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Radionuclide content in lichen thallus in the forests adjacent to the Chernobyl atomic power plant
the Science of the Total Environment
i i,:ll ELSEVIER
iw
t
The Science of the Total Environment 157 (1994) 25-28
Radionuclide content in lichen thallus in the forests adjacent to the Chernobyl atomic power plant L.G. Biazrov Laboratory of Bioindication, Institute of Animal Evolutionary Morphology and Ecology, Russian Academy of Sciences, Leninsky Pr. 33, Moscow 117071, Russian Federation
Abstract
The concentrations of l°6Ru, 134Cs, 137Cs,and 144Cein thalli of lichens Hypogymniaphysodes and Cladina mitis, in the bark of pine tree Pinus siloestris are very high in the immediate vicinity of the Chernobyl atomic power plant. They decrease with increasing distance from the centre of the accident. However, even outside the 30-km zone of population evacuation, they surpass concentrations of these radionuclides from global fallout by hundreds of times.
Keywords: Radionuclides; Lichens; Thalli; Chernobyl
1. Introduction The accident at the Chernobyl atomic power plant (CNPP) in Ukraine on 26 April 1986 caused a considerable emission of fission products from nuclear fuel into the atmosphere. Their spatial distribution depended mainly on local factors such as wind direction in the troposphere and on atmospheric precipitation. On their release, these factors caused the variable pattern of fallout of fission products over the country, reflected both by direct dosimetric measurements and by data on the content of man-made radionuclides in the bodies of organisms (Levi, 1991). Among the latter, fungi and thalloid plants, in particular lichens have an outstanding capacity for accumulation of radionuclides, obtaining everything necessary for their life by the aerial route directly from the atmosphere. Therefore, the content of radionuclides and heavy metals in lichen thalli is rather a true reflection of the Elsevier Science BV. SSDI 0 0 4 8 - 9 6 9 7 ( 9 4 ) 0 4 2 6 3 - M
character of long-term atmospheric pollution in their habitats (Tiirk, 1988). Occasionally, lichens have been called the silent chronists of the Chernobyl accident (Feige et al., 1990). The aims of the present study were (i) to investigate the space distribution of the concentrations of some radionuclides in thalli of different lichens, (ii) a comparison with concentrations of radionuclides in the bark of pine tree, and (iii) an examination of the thalli in their natural habitats to reveal anomalies in their development in the immediate vicinity of the CNPP. 2. Materials and methods The samples were collected between 13-30 July 1988 in pine tree woods and forests at the following sites, adjacent to the CNPP: Site A about 1.5 km to the south-west of the CNPP; B about 7 km to the south-west; C, 12-13 km to the north-
26
L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
west of the CNPP near the boundary of the Gomel region of Byelorussia; D, about 19 km to the south of the CNPP; and site E, about 37 km to the south of the CNPP, outside the 30 km zone of population evacuation. In site E, samples were collected in three close forest habitats (1,2,3). In each plot under study, composite samples of lichen thalli and pine tree bark were collected from several trees and from several points on ground. The volume of the composite sample was about 20-30 g. The activity of some radionuclides was measured in thalli of epiphytic lichen H. physodes representing the life form of foliose inflatedlobate non-rhizoidal lichens (Golubkova and Biazrov, 1989); in the thalli of the epigeal lichen C. mitis, a fruticose erect lichen, and in the bark of pine tree P. silvestris overgrown with specimens of H. physodes. These plants are common species and widespread. At the sampling points, the lichens were thoroughly examined in their natural habitats to reveal anomalies in their development. Then the lichen samples were cleaned from the fractions of substrata, dried at ll0°C for 24 h, pulverized and placed in 70-cm 3 beakers for measurement. The measurement was performed by high resolution gamma spectrometry with a lithium drifted germanium crystal detector and a multichannelanalyser at the Laboratory of Research Station on Urals (Antonenko et al., 1988). The results were calculated for the date about 1000 days after the accident. 3. Results and discussion
Visual examination of lichens directly at sampiing stations did not reveal any departure from the norm in their development: the colour of thalli were normal for representatives of each species, no spots were present, fructification of C. mitis was normal, apothecia were of the usual brownish colour. Abundance of soredia on thalli of H. physodes was also normal. The results of measurement of some of the y-emitting radionuclides are shown in Table 1. As was expected, their highest levels are recorded nearest the location of the accident (A). The lowest values of the activity are recorded in sam-
pies taken beyond the 30-km zone of population evacuation (E). However, here considerable fluctuations in the activity value are observed, e.g. in thalli of H. physodes pointing out the uneven distribution of the fallout of fission products from nuclear fuel after the explosion and I°6Ru levels in pine tree bark. I°6Ru is formed in the uranium fission process with a half-life of 368 days (Levi, 1991). It has been shown experimentally that vascular plants accumulate this radionuclide from soil solution in insignificant quantities, especially in their upper parts (Makhonina et al., 1965). However, lichen thalli in the area of the CNPP manifest a considerable activity of this radionuclide after the accident. In general, a quite regular decreasing trend is observed away from the wrecked reactor. The lichens are known to accumulate large quantities of 137Cs from global fallout. In the years when nuclear arms were tested mainly in the atmosphere of the Arctic Region, the thalli of Cladina there contained about 2.6 B q / g of 137Cs (Alexakhin and Ravikovich, 1969). In the early 80's, in the vicinity of the first Russian commercial Beloyarsk atomicpower plant (in the Central Urals), the activity of 137Cs in thalli of H. physodes was 0.3-0.75 B q / g and in pine tree bark, 0.1-0.25 B q / g (Nifontova et al., 1988). The comparatively low values of 137Cs concentration (0.1-1.3 Bq/g) were recorded in lichen thalli in Austrian forests after nuclear tests made in China in 1980 (Eckl et al., 1986). Isotopes 134Cs and 137Cs are formed in the fission process from uranium and plutonium. The half-life of the first isotope is 2.1 years, and the second is 30.0 years (Levi, 1991). Taking this into consideration, at the moment of the accident, there was almost 2.5 times more 134Cs around the CNPP and if in 1000 days after the accident, the ratio 134Cs/137Cs was about 0.2, it was about 0.5 during the first days after the accfdent. This ratio in thalli of Arctic lichens in the 50s and 60s was about 0.002-0.004 (Hanson et al., 1967). The concentration of these isotopes regularly decreases in lichen thalli and pine tree bark with increasing distance from the CNPP. As a rule, the activity of these radionuclides is higher in the epiphytic lichens than in thalli of the epigeal lichens and in pine tree bark. The order of magnitude of the concentration of 137Cs in thalli of H.
L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
27
Table 1 Concentrations (Bq/g dry wt.) of radionuclides in lichen thalli and pine tree bark in the vicinity of the Chernobyl NPP, 1000 days after the accident Site a
Radionuclide
Hypogymnia physodes
Cladina mitis
Bark of pine tree
A
106Ru 134Cs 137Cs 144Ce
1700 1140 5840 2400
777 561 2700 662
335 258 1260 588
l°6Ru ~34Cs
1130 730 3600 1160
747 570 2850 988
355 257 1210 684
183 92 539 184
394 263 1230 385
23 24 107 34
49 41 200 46
43 26 118 35
137Cs 144Ce l°6Ru 134Cs 137Cs
144Ce l°6Ru
134Cs 137Cs
144Ce E1 2 3
1
106Ru
134Cs
2 3
1
137Cs
2 3
1 2 3
144Ce
34.2 337.0 41.4 26.0 150.0 11.5 80.9 792.0 70.5 24.7 223.0 19.6
20.0 19.9 19.6 12.4 9.6 10.2 58.2 48.7 44.4 12.0 18.0 19.7
ND ND ND ND 86
12
57
22
ND, not determined. a For explanation of locations, see Materials and methods.
physodes, outside the 30-kin zone of evacuation (E) 1000 days after the accident, was the same as that in the Bavarian Forest and/kips (Feige et al., 1990) or in the forests of Austria in August 1986, where the activity of this radionuclide in thalli of the same species was 33.5 B q / g and in spruce trunk, 3.5 B q / g . Before the Chernobyl accident in the same Austrian forests, the concentration of 137Cs in thalli of H. physodes was 0.07 B q / g (Hofmann et al., 1988). The last of the radionuclides studied, 144Ce, is present in emissions of atomic power plants and of plants processing spent nuclear fuel. With in-
creasing distances from the CNPP, the concentration of 144Ce in lichen thalli and pine tree bark regularly decreases. In normal situations, the concentration of this isotope in lichens is comparatively low - - 0.01-0.14 B q / g (Eckl et al., 1986). If the ratios of the concentrations of measured radionuclides are compared, only the ratio 134Cs/137Cs remains the same in all substrata and at all sites. The values of ratios between concentrations of other radionuclides or isotopes of cesium to other nuclides vary within wide limits. Generally, it can be seen that for stations situated closer to the wrecked reactor, the values of the
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L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
ratio between concentrations of radionuclides in thalli of various lichen species and in pine tree bark vary less than for stations remote from the CNPP. 4. Conclusions The concentrations of all measured radionuclides both in lichen thalli and pine tree bark in the region adjacent to the CNPP exceeds the usual levels of these radionuclides in lichens from global fallout before to the accident by hundreds of times and up to tens of thousands of times. The impact of quite high ionizing radiation levels even near the wrecked reactor by observations in July 1988 did not cause any visually discernable anomalies in the development of lichen thalli, quite in agreement with the data on the high resistance of lichens to radioactive irradiation (Brodo, 1964). At greater distances from the wrecked reactor, the values of the concentrations of radionuclides in lichen thalli and pine tree bark decrease. However, even outside the 30-km zone of population evacuation, their concentrations in lichen thalli surpass the values before the accident, probably by hundreds of times. The accident at the CNPP affected a wide area. This fact should be taken into consideration in the interpretation of observations on the global fallout of radionuclides and their accumulation in organisms. The fallout of the fission products from nuclear fuel was patchy, the heterogeneity being both quantitative and qualitative. The concentration of the studied radionuclides is much higher in lichen thalli than in pine tree bark. In lichens, the activity of radionuclides is usually higher in epiphytes than in thalli of epigeal lichen. Acknowledgements I express my gratitude to Mrs A.I. Arkhireeva for the preparation of samples for measurements and to Mr O.V. Tarasov for assistance in making activity measurements using the gamma spectrometry. I'm very obliged to the Swedish Radia-
tion Protection Institute and to the Commission of the European Communities for financially supporting my travel to Stockholm and participation in the Seminar on 'The Dynamic Behaviour of Radionuclides in Forest Ecosystems', 18-22 May 1992, Stockholm, Sweden. References Alexakhin, R.M. and M.M. Ravikovich, 1969. On natural radioactivity of different components of forest biogeocenosis cause from 4°K. Radioact. Isotopes Soils Plants, 16: 122-133 (in Russian). Antonenko, G.I., V.1. Savina, L.I. Pershina, V.L. Usachev, V.Z. Martujshov and O.V. Tarasov, 1988. Measurement methods of radionuclides concentration in soil and samples of plants and animals. In: Ecotoxicology and Protection of Nature. Nauka Press, Moscow, pp. 153-158 (in Russian). Brodo, I.M., 1964. Field studies of the effects of ionizing radiation on lichens. Bryologist, 67: 76-87. Eckl, P., W. Hofmann and R. Tiirk, 1986. Uptake of natural and man-made radionuclides by lichens and mushrooms. Radiat. Environ. Biophys., 25: 43-54. Feige, G.B., L. Neimann and S. Jahnke, 1990. Lichens and mosses - - silent chronists of the Chernobyl accident. Biblioth. Lichenol., 38: 63-77. Golubkova, N.S. and L.G. Biazrov, 1989. Life forms of lichens and lichenosynusia. Bot. Zh. (USSR), 74:794-805 (in Russian). Hanson, W.C., D.C. Watson and R.W. Perkins, 1967. Concentration and retention of fallout radionuclides in Alaskan arctic ecosystems. Conference on Radioecological Concentration Processes, Stockholm, Sweden, 25-29 April, 1966. Pergamon, Oxford, pp. 233-245. Hofmann, W., N. Attarpour and R. Tiirk, 1988. Verteilung von Caesium-137 in Wald-0kosystemen in Bundesland Salzburg (Osterreich). FIM-Symposium 1988. Waldsterben in 0sterreigh: Theorien, Tendenzen, Therapien, Vienna, S.9-11. Levi, H.W., 1991. Radioactive deposition in Europe after the Chernobyl accident and its long-term consequences. Ecol. Res., 6: 201-216. Makhonina, G.I., I.V. Molchanova, E.N. Subbotina, N.V. Timofeev-Resovsky, A.A. Titlyanova, A.N. Tujrujkanov and M. Chebotina, 1965. Distribution of 59Fe, 6°C0, 65Zn, 9°Sr, l°6Ru, 137Cs,144Cein components of biogeocenosis. Works Institute of Biology of Urals Branch. USSR. Acad. Sci., Sverdlovsk, 45:121-125 (in Russian). Nifontova, M.G., N.V. Kulikov, G.I. Tarshis and A.P. Djachenko, 1988. Radioecological investigation of natural ecosystems around atomic power plants. Ecology (USSR), N 3:40-45 (in Russian). Tiirk, R., 1988. Bioinidkation von Luftverunreinigungen mitels Flechten. Okophysiologische Probleme durch Luftverunreinigungen, Karl-Franzens-Universtit~it Graz, Graz, S. 13-27.
i i,:ll ELSEVIER
iw
t
The Science of the Total Environment 157 (1994) 25-28
Radionuclide content in lichen thallus in the forests adjacent to the Chernobyl atomic power plant L.G. Biazrov Laboratory of Bioindication, Institute of Animal Evolutionary Morphology and Ecology, Russian Academy of Sciences, Leninsky Pr. 33, Moscow 117071, Russian Federation
Abstract
The concentrations of l°6Ru, 134Cs, 137Cs,and 144Cein thalli of lichens Hypogymniaphysodes and Cladina mitis, in the bark of pine tree Pinus siloestris are very high in the immediate vicinity of the Chernobyl atomic power plant. They decrease with increasing distance from the centre of the accident. However, even outside the 30-km zone of population evacuation, they surpass concentrations of these radionuclides from global fallout by hundreds of times.
Keywords: Radionuclides; Lichens; Thalli; Chernobyl
1. Introduction The accident at the Chernobyl atomic power plant (CNPP) in Ukraine on 26 April 1986 caused a considerable emission of fission products from nuclear fuel into the atmosphere. Their spatial distribution depended mainly on local factors such as wind direction in the troposphere and on atmospheric precipitation. On their release, these factors caused the variable pattern of fallout of fission products over the country, reflected both by direct dosimetric measurements and by data on the content of man-made radionuclides in the bodies of organisms (Levi, 1991). Among the latter, fungi and thalloid plants, in particular lichens have an outstanding capacity for accumulation of radionuclides, obtaining everything necessary for their life by the aerial route directly from the atmosphere. Therefore, the content of radionuclides and heavy metals in lichen thalli is rather a true reflection of the Elsevier Science BV. SSDI 0 0 4 8 - 9 6 9 7 ( 9 4 ) 0 4 2 6 3 - M
character of long-term atmospheric pollution in their habitats (Tiirk, 1988). Occasionally, lichens have been called the silent chronists of the Chernobyl accident (Feige et al., 1990). The aims of the present study were (i) to investigate the space distribution of the concentrations of some radionuclides in thalli of different lichens, (ii) a comparison with concentrations of radionuclides in the bark of pine tree, and (iii) an examination of the thalli in their natural habitats to reveal anomalies in their development in the immediate vicinity of the CNPP. 2. Materials and methods The samples were collected between 13-30 July 1988 in pine tree woods and forests at the following sites, adjacent to the CNPP: Site A about 1.5 km to the south-west of the CNPP; B about 7 km to the south-west; C, 12-13 km to the north-
26
L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
west of the CNPP near the boundary of the Gomel region of Byelorussia; D, about 19 km to the south of the CNPP; and site E, about 37 km to the south of the CNPP, outside the 30 km zone of population evacuation. In site E, samples were collected in three close forest habitats (1,2,3). In each plot under study, composite samples of lichen thalli and pine tree bark were collected from several trees and from several points on ground. The volume of the composite sample was about 20-30 g. The activity of some radionuclides was measured in thalli of epiphytic lichen H. physodes representing the life form of foliose inflatedlobate non-rhizoidal lichens (Golubkova and Biazrov, 1989); in the thalli of the epigeal lichen C. mitis, a fruticose erect lichen, and in the bark of pine tree P. silvestris overgrown with specimens of H. physodes. These plants are common species and widespread. At the sampling points, the lichens were thoroughly examined in their natural habitats to reveal anomalies in their development. Then the lichen samples were cleaned from the fractions of substrata, dried at ll0°C for 24 h, pulverized and placed in 70-cm 3 beakers for measurement. The measurement was performed by high resolution gamma spectrometry with a lithium drifted germanium crystal detector and a multichannelanalyser at the Laboratory of Research Station on Urals (Antonenko et al., 1988). The results were calculated for the date about 1000 days after the accident. 3. Results and discussion
Visual examination of lichens directly at sampiing stations did not reveal any departure from the norm in their development: the colour of thalli were normal for representatives of each species, no spots were present, fructification of C. mitis was normal, apothecia were of the usual brownish colour. Abundance of soredia on thalli of H. physodes was also normal. The results of measurement of some of the y-emitting radionuclides are shown in Table 1. As was expected, their highest levels are recorded nearest the location of the accident (A). The lowest values of the activity are recorded in sam-
pies taken beyond the 30-km zone of population evacuation (E). However, here considerable fluctuations in the activity value are observed, e.g. in thalli of H. physodes pointing out the uneven distribution of the fallout of fission products from nuclear fuel after the explosion and I°6Ru levels in pine tree bark. I°6Ru is formed in the uranium fission process with a half-life of 368 days (Levi, 1991). It has been shown experimentally that vascular plants accumulate this radionuclide from soil solution in insignificant quantities, especially in their upper parts (Makhonina et al., 1965). However, lichen thalli in the area of the CNPP manifest a considerable activity of this radionuclide after the accident. In general, a quite regular decreasing trend is observed away from the wrecked reactor. The lichens are known to accumulate large quantities of 137Cs from global fallout. In the years when nuclear arms were tested mainly in the atmosphere of the Arctic Region, the thalli of Cladina there contained about 2.6 B q / g of 137Cs (Alexakhin and Ravikovich, 1969). In the early 80's, in the vicinity of the first Russian commercial Beloyarsk atomicpower plant (in the Central Urals), the activity of 137Cs in thalli of H. physodes was 0.3-0.75 B q / g and in pine tree bark, 0.1-0.25 B q / g (Nifontova et al., 1988). The comparatively low values of 137Cs concentration (0.1-1.3 Bq/g) were recorded in lichen thalli in Austrian forests after nuclear tests made in China in 1980 (Eckl et al., 1986). Isotopes 134Cs and 137Cs are formed in the fission process from uranium and plutonium. The half-life of the first isotope is 2.1 years, and the second is 30.0 years (Levi, 1991). Taking this into consideration, at the moment of the accident, there was almost 2.5 times more 134Cs around the CNPP and if in 1000 days after the accident, the ratio 134Cs/137Cs was about 0.2, it was about 0.5 during the first days after the accfdent. This ratio in thalli of Arctic lichens in the 50s and 60s was about 0.002-0.004 (Hanson et al., 1967). The concentration of these isotopes regularly decreases in lichen thalli and pine tree bark with increasing distance from the CNPP. As a rule, the activity of these radionuclides is higher in the epiphytic lichens than in thalli of the epigeal lichens and in pine tree bark. The order of magnitude of the concentration of 137Cs in thalli of H.
L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
27
Table 1 Concentrations (Bq/g dry wt.) of radionuclides in lichen thalli and pine tree bark in the vicinity of the Chernobyl NPP, 1000 days after the accident Site a
Radionuclide
Hypogymnia physodes
Cladina mitis
Bark of pine tree
A
106Ru 134Cs 137Cs 144Ce
1700 1140 5840 2400
777 561 2700 662
335 258 1260 588
l°6Ru ~34Cs
1130 730 3600 1160
747 570 2850 988
355 257 1210 684
183 92 539 184
394 263 1230 385
23 24 107 34
49 41 200 46
43 26 118 35
137Cs 144Ce l°6Ru 134Cs 137Cs
144Ce l°6Ru
134Cs 137Cs
144Ce E1 2 3
1
106Ru
134Cs
2 3
1
137Cs
2 3
1 2 3
144Ce
34.2 337.0 41.4 26.0 150.0 11.5 80.9 792.0 70.5 24.7 223.0 19.6
20.0 19.9 19.6 12.4 9.6 10.2 58.2 48.7 44.4 12.0 18.0 19.7
ND ND ND ND 86
12
57
22
ND, not determined. a For explanation of locations, see Materials and methods.
physodes, outside the 30-kin zone of evacuation (E) 1000 days after the accident, was the same as that in the Bavarian Forest and/kips (Feige et al., 1990) or in the forests of Austria in August 1986, where the activity of this radionuclide in thalli of the same species was 33.5 B q / g and in spruce trunk, 3.5 B q / g . Before the Chernobyl accident in the same Austrian forests, the concentration of 137Cs in thalli of H. physodes was 0.07 B q / g (Hofmann et al., 1988). The last of the radionuclides studied, 144Ce, is present in emissions of atomic power plants and of plants processing spent nuclear fuel. With in-
creasing distances from the CNPP, the concentration of 144Ce in lichen thalli and pine tree bark regularly decreases. In normal situations, the concentration of this isotope in lichens is comparatively low - - 0.01-0.14 B q / g (Eckl et al., 1986). If the ratios of the concentrations of measured radionuclides are compared, only the ratio 134Cs/137Cs remains the same in all substrata and at all sites. The values of ratios between concentrations of other radionuclides or isotopes of cesium to other nuclides vary within wide limits. Generally, it can be seen that for stations situated closer to the wrecked reactor, the values of the
28
L.G. Biazrov / Sci. Total Environ. 157 (1994) 25-28
ratio between concentrations of radionuclides in thalli of various lichen species and in pine tree bark vary less than for stations remote from the CNPP. 4. Conclusions The concentrations of all measured radionuclides both in lichen thalli and pine tree bark in the region adjacent to the CNPP exceeds the usual levels of these radionuclides in lichens from global fallout before to the accident by hundreds of times and up to tens of thousands of times. The impact of quite high ionizing radiation levels even near the wrecked reactor by observations in July 1988 did not cause any visually discernable anomalies in the development of lichen thalli, quite in agreement with the data on the high resistance of lichens to radioactive irradiation (Brodo, 1964). At greater distances from the wrecked reactor, the values of the concentrations of radionuclides in lichen thalli and pine tree bark decrease. However, even outside the 30-km zone of population evacuation, their concentrations in lichen thalli surpass the values before the accident, probably by hundreds of times. The accident at the CNPP affected a wide area. This fact should be taken into consideration in the interpretation of observations on the global fallout of radionuclides and their accumulation in organisms. The fallout of the fission products from nuclear fuel was patchy, the heterogeneity being both quantitative and qualitative. The concentration of the studied radionuclides is much higher in lichen thalli than in pine tree bark. In lichens, the activity of radionuclides is usually higher in epiphytes than in thalli of epigeal lichen. Acknowledgements I express my gratitude to Mrs A.I. Arkhireeva for the preparation of samples for measurements and to Mr O.V. Tarasov for assistance in making activity measurements using the gamma spectrometry. I'm very obliged to the Swedish Radia-
tion Protection Institute and to the Commission of the European Communities for financially supporting my travel to Stockholm and participation in the Seminar on 'The Dynamic Behaviour of Radionuclides in Forest Ecosystems', 18-22 May 1992, Stockholm, Sweden. References Alexakhin, R.M. and M.M. Ravikovich, 1969. On natural radioactivity of different components of forest biogeocenosis cause from 4°K. Radioact. Isotopes Soils Plants, 16: 122-133 (in Russian). Antonenko, G.I., V.1. Savina, L.I. Pershina, V.L. Usachev, V.Z. Martujshov and O.V. Tarasov, 1988. Measurement methods of radionuclides concentration in soil and samples of plants and animals. In: Ecotoxicology and Protection of Nature. Nauka Press, Moscow, pp. 153-158 (in Russian). Brodo, I.M., 1964. Field studies of the effects of ionizing radiation on lichens. Bryologist, 67: 76-87. Eckl, P., W. Hofmann and R. Tiirk, 1986. Uptake of natural and man-made radionuclides by lichens and mushrooms. Radiat. Environ. Biophys., 25: 43-54. Feige, G.B., L. Neimann and S. Jahnke, 1990. Lichens and mosses - - silent chronists of the Chernobyl accident. Biblioth. Lichenol., 38: 63-77. Golubkova, N.S. and L.G. Biazrov, 1989. Life forms of lichens and lichenosynusia. Bot. Zh. (USSR), 74:794-805 (in Russian). Hanson, W.C., D.C. Watson and R.W. Perkins, 1967. Concentration and retention of fallout radionuclides in Alaskan arctic ecosystems. Conference on Radioecological Concentration Processes, Stockholm, Sweden, 25-29 April, 1966. Pergamon, Oxford, pp. 233-245. Hofmann, W., N. Attarpour and R. Tiirk, 1988. Verteilung von Caesium-137 in Wald-0kosystemen in Bundesland Salzburg (Osterreich). FIM-Symposium 1988. Waldsterben in 0sterreigh: Theorien, Tendenzen, Therapien, Vienna, S.9-11. Levi, H.W., 1991. Radioactive deposition in Europe after the Chernobyl accident and its long-term consequences. Ecol. Res., 6: 201-216. Makhonina, G.I., I.V. Molchanova, E.N. Subbotina, N.V. Timofeev-Resovsky, A.A. Titlyanova, A.N. Tujrujkanov and M. Chebotina, 1965. Distribution of 59Fe, 6°C0, 65Zn, 9°Sr, l°6Ru, 137Cs,144Cein components of biogeocenosis. Works Institute of Biology of Urals Branch. USSR. Acad. Sci., Sverdlovsk, 45:121-125 (in Russian). Nifontova, M.G., N.V. Kulikov, G.I. Tarshis and A.P. Djachenko, 1988. Radioecological investigation of natural ecosystems around atomic power plants. Ecology (USSR), N 3:40-45 (in Russian). Tiirk, R., 1988. Bioinidkation von Luftverunreinigungen mitels Flechten. Okophysiologische Probleme durch Luftverunreinigungen, Karl-Franzens-Universtit~it Graz, Graz, S. 13-27.