Discovery of a tephra bed in the Quaternary alluvial sediments of Pune district (Maharashtra), Peninsular India

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Annual fallout of <SUP>32</SUP>Si,<SUP>210</SUP>Pb,<SUP>22</SUP>Na,<SUP>35</SUP>S and <SUP>7</SUP>Be in rains in India

The concentration of radioisotopes <SUP>7</SUP>Be, <SUP>35</SUP>S were measured in Bombay since 1956 and <SUP>22</SUP>Na, <SUP>210</SUP>Pb, <SUP>32</SUP>Si since 1963. In Khandala and other stations such measurements have been made at irregular periods since 1961. In addition several measurements especially that of <SUP>32</SUP>Si were made in 1970. Data available todate from Indian stations is summarised and critically analysed. We conclude that appreciable amounts of <SUP>35</SUP>S, <SUP>22</SUP>Na and <SUP>32</SUP>Si, over and above their production by cosmic rays, were produced during the high yield Russian tests as evidenced by their fallout between 1962-66. Based on the bomb produced excess the half period for their removal from the stratosphere is deduced to be less than 1 year. The 'excess' contribution of <SUP>32</SUP>Si due to bombs is, however, small; about 1% of its inventory in the oceans. The present study shows that for stations where orogeny is the principal mechanism of precipitation, the annual fallout is independent of the annual rainfall