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 bottom 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 after the most intensive period of atmospheric nuclear explosions. It was estimated, that the concentration of radionuclides, especially of artificial origin was much greater in natural lakes than in examined artificial one. That testifies for an accumulation of radioactive substances on the bottom of the water tanks. The confirmation of this thesis may be the fact, that 85% of137Cs detected in Zalew Zemborzycki comes from Chemobyl fallout while in natural lakes this isotope amounts only to 56–60%. Other isotopes, such as210Pb,226Ra, and224Ra were detected in significant amounts. The radioactivity of239,240Pu isotopes reaches 2.2–2.6 Bq/kg for the lakes and 0.7 for Zalew Zemborzycki. The238Pu to239,240Pu ratio suggests, that detected plutonium comes from world fallout.