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

Abstract

The paper presents the results of radionuclides determination in moss (Homolothecium sp., Hypnum Cupressiforme sp., and Brachythecium 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 of the 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.

U radu su predstavljeni rezultati određivanja radionuklida u mahovinama (Homolothecium sp., Hypnum Cupressiforme sp. i Brachythecium sp.) i lišaju (Cladonia sp.) koji su uzorkovani u regionu istočne Srbije tokom 1996-2010 godine. Aktivnosti u mahovinama iznose 100-500 Bq/kg suve materije za 40K, i 5-50 Bq/kg suve materije za 226Ra i 232Th. Dobijeni su transfer faktori 'zemljište-mahovina': 0.45 za 40K, 3 za 226Ra i 0.3 i 232Th. Prostorna distribucija aktivnosti 137Cs je izrazito neuniformna; mawe od 10% uzoraka, uglavnom onih pre 2000. godine, ima aktivnost veću od 1000 Bq/kg suve materije. Varijacije sadržaja prirodnih radionuklida u mahovinama nisu značajne. Frekvencione krive aktivnosti prirodnih radionuklida u lišaju slične su onima u mahovinama, dok su aktivnosti izmerene u lišaju nešto niže. Srednja aktivnost 137Cs u lišaju manja je od 400 Bq/kg suve materije. Srednje aktivnosti 7Be u mahovinama i lišaju, koji su uzorkovani tokom 2006. i 2008. godine, iznose 41-122 Bq/kg suve materije, sa izraženim varijacijama između lokacija.