Americium, Curium and rare earths radionuclides in forest litter samples from Poland

Twenty seven samples of forest litter or humus layers (A0 or A1) collected in 1991 in selected regions of Poland were analysed for the presence of 241Am, Cm isotopes and rare-earth alpha-emitters. Samples were originating from a large research project and were previously analysed for gamma-emitters and plutonium. The measurements were done using alpha spectrometry preceded by a radiochemical separation procedure. Additional low-level gamma spectrometric measurements were performed for the rare-earths fractions of samples with the aim to search for europium gamma-emitters. The applied radiochemical procedure, based on the IAEA recommendations, is described. The maximum observed specific activity of 241Am was found to be equal to (5.00 ± 0.19) Bq/kg, for 243+244Cm it was (0.25 ± 0.02) Bq/kg and for 147Sm it was (0.124 ± 0.009) Bq/kg. The possible origin of each isotope is discussed. The obtained results confirmed the presence of the non-volatile isotopes of the Chernobyl fallout in north-eastern Poland.