RADIOCHEMICAL CONTAMINATION OF BOTTOM SEDIMENTS OF SOME NATURAL AND ARTIFICIAL LAKES OF MIDDLE-EAST POLAND

An investigation of the presence of some radioactive isotopes in the b ottom sediments of two lakes, Piaseczno and Masluchowskie (Middle East of Poland) has been performed. Similar measurements were done at the Zalew Zemborzycki artificial water reservoir, filled up few years afte r the most intensive period of atmospheric nuclear explosions. It was estimated, that the concentration of radionuclides, especially of arti ficial origin was much greater in natural lakes than in examined artif icial one. That testifies for an accumulation of radioactive substance s on the bottom of the water tanks. ?he confirmation of this thesis ma y be the fact, that 85% of Cs-137 detected in Zalew Zemborzycki comes from Chernobyl fallout while in natural lakes this isotope amounts onl y to 56-60%. Other isotopes, such as Pb-210, Ra-226 and Ra-224 were de tected in significant amounts. The radioactivity of Pu-239,Pu-240 isot opes reaches 2.2-2.6 Bq/kg for the lakes and 0.7 for Zalew Zemborzycki . The Pu-238 to Pu-239,Pu-240 ratio suggests, that detected plutonium comes from world fallout.