Temporal Variation of Carbon-14 Concentration in Tree-ring Cellulose for the Recent 50 Years

Abstract

Concentration of organically-bound 14C in the tree-ring cellulose of a pine tree grown in Shika-machi, Ishikawa prefecture, Japan (37.1°N, 136.5°E), was measured for the ring-years from 1949 to 1999 and compared with those in several trees from East Asia region reported by other researchers. The difference of . Δ14C values was found during the period of 1970-1981 between our data and those of other reports, in addition to the difference during the period of 1963-1967 caused by the so-called latitude dependence of the 14C variations in the northern troposphere. These results suggest that the 14C concentration in atmospheric CO2 was considerably disturbed during the period of 1970-1981, especially in 1970, 1976, and 1978-1981, in the East Asia region. This phenomenon may be interpreted by the possibility of the several times of injections of 14C originated from a series of Chinese thermonuclear bomb tests.