Isotopic Composition of Atmospheric Hydrogen and Methane

Abstract

OUR communication on the growth of the tritium content of free hydrogen in the atmosphere was written before the publication by Begemann and Friedman¹ of detailed measurements for the period 1954–56. These showed considerable seasonal variation, but no pronounced increase during the two years following the Castle test series. Their earliest determination in January 1954 before the Castle test series was 9.18 × 10⁴ tritium units compared with 1.66 ± 0.097 × 10⁴ tritium units found by Grosse et al.² in the spring of 1952. This obvious increase was concluded by Begemann and Friedman to be due to the Ivy test series of November 1952. Evidence for an earlier increase based on the value 0.38 ± 0.125 × 10⁴ tritium units obtained by Faltings and Harteck³ in 1948–49 now appears to be refuted by the value of 3.5 × 10⁴ tritium units reported by Bainbridge, Suess and Friedman. It may be noted, however, that this value is more than twice that observed by Grosse in 1952. With three sets of observations indicating a substantial increase prior to the Castle tests, it is difficult to support the conclusion of Bainbridge et al. that such an increase is “unlikely”.