Chernobyl90Sr in bilberries from Poland

90Sr and stable element levels in bones of brown bears: long-term trends in bear populations from Croatia and Poland

The aim of this study was to investigate the temporal trends and geographical differences in ⁹⁰Sr and stable element (Ba, Ca, Mn, Sr, Pb, Zn) levels in the bones of Croatian and Polish brown bear (Ursus arctos) populations. Experimental data suggest that in the decades after nuclear weapon tests and the Chernobyl accident, ⁹⁰Sr bone activity concentrations decreased from 352 to 11 Bq kg^-1 in the Croatian bear population (period 1982-2015) and from 831 to 27 Bq kg^-1 in Polish bears (period 1962-2020). Calculated effective and ecological half-lives were 9 and 13 years for Croatian bears, and 15 and 31 years for Polish bears, respectively. Different temporal trends were noted in levels of Ba, Mn, Pb and Zn between the two countries with majority of bones having lower Pb, Sr and Zn in Croatian than in Polish bears. Estimated values for the soil-to-bear transfer of ⁹⁰Sr were the same order of magnitude in the studied populations. Contrary to this, the estimated transfer of stable Sr was an order of magnitude lower for the Croatian bear population compared to Polish bears. The observed differences in soil-to-bear transfer between stable Sr and ⁹⁰Sr found for Croatian bears might suggest the need for careful consideration on the use of stable Sr data as an analogue for ⁹⁰Sr. To our knowledge, this is the first study that analysed ⁹⁰Sr activity in tissue of brown bears. As such, it provides insight into the fate and behaviour of one of the most relevant anthropogenic radionuclides at the top of the food chain.

Sources and variation of isotopic ratio of airborne radionuclides in Western Arctic lichens and mosses

This research concerned radioactivity of lichens and mosses from coastal zones of the Canadian Arctic and Alaska. Over 50 samples were collected from 7 positions during two scientific expeditions in 2012 and 2013. The tundra contamination caused by anthropogenic radionuclides was relatively low, reaching mean values with SD's of: 17.4 ± 3.5 Bq/kg for ⁹⁰Sr, 14.0 ± 2.9 Bq/kg for ¹³⁴Cs, 38.4 ± 7.5 Bq/kg for ¹³⁷Cs, 0.86 ± 0.24 Bq/kg for ^239+240Pu, 0.065 ± 0.017 Bq/kg for ²³⁸Pu and 0.50 ± 0.13 Bq/kg for ²⁴¹Am. The increase of activity concentration with increasing latitudes was noticed mostly in regard to ⁹⁰Sr, Pu isotopes and ²⁴¹Am. The analysis of isotopic ratios exhibited dominant contribution of the global fallout (+SNAP 9A satellite re-entry fallout) for the presence of plutonium isotopes and ²⁴¹Am. The Fukushima fallout signature was identified in a few lichens from Alaska. However, the influence of additional unknown factor on the occurrence of ⁹⁰Sr and ¹³⁷Cs has been detected in western part of Canadian Arctic. Natural radioisotopes of thorium and uranium were found throughout the entire investigated region and the average values of activity concentration with SD's were as follows: 2.92 ± 0.47 Bq/kg for ²³⁰Th, 2.61 ± 0.48 Bq/kg for ²³²Th, 4.32 ± 0.80 Bq/kg for ²³⁴U and 3.97 ± 0.71 Bq/kg for ²³⁸U. Examined Western Arctic tundra was not affected with any technically enhanced natural radioactivity.

Determination of plutonium isotopes in bilberry using liquid scintillation spectrometry and alpha-particle spectrometry

This paper presents α-particle spectrometry and liquid scintillation spectrometry methods to determine plutonium isotopes in bilberry. The analytical procedure involves sample preparation steps for ashing, digestion of bilberry samples, radiochemical separation of plutonium radioisotopes and their measurement. The validity of the method was checked for coherence using the ζ test, z-test, relative bias and relative uncertainty outlier tests. The results indicated that the recommended procedures for both measurement systems could be successfully applied for the accurate determination of plutonium activities in bilberry samples.

137Cs and 40K in fruiting bodies of different fungal species collected in a single forest in southern Poland

Fruiting bodies of fungi belonging to more than 70 species were collected within a few thousand square meter area of one forest during 2006 and 2007. The soil profile was collected to check the cumulative deposition of (137)Cs, which was relatively high, equal to 64 +/- 2 kBq/m(2) (calculated for October 2006). The majority of this activity was in the first 6 cm. Fruitbodies were analyzed for radiocesium and (40)K by means of gamma-spectrometry. The highest (137)Cs activity was 54.1 +/- 0.7 kBq/kg (dry weight) for a sample of Lactarius helvus collected in 2006. The results for 2006 were higher than those for 2007. In a few cases the traces of short-lived (T(1/2) = 2.06 a) (134)Cs were still found in samples. The importance of mycorrhizal fungi for radiocesium accumulation is confirmed. The differences in activity among the species are discussed in relation to observations and predictions from previous studies, where the change in relative accumulation between fruiting bodies of different species was at least partially explained by the differences in the depth of the mycelium localization in a litter/soil system. It is concluded that in some cases, such as Boletus edulis and Xerocomus badius, this prediction is fulfilled and therefore this explanation confirmed.

Geographical distribution of 90Sr contamination in Poland

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.

Pu-241 in samples of forest soil from Poland

241Pu activity measurements in coniferous forest soil samples from Poland are presented. The results were obtained in two ways: by alpha spectrometric remeasurements of the plutonium sources 3-4 years after their preparation (i.e. by the 241Am ingrowth) and by direct measurements of 241Pu using liquid scintillation (LS) spectrometry. Both methods gave consistent results. The maximum observed activity concentration obtained by the 241Am ingrowth was (254 +/- 43) Bq/kg, and by direct measurements it was (284 +/- 31) Bq/kg (the same sample, activities calculated for May 1, 1986). Enhanced levels of 241Pu were observed in all samples from the farthest north-eastern Poland. The estimated 241Pu maximum deposition from Chernobyl fallout in this area (sum of deposition for two examined layers of one site) was (1.025 +/- 0.110) kBq/m2. This will result after 70 years in an additional 241Am activity of about (30.1 +/- 3.2) Bq/m2. The average ratio for 241Pu to total 238,239,240Pu was of the order of 25. The obtained average Chernobyl ratios for 241Pu to 239,240Pu were about 86, and those for 241Pu to 238,239,240Pu were 56.