P. Gaca

Radioactive Contamination of Lichens and Mosses Collected in South Shetlands and Antarctic Peninsula

Samples belonging to two species of lichen and one of moss collected on the Antarctic seashore (King George Island, Deception, Antarctic Peninsula) were analysed for gamma-emitters using HPGe gamma-spectrometry, and for alpha-emitters using alpha-spectrometry with silicon detectors. Observed 137Cs activities show large variations: from 4.1±0.4 to 74±3 Bq/kg. Total activity of 210Pb changed from <2 to 125±35 Bq/kg. The 2391240Pu activity ranged from 0.07±0.02 to 2.95±0.16 Bq/kg. The activity of 238Pu ranged from <0.02 to 0.64±0.04 Bq/kg. Maximum 238U and 234U activity was 7 Bq/kg, respectively, and 0.3 Bq/kg for 235U, whereas minimum activities were below 0.5 Bq/kg for 234U and 238U and about 0.02 Bq/kg for 235U. The 235U to 238U activity ratio for most of the samples was natural. Thorium activities were about two times lower than those for uranium. The activities of 147Sm ranged from 0.014±0.002 to 1.0±0.2 Bq/kg. One sample had relatively high activity of 241Am: 3.38±0.11 Bq/kg, another did not exceeded 1 Bq/kg. Observed activity ratios confirmed differences between mosses and lichen accumulation properties for radionuclides. Lichens are more selective for plutonium accumulation. Some radiocesium and probably also americium can be leached from them.

Geographical distribution of 90Sr contamination in Poland

Summary The paper presents results on determination of 90Sr in bilberry and cowberry leaves (Vaccinium myrtillus and Vaccinium vitis-idaea) and the use of these plants as bio-monitors of radiostrontium contamination in Poland. Radiostrontium was determined by mean of liquid scintillation spectrometry preceded by radiochemical separation using Sr-resin and 85Sr tracer. The approximate map of 90Sr contamination of Poland is presented. The activity ratio between 90Sr and obtained earlier data for 137Cs in the same samples is discussed. The enhancement of radiostrontium content observed in northeastern Poland seems to be the trace of hot-particles fallout from initial Chernobyl cloud, which passed over Polish territory toward Scandinavia.

Soil-to-fungi transfer of 90Sr, 239+240Pu, and 241Am

Summary Fungi have up to now generally been used as bioindicators of radiocaesium in terrestrial ecosystems. However there is little knowledge about the behaviour of other man-made radionuclides. In the present work, we analyzed the soil-to-fungi transfer of 90Sr, 239+240Pu, and 241Am by collecting several species of fungi and the corresponding surface soil (0−5 cm) of a selected semi-natural ecosystem. The transfer of these radionuclides was then quantified by means of the traditional transfer factor, TF, defined as the ratio between the content in the fruiting bodies and in the total fraction of soil. As a general rule, the 90Sr TF values were higher than those of 239+240Pu and 241Am. This definition of the transfer factor can underestimate the transfer of radionuclides of which a large percentage are bound to soil particles. We therefore also used a definition based on the amount of radionuclide available to be transferred instead of the total content of the soil — the available transfer factor, ATF — which would be closer to the actual process of transfer. Hebeloma cylindrosporum and Lycoperdon perlatum presented 239+240Pu and 241Am ATF values that were greater than or similar to those of 90Sr. These species may thus be used as bioindicators for 239+240Pu and 241Am in a forest ecosystem.

137Cs, 40K, 238Pu, 239+240Pu and 90Sr in biological samples from King George Island (Southern Shetlands) in Antarctica

There are few data reported on radionuclide contamination in Antarctica. The aim of this paper is to report 137Cs, 90Sr and 238,239+240Pu and 40K activity concentrations measured in biological samples collected from King George Island (Southern Shetlands, Antarctica), mostly during 2001–2002. The samples included: bones, eggshells and feathers of penguin Pygoscelis papua, bones and feathers of petrel Daption capense, bones and fur of seal Mirounga leonina, algae Himantothallus grandifolius, Desmarestia anceps and Cystosphaera jacquinotii, fish Notothenia corriceps, sea invertebrates Amphipoda, shells of limpet Nacella concina, lichen Usnea aurantiaco-atra, vascular plants Deschampsia antarctica and Colobanthus quitensis, fungi Omphalina pyxidata, moss Sanionia uncinata and soil. The results show a large variation in some activity concentrations. Samples from the marine environment had lower contamination levels than those from terrestrial ecosystems. The highest activity concentrations for all radionuclides were found in lichen and, to a lesser extent, in mosses, probably because lichens take up atmospheric pollutants and retain them. The only significant correlation (except for that expected between 238Pu and 239+240Pu) was noted for moss and lichen samples between plutonium and 90Sr. A tendency to a slow decrease with time seems to be occurring. Analyses of the activity ratios show varying fractionation between various radionuclides in different organisms. Algae were relatively more highly contaminated with plutonium and radiostrontium, and depleted with radiocesium. Feathers had the lowest plutonium concentrations. Radiostrontium and, to a lesser extent, Pu accumulated in bones. The present low intensity of fallout in Antarctic has a lower 238Pu/239+240Pu activity ratio than that expected for global fallout.

Plutonium, 137Cs and 90Sr in selected invertebrates from some areas around Chernobyl nuclear power plant.

Results are presented for (137)Cs, (90)Sr and plutonium activity concentrations in more than 20 samples of terrestrial invertebrates, including species of beetles, ants, spiders and millipedes, collected in the highly contaminated area of the Chernobyl exclusion zone. The majority of samples were collected in Belarus, with some also collected in the Ukraine. Three other samples were collected in an area of lower contamination. Results show that seven samples exceed an activity concentration of 100 kBq/kg (ash weight--a.w.) for (137)Cs. The maximum activity concentration for this isotope was 1.52+/-0.08 MBq/kg (a.w.) determined in ants (Formica cynerea). Seven results for (90)Sr exceeded 100 kBq/kg (a.w.), mostly for millipedes. Relatively high plutonium activity concentrations were found in some ants and earth-boring dung beetles. Analyses of activity ratios showed differences in transfer of radionuclides between species. To reveal the correlation structure of the multivariate data set, the Partial Least-Squares method (PLS) was used. Results of the PLS model suggest that high radiocesium activity concentrations in animal bodies can be expected mainly for relatively small creatures living on the litter surface. In contrast, high strontium activity concentrations can be expected for creatures which conduct their lives within litter, having mixed trophic habits and a moderate lifespan. No clear conclusions could be made for plutonium.

Gamma Emitters on Micro-Becquerel Activity Level in Air at Kraków (Poland)

The Petryanov air filters combined into half-year sets were analyzed for the presence of 40K, 137Cs and 22Na by means of low-background gamma rays spectrometry. Each sample contains aerosols from more than 1 Mm3 of air. Samples were collected in ground level air at Kraków (Southern Poland) from 1996 to 2002. Activity concentrations of 40K are almost constant with the mean of 14.7± 4.5 μ Bq m−3. Activity concentrations of 137Cs, which are on the level of single μ Bq m− 3 show exponential decrease with effective half-life time of 7.07± 0.77 years. The cosmogenic 22Na shows a strong seasonal variation with significant different mean values activity concentration between 0.333± 0.095 μ Bq m−3 and 0.137± 0.045 μ Bq m−3, for summer and winter, respectively. Moreover, the activity ratio for two cosmogenic radionuclides: 22Na and measured previously 7Be show also changes with statistically significant seasonal differences. The lower values were found during winters. The mechanisms which might govern this ratio are discussed. The conclusion is that transport of 22Na during summer seems to be so much effective, that results in kind of relative depletion of stratosphere of this nuclide.

Traces of DU in samples of environmental bio-monitors (non-flowering plants, fungi) and soil from target sites of the Western Balkan region

This paper reports results of gamma and alpha spectrometric measurements for mosses, lichens, fungi and soil samples from areas in the Balkans targeted by depleted uranium (DU). Samples were collected in 2002 and 2003 in the vicinity of several villages, principally Han Pijesak (Bosnia and Herzegovina, hit by DU in 1995) and Bratoselce (South Serbia, hit by DU in 1999) and in lesser numbers from Gornja Stubla, Kosovo (which is identified as a high natural radon/thoron area) and Presevo close to the Kosovo border. In the course of gamma spectrometric measurements some results suggested samples with unusual high uranium contents which might be considered to be a signature for the presence of DU, although many samples had very high detection limits. Alpha spectrometric measurements directly proved the presence of DU for five samples, all from directly targeted places. These were samples of mosses, lichens and soil. For some samples homogeneity tests were applied which showed a rather even distribution of DU in these samples. No trace of DU was found in any sample from a dwelling.

Geotrupine beetles (Coleoptera: Scarabaeoidea) as bio-monitors of man-made radioactivity

Adults of the geotrupine beetle Anoplotrupes stercorosus (Coleoptera, Geotrupidae), a common European forest insect species, were used in the role of bio-monitors for mainly man-made radionuclides in a forest environment. Activities of 137Cs, 40K, 238Pu, (239+240)Pu, 90Sr and 241Am were studied. Samples originated from four areas in Poland, two from the north-east and two from the south of the country. The north-eastern areas were previously recognized as the places where hot particle fallout from Chernobyl took place. Results confirmed the differences in the activities between north-eastern and southern locations. Significant correlations were found between activities of 40K and 137Cs, and between activities of plutonium and americium isotopes. An additional study of the concentration of radionuclides within the bodies of beetles showed a general pattern of distribution of radioisotopes in the insect body.

Elevated plutonium and americium content in skulls of small mammals

It has been found that in skull bones of small mammals have significantly higher Pu and Am concentrations than ever found in bones of any other species in areas contaminated by global fallout. Since there was no difference between skulls of rodents and insectivorous, an explanation is proposed that the contamination takes place by the inhalation of Pu and Am tiny soil particles.

Radionuclides in raised bogs: a case study of Bór za Lasem

Bór za Lasem is a raised bog in the Orawsko-Nowotarska Valley (southern Poland). About half of the Bór za Lasem area has been exploited while the rest is undisturbed. Peat samples from both parts of the bog were analysed. Measurements of 137Cs, 134Cs, 239,240Pu, 238Pu, 40K, 228Ra, and 226Ra activity concentrations in all samples were performed. Comparison of the results of radiocaesium and plutonium activity concentrations reveals the highest activity concentrations of radionuclides in the undisturbed part of the peat-bog area. The radiocaesium content decreased with depth, whereas the plutonium concentration had a maximum value at a depth of 15-20 cm. The lowest activity concentrations were found in the exploited part of the bog. Potassium and radium isotopes were detected only in shallow openings within the heavily exploited part of the bog, which might suggest partial mixing of the peat with the mineral sub-soil. The growth rate of the top layer of the undisturbed part of the bog obtained from plutonium distribution was estimated as approximately 0.5 cm per year.