Factors affecting the transfer of radiocaesium from soil to roe deer in forest ecosystems of southern Germany

Long-term effects of potassium chloride, wood ash, and EDTA on 137Cs soil-plant transfer in a mixed forest of Ukraine

We conducted a 10-year field experiment to study the effects of potassium chloride, wood ash, zinc, and manganese on reducing 137Cs uptake by young leaves and green shoots of common dwarf shrubs and tree species near the Chornobyl Nuclear Power Plant. A field experiment had four treatments: a control with no fertilisation, and three fertilised treatments: potassium fertiliser (KCl), a combination of potassium fertiliser and wood ash (KCl + Ash), and a solution providing zinc and manganese (EDTA). There was approximately 30 % decrease in 137Cs uptake by most of the studied plants species growing on plots fertilised with KCl compared to unfertilised plots during intermediate (2014-2016) and late (2018-2021) periods. Combining KCl with wood ash was found to be the most effective countermeasure, reducing 137Cs uptake by up to 60% in most species, while treatment with EDTA was less effective. Generally, the decline in 137Cs uptake by plants over the study years following treatments with fertilisers was more pronounced than in the control, indicating the efficiency of fertilisation in reducing 137Cs uptake by forest plants. Our research suggests that a combination of potassium chloride and wood ash can still effectively reduce 137Cs transfer in most common forest species, even years after the accident.

Levels of caesium-137 in food of animal origin in Poland

Introduction

Radioactive contamination of the environment is one of the greatest threats after a nuclear accident due to released radionuclides. From a radiotoxicological point of view, the most important radionuclide is caesium-137. Formed mainly during nuclear explosions, caesium-137 can persist in the soil for many years, from where it constantly enters the food chain. One of the elements of ensuring food safety is the monitoring of its radioactive contamination, mainly with radioactive caesium isotopes. The aim of the study was to determine the content of caesium-137 in food of animal origin.

Material and Methods

A total of 1,416 muscle samples from cattle, sheep, pigs, game and fish, as well as chicken eggs and dairy products were examined using gamma-ray spectrometry.

Results

Caesium-137 activities ranged from below the minimum detectable activity concentration (MDC) to over 4,000 Bq/kg wet weight (w.w.). Most often, the values did not exceed the MDC or were in a range below 100 Bq/kg. The exception was the muscle tissue of game animals, especially wild boar, where a significant activity of caesium-137 was recorded, the highest of which was 4,136.8 ± 238 Bq/kg w.w. Committed effective doses determined for each matrix ranged from 0.01 to 0.83 µSv/kg, with the highest value determined for wild boar.

Conclusion

The calculated exposure doses with values well below the accepted low radiation dose (100 mSv) did not indicate any significant amounts of ionising radiation from the food consumed.

Time dependence of 137Cs contamination in wild Japanese monkeys after the Fukushima Daiichi nuclear accident

Over the 10 years immediately after the Fukushima Daiichi nuclear accident, we measured the changes in the muscle ¹³⁷Cs concentration (Bq/kg) of wild Japanese monkeys living in Fukushima City, which is located approximately 70 km from the Fukushima Daiichi Nuclear Power Plant. The muscle¹³⁷Csconcentration, which was observed at a maximum of 13,500 Bq/kg immediately after the accident, had decreased to several hundred Bq/kg 10 years later. The muscle ¹³⁷Cs concentration was significantly related to the soil contamination levels (10,000-30,000, 30,000-60,000, 60,000-100,000, and 100,000-300,000 Bq/m²), sex, age class (immature, mature), body weight (> 5000 g, 5000-10,000 g, < 10,000 g), and seasons (the cold period from December to April, the warm period from May to November).The value of muscle ¹³⁷Cs concentration and the aggregated transfer factor (T_ag: calculated by dividing muscle ¹³⁷Cs concentration [Bq/kg] by soil ¹³⁷Cs deposition density at the capture site [Bq/m²]) apparently decreased with time for several years. However, post hoc pairwise comparisons showed no difference from 2017 to 2020, and the accumulation of ¹³⁷Cs in muscle may continue for some time.

Effects of indoor and outdoor cultivation conditions on 137 Cs concentrations in cultivated mushrooms produced after the Fukushima Daiichi Nuclear Power Plant accident

BACKGROUND

Radiocesium (¹³⁴ Cs and ¹³⁷ Cs) in mushrooms has been a matter of public concern after the accident at Fukushima Daiichi Nuclear Power Plant. To minimize the internal dose by ingestion of cultivated mushrooms, the Japanese government set a guideline level with respect to the radiocesium concentration in bed-logs and mushroom beds; however, the effects of indoor and outdoor cultivation methods on radiocesium concentrations in cultivated mushrooms were not clear.

RESULTS

The effects of indoor and outdoor cultivation on the radiocesium concentrations in mushroom were examined using published food monitoring data. ¹³⁷ Cs concentration data in Lentinula edodes from the Aizu area in Fukushima Prefecture and seven prefectures outside Fukushima were used for the analysis. No statistically significant ¹³⁷ Cs concentration differences were found between these two cultivation methods. Using detected ¹³⁷ Cs data in shiitake, the geometric means from each prefecture were less than one-quarter of the standard limit (100 Bq kg^-1 ) for total radiocesium under both cultivation conditions.

CONCLUSION

It was suspected that re-suspended radiocesium might have been taken up by mushrooms or that radiocesium might have been absorbed into the mushrooms from the soil in the outdoor cultures. However, neither effect was significant for cultivated mushrooms in the areas examined. © 2016 Society of Chemical Industry.

Modelling (137)Cs concentrations in moose (1986-2012) from areas highly contaminated by the Chernobyl fallout

Data from long term annual monitoring of (137)Cs concentrations in harvested moose (Alces alces) were empirically modelled by applying multivariate data analysis that is able to from relatively raw datasets show how the many various impact variables are related (Principal component analysis, PCA). In the later stage regression modelling (Partial least squares, PLS) was applied to analyse which environmental and physiological factors were significant (i.e. of predictive value) based on the measured (X) activity concentrations in moose meat. The data sets originate from two different forest dominated areas in Sweden. One area is located inland (Heby municipality) and the other borders to the Baltic Sea (Gävle municipality). In inland with 20% farmland, GIS-software was used to calculate the proportion of different habitat types and (137)Cs deposition around individual killing spots. This model reveals that the proportions of farmland and forest around the killing spot were significant parameters, second to deposition and years since fallout. Significance was also obtained for the proportions of mire and water bodies, the amount of rain in summer and the age of the moose. In the other model based on data from the coastal area with only about 4% farmland, the coordinates of the moose killing spots were not recorded in the data sets. In the resulting model the temperature in July was the most important parameter, second to years since fallout. Significance was also found for the following parameters: temperature and rainfall in several summer months, the approximate north- and eastward location of the killing spot and to which age category (adult/calf) the harvested moose belonged.

Time-dependence of ¹³⁷Cs activity concentration in wild game meat in Knyszyn Primeval Forest (Poland)

Wild game meat samples were analysed from the region of the Podlasie province (Knyszyn Primeval Forest). (137)Cs content in meat was determined by gamma spectrometry in 2003 (33 samples), 2009 (22 samples) and 2012 (26 samples). The samples were collected in the autumn of 2003, 2009 and 2012 and were compared with data from 1996. Mean concentrations of (137)Cs in the respective years were as follow: 42.2 Bq kg(-1), 33.7 Bq kg(-1) and 30.5 Bq kg(-1), respectively. On the basis of mean values of (137)Cs in the meat samples of red deer (Cervus elaphus), roe deer (Capreolus capreolus) and wild boars (Sus scrofa) between 1996/2012, the effective half-life of (137)Cs was determined for specific species. For red deer equaled 8.9 years, for roe deer 11.6 years while for wild boar it exceeded the physical half-life and equaled 38.5 years. Mean value CR obtained for all three species equaled 1.7 ± 1.5 out of 102 measurements in animals muscles.

The effect of environmental remediation on the cesium-137 levels in white-tailed deer

Due to activities involving nuclear energy research during the latter half of the 1900 s, environmental contamination in the form of elevated cesium-137 levels was observed within the Brookhaven National Laboratory, a US Department of Energy facility. Between the years 2000 and 2005, the laboratory carried out a major soil cleanup effort to remove cesium-137 from contaminated sites. In this study, we examine the effectiveness of the cleanup effort by comparing the levels of cesium-137 in the meat of white-tailed deer found within and around the laboratory. Results suggest that the cleanup was effective, with mean concentration of cesium-137 in the meat from within the laboratory decreasing from 2.04 Bq/g prior to 1.22 Bq/g after cleanup. At the current level, the consumption of deer would not pose any human health hazard. Nevertheless, statistically higher levels of cesium-137 were detected in the deer within the laboratory as opposed to levels found in deer 1 mi beyond the laboratory site.

Long-term ¹³⁷Cs activity monitoring of mushrooms in forest ecosystems of the Czech Republic

This paper reports on results of activity mass concentration analyses performed in various forest mushrooms in the Czech Republic within 1986 and 2011. The estimated effective half-life of (137)Cs and its environmental half-life (i.e. the effective half-life minus the effect of physical decay) were found to be 5.6 ± 0.6 and 6.9 ± 0.7 y, respectively. Non-homogeneity in (137)Cs surface contamination over the country's territory and fungus species-based (137)Cs accumulation capacity then account for a span of up to 4 orders of magnitude in activity mass concentrations measured each year after the Chernobyl accident. The highest geometric activity mass concentration (Bq kg(-1) of dry weight) means of (137)Cs (obtained from samples between years 2004 and 2011) were measured in Suillaceae (1050 Bq kg(-1)) and Boletus badius (930 Bq kg(-1)), the lowest in Agaricus (1 Bq kg(-1)). The geometric mean of all mushrooms amounted to 230 Bq kg(-1), being 440 Bq kg(-1) in Boletales, 150 Bq kg(-1) in Russulales and 21 Bq kg(-1) in Agaricales. Geometric standard deviation levels were generally high. The highest Cs accumulation capacity was observed in Boletales (namely in Suillaceae), while the lowest in Agaricales, being over 3 orders of magnitude lower than in Suillaceae.

Dynamics of radionuclides in forest ecosystems

The unique physiology and the layered structure of forest ecosystems result in dynamic transport and transfer processes which greatly differ from those in agricultural ecosystems. Radionuclides are retained in the upper organic horizons of forest soil for several decades and remain highly available for uptake by fungi and green plants. Contamination levels of mushrooms and game may therefore by far exceed those of agricultural produce. The efficient cycling of nutrients and radionuclides, which is characteristic for ecosystems poor in nutrients, can largely be attributed to forest soil with its complex and multi-layered structure and fungal activity. Fungi directly affect dynamic processes, playing a key role in the mobilization, uptake and translocation of nutrients and radionuclides. Fungal fruit bodies may be highly contaminated foodstuff and fodder. They are most likely the cause of the surprising trend of increasing contamination of wild boar which has been observed in the last few years in Germany. This paper is intended to give a qualitative survey of dynamic transport processes in forests and their relevance for radiation exposure to man.

Long-term effects of single potassium fertilization on 137Cs levels in plants and fungi in a boreal forest ecosystem

We examined the long-term effects of a single application of potassium (K) fertilizer (100 kg K ha(-1)) in 1992 on (137)Cs uptake in a forest ecosystem in central Sweden. (137)Cs activity concentrations were determined in three low-growing perennial shrubs, heather (Calluna vulgaris), lingonberry (Vaccinium vitis-idaea) and bilberry (Vaccinium myrtillus), and in four wild fungal species (Cortinarius semisanguineus, Lactarius rufus, Rozites caperata and Suillus variegatus). Uptake of (137)Cs by plants and fungi growing on K-fertilized plots 17 years after application of the K fertilizer was significantly lower than in corresponding species growing in a non-fertilized control area. The (137)Cs activity concentration was 21-58% lower in fungal sporocarps and 40-61% lower in plants in the K-fertilized area compared with the control. Over the study period, this decrease in (137)Cs activity concentration was more consistent in plants than in fungi, although the effect was statistically significant and strongly pronounced in all species. The effect of K fertilization in reducing (137)Cs activity concentration in fungi and plants decreased over time but was still significant in 2009, 17 years after fertilization. This suggests that application of K fertilizer to forests is an appropriate and effective long-term measure to decrease radiocaesium accumulation in plants and fungi.

Distribution of 210Pb and 210Po concentrations in wild berries and mushrooms in boreal forest ecosystems

The activity concentrations and distribution of 210Pb and 210Po in wild berries and edible mushrooms were investigated in Finnish forests. The main study areas were located in Scots pine (Pinus sylvestris L.) forests in southern and northern Finland. The activity concentrations of 210Pb and 210Po in blueberry (Vaccinium myrtillus L.) and lingonberry (Vaccinium vitis-idaea L.) samples decreased in the order: stems>leaves>berries (i.e. fruits). The activity ratios of 210Po/210Pb in the wild berry samples were mainly higher than one, indicating elevated activity concentrations of polonium in the samples. In mushrooms the activity concentrations of 210Pb and especially 210Po were higher than in fruits of the wild berries. The highest activity concentration of 210Pb was detected in Cortinarius armillatus L. (16.2 Bq kg(-1) d.w.) and the lowest in Leccinum vulpinum L. (1.38 Bq kg(-1) d.w.). The 210Po activity concentrations of the whole fruiting bodies ranged from 7.14 Bq kg(-1) d.w. (Russula paludosa L.) to 1174 Bq kg(-1) d.w. (L. vulpinum L.). In general, the highest activity concentrations of 210Po were recorded in boletes. The caps of mushrooms of the Boletaceae family showed higher activity concentrations of 210Po compared to the stipes. In most of the mushrooms analyzed, the activity concentrations of 210Po were higher than those of 210Pb. 210Po and 210Pb dominate the radiation doses received via ingestion of wild berries and mushrooms in northern Finland, while in southern Finland the ingested dose is dominated by 137Cs from the Chernobyl fallout.

Time-dependency of the 137Cs contamination of wild boar from a region in Southern Germany in the years 1998 to 2008

Following the Chernobyl accident, (137)Cs contamination levels of wild boar in some districts of Southern Germany are still exceeding thousands of Bq kg(-1). While the long term (137)Cs concentration in forest plants, mushrooms, and roe deer meat has decreased significantly, for wild boar it has remained constant during the last decade. Between 1998 and 2008, we analysed the muscle meat of 656 wild boars shot in the district ("Landkreis") Ravensburg. The (137)Cs activity concentration showed considerable variability from less than 5 up to 8266 Bq kg(-1) and it followed a seasonal pattern, which is attributed to changes in dietary habits, fodder availability, meteorological conditions and specific behaviour of (137)Cs in wild boar organism. T(ag) values for wild boars from the district Ravensburg varied from 0.008 to 0.062 m(2)kg(-1) during 2000-2008.

Accumulation of polonium 210Po in tissues and organs of deer carvidae from Northern Poland

This study was undertaken to provide information on accumulation of polonium in tissues and organs of deer carvidae in order to assess the potential transport of this element via food-chain to game meat consumers. Livers, kidneys and muscles of large herbivorous animals belonging to three species: roe deer (Capreolus capreolus), red deer (Cervus elaphus) and fallow deer (Dama dama), collected in Northern Poland, were the subject of the present investigation. Activities of (210)Po were determined by means of alpha spectrometry along with relevant radiochemical procedures. The concentration of (210)Po in analyzed animals decreased in the order kidney > liver > muscle tissue. The average activity concentrations of (210)Po ranged between 0.02 +/- 0.01 Bq. kg(- 1) w.w. in muscles and 7.15 +/- 0.12 Bq. kg(- 1) w.w. in kidneys. Levels of polonium were not influenced by sampling location, sex, age and species of animals.

Time trends (1986-2003) of radiocesium transfer to roe deer and wild boar in two Austrian forest regions

Starting shortly after the Chernobyl accident, samples of roe deer and wild boar from two comparatively highly contaminated Austrian forest stands have been regularly analysed for (137)Cs. Until 1995 average (137)Cs concentrations exceeded 1000 Bq kg(-1) in both roe deer and wild boar. Long-term and seasonal trends are similar in both investigation sites. While (137)Cs aggregated transfer factor (T(ag)) values show a significant decreasing trend in roe deer (ecological half-time 8.6 and 7.2 years, respectively), T(ag)-values in wild boar are highly variable, but rather increasing values are observed over the last years. T(ag)-values for roe deer are between 0.04 and 0.008 m(2)kg(-1) fresh weight (1987-2003); values for wild boar are between 0.008 m(2)kg(-1) (1988) and 0.046 m(2)kg(-1) (1996) fresh weight. Seasonal trends for both species are in good agreement with observations from German forests: increased mushroom ingestion leads to higher (137)Cs T(ag)-values for roe deer in the second half of the year (August-December) compared to the first half (January-July). T(ag)-values for wild boar are highest in the first half of the year.

Concentrations of 137Cs in lynx (Lynx lynx) in relation to prey choice

Concentrations of (137)Cs were determined in 747 lynxes killed in Norway during the period 1986-2001. Highly variable (137)Cs concentrations and aggregated transfer coefficient values were observed, probably caused by variable (137)Cs concentrations in prey and the lynx's extensive home ranges and roaming distances. Adult lynxes had higher (137)Cs concentrations than sub-adults, and lynxes killed in regions with extensive reindeer grazing areas were more contaminated than others. A model with (137)Cs deposition density, the year lynxes were killed, age, and extent of reindeer grazing area accounted for 50% of the variability in observed (137)Cs concentrations. The analyses were equivocal regarding the influence of stomach content on (137)Cs concentrations in lynx muscle, i.e., on the lynx's specialization in prey species. Gender was not significant. Information on caesium retention in lynx and better estimates of deposition densities in lynxes' home ranges are important for further elucidation of factors influencing (137)Cs contamination in lynxes.

Fungi ingestion as an important factor influencing heavy metal intake in roe deer: evidence from faeces

In nature, animals have to cope with the fluctuating bioavailable metal pool in their habitat, which results in a seasonal variability of heavy metal levels in the animal body. Indeed, a pronounced summer-autumnal peak of heavy metals in roe deer (Capreolus capreolus L.) kidney was recently found in Slovenia. Considering the well-known hyperaccumulative ability of fungi, their ingestion was hypothesised to be one of the main reasons for the peak. Although fungi as a group are known to be a seasonally important food source for roe deer, data on their composition in the nutrition of the species have been lacking. To ascertain the importance of fungi ingestion on heavy metal intake in roe deer, we simultaneously studied fungal spores (by microscopic determination) and heavy metal levels (by inductively coupled plasma mass spectrometry and atomic absorption spectrometry) in roe deer faeces, collected in the period July-November 2001 at Veliki Vrh, the Salek Valley, Slovenia. Irrespective of species, fungal spores were present in 89% of faeces; the following genera were found to be consumed by roe deer: Lycoperdon, Calvatia, Hypholoma, Coprinus, Russula, Elaphomyces, Xerocomus, Enteloma, Amanita, Cortinarius, Agaricus, Inocybe, Boletus, Macrolepiota, Suillus and Pluteus. While the importance of fungi ingestion on the seasonal variability of other metals is less clear, it doubtless influences Hg intake in roe deer, which is confirmed by: (a) the high frequency of fungi in roe deer nutrition; (b) their hyperaccumulative ability; (c) the temporal distribution of Hg in roe deer faeces; (d) differences among three classes of faeces established on the basis of the frequency of spores present; (e) the correlation between the number of fungal genera present and Hg levels in faeces. Therefore, the influence of fungi ingestion has to be taken into consideration in assessing the hazard due to the accumulation of mercury along the food-chain.

Seasonal variability of mercury and heavy metals in roe deer (Capreolus capreolus) kidney

The seasonal variability of Hg, Pb, Cd and Zn was determined in the kidney of 164 roe deer, shot in three areas of Slovenia in 1998. We found a strong seasonal influence on Hg and Pb levels, which were significantly higher in late summer and early autumn. Cd and Zn levels showed a similar seasonal pattern, although not so pronounced; for these elements differences among periods were probably not a consequence of season per se. Seasonal variability in metal levels in roe deer kidney originated in both quantitative and qualitative differences in nutrition of the species. Since the seasonal peaks for the majority of metals appeared in a very narrow summer autumnal period (August-September), it seems that some plant taxons, such as fungi, might represent an important pathway for heavy metal intake into the mammalian organism. The season of sample collection has to be considered whenever using wildlife as an accumulative bioindicator of environmental pollution. Moreover, the influence of the season should be born in mind whenever a hazard due to accumulation of heavy metals along the food chain is assessed.

Time-dependence of the radiocaesium contamination of roe deer: measurement and modelling

In spruce forest and peat bog, the migration of 137Cs from soil to plants, fungi, roe deer and consumers has been surveyed. In spruce forest the 137Cs activity concentration in roe deer decreases slowly with time and has superimposed periodic maxima in autumn which are correlated with the mushroom season. The decrease with time can be described by an effective half-life of 3.5 yr caused by a fraction of the 137Cs in the soil becoming unavailable for green grazing plants with time. The additional transfer of 137Cs into roe deer meat during the mushroom season depends on precipitation in July, August and September which also determines the yield of fungi in autumn. Our model confirms the assumption that fungi also have access to a fraction of the 137Cs in the soil which is unavailable for green plants. On peat bog the 137Cs activity concentration in roe deer is higher than in spruce forest and its effective half-life is about 17 yr, due to reversible binding of 137Cs to organic matter in the peat bog.

Radionuclide behaviour and transport in a coniferous woodland ecosystem: vegetation, invertebrates and wood mice, Apodemus sylvaticus

Activity concentrations of radionuclides (134Cs, 137Cs, 238Pu, 239 + 240Pu and 241Am) were measured in vegetation, invertebrates and wood mice, Apodemus sylvaticus, collected in Lady Wood, a coniferous woodland in the vicinity of the British Nuclear Fuels reprocessing plant at Sellafield, Cumbria, UK. Vegetation was of low diversity and biomass with activity concentrations ranging from 1 to 5 Bq kg-1 (134Cs), 0.3-0.5 Bq kg-1 (238Pu), 0.8-8 Bq kg-1 (239 + 240Pu), and 0.6-16 Bq kg-1 (241Am), dry wt. Caesium-137 activity concentrations were high compared to the reference site in Cheshire, varying between 65 and 280 Bq kg-1. Marked inter-specific and temporal differences in radionuclide activity concentrations were recorded for invertebrate populations. Caesium-137, 238Pu, 239 + 240Pu and 241Am activity concentrations in detritivorous invertebrates were consistently higher than in all other invertebrate groups reflecting contamination of the leaf litter. The activity concentrations in detritivores increased during the autumn and winter, reflecting changes in diet as food sources varied throughout the year. Activity concentrations in invertebrates caught in Lady Wood were generally an order of magnitude higher than for the reference site. Activity concentrations in wood mice varied between 7 and 150 Bq kg-1 (137Cs), 0.1-0.3 Bq kg-1 (238Pu), 0.1-0.6 Bq kg-1 (239 + 240Pu) and 0.2-0.4 Bq kg-1 (241Am). There were clear differences in the activity concentration of 137Cs (P < 0.01), 239 + 240Pu (P < 0.05) and 241Am (P < 0.05) in animals caught in Lady Wood compared to the reference site. However, the activity concentrations for 238Pu were similar at both sites, reflecting a low gastrointestinal transfer. Seasonal variation in activity concentrations was observed for 137Cs, 238Pu and 241Am. This variation is attributed to changes in the age structure of the population and diet throughout the year.

Radiocesium accumulation in edible wild mushrooms from coniferous forests around the Nuclear Centre of Mexico

Cs-137 and K-40 have been determined in soil samples and in wild edible mushrooms from a forest ecosystem located at the Nuclear Centre of Mexico (NCM) and in several surrounding localities. The transfer factors for Cs-137 were studied in 21 mushroom species from 1993 to 1997. The Cs-137 and K-40 determinations were performed using a gamma spectrometer system of low level counting with a high purity germanium (HPGe) detector. The local mushroom species that were found to show higher Cs-137 transfer factors were Clavariadelphus truncatus, Cortinarius caerulescens, Gomphus floccosus and Lyophyllum decastes. The Cs-137 levels obtained at the NCM in some mushroom samples were slightly lower than those from surrounding localities indicating that the nuclear facility has not emitted Cs-137 to the atmosphere.