Jerzy W. Mietelski

Radioactive contamination of Polish mushrooms

Abstract The results of a 5-year investigation on the radioactive contamination of mushrooms are presented. More than 400 samples of various mushrooms species have been examined for γ-emitters. Some samples have also been analysed for strontium-90 and plutonium isotope content. Maps of caesium-137, caesium-134 and potassium-40 activities, based on the measurements of 278 samples of Xerocomus badius collected in 1991 throughout Poland are presented. The highest measured activity of caesium-137 was 157 kBq/kg dry mass ( Xerocomus badius ). A dosimetric interpretation of the observed contamination levels is proposed.

Plutonium and other alpha emitters in mushrooms from Poland, Spain and Ukraine.

The paper presents results on Pu, U and Th isotope activity concentration measurements in some mushroom samples collected in Poland, Spain and Ukraine. The sampling sites differ a lot with regard to observed levels of Pu, its origin and isotope ratios as well as the environmental properties. Some of the Polish samples were collected in the northeastern part of the country with up to 30 Bq/m2 of Chernobyl Pu deposition. Other Polish and the Spanish samples are from areas with almost exclusively global fallout Pu present. Ukrainian samples were collected in a highly contaminated area with a deposition of about 3.7 kBq/m2 of Chernobyl (239-240)Pu. The maximum (239+240)Pu activity concentration was found equal to (54+/-4) Bq/kg (dw--dry weight) for a Ukrainian Cantharellus cibarius sample. Ukrainian samples have an extremely high radiocesium level, with maximum of (51+/-4) MBq/kg (dw). The maximum (239+240)Pu activity concentration for Polish samples was (81+/-5) mBq/kg (dw) for Xerocomus badius. From the isotopic ratio in this sample it can be concluded that Chernobyl fallout is the origin of Pu. More than twice as large was the Spanish maximum for Hebeloma cylindrosporum but with only global fallout Pu. Some aspects of the transfer of nuclides to fruit bodies is discussed and in some cases the transfer factors or aggregation coefficients were calculated. Especially high transfer factors were found for Hebeloma cylindrosporum from Spain.

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.

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.

The method of measurement used in the investigation of radioactive contamination of forests in Poland

Abstract The method applied in a programme for the investigation of radioactive contamination in forests of Poland is presented. The method is discussed in three parts: sampling, calibration of the spectrometers, and presentation of the results.

90Sr and239+240Pu238Pu241Am in some samples of mushrooms and forest soil from Poland

Strontium-90, plutonium and americium activity concentrations in a few samples of forest soils, some species of mushrooms and fern leaves have been determined. These results are compared with cesium activity concentrations in the same materials obtained in a previous work. Radiochemical procedures are described. The origin of the contamination (Chernobyl accident or nuclear test explosion release) is discussed. The90Sr activity concentration ranges from 0.6 Bq/kg (mushroom samples) to 48.4 Bq/kg (fern leaves). For239+240Pu, it ranges from not detected above background (mushrooms, fern) to 10.8 Bq/kg (humus layer of forest soil). The maximum concentration of241Am is found to be 2.4 Bq/kg (humus sample) and for238Pu it is 0.85 Bq/kg (also in the humus sample).

Sources and distributions of 137Cs, 238Pu, 239,240Pu radionuclides in the north-western Barents Sea

Sediment deposits are the ultimate sink for anthropogenic radionuclides entering the marine environment. The major sources of anthropogenic radionuclides to the Barents Sea are fallout from nuclear weapons tests, long range transport from other seas, and river and non-point freshwater supplies. In this study we investigated activity concentrations, ratios, and inventories of the anthropogenic radionuclides, 137Cs, 238Pu, 239,240Pu in dated sediment cores collected along a north-south transect in the northwestern Barents Sea. The data were used to evaluate the influence of different sources on the derived spatial and temporal patterns of anthropogenic radionuclides in seafloor sediment deposits. Activity concentrations of 137Cs ranged from <0.1 Bq/kg to 10.5 Bq/kg while 239,240Pu ranged from <0.01 Bq/kg to 2.74 Bq/kg and 238Pu activity concentrations ranged from <0.01 Bq/kg to 0.22 Bq/kg. Total inventories of 137Cs ranged from 29.5+/-1.5 Bq/m2 to 152.7+/-5.6 Bq/m2 and for 239,240Pu inventories (6 sediment layers only) ranged from 9.5+/-0.3 Bq/m2 to 29.7+/-0.4 Bq/m2. Source contributions varied among stations and between the investigated radionuclides. The 238Pu/239,240Pu ratios up to 0.18 indicate discharges from nuclear fuel reprocessing plants as a main contributor of plutonium. Based on 238Pu/239,240Pu ratio, it was calculated that up to 19-27% of plutonium is supplied from sources other than atmospheric global fallout. Taking into account Atlantic current flow trajectories and that both activity concentrations and inventories of plutonium negatively correlate with latitude, Sellafield is a major source for the Barents Sea. Concentrations and inventories of 137Cs correlate positively with latitude and negatively with distance from the Svalbard archipelago. The 137Cs concentrations are highest in an area of intensive melting of sea ice formed along the Siberian coast. Thus, sea ice and supplies from Svalbard may be important source of 137Cs to the Barents Sea seafloor.

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.

Strontium-90 activity concentration in soil samples from the exclusion zone of the Fukushima daiichi nuclear power plant

The radioactive fission product 90Sr has a long biological half-life (˜18 y) in the human body. Due to its chemical similarity to calcium it accumulates in bones and irradiates the bone marrow, causing its high radio-toxicity. Assessing 90Sr is therefore extremely important in case of a nuclear disaster. In this work 16 soil samples were collected from the exclusion zone (<30 km) of the earthquake-damaged Fukushima Daiichi nuclear power plant, to measure 90Sr activity concentration using liquid scintillation counting. 137Cs activity concentration was also measured with gamma-spectroscopy in order to investigate correlation with 90Sr. The 90Sr activity concentrations ranged from 3.0 ± 0.3 to 23.3 ± 1.5 Bq kg−1 while the 137Cs from 0.7 ± 0.1 to 110.8 ± 0.3 kBq kg−1. The fact that radioactive contamination originated from the Fukushima nuclear accident was obvious due to the presence of 134Cs. However, 90Sr contamination was not confirmed in all samples although detectable amounts of 90Sr can be expected in Japanese soils, as a background, stemming from global fallout due to the atmospheric nuclear weapon tests. Correlation analysis between 90Sr and 137Cs activity concentrations provides a potentially powerful tool to discriminate background 90Sr level from its Fukushima contribution.

Plutonium and other alpha-emitters in bones of wild, herbivorous animals from north-eastern Poland.

The results of the investigation of (239+240)Pu, 241Am and thorium isotope activity concentrations in bones of wild herbivorous animals (deer, roe-deer, boars, elks) from north-eastern Poland are presented. The area on which the animals were living had relatively high Chernobyl plutonium fallout. Possible traces of plutonium were seen only in four samples, but only for one it was it 3sigma above background, at 6.2 +/- 2.4 mBq/kg (ash). The 241Am activity concentration was below the detection limits in all samples. The maximum 228Th concentration in the samples was 7.81 +/- 0.44 Bq/kg (ash), calculated under the assumption of 100% thorium recovery. This isotope seems to originate in bones not from direct incorporation but from the decay of 228Ra. Large variations in activity concentration wose observed, as well as some differences between boars and the chewing animals.