"Atom Bomb Effect"—Recent Increase of Carbon-14 Content of the Atmosphere and Biosphere

Abstract

An indication of increasing /sup 14/C content of the atmosphere was found during a project of sampling atmospheric CO/sub 2/ in New Zealand in 1954. The collection of samples was continued in order to determine whether the enrichment was due to seasonal variation of C/sup 14/, or an enrichment of the atmosphere, caused by atomic explosions. The 9 samples, assayed since 1953, showed an enrichment of 7.8 percent with respect to the New Zealand wood standard of 1953. This value, correlated for industrial effect, (depletion of atmosphere C/sup 14/ due to combustion of fossil fuel), was found to be 4.8 +- 0.5 per cent of the atmosphere of the southern hemisphere. Other methods of sampling were used to verify this result. One was to expose a tray, filled with Ba(OH)/sub 2/ solution to the atmosphere; such samples showed an increase in C/sup 14/ specific activity of 4.8 +- 0.6 per cent between May 1955 and May 1957. This increase was detectable in leaves, trees, and grass from a location from which samples had been previously assayed. By using Libby's data (C.A. 50, 10522h) to estimate from the C/sup 14/ increase the total power of atomic weapons to date, the 4.8more » per cent increase for the atmosphere would account for 48 megaton of TNT equivalent of fission for the southern hemisphere and greater for the northern hemisphere, where all the atomic tests look place. From a comparison of the atmosphere C/sup 14/ specific activity with time in the 2 hemispheres, the possible rate and mechanism of mixing can be estimated.« less