TRANSPLANTED EPIPHYTIC LICHENS AS BIOMONITORS OF AIR-CONTAMINATION BYNATURAL RADIONUCLIDES AROUND THE ZIROVSKI VRH URANIUM-MINE, SLOVENIA

Samples of Hypogymnia physodes were transplanted to the environment of the former uranium mine at Zirovski vrh, Slovenia for two exposure ex periments. The levels of the long-lived radionuclides, U-238, Ra-226 a nd Pb-210 in lichen material were measured after 4 and 7 months in the first experiment, and 4, 8 and 12 months in the second, and compared with the levels in lichens growing in-situ from the same sampling loca tions. They were also compared with the nuclide levels found in air pa rticulates by gamma spectrometry obtained at the regular site monitori ng stations. The results showed that each of the radionuclides had its own distribution pattern in this environment. The highest Ra-226 leve ls were found in lichens in the near vicinity of the dry-tailings pile , while U concentrations were high in the valley of the confluence of the Todrascica and Brebovscica streams close to the former yellow-cake production plant in Todraz, and then decreased downstream. (210)pb wa s the most uniformly distributed radionuclide and exhibited the highes t level. The results also confirm that active biomonitoring with trans planted lichens can be a useful and cheap supplement to instrumental a ir pollution monitoring. (C) 1995 The British Lichen Society