Variations in <sup>14</sup>C concentrations of tree rings (1945-1983)

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  • 樹木年輪(1945-1983)の<sup>14</sup>C濃度変動
  • 樹木年輪(1945-1983)の14C濃度変動
  • ジュモク ネンリン 1945-1983 ノ 14C ノウド ヘンドウ

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Abstract

A Japanese cypress (Kiso hinoki) grown in Gifu prefecture, Central Japan and a Shorea spruce in Sabah, Malaysia were analyzed for the 14C concentrations of annual tree rings (1945-1983). Each of annual rings (1958-1966) for the hinoki was divided radially into 3 or 4 consecutive sections. The 14C concentrations, Δ14C, of the sections were measured with a Tandetron accelerator mass spectrometer and compared with those of atmospheric CO2. The good agreement was found between them; this suggested evidently that the Δ14C values of tree rings could be used to estimate the Δ14C values of atmospheric CO2 in the past. Variations in Δ14C of annual tree rings (1945-1983 ) for the hinoki were found to be closely related with the history of executing the nuclear weapon tests in the atmosphere, by considering that the residence time was about 2 years for transferr-ing CO2 from stratosphere to troposphere. By using the variation pattern of Δ14C common to most of trees, the average growth rate of the Shorea spruce (ca. 90cm in trunk diameter), having no growth ring, was estimated to be 5.5mm/yr. A latitude dependence of the Δ14C variations was found for annual rings (1963-1970) of trees grown in the northern troposphere (6°N-42°N). This phenomenon seemed to be closely related with the mechanism of global mixing for bomb-produced 14CO2 in the atmosphere.

Journal

  • Chikyukagaku

    Chikyukagaku 21 (1), 7-12, 1987

    The Geochemical Society of Japan

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