• V N Nijampurkar

      Articles written in Journal of Earth System Science

    • Annual fallout of32Si,210Pb,22Na,35S and7Be in rains in India

      D Lal V N Nijampurkar G Rajagopalan B L K Somayajulu

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      The concentration of radioisotopes7Be,35S were measured in Bombay since 1956 and22Na,210Pb,32Si since 1963. In Khandala and other stations such measurements have been made at irregular periods since 1961. In addition several measurements especially that of32Si were made in 1970. Data available todate from Indian stations is summarised and critically analysed.

      We conclude that appreciable amounts of35S,22Na and32Si, 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 of32Si 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.

    • Radiometric age of the snout ice of Nehnar glacier

      N Bhandari D I Bhatt V N Nijampurkar R K Singh D Srivatsava C P Vohra

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      The surface ice taken from the snout of the Nehnar glacier (Kashmir) in western Himalaya has been dated using radioisotopes32Si and210Pb to be 500 years. Based on the age distribution of ice and the expected activity of32Si in the fallout, the average rate of glacier movement over a period of the last few centuries is estimated to be about 6 m/yr.

      The data obtained on32Si and210Pb activities in the surface ice samples in the ablation zone support our previous observation about the existence of five zones of alternately high and low activity of210Pb, which probably is a consequence of complex dynamics of Nehnar glacier.

      The vertical profile of210Pb activity in an ice core correlates directly with the total beta activity. This radioactive horizon at an altitude of 4140 m appears to be located at a depth of 10–12m, which is lower compared to the 2–3 m observed earlier at an altitude of 4150 m.

    • Isotopic and related studies of Antarctic ice samples

      N Bhandari S K Bhattacharya V N Nijampurkar D Sengupta V G Shah A K Singhvi P N Shukla K M Suthar C P Vohra

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      The ice samples obtained from Dakshin Gangotri, Antarctica show the presence of nuclear debris, attributed mainly to French nuclear explosions. Cosmogenic7Be occurs at levels of 30 dpm/L. The vertical profile ofδD in 6 m long drill core ranges between −130 and −180‰ compared to Standard Mean Ocean Water (SMOW). No systematic change with depth is seen. Small amounts of dust obtained by filtering melt water show presence of metallic spherules. Absence of elements characteristic of meteoritic or cometary debris suggests that most of them are of volcanic or industrial origin.

    • Basal flow rate of Changme-Khangpu glacier, Sikkim Himalaya based on32Si and210Pb chronology

      V N Nijampurkar

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      Using environmental radioisotopes silicon-32 and lead-210, the radiometric ages of ice at the surface and at 5 m depth at the snout of the Changme-Khangpu (ck) glacier have been calculated to be 100 and >650 years respectively. Based on i) these age estimates, ii) a net uniform accumulation rate of 0·7 m/yr of ice in the accumulation zone; and iii) applying a simple ice flow model assuming melting of ice of 1 cm/yr at the base of the glacier, it is demonstrated that the average basal flow rate of theck glacier is much smaller (at least by a factor of three) than that of 40 m/yr estimated for the surface ice. This observation is in good agreement with the earlier work on basal flow rates and indicates that the deeper ice near the bed rock travels much slower than the surface ice.

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