Accelerator-Measured 14C Activity in Tree Rings from the Vicinity of the First Atomic Bomb Test

Abstract

Detonation of the first fission bomb at White Sands, New Mexico, on July 16, 1945, produced a tremendous neutron flux capable of creating tritium and radiocarbon byproducts. We sampled a 115-year-old pinyon (Pinus edulis) 10km east of the Trinity test site to determine 14C evidence of this event. The most likely mechanism for this enrichment in the 1945 tree ring would be fixation of 14CO2 produced at the blast site and carried with the fallout cloud over the pinyon site. Analysis of cellulose of the 1944 and 1945 rings shows delta-13C values of -19.9 and -19.5 per mil, respectively, and 14C activity (fraction of modern uncorrected for delta-13C) as 0.991 +/- .005 and 0.991 +/- .006, respectively. It is likely that the duration and/or concentration of the 14CO2 exposure was not sufficient to increase 14C activity expected for that year.