Distribution of Cs-137 in the forest litter taken from different forest types of Latvia

Full text: The radioactive pollution of the environment from the Chernobyl catastrophe has only slightly touched Latvian territory. Nevertheless it has changed the usual radioactive background. After the decay of the short and medium - lived radionuclides, the radioactivity background due to that is mainly created by radionuclide Cs-137. Measurements of this radionuclide in soil, moss and mushrooms show rather different results in various areas of Latvia. That is explained by various meteorological conditions in Latvia at the time of the catastrophe. For our study of the radioactive pollution we chose forest litter. This choice was made because the greatest accumulation of the products of radioactive fission from atmosphere is discernible in forest. We chose two areas where we could expect different levels of radioactive pollution: Rucava and Taurene. Samples were gathered at various depths (5 levels: from 0 to 25 cm) and under various tree species (pine, spruce, birch), as well as in forest openings. Samples were dried and then homogenized in ''runner mill''. Radioactivity was determined using gamma spectrometer with 70 cm3 Ge detector. Measurements were made shielded by lead, thus minimizing background radioactivity. Results are shown in a table. The statistical error measurements does not exceed 20% of Taurene and 10% Rucava samples. Cs-137 content in soils of Latvia is 5.4-19.6 Bk/kg, which is several times lower than that found in forest litter. We can conclude that determine radioactive pollution forest litter should be used, preferably that found under spruce trees