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

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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.