• S Krishnaswami

      Articles written in Proceedings – Section A

    • Radon concentration of air over the Eastern Arabian Sea

      S G Bhat S Krishnaswami Rama

      More Details Abstract Fulltext PDF

      The radon concentrations of air samples collected during the South West monsoon period at altitudes up to 4 km over the Arabian Sea at two locations,i.e., 0–50 km and 300–400 km west of Bombay, are reported. Radon was extracted from air, using a simple single stage apparatus. The concentration of radon in the monsoon air mass was found to range around 80–100 dpm/m3 STP, indicative of its recent continental origin. The results suggest that the coastal monsoon air mass, up to 400 km west of Bombay coast, is generally homogeneous and vertically well mixed.

      During the post-monsoon condition, a strong gradient in the radon concentration in the vertical is observed. The concentration of radon decreases from 157 dpm/m3 at sea level to 35 dpm/m3 at about 3·7 km altitude, suggesting a vertical turbulent diffusion coefficient of ∼6×104 cm2/sec. In contrast, the near absence of vertical gradient of radon in the monsoon air mass indicates that the vertical turbulence is much stronger during the monsoon period.

    • Man-made plutonium in freshwater and marine environments

      S Krishnaswami

      More Details Abstract Fulltext PDF

      Significant concentrations of plutonium isotopes are found in lake and coastal marine sediments accumulating at rates of 1–5 mm/yr. The activity levels of239, 240Pu range between 0·7–3·3 dpm/g for post 1960 sediments. The measured and the calculated integrated activities of239Pu in the lake sediments are in agreement. This suggests that plutonium is chemically reactive in freshwater environments and it is removed to sediments from the water column shortly after its injection.

      A delay of about three years has been observed between the peak of plutonium fallout and its incorporation in the varved sediment from Santa Barbara basin. Based on this observation the mean size of particles transporting plutonium to the basin sediments is estimated to be about three microns.

      The usefulness of plutonium isotopes as a tracer nuclide for estimating sedimentation rates for the last two decades have been evaluated.


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