An examination of possible sources of radioiodine found in samples of milk in the midwestern states during May and early June 1962 shows that atmospheric testing at Christmas Island was the principal contributor to incidents of significant concentrations of iodine-131 in milk (exceeding 300 picocuries per liter). Underground testing at Nevada played at most only a minor role during this period. There is a cause-and-effect relationship between the penetration of thunderstorms into high concentrations of nuclear debris in the lower stratosphere and the subsequent amount of iodine-131 in milk. Analyses of samples of rainwater confirm the importance of this "scavenging" mechanism. The relative contributions of atmospheric and underground testing to the iodine-131 found in milk samples from September 1961 to December 1963 has been reviewed and only one incident in which the amount of iodine-131 exceeded 300 picocuries per liter could be attributed to an underground test.
Two meteorologically interesting radioactive tracers, Cd-109 injected in 1962 at 400 km by a rocket-borne nuclear device and Pu-238 resulting from the reentry burnup in 1964 of a nuclear powered satellite in the 40-60 km altitude range, are examined and compared with the results of the Rh-102 experiment conducted in 1958. Although detonated at 17" N, the maximum concentration of Cd-109 was detected by the highaltitude balloon samples collected at 34" s. It first appeared at the highest altitude sampled, 32 km, and subsequently seemed to propagate downward at about 1.5 k m per month. A second similar surge of Cd-109 was observed at 34" S about a year later. Maximum concentration of Pu-238 also occurred at 32 km at 34" S. Slightly lower concentrations were observed at this altitude in northern temperate and polar regions while concentrations near the equator were an order of magnitude lower. Although the Pu-238 distribution could result from either diffusive mixing along sloping surfaces or from meridional transport, the two surges of Cd-109 suggest poleward transport and subsequent reinforcement from a polar reservoir.
The depletion of the stratospheric burdens of particulate "'Zr for times up to around 1 year, and gaseous HTO for times up to 3 years, attributed to the November 17, 1976 Chinese high-yield test indicates that both have about the same residence half-time (10 months). The indications are that gravitational settling of particles in the lower stratosphere can be considered to be negligible in studying transport processes. The rate of depletion of the stratospheric burden of HTO from the high-yield Chinese test of June 27, 1973 is not as well-defined in part due to greater uncertainties in calculating the stratospheric burdens.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.