Natural radionuclides and 137 Cs in moss and lichen in Eastern Serbia

Abstract

The paper presents the results of radionuclides determination in moss (Homolothecium sp., Hypnum Cupressiforme sp., andBrachythecium sp.) and lichen (Cladonia sp.) sampled in the region of Eastern Serbia during 1996-2010. The activities in moss are in the range of 100-500 Bq/kg d. w. for 40K, and 5-50 Bq/kg d. w. for 226Ra and 232Th, while the "soil-to-moss" transfer factors are 0.45 for 40K, 3 for 226Ra, and 0.3 for 232Th. The spatial distribution of the 137Cs activities is highly non-uniform; some values reach 500 Bq/kg d. w., with less than 10% of the samples, mainly the ones taken prior to 2000, with the activity above 1000 Bq/kg d. w. The variations in the content of natural radionuclides among the moss species are not significant. The frequency pattern ofthe activities of natural radionuclides in lichen is similar to the one in moss, but the activities in lichen are to some extent lower. The mean activity of 137Cs in lichen is below 400 Bq/kg d. w. The mean activities of 7Be in moss and lichen sampled in 2006 and 2008 are in the range of 41-122 Bq/kg d. w., with pronounced variations between the sampling sites.