Accelerator-measured ¹⁴C activity in tree rings from the vicinity of the first atomic bomb test

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. The authors sampled a 115-year-old pinyon Pinus edulis 10km E 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 δ¹³C values of -19.9 and -19.5‰, respectively, and ¹⁴C activity (fraction of modern uncorrected for δ¹³C) 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. -Authors