RESTORATION OF RADIATION EVENTS OF THE PAST BY ANTEDATED LAKES BOTTOM SEDIMENT LAYERS

摘要

The principles and survey procedure of the identification of past radiation events on the basis of antedated layers of pond bottom sediments are described. Results of experimental investigations (2005-2006) of sediment samples taken in the Timiryazev Garden pond in Moscow and in the pond of a village Podkhozheye in Moscow district are presented. Dating of bottom layers have been carried out using ~(210)Pb. This radionuclide is used as a tracer to estimate the sedimentation rate in ponds (0.3-0.4 cm/year.). It is shown that the content of ~(137)Cs, the main anthropogenic radionuclide in all fallout of the second part of the 20th century, is relatively higher at the depth 7-8 cm below the bottom surface. This can be explained by the Chernobyl fallout. A second maximum of 11-13 and 17-22 cm (for each of the ponds) can be explained by a global origin. The origin of both of these maxima is confirmed by radionuclide ratios, which are typical for global and Chernobyl depositions at the Moscow region.