Retrospective of radioactive fallout from data on sampled bottom sediments in closed water bodies |
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| Authors: | E V Kvasnikova S K Gordeev V N Golosov M V Markelov O M Zhukova V A Rodikova |
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| Institution: | (1) Institute of Global Climate and Ecology, Roshydromet and Russian Academy of Sciences, ul. Glebovskaya 20b, Moscow, 107258, Russia;(2) Radon Moscow Scientific Industrial Association, Sed’moi Rostovskii per. 2/14, Moscow, 119121, Russia;(3) Moscow State University, Vorob’evy gory, Moscow, 119899, Russia |
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| Abstract: | A method for identifying past radiation events from dated layers of bottom sediments in stagnant water bodies is described. Results of an experimental study (2005–2006) of the samples of bottom sediments in the pond of the Timiryazev dendropark in Moscow are considered. The sediment layers are dated with 210Pb. The same radionuclide is used as a tracer for calculating the rate of sedimentation in the pond, which is estimated at 0.3–0.4 cm/year. The maximum 137Cs values are detected in the 0–24 cm column at depths of 7 and 13 cm. The 137Cs peak at a depth of 13 cm is dated as 1963, which reflects the maximum global fallout from the atmospheric nuclear weapon tests. A small peak of this radionuclide at 7 cm is dated as 1986. It appears to be attributed to the long-range fallout after the Chernobyl NPP accident. The origin of the 137Cs maximum at a depth of 13–14 cm is confirmed by characteristic ratios of radionuclide pairs available in the global fallout in the Moscow region. The ratios of 90Sr/137Cs = 0.6 and 239,240Pu/137Cs = 0.03 in the 13–14 cm layer are characteristic of the global radioactive fallout from nuclear explosions. In the layers above this maximum, such ratios vary sharply toward the enhanced 137Cs content in the fallout. |
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