中记录重金属对环境污染的转变提供了可能。

In order to clarify environmental pollution by the radioactive substance which had been caused in the past, the radioactivity in the tree annual rings were measured. The concentration profiles of ^<90>Sr and ^<137>Cs in the stems of sugi from Nagasaki and Hiroshima, which grew in the black rain fall area caused by atomic bomb were determined. By analyzing the ^<90>Sr/Sr ratio profile obtained from the sugi from Nagasaki and with appropriate corrections, the fallout of the Nagasaki atomic bomb on the local soil environment could be distinguished from a broad spectrum of the atomic nuclear weapons tests.The concentration profiles of 22 elements along radial direction in the stem of healthy trees and growth defect trees for sakura and ume were also determined by neutron activation analysis and/or the ICP-MS method. The concentration of elements was not so high as the growth of the tree was inhibited. The small peaks in distribution profiles of elements such as manganese, nickel, and zinc in several trees, were detected at the rings formed around 1987.This suggests the possibility to record the transition of environmental pollution with heavy metals in the annual ring.