Seasonal variations of naturally occurring radionuclides and cs-137 in the leaves of deciduous tree species at sites of background radioactivity levels

Activity concentration of natural radionuclides and Cs-137 were studied in leaves of the deciduous trees. In the spring and autumn season, leaves were collected in the area of normal BACKGROUND: radiation levels represented by city parks in a multi-year period (2002-2012). Measurements by means of gamma-ray spectrometry showed Ra-226 and (210)pb seasonal accumulation in leaves, while U-238 and U-235 could be detected only in autumn. Difference between seasons was not found significant for K-40 and Cs-137. The study of radionuclides transfer factors was conducted by analyzing its relationships with basic soil properties at the beginning and the end of the vegetation period