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Radioisotopes P 32 , Be 7 , and S 35 in the atmosphere

1960; American Geophysical Union; Volume: 65; Issue: 2 Linguagem: Inglês

10.1029/jz065i002p00669

2156-2202

D. Lal, Rama, P. K. Zutshi,

Astro and Planetary Science

We have made simultaneous determinations of the concentrations of the radioisotopes P32, Be7, and S35 in several rains collected at Bombay during the monsoon period of 1958. The observed annual deposition rates of P32 and Be7 are found to agree within the expected meteorological fluctuations with those measured in the preceding two years at Bombay and other stations in India. S35 deposition, however, has varied significantly outside normal fluctuations. From the observed variations in the annual fallout of these isotopes during 1956–1958 and relative isotope concentrations in individual rains, it has been concluded that nuclear weapons have not resulted in any appreciable contributions to the observed Be7 and P32 activities. However, S35 was contributed in appreciable quantities. During 1958, S35 concentrations were very large, amounting to as much as 35 per cent of the observed Sr89 concentrations in some rains. The relative concentrations of the isotopes Be7 and P32 in rains vary in a manner that would be expected for their production in the troposphere by cosmic rays, and their removal by wet precipitation with an average removal period of about 40 days. None of the rain samples analyzed so far could have resulted in precipitation occurring from an air mass which descended in the troposphere after an irradiation in the stratosphere for time periods that are long compared with the half-lives of the isotopes.