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Accumulation of 137Cs by fungal mycelium in forest ecosystems of Ukraine
Abstract
During 1996-1998, 16 fruit bodies of different species and 204 soil samples down to 10 cm in the close vicinity of the fruit body sites were collected in a coniferous forest in the Ovruch region of Ukraine. The soil samples were sliced into 1 or 2 cm layers and the fungal mycelium was prepared from each of the layers. The 137Cs activity concentration was determined in both soil and mycelium. The mean weight of fungal mycelium was 13.8 mg g(-1) of soil in the upper 4 cm and 7.3 mg g(-1) when measured for the upper 10 cm. At the sites of Paxillus involutus and Sarcodon imbricatus, the mycelium was rather homogeneously distributed in the upper 10 cm and at sites of Xerocomus subtomentosus and Cantharellus cibarius, the mycelium was distributed mostly in the upper layers. The highest 137Cs activity concentrations were found in the upper layers of the soil profile. The 137Cs activity concentrations were usually higher in the fruit bodies compared with the mycelium, with ratios ranging from 0.1 to 66 and a mean of 9.9. The percentage of the total inventory of 137Cs in the soil found in the fungal mycelium ranged from 0.1 to 50%, with a mean value of 15%.
... Разом з тим, 137 Cs, що надійшов у довкілля після аварії та АЕС Фукусіма у 2011 р., все ще залишається одним із критичних продуктів поділу. Міграція радіоцезію в лісових екосистемах істотно відрізняється від його поведінки в інших екосистемах, насамперед через велику кількість грибного міцелію у верхніх, багатих на органічну речовину горизонтах ґрунту [13]. У ґрунтах бореальних лісових екосистем гриби є домінуючим компонентом біомаси мікроорганізмів, а міцелій як сапротрофних, так і мікоризних видів відіграє важливу роль і в руйнуванні органічної речовини, і у процесах мінерального живлення рослин через густу мережу симбіотичних мікоризних асоціацій [10]. ...
... Екзоферменти, що виділяються грибним міцелієм, сприяють вивільненню елементів живлення з органічних субстратів, у результаті чого як міцелій, так і плодові тіла грибів здатні накопичувати значну кількість як есенціальних макроелементів, так і тих стабільних і радіоактивних природних ізотопів, які, будучи антропогенними забруднювачами, можуть за підвищених концентрацій бути токсичними для людини [12]. Особлива роль належить грибам у процесах міграції радіоактивного цезію у ґрунтах лісових екосистем [13]. ...
... Незважаючи на важливість радіоекологічних функцій грибів у лісових системах [1,13], причини та механізми, що пояснювали би високі концентрації цього радіонукліду у грибах, порівняно з рослинами, залишаються недостатньо вивченими. Крім радіоцезію, гриби також ефективно накопичують у своїх плодових тілах лужні елементи: калій (K), рубідій (Rb) і стабільний цезій ( 133 Cs) [5,8]. ...
У статті узагальнено результати кількісної оцінки вмісту лужних і лужноземельних металів, а також окремих актиноїдів у вільноростучому міцелії ектомікоризних грибів верхніх (0–10 см) шарів ґрунту бореальних лісових екосистем Швеції. Досліджено та порівняно вміст цих елементів у загальній масі ґрунту, ризоплані, ризосфері та плодових тілах грибів. У згаданих фракціях було досліджено вміст і дано порівняльну оцінку калію (K), рубідію (Rb), стабільного цезію ( 133 Cs), радіоактивного цезію ( 137 Cs), кальцію (Ca), стронцію (Sr), а також торію (Th) та урану (U). Показано, що у грибниці може бути локалізовано до 50 % (у середньому ≈ 15 %) радіонукліду від загального його вмісту в даному шарі ґрунту. Плодові тіла грибів містять приблизно на порядок меншу частку радіонукліду – не більше 0,12 % від загальної кількості радіоцезію, зосередженого у надземній фітомасі лісових рослин. Крім радіоактивного цезію, всі три лужні метали – K, Rb та 133 Cs також активно накопичуються як міцелієм грибів, так і їхніми плодовими тілами. Концентрація калію в міцелії грибів у 4–5, а у плодових тілах ≈ у 70 разів перевищує вміст цього елемента в загальній масі ґрунту – едафосфері. Вміст рубідію у міцелії грибів перевищує його вміст у ґрунті у 3,5 разу, а у їхніх плодових тілах – майже у 70 разів. Концентрація стабільного цезію у міцелії грибів та їхніх плодових тілах перевищує його вміст в едафосфері майже у 3 та 20 разів відповідно. У той же час гриби не накопичують лужноземельні метали Ca і Sr – у міцелії грибів та едафосфері концентрація цих елементів приблизно однакова. Концентрація актиноїдів (Th та U) у міцелії грибів є помітно нижчою, ніж в едафосфері. Встановлено, що у міцелії грибів може бути зосереджено від ≈ 2 % (Th) до ≈ 27 % (К) від загального вмісту елемента у верхньому (0–10 см) шарі лісового ґрунту.
... Only rarely has the stalk been found to have more radiocaesium than the cap or gills (Heinrich, 1993). Fungal mycelium in soil can accumulate a significant percentage of the radiocaesium content of soil (Olsen et al., 1990;Vinichuk and Johansson, 2003). Some species of arbuscular mycorrhizal fungi, in symbiosis with a host plant, can reduce the uranium uptake by roots, potentially suggesting a uranium accumulation by mycelium (Dupr e de Boulois et al., 2008). ...
... Mycelium has been reported to be able to accumulate a significant percentage of total radiocaesium inventory in soil (range 0.1e50%, mean value 15%) (Vinichuk and Johansson, 2003). The mycelium production in the upper 10 cm of soil in Swedish forests was reported to be about 200 kg dm/(ha $ y) with a range of Table 1 Mean values of mass and dimensions of different species of fungi, which were used to develop fungi and mycelium geometries in ERICA Tool. ...
... This value was converted into a fresh mass mycelium concentration in soil, assuming 1 year mycellium production, a soil depth of 10 cm, soil density of 1.5 g dm/cm 3 , and an assumed dry/fresh ratio for mycelium of 0.10 g dm/g fm. Thus, 200 kg dm/(ha$y) would be equivalent to 1.3$10 À3 kg fm mycelium/kg soil, which is within the range of fungal mycelium in soil reported by Vinichuk and Johansson (2003). The radiocaesium mycelium concentration was estimated using equation (2) assuming the mean percentage of soil Cs in mycelium as reported by Vinichuk and Johansson (2003). ...
Fungi are used as biomonitors of forest ecosystems, having comparatively high uptakes of anthropogenic and naturally occurring radionuclides. However, whilst they are known to accumulate radionuclides they are not typically considered in radiological assessment tools for environmental (non-human biota) assessment. In this paper the total dose rate to fungi is estimated using the ERICA Tool, assuming different fruiting body geometries, a single ellipsoid and more complex geometries considering the different components of the fruit body and their differing radionuclide contents based upon measurement data. Anthropogenic and naturally occurring radionuclide concentrations from the Mediterranean ecosystem (Spain) were used in this assessment. The total estimated weighted dose rate was in the range 0.31–3.4 μGy/h (5th–95th percentile), similar to natural exposure rates reported for other wild groups. The total estimated dose was dominated by internal exposure, especially from ²²⁶Ra and ²¹⁰Po. Differences in dose rate between complex geometries and a simple ellipsoid model were negligible. Therefore, the simple ellipsoid model is recommended to assess dose rates to fungal fruiting bodies. Fungal mycelium was also modelled assuming a long filament. Using these geometries, assessments for fungal fruiting bodies and mycelium under different scenarios (post-accident, planned release and existing exposure) were conducted, each being based on available monitoring data. The estimated total dose rate in each case was below the ERICA screening benchmark dose, except for the example post-accident existing exposure scenario (the Chernobyl Exclusion Zone) for which a dose rate in excess of 35 μGy/h was estimated for the fruiting body. Estimated mycelium dose rate in this post-accident existing exposure scenario was close to the 400 μGy/h benchmark for plants, although fungi are generally considered to be less radiosensitive than plants. Further research on appropriate mycelium geometries and their radionuclide content is required. Based on the assessments presented in this paper, there is no need to recommend that fungi should be added to the existing assessment tools and frameworks; if required some tools allow a geometry representing fungi to be created and used within a dose assessment.
... Науковий інтерес до вивчення грибів виявляється у тому числі і через здатність останніх до вибіркового поглинання елементів, небезпечних для людини. Добре відома здатність грибів накопичувати радіонукліди [16]), у тому числі і природні радіоізотопи [2]. Плодові тіла багатьох видів макроміцетів можуть містити важкі метали, у тому числі і кадмій, який накопичується грибами найінтенсивніше [9]. ...
... Переважна частина біомаси тіла гриба (міцелій) міститься у верхніх, багатих на органічну речовину шарах лісового ґрунту. Здатність міцелію грибів накопичувати елементи, у тому числі радіоізотопи, досліджена недостатньо [16]. Відомі лише декілька праць, у яких зроблено спроби проаналізувати вміст мікроелементів у міцелії грибів, що зростають у природних умовах [3; 13]. ...
... Приготовлений у такий спосіб зразок містив різні форми міцелію: окремі ниткоподібні відгалуження гриба, міцеліальні тяжі, ризоморфи, окремі склероції та невелику кількість інфікованих мікоризних кінчиків коренів. Метод вилучення міцелію наведено у Vinichuk & Johanson [16]. Із ґрунтових зразків вилучали фракції ґрунту відповідно до методики, наведеної у Gorban & Clegg [6]. ...
The content of thorium (Th) and uranium (U) in fractions of soil edaphosphere, rhizosphere, rhizoplane, fungal mycelium and fruit bodies were investigated. The concentrations of thorium in edaphosphere and rhizosphere fractions and mycelia of fungi are not different significantly and vary in the range of 0.74–1.45 mg kg–1 dry matter. The concentration of thorium in the rhizoplane fraction is 4 times lower than in the bulk soil – edaphosphere. The concentrations of uranium in edaphosphere, rhizosphere and rhizoplane fractions and fungi mycelium are not significantly different and vary between 3.11 and 9.36 mg kg–1 dry matter. The content of the studied natural isotopes in fruit bodies of fungi is 270 times lower than in the bulk soil: biological absorption coefficients of uranium and thorium in fruit bodies are on average 0.035 and 0.006, respectively. The contents of thorium and uranium in fungal mycelium and fruit bodies increase with increasing their concentrations in the soil. It is shown that in the fungi mycelium of the upper (0–5 cm) layer of forest soil can be allocated 2.0–5.0 and 1.4–2.7 % of the total thorium and uranium soil content, respectively.
... Soil-fungi-plant transfer is the first step by which 137 Cs enters food chains in forest ecosystems. The behavior of 137 Cs in forest ecosystems differs substantially from other ecosystems, due to the abundance of fungal mycelia in soil, which contribute to the persistence of Chernobyl radiocesium in the upper horizons of forest soils (Vinichuk & Johanson, 2003). In the microbial biomass in boreal forest soil, fungi are dominant. ...
... The presence of single strains of saprotrophic fungi in organic matter considerably enhances the retention of Cs in organic systems, with ≈ 70% of the Cs spike being strongly (irreversibly) bound (remains non-extractable) (Parekh et al. 2008), compared to only ≈ 10% in abiotic (sterilized) systems. Chapter 2 Cesium ( 137 Generally, fungal mycelium contains a substantial amount of radiocesium: up to 50% of the total 137 Cs may be located within the upper 0-10 cm layers in Swedish and Ukrainian forest soils (Vinichuk & Johanson, 2003, Vinichuk et al. 2004). In terms of the total radiocesium within a forest ecosystem, fungal sporocarps contain a relatively little and may only account for about 0.5 % (McGee et al. 2000) or even less − 0.01 to 0.1% ) of the total radiocesium deposited within a forest ecosystem. ...
... Although activity concentration in sporocarps is probably higher than in mycelium (Vinichuk & Johanson, 2003, Vinichuk et al. 2004, sporocarps constitute only about 1% of the total mycelia biomass in a forest ecosystem. ...
Introduction
This study focuses on the distribution of radiocesium (137Cs) and selected metals in soil fractions and soil fungi of boreal forest ecosystems. The accumulation of selected metals in soil fractions: bulk soil, rhizosphere, soil-root interface and fungal mycelium and sporocarps of mycorrhizal fungi were compared in a Swedish forest. Special attention is given to radiocesium released into the environment as a result of nuclear weapons testing and the Chernobyl accident in 1986, and alkali metals, potassium (K), rubidium (Rb), and cesium
(133Cs), whose chemical behavior can be expected to be similar to 137Cs. The behavior of 137Cs in forest ecosystems differs from other ecosystems due to the abundance of fungal mycelia in soil, which contribute to the persistence of the Chernobyl radiocesium in the upper horizons of forest soils, as the fungi enhance uptake of these elements into host plants. Even many years after fallout, people in Sweden consume wild fungi and game obtained from these contaminated forests. Substantial research has been conducted in Sweden after the fallout from nuclear weapons testing and the Chernobyl accident and some results presented in this book are published in a series of several articles and book chapters in collaboration with Profs K. J. Johanson, H. Rydin, and Dr. A. Taylor (Vinichuk et al. 2004; 2010a; 2010b; 2011a; 2011b). Fungi are effective in accumulating a wide range of metals, as well as radioactive isotope 137Cs. Many trace elements, including some micronutrients, such as mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), nickel (Ni), and cobalt (Co) are generally considered the most toxic, and numerous studies indicate accumulation of metals by fungal sporocarps (Mietelski et al. 2002; Campos et al. 2012). However, the contribution of wild growing mycelia and soil fractions, such as the rhizosphere and soil-root interface, with metal accumulation and distribution
within forest soil is not well studied. Therefore, we attempted to quantify the Introduction VI uptake and distribution of selected metals in the soil-mycelium-sporocarps compartments in various transfer steps: bulk soil, rhizosphere, soil-root interface, fungal mycelium, and sporocarps. The relationships between the concentrations of metals studied in bulk soil, soil mycelia, and fungal sporocarps were estimated. The 137Cs activity concentration and mass concentration of alkali metals K, Rb, and 133Cs were also analyzed within individual Sphagnum plants (down to 20 cm depth) in boreal ombrotrophic bogs in the northern hemisphere. The distribution of Cs (133Cs and 137Cs), K, and Rb in the uppermost capitulum and subapical segments of Sphagnum mosses were compared to determine the possible mechanisms involved in radiocesium uptake and retention within Sphagnum plants. This book attempts to summarize the knowledge acquired from studies within Sweden and to place them in a larger context, and to update data on metals concentrations in fungal compartments of forest soil, especially in wild growing mycelium. The discussion of the summarized results addresses the issues of radiocesium (137Cs) activity concentrations, K, Rb, and stable 133Cs concentrations in soil fractions, fungal compartments and Sphagnum plants (Chapter 2); alkali Earth metals calcium (Ca) and strontium (Sr) (Chapter 3); transition metals chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), Mercury (Hg), and lead (Pb) (Chapter 4); semimetals arsenic (As) (Chapter 5); and, actinides thorium (Th) and uranium (U) (Chapter 6).
... A thorough investigation of each transfer step in the process is essential (Clint and Dighton, 1992;Dupré de Boulois et al., 2008). Numerous factors influence 137 Cs uptake by mushrooms, such as distribution and density of fungal mycelia (Giovani et al., 1990;Kammerer et al., 1994), soil or substrate with its characteristics which also vary in depth (such as soil organic matter content and pH) (Guillitte et al., 1994;Yoshida and Muramatsu, 1994;Rühm et al., 1997), forest type and fruit body location (Grueter, 1964;Andolina and Guillitte, 1990;Vinichuk and Johanson, 2003) or trophic status (saprotrophic, parasitic or mycorrhizal). Often, a higher 137 Cs concentration is detected in mycorrhizal mushrooms, if compared to saprotrophic or parasitic ones (Guillitte et al., 1994;Kammerer et al., 1994;Yoshida and Muramatsu, 1994;Gillet and Crout, 2000). ...
... Due to a large range of 137 Cs activities found in mushrooms within the same group, especially mycorrhizal, the comparison between two very common ectomycorrhizal fungi -Boletus sp. and Hydnum repandum was made. Boletus mushrooms express high affinity for Cs (Heinrich, 1993;Kammerer et al., 1994;Toal et al., 2002;Vinichuk and Johanson, 2003;Řanda and Kučera, 2004), while some studies declare Hydnum repandum as one of the greatest Cs accumulators among mushrooms (Heinrich, 1993;Kammerer et al., 1994;García et al., 2015). As emphasized in previous studies (Mietelski et al., 1994;Shutov et al., 1996;Skuterud et al., 1997;Kalač, 2001), it should be indicated that in case of elevated 137 Cs activity in mushrooms, the annual dose due to their consumption should not be neglected. ...
The aim of this study was to select species with higher potential to accumulate (137)Cs among the available mushroom species, by determining the activity concentrations of (137)Cs in mushrooms collected along north and north-western part of Croatia. A total of 55 samples of 14 different species were analyzed and the potential of mycorrhizal and saprotrophic species to accumulate (137)Cs was compared. A wide range of the dry weight activity concentrations of (137)Cs was detected, ranging from 0.95 to 1210 Bq/kg (154 Bq/kg mean value; 52.3 Bq/kg geometric mean) in mycorrhizal and 1.05-36.8 Bq/kg (8.90 Bq/kg mean value; 5.49 Bq/kg geometric mean) in saprotrophic species. Statistical analyses showed that mycorrhizal species accumulate significantly higher concentrations of (137)Cs and thus could perform better as long-term bioindicators of environmental pollution by radiocaesium then saprotrophic species. The comparison of Boletus sp. and Hydnum repandum (both mycorrhizal species commonly found in Croatia) showed, in general order of magnitude, higher accumulation in Hydnum repandum. Clearly, mushrooms, especially mycorrhizal species, can be used as significant indicators even decades after the occurrence of any serious (137)Cs contamination event. However, as a wide range of values indicates that various parameters may influence the total uptake of the (137)Cs into the mushroom fruit bodies, it is necessary to emphasize that (137)Cs activity detected in a single mushroom sample is very site-specific.
... A thorough investigation of each transfer step in the process is essential (Clint and Dighton, 1992;Dupré de Boulois et al., 2008). Numerous factors influence 137 Cs uptake by mushrooms, such as distribution and density of fungal mycelia (Giovani et al., 1990;Kammerer et al., 1994), soil or substrate with its characteristics which also vary in depth (such as soil organic matter content and pH) (Guillitte et al., 1994;Yoshida and Muramatsu, 1994;Rühm et al., 1997), forest type and fruit body location (Grueter, 1964;Andolina and Guillitte, 1990;Vinichuk and Johanson, 2003) or trophic status (saprotrophic, parasitic or mycorrhizal). Often, a higher 137 Cs concentration is detected in mycorrhizal mushrooms, if compared to saprotrophic or parasitic ones (Guillitte et al., 1994;Kammerer et al., 1994;Yoshida and Muramatsu, 1994;Gillet and Crout, 2000). ...
... Due to a large range of 137 Cs activities found in mushrooms within the same group, especially mycorrhizal, the comparison between two very common ectomycorrhizal fungi -Boletus sp. and Hydnum repandum was made. Boletus mushrooms express high affinity for Cs (Heinrich, 1993;Kammerer et al., 1994;Toal et al., 2002;Vinichuk and Johanson, 2003;Řanda and Kučera, 2004), while some studies declare Hydnum repandum as one of the greatest Cs accumulators among mushrooms (Heinrich, 1993;Kammerer et al., 1994;García et al., 2015). As emphasized in previous studies (Mietelski et al., 1994;Shutov et al., 1996;Skuterud et al., 1997;Kalač, 2001), it should be indicated that in case of elevated 137 Cs activity in mushrooms, the annual dose due to their consumption should not be neglected. ...
Mathematical efficiency calibrations for the specific matrices such as honey and borosilicate filters are performed. Their reliability is experimentally tested. The influence of the choice of the matrix composition in the mathematical calibration on the results is investigated. After the verification of the mathematical models, the results for activity concentrations in the test samples are presented.
... A substantial (up to 70%) part of 137 Cs activity may be bound within organic matter (Koarashi et al., 2019), additionally, up to 50% of the total 137 Cs activity may be retained within fungal mycorrhizal structures (Vinichuk and Johanson, 2003) and forest vegetation (McGee et al., 2000). This fraction of 137 Cs activity becomes available for plant uptake due to recycling of 137 Cs in the organic surface horizons and transformation of litter within the F-layer (Mensah et al., 2021). ...
The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces 137Cs uptake by forest plants many years after the radionuclide fallout. The effects of one-time point fertilisation with 137Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on 137Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012-2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between 137Cs uptake by species and years. Soil amendment with 137Cs-contaminated wood ash generally did not affect 137Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased Tag for 137Cs in the following years. The effect of a single application of 137Cs-uncontaminated wood ash on reducing 137Cs uptake by plants was generally negligible. Application of 137Cs-contaminated wood ash in combination with KCl reduced plant 137Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to 137Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce 137Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.
... We hypothesize that biological processes such as fungal activity may be associated with the soil-to-air emission of radionuclides deposited over the soil surface from the F1NPP accident [3,16,19]. Fungi can uptake various nutrient metal ions including potassium and radioactive Cs from soil surface using the fungal network system [20][21][22]. Fungi accumulate radioactive Cs due to the uptake similar to potassium, which is known because of the experiences of contaminations by weapon tests' global fallout and because of the Chernobyl accident [14,23]. ...
Even after 7 years of the nuclear accident that occurred in 2011 at the Fukushima Dai-ichi nuclear power plant (F1NPP), high levels of 137Cs have been detected in ambient aerosols from some polluted areas of Fukushima. Higher levels of radionuclides were often observed in the atmosphere during and after rain events. We presume that biological processes such as fungal activity associated with higher relative humidity may be involved with a possible emission of radioactivity to the atmosphere, which was originally emitted from the F1NPP accident and was deposited over the ground, forest, soil, etc. Here, we report, for the first time, relationships of 137Cs and organic tracers of fungal spores (i.e., arabitol, mannitol and trehalose) in the aerosol samples collected from Fukushima, Japan. Although we found twice-higher concentrations of 137Cs at nighttime than at daytime, fungal spore tracers did not show a consistent trend to 137Cs, that is, organic tracers at nighttime were similar with those at daytime or were even higher in daytime. This study has not clearly demonstrated that fungal spores are the important source of high levels of 137Cs at nighttime. The current unclear relationship is probably associated with the sampling strategy (four consecutive days with a sampling on/off program for day/nighttime samples) taken in this campaign, which may have caused a complicated meteorological situation.
... For example, radionuclide levels and their localization in fruiting bodies have been analyzed in various fungal species (Nakajima and Sakaguchi, 1993;Dighton et al., 2008). Others have investigated the transfer factors of radionuclides from the soil into fruiting bodies Bazała et al., 2008), with additional studies detailing the radionuclide binding potential of living or dead fungal mycelium (Gray et al., 1996;Vinichuk and Johanson, 2003;Bishnoi, 2005;Vázquez-Campos et al., 2015). Indeed, fungal mycelium tend to grow vigorously in soil, thus providing a large surface area for interacting with radionuclides and increasing the possibility for soil-plant transfer. ...
After the Chernobyl and Fukushima incidents it has become clear that fungi can take up and accumulate large quantities of radionuclides and heavy metals, but the underlying processes are not well understood yet. For this study, the molecular interactions of uranium(VI) with the white-rot fungi, Schizophyllum commune and Pleurotus ostreatus, and the soil-living fungus, Leucoagaricus naucinus, were investigated. First, the uranium concentration in the biomass was determined by time-dependent bioassociation experiments. To characterize the molecular interactions, uranium was localized in the biomass by transmission electron microscopy analysis. Second, the formed uranyl complexes in both biomass and supernatant were determined by fluorescence spectroscopy. Additionally, possible bioligands in the supernatant were identified. The results show that the discernible interactions between metals and fungi are similar, namely biosorption, accumulation, and subsequent crystallization. But at the same time, the underlying biochemical mechanisms are different and specific to the fungal species. In addition, Schizophyllum commune was found to be the only fungus that, under the chosen experimental conditions, released tryptophan and other indole derivatives in the presence of uranium(VI) as determined by nuclear magnetic resonance spectroscopy. These released substances most likely act as messenger molecules rather than serving the direct detoxification of uranium(VI).
... It was observed (Vinichuk and Johanson 2003), that the 137 Cs levels tend to be lower in the underground ECM fungal mycelia than in the above-ground fruiting bodies. Heinrich (1992) noted that the stems and caps or fruiting mushrooms bodies are richer in 137 Cs as compared to their mycelium. ...
PhD thesis was carried out in the Institute of Environmental Sciences in Plant-Microbial Interactions Research team under the supervision of Prof. Dr. hab. Katarzyna Turnau.
The role of arbuscular mycorrhizal (AM) fungi on the acquisition of radiocaesium by plants remains poorly understood and controversial. The lack of clear results on the capacity of AM fungi to accumulate or transport Cs could be principally attributed to different and inadequate experimental systems used in previous studies. Also, the concentration of potassium in the soil could have interfered with the capacity of AM fungi to accumulate or transport Cs. Furthermore, the various AM fungi and plants studied could also explain the controversial conclusions obtained, since AM fungi and plants have probably different capacity to accumulate and transport radiocaesium. As a consequence, it was successively suspected that AM fungi could accumulate radiocaesium in their extraradical or intraradical structures, transport Cs to their hosts and influence on its distribution among plant roots/shoots.
The objectives of this work were therefore to identify:
˗ the capacity of AM fungi to take up and transfer caesium isotopes to their hosts;
˗ the influence of arbuscular mycorrhiza on radioactive and stable caesium uptake by plants;
˗ the impact of AM fungi on plant vitality under stress condition;
˗ the influence of caesium isotopes on plant mycorrhizal colonization;
˗ the influence of AM fungi on radiocaesium root to shoot translocation;
˗ the capacity of AM fungi to accumulate Cs isotopes in their extraradical and intraradical structures, and
˗ to estimate the possibility of AM fungal symbionts application in phytoremediation strategies.
... These results suggest that the proportion of mushroom samples with radiocesium concentrations above 100 Bq/kg did not dramatically change in Fukushima over 8 years. Radiocesium concentrations in mushrooms can be affected by many factors of forest, such as species, mycelium habitat and depth, minerals in the soil and contamination level of soil [6,[26][27][28]. Long-term comprehensive follow-up should be conducted because the existing data is insufficient to characterize risk. ...
Following the Fukushima Daiichi Nuclear Power Plant accident in March 2011, radionuclides such as iodine-131, cesium-134 and cesium-137 were released into environment. In this study, we collected wild mushrooms from the Kawauchi Village of Fukushima Prefecture, located less than 30 km southwest of the Fukushima nuclear power plant, to evaluate their radiocesium (¹³⁴Cs+¹³⁷Cs) concentrations and the risk of internal radiation exposure in local residents. 342 mushroom samples were collected from 2016 to 2019. All samples were analysed for radiocesium content by a high–purity germanium detector. Among 342 mushroom samples, 260 mushroom samples (76%) were detected the radiocesium exceeding the regulatory limit of radiocesium (100 Bq/kg for general foods in Japan). The median of committed effective dose from ingestion of wild mushrooms was in the range of 0.015–0.053 mSv in 2016, 0.0025–0.0087 mSv in 2017, 0.029–0.110 mSv in 2018 and 0.011–0.036 mSv in 2019 based on the assumption that Japanese citizens consumed wild mushrooms for 1 year. Thus, our study showed that although radiocesium is still detected in mushrooms collected in Kawauchi village even after 5 to 9 years later, the committed effective dose due to consuming mushrooms was lower than 1 mSv per year. Long-term comprehensive follow-up should monitor radiocesium concentrations in wild mushrooms to support the recovery of the community after the nuclear disaster.
... At 2 years after the accident, more than 75% of the deposited 137 Cs accumulated in the forest floor [12]. 137 Cs in the forest floor has been retained in the top soil [13][14][15][16] due to strong adsorption/fixation by clay minerals [3] and assimilation by fungal mycelium [17,18]. This strong association leads to 137 Cs mobilization via soil erosion. ...
Changes in ¹³⁷Cs export over time following clearcutting were investigated in a Japanese forested catchment affected by the Fukushima nuclear accident. A total of 13% of the catchment area was clear-cut 2 years after the accident. Annual suspended solids (SS) export at the catchment outlet increased 1.4 to 2.0 times after clearcutting; however, ¹³⁷Cs export increased slightly (up to 1.1 times), corresponding to 0.21% to 0.30% of the ¹³⁷Cs inventory in the catchment. The smaller change in ¹³⁷Cs export than in SS export was due to a rapid decrease in the activity concentration following clearcutting. This decrease was likely caused by both natural attenuation and SS derived from sources with a low activity concentration in the clear-cut area. Monitoring of the sediment transport from hillslopes in small-scale experimental plots showed that the ¹³⁷Cs yield in the skid trail was 3.6 to 21 times greater than those in clear-cut and unlogged forest floors. This significant ¹³⁷Cs transport was due to greater soil erosion (by up to two orders of magnitude) along the skid trail, despite the lower activity concentration than those in the other plots. This indicates that while skid trails were involved in the rapid decrease of the activity concentration of SS, they were a potential source of the increased export of ¹³⁷Cs and SS. Net ¹³⁷Cs export increased by clearcutting (the export excluding the decrease accompanied by natural attenuation) was estimated to account for only 0.092% of the inventory in the catchment for 2.5 years. These results imply that the impact of clearcutting on ¹³⁷Cs export was temporary in this catchment.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
This open access book presents the findings from on-site research into radioactive cesium contamination in various agricultural systems affected by the Fukushima Daiichi Nuclear Power Plant accident in March 2011. This third volume in the series reports on studies undertaken at contaminated sites such as farmland, forests, and marine and freshwater environments, with a particular focus on livestock, wild plants and mushrooms, crops, and marine products in those environments. It also provides additional data collected in the subsequent years to show how the radioactivity levels in agricultural products and their growing environments have changed with time and the route by which radioactive materials entered agricultural products as well as their movement between different components (e.g., soil, water, and trees) within an environmental system (e.g., forests). The book covers various topics, including radioactivity testing of food products; decontamination trials for rice and livestock production; the state of contamination in, trees, mushrooms, and timber; the dynamics of radioactivity distribution in paddy fields and upland forests; damage incurred by the forestry and fishery industries; and the change in consumers’ attitudes. Chapter 19 introduces a real-time radioisotope imaging system, a pioneering technique to visualize the movement of cesium in soil and in plants. This is the only book to provide systematic data on the actual change of radioactivity, and as such is of great value to all researchers who wish to understand the effect of radioactive fallout on agriculture. In addition, it helps the general public to better understand the issues of radio-contamination in the environment. The project is ongoing; the research groups from the Graduate School of Agricultural and Life Sciences of The University of Tokyo continue their work in the field to further evaluate the long-term effects of the Fukushima accident.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
On June 28, 2011, 26 pigs were rescued from the alert area, 17 km northwest of the Fukushima Daiichi Nuclear Power Plant, where radiation levels were approximately 1.9–3.8 μSv/h. The pigs were transferred outside of the radiation alert area to the Animal Resource Science Center (ARSC), The University of Tokyo. It was confirmed by the farm owner that the pigs were never fed radiation-contaminated concentrate and they had access to uncontaminated groundwater (http://www.env.go.jp/press/press.php?serial=16323) while living inside the radiation alert area; however, radiocesium was detected in the rescued pigs’ organs, testis/ovary, spleen, liver, kidney, psoas major, urine, and blood, within nine months after the nuclear disaster. Radiocesium levels in samples collected in early January 2012 were significantly lower than those collected in either early or late September 2011, indicating a continuing decrease in radiation levels over that duration. Radiocesium was not detected in organs collected in August 2012. In September 2011, the authors of the present study visited a local farm to collect samples from pigs who remained inside the radiation alert area. Radiocesium concentration in these pigs was nearly ten times higher than from the rescued pigs.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
Radioactive materials, primarily radiocesium (134Cs + 137Cs), were released into the environment by the Fukushima Daiichi Nuclear Power Plant accident in March 2011. The percentage of soybean plants that had a concentration of radiocesium over 100 Bq/kg was higher than that of other crops. To examine the reason why the concentration of radiocesium in soybeans was high, its concentration and distribution in seeds were analyzed and compared to rice. Potassium fertilization is one of the most effective countermeasures to reduce the radiocesium uptake by soybean and nitrogen fertilizer promotes soybean growth. To use potassium and nitrogen fertilizers safely and efficiently, applied potassium behavior in soil and the effect of nitrogen fertilizer on radiocesium absorption in soybean were studied.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
We have investigated the redistribution dynamics of radiocesium deposited after the nuclear power station accident in March 2011 in a forested catchment located in North Fukushima over a four-year period (2012–2015). At the catchment scale, 137 Cs accumulation decreased drastically by 50% of the estimated initial accumulation during the first 2 years. Cs-137 accumulation in the forest floor occurred in the litter layers and the surface part of mineral soils and have accounted for about 90% of the total catchment scale accumulation. The internal 137Cs cycle among the soil-plant system was also identified as a retention mechanism and was biologically dynamic. Monitoring the decreasing and retaining mechanisms of radioactivity at the ecosystem scale will be required for effective forest and water resource management.Keywords
37CsInventoryEnvironmental half-lifeForest ecosystemInternal cycleFukushima
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
We aimed to develop a rapid and sensitive method to analyze the radioactivity of ⁹⁰Sr by combining multiple techniques, including online solid-phase extraction (SPE) and inductively coupled plasma mass spectrometry (ICP-MS). An automatic analytical system was designed to execute the proposed process from sample injection to measurement. The analysis time is approximately 20 min and the limit of detection is 0.3 Bq/L (equivalent to 0.06 pg/L) with 50 mL of the sample. Although several challenges were encountered with the ICP-MS measurements of ⁹⁰Sr, several techniques were leveraged to overcome them. Online solid-phase extraction (SPE) was used to concentrate the sample automatically; the interference from polyatomic ions and isobars was removed by an oxidation, and the extraction and recovery ratio of solid phase were measured by split-flow injection with internal standard correction during the transient signal measurement. These improvements were shown to allow measurements of ⁹⁰Sr in various kinds of samples to be conducted more quickly than by alternative conventional radiometric methods.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
Immediately after the Fukushima nuclear plant accident (FNPA), 40–50 researchers at the Graduate School of Agricultural and Life Sciences, the University of Tokyo, analyzed the behavior of the radioactive materials in the environment, including agricultural farmland, forests, rivers, etc., because more than 80% of the contaminated land was related to agriculture. Since then, a large number of samples collected from the field were measured for radiation levels at our faculty. A feature of the fallout was that it has hardly moved from the original point contaminated. The fallout was found as scattered spots on all surfaces exposed to the air at the time of the accident. The adsorption onto clay particles, for example, has become firm with time so that it is now difficult to be removed or absorbed by plants. 137Cs was found to bind strongly to fine clay particles, weathered biotite, and to organic matter in the soil, therefore, 137Cs has not mobilized from mountainous regions, even after heavy rainfall. In the case of farmland, the quantity of 137Cs in the soil absorbed by crop plants was small, and this has been confirmed by the real-time imaging experiments in the laboratory. The downward migration of 137Cs in soil is now estimated at 1–2 mm/year. The intake of 137Cs by trees occurred via the bark, not from the roots since the active part of the roots is generally deep within the soil where no radioactive materials exist. The distribution profile of 137Cs within trees was different among species. The overall findings of our research is briefly summarized here.Keywords
137CsFukushima nuclear plant accidentAgricultureSoilPlantForest
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
The eastern area of Fukushima Prefecture, where the Fukushima Daiichi nuclear power plant is located, is covered mainly with weathered granitic soil originated from the geology of this area. Weathered biotite (WB), or partially to almost vermiculitized biotite, is abundant in the soil. WB has frequently been found as radioactive soil particles sorbing radiocesium and has been identified as “bright spots” by autoradiography. Laboratory experiments using the ¹³⁷Cs radioisotope indicated that WB collected from Fukushima sorbed ¹³⁷Cs far more efficiently than other clay minerals from ¹³⁷Cs solutions whose concentration was comparable to that expected for the radioactive contamination in Fukushima. This supports the abundance of radioactive WB particles in the actual contaminated soil. The Cs-desorption property of WB was also different from those of other minerals. If the period of immersion in the Cs solution was more than a few weeks, the sorbed Cs in the WB were hardly desorbed by ion-exchange with any electrolyte solutions. These results imply that decontamination of the radioactive soils is difficult if using “mild” chemical treatments and that most radioactive Cs are now fixed stably (dare one say “safely”) by WB in the soil of the Fukushima area.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
The recovery of Fukushima fisheries remains sluggish 6 years after the disaster. The Fukushima Fisheries Cooperative Association (FCA) decided to allow limited fishing in June 2012 (known as the trial operation). Total landing value of fish and fishery products from the trial operation has been gradually increasing due to the increased number of catchable target species and increased fishing areas. But the landing value in 2016 was only 5% of the value recorded in the pre-disaster years. Safety of the products has been demonstrated by various surveys conducted by the government authorities and independent researchers. Several studies indicated that the population of key fish species in Fukushima waters showed a tangible increase after the 2011 disaster reflecting low fishing pressures in this period. Weak consumer confidence would have contributed to the extremely slow recovery of Fukushima fisheries. In addition to the consumers’ attitudes, fish distributors’ risk-averse attitudes could have brought additional adverse effects against the recovery of Fukushima fisheries. This situation could continue for several more years. Continued support for fishers in Fukushima is needed for the foreseeable future to sustain the livelihood of small fishing households as well as maintain societies, traditional knowledge, and other human or social capital in the region.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
Although Lake Kasumigaura stores twice as much radiocesium compared to the direct fallout onto the lake surface, the additional source of radiocesium has not been determined. The present study examined the major source of radiocesium deposited in the lake based on surveys of the dry beds of the rivers flowing into the lake. The basin of four rivers, two of which flow through an urbanized region and the other two through a rural region to Lake Kasumigaura, were selected. The radioactivity per unit area of the dry river bed and the top of the river bank was measured. On the dry river beds of the rivers flowing from the urbanized area, the deposition of radiocesium per unit area was found to be much higher than the direct fallout per unit area, revealing a considerable amount of radiocesium had been discharged from the urbanized upstream of the rivers by flooding events. On the other hand, rivers flowing from the rural area stored almost the same amount of radiocesium as the direct fallout. These observations revealed that the urbanized areas located upstream to Kasumigaura Lake were a major additional source of radiocesium contamination in the lake.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
Rice contaminated with high concentrations of radiocesium was found in some local areas after the nuclear accident in Fukushima Prefecture in 2011. Here we discuss the issues of cultivating rice in contaminated areas through our field experiments. The transfer of radiocesium to commercial rice has been artificially down-regulated by potassium fertilizer in radiocesium-contaminated areas in Fukushima. Since 2012, we have continued to cultivate rice experimentally in paddy fields under conventional fertilizer to trace the annual change of radiocesium uptake. The radiocesium concentration in rice cultivated under conventional fertilizer has seen almost no change since 2013. One of the reasons for this is that radiocesium fixation in soil has hardly progressed in these paddy fields.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
We have tested several ways to revitalize agriculture in Fukushima by developing farmland decontamination methods that farmers can undertake by themselves. As a result, the rice harvested in a test field passed the official inspection of Fukushima Prefecture in 2014. Despite the efforts of local people, we have not yet succeeded to dispel the anxieties in the general public who believe that Fukushima’s agricultural crops might contain radioactive cesium. Such “harmful rumors” are hampering the recovery of local agriculture in Fukushima. In this chapter, we review the challenges of agricultural land remediation and renewal of agriculture from a collaboration between researchers and a non-profit organization (NPO) and propose the scenario for the recovery of local agriculture and village life.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
In this chapter, we introduce the effects of radiocesium released by the Fukushima Daiichi nuclear accident on fruit trees, especially the change of radiocesium in fruit during the past 6 years. We investigated radiocesium and ⁴⁰K in peach during the maturity of its fruit chronologically for 6 years. In the investigation during one crop period, the concentration of radiocesium in young fruit 15 days after the full bloom was the highest, and this result was common in all the investigated years. After that, the concentration of radiocesium decreased as the fruit became bigger; the decrease until 60 days after the full bloom was considerable. This tendency was also common among all investigations conducted until 2016. Though the concentration of ⁴⁰K during the same period also decreased in the same way as radiocesium, the rate of the decrease from 15 to 30 days after the full bloom was different. When looking at the chronological transition, the concentration of radiocesium in harvested fruit decreased by one third every year from 2011 to 2013. However, such decrease could not be seen from 2014 to 2016. While the concentration in the harvested fruit tended to stop decreasing, the concentration in fruit 15 days after the full bloom tended to decrease over the years from 2012 to 2016. During the past 6 years, there was no year-over-year decrease in the concentration of ⁴⁰K in fruit. The reason why the transition of radiocesium in fruit varied according to their stage of maturity was because the difference in timing to use the tree’s nutrient reserves.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
Dynamics of radiocesium in wild mushrooms, especially in mycorrhizal fungi, in forest ecosystems were investigated for 5 years after the Fukushima nuclear accident, in relation to substrates such as litter, soil and wood debris. Some mushroom species contained a high level of radiocesium in the first or second year, and then the radiocesium content decreased. Changes in radiocesium activities were ambiguous for many other mushrooms. Radiocesium accumulation with time was not common contrary to expectations. Reduction of radiocesium activities in litter and increase in mushrooms and soils, i.e. transfer of radiocesium from litter to mushrooms and soils, was recognized in the first and second year, but it was not obvious in subsequent years. Radiocesium accumulated in several mushroom species, especially in mycorrhizal fungi, while radiocesium in the other mushrooms did not exceed those in the neighboring forest litter. Similar differences in radiocesium level among mushroom species were observed in relation to ⁴⁰K levels, though ¹³⁷Cs/⁴⁰K ratio in mushrooms was lower than in O horizon, but at the same level of the A horizon in general. These facts suggested differences in the mechanisms of cesium accumulation. Residual ¹³⁷Cs due to nuclear weapons tests or the Chernobyl accident still remained in mushrooms and soils. From the ratio of the past residual ¹³⁷Cs, it was suggested that the residual ¹³⁷Cs was tightly retained in the material cycles of forest mushroom ecosystem, whereas ¹³⁷Cs emitted from the Fukushima accident was still fluid.
... Another feature of fungi is the considerable proportion of 137 Cs in forest soil is retained by the fungal mycelia, and fungi are considered to prevent the elimination of radiocesium from ecosystems (Brückmann and Wolters 1994;Guillitte et al. 1994;Vinichuk and Johanson 2003;Vinichuk et al. 2005). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997;Steiner et al. 2002;Muramatsu 1994, 1996). ...
We have developed a real-time radioisotope imaging system (RRIS) to visualize ion transport in plants, and to measure radioactivity in living plants. To know the mechanisms of ion transport in plants, the use of living plants allows us to visualize ion movement in real time. In addition, the RRIS can analyze how a change to the plant environment affects ion transport. In this chapter, we will introduce some of the applications of the RRIS. We analyzed the effect of light on cesium, potassium, magnesium, phosphate, and calcium transport in plants using the RRIS. The results show that magnesium, potassium, and calcium transport in plants were not influenced by light. On the other hand, the amount of cesium and phosphate absorption in roots decreased after light-off. Moreover, the amount of phosphate transport from root to shoot also decreased after light-off.
... In contrast, some studies reported considerably higher concentration ratios of these radionuclides in fungi, e.g. 12-62 (Vinichuk and Johanson, 2003) or 14-16.7 (Lux et al., 1995) for 137 Cs and 0.39 for 239 Pu (Lux et al., 1995), but lower ones like 0.03 (Lux et al., 1995) for 90 Sr. Consequently, it is likely that the dose rates estimated for fungi in Table 1 can in fact be an order of magnitude higher, up to 10 Gy/h. ...
Ionizing radiation (IR) produces multiple types of damage to nucleic acids, proteins and other crucial cellular components. Nevertheless, various microorganisms from phylogenetically distant taxa (bacteria, archaea, fungi) can resist IR levels many orders of magnitude above natural background. This intriguing phenomenon of radioresistance probably arose independently many times throughout evolution as a byproduct of selective pressures from other stresses (e.g. desiccation, UV radiation, chemical oxidants). Most of the literature on microbial radioresistance is based on acute γ-irradiation experiments performed in the laboratory, typically involving pure cultures grown under near-optimal conditions. There is much less information about the upper limits of radioresistance in the field, such as in radioactively-contaminated areas, where several radiation types (e.g. α and β, as well as γ) and other stressors (e.g. non-optimal temperature and nutrient levels, toxic chemicals, interspecific competition) act over multiple generations. Here we discuss several examples of radioresistant microbes isolated from extremely radioactive locations (e.g. Chernobyl and Mayak nuclear plant sites) and estimate the radiation dose rates they were able to tolerate. Some of these organisms (e.g. the fungus Cladosporium cladosporioides, the cyanobacterium Geitlerinema amphibium) are widely-distributed and colonize a variety of habitats. These examples suggest that resistance to chronic IR and chemical contamination is not limited to rare specialized strains from extreme environments, but can occur among common microbial taxa, perhaps due to overlap between mechanisms of resistance to IR and other stressors.
... For humus, we considered that fungal biomass turnover in addition to chemical reactions in rhizosphere soil were potential sources of rCs recurrent removal from the unavailable pool towards the available pool. We considered that fungal mycelium may contain at least 15% of the total Cs inventory in humus in line with measurements made in forest ecosystems of Ukraine (Vinichuk and Johanson, 2003). Rhizospheric processes linked to potassium depletion and local acidification can lead to additional mobilization of rCs , with rhizospheric extraction rates as high as 8-23% in our soil conditions (Goor et al., 2007). ...
The management of vast forested zones contaminated by radiocesium (rCs) following the Chernobyl and Fukushima fallout is of great social and economic concern in affected areas and requires appropriate dynamic models as predictive or questioning tools. Generally, the existing radio-ecological models need less fragmented data and more ecological realism in their quantitative description of the rCs cycling processes. The model TRIPS (“Transfer of Radionuclide In Perennial vegetation Systems”) developed in this study privileged an integrated approach which makes the best use of mass balance studies and available explicit experimental data for Scots pine stands. A main challenge was the differentiation and calibration of foliar absorption as well as root uptake in order to well represent the rCs biocycling. The general dynamics of rCs partitioning was simulated with a relatively good precision against an independent series of observed values. In our scenario the rCs biological cycling enters a steady-state about 15 years after the atmospheric deposits. At that time, the simulations showed an equivalent contribution of foliage and root uptake to the tree contamination. But the root uptake seems not sufficient to compensate the activity decline in the tree. The initial foliar uptake and subsequent internal transfers were confirmed to have a great possible impact on the phasing of tree contamination. An extra finding concerns the roots system acting as a buffer in the early period. The TRIPS model is particularly useful in cases where site-specific integrated datasets are available, but it could also be used with adequate caution to generic sites. This development paves the way for simplification or integration of new modules, as well as for a larger number of other applications for the Chernobyl or Fukushima forests once the appropriate data become available. According to the sensitivity analysis that involves in particular reliable estimates of net foliar uptake as well as root uptake not disconnected from rCs exchange reactions in soil.
... They also suggested that low abundance of several fungal taxa sometimes contributes to decomposition processed in soil. Several studies have indicated the importance of mycelia on the accumulation of radiocesium in surface soils (Guillitte et al. 1994;Brückmann and Woters 1994;Vinichuk and Johanson 2003;Yoshida et al., 2004). Regarding the distribution of fine roots in soils under coniferous stands (Picea abies), Børja et al. (2008) found that the highest root biomass was in the upper soil layers (humus layer and upper portion of mineral soil). ...
Purpose
This study examined the current distribution and downward migration of ¹³⁷Cs in the humus horizon under temperate coniferous stands in the Czech Republic. Depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) were also traced to find any indication regarding the ¹³⁷Cs dynamics within the humus horizon.
Materials and methods
Soil (bulk soil) samples were collected manually from the uppermost down to a depth of 20 cm at three points situated 10–20 m apart in three locations diversely affected by the Chernobyl accident in 1986. Humus samples (about 6 cm in thickness) were separately collected at three points adjacent to the bulk soil sampling. The humus samples were divided into three fractions (upper, middle, and lower) denoted to Hu, Hm, and Hl, respectively, depending on their depths. Activity concentration of ¹³⁷Cs and the amount of alkali metals (K, Rb, and Cs) in each humus fraction were determined with gamma spectrometry and ICP spectrometry, respectively. Some properties (pH, density, SOM, and identification of clay minerals), of both bulk soils and humus horizons were also investigated.
Results and discussion
The highest activity concentration of ¹³⁷Cs (Bq kg⁻¹) appeared in the upper portion of the soil (mainly humus horizon) under three coniferous stands about 30 years after the Chernobyl accident. Increasing activity of ¹³⁷Cs (Bq) was found in the lower humus fraction (Hl, 4~6-cm depth range) with no appreciable amounts of clay minerals like illite and smectite in the investigated sites. The findings suggest that the fallout ¹³⁷Cs moves downward at a speed of 0.13~0.19 cm year⁻¹ with degrading organic matter within the humus horizon. Possible association of ¹³⁷Cs with alkali metals (K, Rb, and Cs) was suggested by depth distribution profiles of lithogenic alkali metals (K, Rb, and Cs) in humus.
Conclusions
The humus horizon under temperate coniferous stands plays an important role in retaining fallout ¹³⁷Cs for a long time. Comparing the depth distributions of the fallout radionuclide ¹³⁷Cs with the depth distributions of lithogenic alkali metals (K, Rb, and Cs) gives valuable information for clarifying mechanism of ¹³⁷Cs movement in humus. Further investigation is needed to elucidate mechanism of ¹³⁷Cs migration within humus horizon by tracing ¹³⁷Cs speciation and decomposing soil organic matter simultaneously.
... Автори дослідження [1] показали, що понад 40 % акумульованого радіоцезію зв'язано з гіфами, що переконливо свідчить про те, що у ґрунтах грибна біомаса може іммобілізувати значну кількість радіоцезію на невизначено довгий період. За даними, наведеними в [64], міцелій у верхньому органічному шарі ґрунту може містити до 50 % 137 Сs, локалізованого у 0-10-сантиметровому шарі лісових ґрунтів Швеції та України. Встановлено, що гриби здатні не лише безпосередньо зв'язувати або фіксувати радіонукліди, а й опосередковано впливати на форми, в яких вони знаходяться і переміщуються в лісових ґрунтах [3]. ...
This article rewiews literature and original data on radionuclides of natural and technogenous origin in wild-grown
macromycetes. Wild edible mushrooms from contaminated areas (as a result of the Chornobyl catastrophe) until now are
dangerous for health in the case of medicinal and food use. Taking into account the complex nature of radionuclides
contamination of wild macromycetes, the need for long-term radio-ecological monitoring is emphasized.
... Poland, 1991 (n = 106) 830 (80-2300) ( Grabowski et al. 1994) Poland, 1995 Ukraine, 29 km from the ChNPP, 1989 400* # ( Tsvetova and Shcheglow, 1994) Ukraine, Ivankiv district, 1993 (n = 1) 3800 ( Grodzinskaya et al. 2003) Ukraine, 30 km zone from the ChNPP, 1996 4600 ( Grodzinskaya et al. 2011) Ukraine, 30 km zone from the ChNPP, 1996 12,000 ( Grodzinskaya et al. 2011) Ukraine, Żytomierz, 1996Ukraine, Żytomierz,-1999 ( Vinichuk and Johanson, 2003) France, Burgundy, Charolais, 1993 49 ± 1-79 ± 2 ( Kirchner and Daillant, 1998) France, 1995 50 ± 3-1640 ± 60 Slovak Republic, Klaštorisko, 2001 (n = 1) < 10 ( Dvořák et al. 2006) Czech Republic, 1995190 ± 20 (Calmet et al. 1998) Czech Republic, 1987 170 ( Horyna and Řanda, 1988) Czech Republic, Temelín, 1987-1992 180 (110-290) ( Švadlenková et al. 1996) Czech Republic, Šumava, 1989 6600 (2700-10,600) ( Gerzabek et al. 1988) Austria, Tyrol and Vorarlberg, 1974 ∼ 500 ( Haselwandter et al. 1988) Austria, Salzburg Province, 1981 160 ± 180-310 ± 110 # ( Eckl et al. 1986) Austria, Salzburg Province, 1982 580 ± 110 # ( Eckl et al. 1986) Austria, 1986; n = 9 (217)* 1300 ± 1100 (up to 8500) # ( Gerzabek et al. 1988) Austria, Tyrol and Vorarlberg, 1986 ∼ 900 ( Haselwandter et al. 1988) Austria, upper, 1986-1991 (n = 46) 1200 (140-5200)** ( Ismail 1994) Austria, 1987 (n = 4) 520-4200 # ( Teherani 1988) Austria, Styria 2500-5000 (10-20,000) ( Heinrich 1993) Austria, Tyrol, 1991-1993 640 ± 500 ( Ismail et al. 1995) Italy, northeastern, 1986 (n = 1) 400 ( Battiston et al. 1989) Italy, Venezia Giulia, 1987 (n = 7) 4000 ( Giovani et al. 2002) Italy, Regio Emilia, 1993 (n = 2) 68-2400 [ ¶ ¶] Italy, Reggio Emilia, 1994 (n = 1) 1000 [ ¶ ¶] Germany, southwestern Bavaria, 1986 60 ± 5 ( Elsner et al. 1989) Germany, southwestern Bavaria, 1987 50 ± 15 ( Elsner et al. 1989) Germany, southern Bavaria, 1987-1990 (n = 4) 1700-8400** ( Kammerer et al. 1994) Germany, Baden-Wuerttemberg, 1987 (n = 1) 620** ## ( Dietl and Breitig, 1988) Romania, 1995 85 ± 5-140 ± 2 ( Calmet et al. 1998) Bulgaria, 1995 62 ± 4 ( Calmet et al. 1998) Spain, Galicia, 2011-2012 (n = 9) 73 ± 120 (3.0-380) ( García et al. 2015) Turkey, Samsun, 2004-2005 (n = 5) 32 ± 1-34 ± 2 ( Turhan et al. 2007) China, Yunnan, 2013; n = 1 (33)* 1.2 ± 0 ...
The activity concentrations of (137)Cs and (40)K in mushrooms of the genus Cantharellus (Cantharellus cibarius, Cantharellus tubaeformis, and Cantharellus minor) collected across Poland from 1997 to 2013 and in Yunnan province of China in 2013 were determined using gamma spectrometry with an HPGe detector, respectively. Activity concentrations of (137)Cs in C. cibarius from the places in Poland varied from 64 ± 3 to 1600 ± 47 Bq kg(-1) db in 1997-2004 and 4.2 ± 1.2 to 1400 ± 15 Bq kg(-1) db in 2006-2013. In the Chinese Cantharellus mushrooms, the activity level of (137)Cs was very low, i.e., at a range <1.2 to 1.2 ± 0.6 Bq kg(-1) dry biomass. The natural radionuclide (40)K was at similar activity level in C. cibarius collected across Poland and in China, and fluctuations in levels of (40)K over the years and locations in Poland were small. In C. cibarius from diverse sites in Poland, content of (137)Cs highly fluctuated in 1998-2013 but no clear downward trend was visible (Fig. 1). Published activity levels of (137)Cs in fruitbodies of Cantharellus such Cantharellus californicus, Cantharellus cascadensis, C. cibarius, Cantharellus cinnabarius, Cantharellus formosus, Cantharellus iuteocomus, Cantharellus lutescens, Cantharellus minor, Cantharellus pallens [current name C. cibarius], Cantharellus subalbidus, Cantharellus subpruinosus, and C. tubaeformis collected worldwide were compared. In the Polish cuisine, mushrooms of the genus Cantharellus are blanched before frying or pickling, and this kind of treatment, and additionally also pickling, both very efficiently remove alkali elements (and radioactivity from (134/137)Cs) from flesh of the species.
... In Fukushima, the vertical distribution of 137 Cs in forests, 1.5 years after the nuclear incident, indicates that organic matter on the forest floor acts as a large sink [3]. Mushrooms contribute to the long-term retention of 137 Cs in the surface layer because, as decomposers in forest ecosystems, they play an important role in mineral circulation [4, 5]. Mushrooms are reported to contain more 137 Cs than plants [6]; the 137 Cs concentration of mushrooms depends on the 137 Cs concentration of the substrates in which their hyphae grow789. ...
Cesium-137 (137Cs) accumulation by mushrooms and trees was evaluated based on the aggregated transfer factor (T
ag) value at one and a half years after the Fukushima Daiichi Nuclear Power Plant accident. Our results suggest that (1) some genera of fungi tend to accumulate more 137Cs than others, (2) not only 137Cs concentration of the substrates but also its availability for fungi is an important factor determining the 137Cs concentration in mushrooms and (3) ectomycorrhizal fungi do not necessarily enhance 137Cs uptake by host plants when compared to arbuscular mycorrhizal fungi.
... Forest soil is abundant in organic compounds; therefore, less radiocesium should be adsorbed. However, considerable proportion of 137 Cs in forest soil is retained by the fungal hyphae, and fungi are considered to prevent the elimination of cesium from ecosystems (Brückmann and Wolters 1994 ;Guillitte et al. 1994 ;Vinichuk and Johanson 2003 ;Vinichuk et al. 2005 ). Thus, fungal activity is likely to contribute substantially to the long-term retention of radiocesium in the organic layers of forest soil by recycling and retaining radiocesium between fungal mycelia and soil (Muramatsu and Yoshida 1997 ;Steiner et al. 2002 ;Muramatsu 1994 , 1996 ). ...
High concentrations of radionuclide contamination of wild mushrooms occurred near the Fukushima Daiichi nuclear power plant and along the path of radioactive plumes. This is a serious problem for the forest ecosystem and commercial wild mushroom production. Radioactivity in wild mushrooms collected from low-level contamination forest areas throughout Japan was measured approximately 6 months after the accident. In general, the radioactivity in mushrooms did not exceed those in the neighboring forest litter. However, further accumulation of 137Cs is expected in mushrooms; therefore, continuous monitoring is necessary even in low-contamination areas. We also found that residual 137Cs radioactivity due to nuclear weapons tests, mainly in 1950s, besides fallout from the Fukushima nuclear accident still remained in soil and was accumulated by mushrooms.
... Generally, TFs of 137 Cs vary depending on soil type, pH, solid/liquid distribution coefficient, exchangeable potassium, organic matter content, soil microbial activities, climatic conditions and the physiology of plant species (Absalom et al., 1999;IAEA, 2006). In soils with high clay contents, 137 Cs is bound and fixed to clay minerals, whereas 137 Cs can be bound either to organic matter (Rigol et al., 2002) or microorganisms (Vinichuk and Johansson, 2003;Koarashi et al., 2012) in soils with an organic matter content. Although the fraction of radionuclides associated with microorganisms may be relatively small, these organisms and various fungi and bacteria play an important role in the retention of radiocesium in agricultural and forest soils. ...
The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.
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... Presence of 137 Cs in nature is of special concern due to its long half-life period (30.1 years), easy migration in the trophic chains (high water solubility), and great bioavailability (biological behavior similar to potassium and rubidium) (Ipatyev et al. 1999). Cesium is dominantly present in the upper surface area of soil in a depth from 0 to 5 cm and deeper than 5 cm (Elstner et al. 1989;Muramatsu et al. 1994;Vinichuk et al. 2004) being mostly concentrated in fungal mycelia in amount of 30-50 % (Yoshida and Muramatsu 1997;Vinichuk and Johanson 2003). These facts are consequence of linking Cs together with complexes of organic matter, clay particles, or its precipitation on mineral surface area giving low concentration in soil solution and low migration in soil profiles (Brunner et al. 1996). ...
Edible and medicinal macrofungi used in human diet represent not only important sources of nutritive elements but toxic substances as well (heavy metals and radionuclides). Radioactivity levels of four radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra) were determined in the basidiomata (fruiting bodies of a Basidiomycetes) of six lignicolous (Fomitopsis pinicola, Ganoderma applanatum, Hericium clathroides, Megacollybia platyphylla, Pluteus cervinus, Trametes gibbosa) and three mycorrhizal (Boletus luridus, Boletus sp. 1, Boletus sp. 2) species as well as their soil (wood) substrates by gamma spectrometry (high-resolution high-purity germanium (HPGe) detector). The aim was to investigate their ability for radionuclide absorption according to transfer factors (from soil and wood), to predict potential bioindicator species as well as species with potential risk for human use. Samples were taken during years 2011 and 2012, at two sites in forest ecosystem of Tara Mountain (Serbia). Observed concentration ranges per dry weight were as follows: 29-3,020 Bq/kg ((40)K), 21.9-735 Bq/kg ((137)Cs), 3-39 Bq/kg ((226)Ra), and 2.0-18 Bq/kg ((228)Ra). Obtained results indicate that the type of basidiome (fleshy/tough), most likely due to a different metabolic rate, has a very important role in radionuclide accumulation. The highest activity concentrations of all analyzed radionuclides were found in species with fleshy basidiomata-P. cervinus, H. clathroides, M. platyphylla, and Boletus species. A species-specific influence on radionuclide uptake was more prominent comparing to habitat differences and the role of fungal trophic mode. No significant variations were observed regarding radionuclide activity among the same fungal species from different sampling sites.
Research on mycorrhizal symbiosis has been slowed by a lack of established study systems. To address this challenge, we have been developing Suillus, a widespread ecologically and economically relevant fungal genus primarily associated with the plant family Pinaceae, into a model system for studying ectomycorrhizal (ECM) associations. Over the last decade, we have compiled extensive genomic resources, culture libraries, a phenotype database, and protocols for manipulating Suillus fungi with and without their tree partners. Our efforts have already resulted in a large number of publicly available genomes, transcriptomes, and respective annotations, as well as advances in our understanding of mycorrhizal partner specificity and host communication, fungal and plant nutrition, environmental adaptation, soil nutrient cycling, interspecific competition, and biological invasions. Here, we highlight the most significant recent findings enabled by Suillus, present a suite of protocols for working with the genus, and discuss how Suillus is emerging as an important model to elucidate the ecology and evolution of ECM interactions.
We investigated the changes in the dynamics of radiocesium in wild forest mushrooms, mainly mycorrhizal fungi, in the University of Tokyo Forests in relation to soils during the 10 years following the Fukushima accident. Overall, there was a clear tendency for the ¹³⁷ Cs activity concentration to decrease over time in the O horizon. It seems that part of the ¹³⁷ Cs in the O horizon was transferred to the A or C/O horizon, but there was no clear continuous increase or decrease in the A or C/O horizon. A large difference in the temporal change of ¹³⁷ Cs concentration in mushrooms was observed, but in general, ¹³⁷ Cs was stably retained from the beginning, or partially decreased and then shifted to patterns of retention. Further analyses such as the ratio of ¹³⁷ Cs/ ¹³⁴ Cs corrected for decay, and the ratio of remaining pre-Fukushima ¹³⁷ Cs calculated from the ratio with ¹³⁴ Cs, ¹³⁷ Cs from the global fallout before the Fukushima accident due to the nuclear weapons test and Chernobyl accident is held in mushrooms and soil. In addition, while the ¹³⁷ Cs derived from the Fukushima accident is initially fluid and migrates relatively easily from the mushrooms and O horizon, the ¹³⁷ Cs from the global fallout tends to be firmly retained in the ecosystem.
Objective
To explore the concentration level of radionuclide in mushrooms in northeast China, and to analyze the risk of the effective dose of edible mushrooms to the human body.
Methods
A total of 68 samples of 18 species of mushrooms from three regions in northeast China and Beijing as control were collected from 2017 to 2020. The activity of radionuclide in mushrooms was measured by gamma-spectrometry, and the activity was analyzed by statistical analysis method. The relationship between ¹³⁷Cs and ⁴⁰K content in mushrooms was explored.
Results
²³⁸U was undetected in all samples. The activity concentration of ²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs were in range of 1–34.3, 2.26–32.3, 208–2388 and 0.6–130.3 Bq/kg, respectively. The ¹³⁷Cs and ⁴⁰K concentrations in mushrooms were not correlated. The risk analysis of radioactivity in the collected mushrooms showed that the highest effective dose of the 18 kinds of mushrooms was 0.042 mSv.
Conclusion
The radionuclide content of mushrooms in northeast China is within the normal range. The mushrooms will not cause risk to human health.
In the 2017-2018 mushrooming seasons at the (Bohemian-Moravian Highlands near Dolní Rožínka) a total of 505 mushrooms belonging to 9 species were collected, and analyzed by gamma spectrometry for 137Cs activity. The maximum 137Cs activity of 575 Bq.kg-1 was detected in Boletus edulis species, what in native state, is just below the allowed limit. In contrast, in mushroom Imleria badia, which is reported to be associated with the highest cumulative capability from all fungi species, detected activity level was only 316 Bq. kg-1. However, differences in mean contamination values were not significant due to high variability. It was shown, that activity concentration is not dependent on the weight (size) of Imleria badia. Our results also confirmed generally well known lower 137Cs activity in the Russula species representatives belonging to the group of gills or lamella bearing mushrooms.
Використання арбускулярних мікоризних грибів Glomus mosseae при вирощуванні огірків показує відсутність їх стимуляційного впливу як на величину біомаси досліджуваних рослин, так і на рівень накопичення ними радіоцезію. Показано, що значення коефіцієнтів накопичення 137Cs (КН) рослинами огірків не залежать від інтенсивності мікоризної інфекції бічних та додаткових коренів рослин.
It was demonstrated that rhizospheric processes involving mycorrhizal fungi can influence root uptake of radiocaesium. The ability of both ectomycorrhizal and endomycorrhizal fungi to limit radiocaesium availability to their host plants was considered. The ectomycorrhizal fungi grown in forest ecosystems were suggested to immobilize between 10 and 100 % of the total 137Cs activity. Radiocaesium was found to be accumulated in mycelium and fruit bodies of ectomycorrhizal fungi by simple diffusion and facilitated transport. Ectomycorrhizal fungi was considered to be efficient indicators of cumulative biogeochemical fluxes of radiocaesium in terrestrial ecosystems and thus to be appropriate candidates for phytoremediation technique.
The significance of arbuscular mycorrhizal fungi as participants in radiocaesium cycle in the upper soil layers was discussed. Up to date, their role in processes of radiocaesium uptake by plants remains incompletely understood and controversial. It was demonstrated that arbuscular mycorrhizal fungi could accumulate 137Cs in their extraradical or intraradical structures, transport the radionuclide to their hosts and influence its distribution among plant roots/shoots. Depending on arbuscular mycorrhizal fungi and plant species used, the significant reduction or increase of radiocaesium transfer to aboveground plants biomass was found. The perspectives of arbuscular mycorrhizal fungi application in phytoremediation techniques were discussed.
Radiocaesium isotopes are among the long-lived radionuclides which were released in largest quantities into the environment as a consequence of the atmospheric nuclear weapon tests and accidents involving nuclear material (Chernobyl and Fukushima, etc.). Its transfer to plants, especially those for human or animal food, can be a major pathway for human intake and, therefore, have a significant radiological impact. There are many factors that can affect the radiocaesium transfer to plants, which are reviewed in this chapter, such as the considered plant species, its habitat, climatic conditions, type of soil (clay content, physico-chemical characteristics, organic matter, use of amendments, etc.).
The occurrence in nature of radionuclides, whether anthropogenic or naturally occurring, poses some major questions concerning their environmental behaviour and potential hazard for man. Their behaviour is mainly governed by the quantity and chemical forms in which they occurred or were deposited as a consequence of different radioactive releases (global fallout, Chernobyl, Fukushima, etc.), by the characteristics and properties of the soil such as pH, organic matter content, clay materials, etc., and by the climatic characteristics of the ecosystem. These factors condition the availability of radionuclides for transfer to other compartments in the ecosystem. However, not all the radionuclides present in soil can be transferred, only that fraction which is not strongly attached to soil particles. The association of radionuclides with soil particles is usually determined empirically by means of sequential extraction procedures, in which soil is sequentially treated with chemical solutions of increasing replacement/dissolving power. Radiostrontium in soil tends to be more mobile and available than other anthropogenic radionuclides such as radiocaesium, plutonium, and americium. Radiocaesium has a high affinity to becoming irreversibly bonded with clay minerals. Plutonium and americium are mainly associated with humic substances in the soil. The association of anthropogenic radionuclides with soil particles is not constant. Due to weathering processes or to the ageing effect of the released particles, it varies with the time elapsed since their deposition. Naturally occurring radionuclides can also present environmental problems in areas with high content or affected by NORM (Natural Occurring Radioactive Material) industries such as uranium mining, coal-fired power plants, etc. In such industries, the content of natural radionuclides already present in the raw materials is enhanced, usually also accompanied by changes in their chemical forms and hence their bioavailability. Aquatic ecosystems are also of great significance to man. Different fractionation techniques (filtration, centrifugation, charge fractionation) are used to determine the association of radionuclides with molecules of different masses. Radiostrontium is usually attached to low mass fractions. Also theoretical models can be used to estimate the main inorganic chemical compounds, charged or neutral, in solution formed by radionuclides at different pH's. The knowledge of the different degrees of availability of radionuclides by means of speciation techniques is especially useful in order to design countermeasures to reduce the transfer of radionuclides between different compartments of a given ecosystem.
Understanding the environmental behaviour of radionuclides in forest ecosystems is of great importance to ensure an adequate level of radioprotection. The accumulation of radionuclides by fungi and the process of their transfer from the soil play a significant part in this behaviour because of the ability of these organisms to accumulate heavy metals, including most radionuclides. As a consequence of radioactive fallout and nuclear accidents, anthropogenic radionuclides have entered forest ecosystems, with radiocæsium being among the most hazardous in the medium-to-long term. As a general rule, fungi are able to accumulate radiocæsium very efficiently. However, there is a large range of variation, about seven orders of magnitude, in its content as reported in the literature. In areas heavily affected by a radioactive deposition, the consumption of mushrooms by man or animals contributes to increasing their body's radiocæsium content. There have been fewer studies of radionuclides other than radiocæsium, but on occasions they can also be of importance. In areas with low or almost negligible levels of anthropogenic radioactive contamination, the content of radionuclides belonging to the natural radioactive decay series, such as 210Po and 210Pb, contributes significantly to the internal dose of the general population. The uptake of naturally occurring radionuclides also shows a great range of variation, although not as wide as that observed for radiocæsium. Not all species of fungi accumulate radionuclides at the same level. There is also a difference based on the fungus's nutritional mechanism, with mycorrhizae generally having a greater radiocæsium content than saprophytes. But there are also other factors that influence the accumulation and the transfer of radionuclides from the soil, such as the quantity of radionuclides deposited as a consequence of the fallout event, the chemical form of those radionuclides, and the soil's properties (pH, and organic matter and clay contents), among others.
This field study was undertaken to quantify the transfer factor of Cs-137 from agricultural soil to wheat grains and ingestion dose evaluation around Narora Atomic Power Station, Narora, India from 2010 to 2012. Cs-137 activity was measured using NaI (Tl) well type gamma-spectrometry system. Transfer factor of Cs-137 from soil to wheat grain samples was in the range of 0.12-0.46. Annual ingestion dose to man from Cs-137 activity was significantly lower than permissible limit (1.0 mSv year(-1)). The risk measured due to Cs-137 is also insignificant to members of public residing around Narora Atomic Power Station, Narora, India.
Mushrooms are a complementary foodstuff and considered to be consumed locally. The demand for mushrooms has increased in recent years, and the mushroom trade is becoming global. Mushroom origin is frequently obscured from the consumer. Mushrooms are considered excellent bioindicators of environmental pollution. The accumulation of radionuclides by mushrooms, which are then consumed by humans or livestock, can pose a radiological hazard. Many studies have addressed the radionuclide content in mushrooms, almost exclusively the radiocaesium content. There is a significant lack of data about their content from some of the main producer countries. An exhaustive review was carried out in order to identify which radionuclide might constitute a health hazard, and the factors conditioning it. Regulatory values for the different radionuclides were used. The worldwide range for radiocaesium, 226Ra, 210Pb, and 210Po surpasses those values. Appropriate radiological protection requires that the content of those radionuclides in mushrooms should be monitored.
Sporocarps and sclerotia were collected for a one-year period in 23- and 180-year-old Abies amabilis stands in western Washington. All sporocarps were classified and chemically analyzed for N, P, K, Ca, Mg, Na and Fe. Lactarius sp. and Cortinarius sp. contributed the largest proportion of the total annual epigeous sporocarp production in both stands. Annual epigeous production was 34 kg/ha in the young stand and 27 kg/ha in the mature stand. Hypogeous sporocarp production increased from 1 kg ha-1 yr-1 to 380 kg ha-1 yr-1 with increasing stand age. High sclerotia biomass occurred in the young (2,300 kg/ha) and mature (3,000 kg/ha) stands. Peak sclerotia and epigeous sporocarp biomass in the young stand and epigeous and hypogeous sporocarp biomass in the mature stand coincided with the fall peak of mycorrhizal root biomass.
In the young stand, sporocarps produced by decomposer fungi concentrated higher levels of Ca and Mn than those produced by mycorrhizal fungi. In the mature stand, sporocarps of decomposer fungi concentrated higher levels of N, P, Mn, Ca and Fe than sporocarps of mycorrhizal fungi. Epigeous and hypogeous sporocarps concentrated higher levels of N, P, and K than sclerotia or mycelium. The highest concentration of N (4.36%), P (0.76%), K (3.22%) and Na (1,678 ppm) occurred in epigeous sporocarps. Highest Mn (740 ppm) and Ca (20,600 ppm) concentrations occurred in mycelium, while highest Mg (1,929 ppm) concentrations were in hypogeous sporocarps and highest Fe (4,153 ppm) concentrations were in sclerotia.
A study of the sporophore production of the agarics and boleti of a Scots pine plantation in Scotland from 1965 to 1969 was made, with particular reference to Russula emetica (Schaeff. ex Fr.) S. F. Gray. Estimates of total productivity ranged from 0·24 to 0·49 million sporophores/ha/year and 265 to 460 kg/ha/ year fresh wt. Productivity from August to October accounted for 90% of the total, with the peak in September. Estimates of sporophore life for different species ranged from 1 to 3 days for Mycena and Galerina, 4–7 for R. emetica and Lactarius rufus (Scop, ex Fr.) Fr., to 12–20 for Boletus badius Fr., Hygrophorus hypothejus (Fr. ex Fr.) Fr., Paxillus involutes (Batsch ex Fr.) Fr. and Hygrophoropsis aurantiaca (Fr.) Maire. Population decay curves indicated that with weekly visiting, about one-quarter of the population would not be observed, and with fortnightly visiting this figure could be as much as a half. The mean interval between visits was 3–5 days in peak season, and this higher frequency is thought to be responsible for the higher estimates of productivity compared with earlier studies, as well as the fact that it was from a coniferous wood which, in earlier studies have also proved to be relatively more prolific than deciduous ones.
Fruiting bodies and forest floor samples were collected and analyzed for N, P, K, Ca, Mg, Mn, and Na content in red alder, Douglas-fir, western hemlock, and Pacific silver fir ecosystems in western Washington. Different genera and species of fungi showed wide variation in the capability of concentrating nutrients within their fruiting bodies. Ranges of nutrient content for fruiting bodies were 0.66–11.27% N, 0.04–2.39% P, 7 – 32 080 ppm Ca, 2975 – 57 404 ppm K, 10–7096 ppm Mg, 3–1727 ppm Mn, 15–3975 ppm Fe, 18–6763 ppm Na, and 15–278 ppm Zn. Nitrogen, P, and K were concentrated in significantly higher levels in fruiting bodies versus the forest floor in all ecosystems. Nitrogen and K were concentrated at levels higher than 1% while P, Ca, Mg, Mn, and Na were concentrated at levels less than 1% of the dry weight of the fruiting bodies. Calcium was not concentrated by fungi in sporocarps, except for Armillariella mellea rhizomorphs (3.2% on dry weight basis). Lignicolous fungi were lower in N and K than nonlignicolous fungi.
The Cs-137 content of the microbial biomass in the organic layers of 10 German forest sites was quantified with a modified fumigation/extraction method. A K(Cs) factor was calculated for biomass Cs-137 from the difference between unfumigated and fumigated samples by means of laboratory cultures. The size of the estimated K(Cs) factors varied between 1.54 and 2.90 (mean, 2.17; S.D., 0.48). The microflora at the different forest sites contained between 1 and 56% of the total amount of Cs-137 found in the organic layers (mean, 13%). Litterbag experiments showed that Cs-137 was actively transported into the L layer by the microflora and that this effect was enhanced by the mesofauna. It is concluded that the immobilization and recycling of Cs-137 by the microflora in the organic layer of forest soils is determined by three major factors: Cs-137 availability, growth conditions of the microflora and biotic interactions.
Field and laboratory studies demonstrate two processes involved in 137Cs migration in coniferous forest soil. The data illustrate that the effects of leaching and litter accumulation combine, over the time interval since deposition, to achieve the observed distribution of 137Cs in the soil profile. Today, under normal field conditions the rate of 137Cs leaching from forest humus is low and even extreme environmental conditions do not increase greatly the extent of 137Cs mobilisation by leaching. A three-phase model of 137Cs migration in the organic horizons of coniferous forest soils is proposed. The phases are discrete but at any point in time the behaviour of some portion of deposited 137Cs will be characteristic of one of the three phases. In the first phase 137Cs intercepted by the canopy is washed to the forest floor where a proportion (20–40% is reported) rapidly percolates through the organic horizons reaching the underlying soil; the remainder is retained in the organic horizons. In the second phase, which our study estimates to last about 5 years, the 137Cs contained within the Ol and Of horizons moves to the Oh horizon. Accumulation of relatively uncontaminated litter on top of the Ol horizon contributes to this migration, while 137Cs mobilised from the Ol and Of horizons by decomposition is leached to the Oh horizon. The 137Cs which reaches the Oh horizon, either by leaching or by decomposition and burial, enters the third phase in which the pace of migration is greatly reduced. Decomposition is slowest in the Oh horizon and the accumulation and turnover of Oh material is also very slow. At the site investigated in this study the bulk of the deposited 137Cs is in this third phase and we suggest that this phase will persist for many years to come.
137Cs and stable Na, K, Rb, Cs, Mg, Ca, Sr, Ba and Al were determined in 29 mushrooms and 8 plants collected from a Japanese pine forest. Concentrations of 137Cs, Cs and Rb in mushrooms were one order of magnitude higher than those in plants growing in the same forest. On the other hand, concentrations of Ca and Sr in mushrooms were obviously lower than those in plants. A good correlation (r=0·99,p<0·01) between 137Cs and stable Cs concentrations was observed for mushrooms. The 137Cs/Cs ratios were almost constant (137Cs/Cs=134±36 Bq mg-1 in 1990) and were significantly higher than that in the surface soil (27 Bq mg-1). The ratios for plants were almost the same as those for mushrooms. In plant samples, good correlations were observed among the concentrations of K, Rb, Cs and Mg. Correlation between those of Ca and Sr was also good. In contrast, Cs was not correlated with K in mushrooms, indicating that the mechanism of Cs uptake was different from that for K. Rb showed a correlation with Cs (r=0·82).
At different locations in spruce stands spread rather homogeneously over southern Baden-Württemberg, samples of soil and plants were taken and the vertical distribution of the caesium radionuclides in the soil was studied. As a direct measure of the bioavailability, the aggregated transfer factor, Tag, was determined for fern, bilberry, raspberry, blackberry, and clover. The Tag (in m2 kg−1) is defined by the specific caesium activity (in Bq kg−1) of the dry mass of the plants, divided by the total inventory (in Bq m−2) of the soil. It varies between 0·5 and 0·001 m2kg−1, being highest for fern and lowest for blackberry or clover at all sampling sites. Most decisive for the value of the Tag are kind of humus deposit, thickness and pH value of the humus layers. Also important are the soil properties, whereas geology has only a minor influence on Tag. At different sampling sites in spruce forests, the Tag can vary by two orders of magnitude for one plant species. Caesium desorption experiments were performed. We could not find a dependence of the transfer of caesium to the plant on the desorbability of caesium from the soil, which implies a more complex transport mechanism than simple ion exchange in the soil solution. It is suggested that the transport of caesium is mediated by mycorrhiza fungi. Therefore, we studied the density of mycorrhiza hyphae in the Of, Oh and Ah soil horizons of two sites differing in Tag by a factor of 10. The densities of mycorrhiza hyphae in the Oh and Ah soil horizons each differ by a factor of 2 for the two sites. Yet, the effect of the hyphae density on radiocaesium uptake has to be a subject of further investigation.
Mycorrhizas were collected from three Norway spruce (Picea abies) stands in southwest Germany, sorted on the morphotype level and analysed by fluorescein diacetate vital fluorescence staining and the accumulation of elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and electron energy-loss spectroscopy (EELS). Xerocomus badius - Picea abies mycorrhizas showed a higher frequency of active hyphal sheaths and a higher potential to store nitrogen, phosphorus, potassium, magnesium, iron and zinc than other mycorrhizal types. Phosphorus and nitrogen were localized by EELS in vacuolar bodies which occurred consistently in the sheath of X. badius mycorrhizas. The results indicate that X. badius is well adapted to acidic stands and that its mycorrhizas are very efficient in uptake and storage of macronutrients.
Significant microbial immobilization of mineral elements in the forest floor was demonstrated by exposing decaying and sterile Liriodendron leaves with 137 Cs in untagged forest floor and by exposing similar leaves without 137 Cs in a forest floor tagged with the isotope. Net immobilization on the tagged leaves was 7% of the initial 137 Cs content. Immobilization of 137 Cs from the forest floor more than doubled the accumulation of 137 Cs by the exposed leaves.
The development of fungal biomass and increase of amounts of N was studied in decomposing pine needle litter for about 3 yr. After a relatively rapid increase of the amount of mycelium the fungal biomass became rather constant after about 2 yr. The absolute amount of N in the needles increased between the 4th and the 16th months and this increase was correlated to the increase of fungal biomass in the needles.
Since 1987, 134Cs and 137Cs activities have been measured in about 250 soil samples and about 350 samples of different fungal species grown in a coniferous forest in Bavaria, Germany. Variations of 137Cs134Cs ratios are less than 10% within samples from the same soil horizon and year. Similarly, 137Cs134Cs ratios vary within less than 10% in mushroom samples of the same species and year. In contrast, the specific activities of 134Cs and 137Cs in soil samples of the same horizon and in mushroom samples of the same species vary by up to one order of magnitude. Two approaches are presented to estimate mycelium location of fungi. In the static approach, 137Cs134Cs ratios in soil and mushrooms, corrected to May 1986 and averaged over 1987–1994, are analysed. These ratios range from 1.74 ± 0.06 in the L-horizon to 2.41 ± 0.46 in the B-horizon. The corresponding ratios measured in 14 fungal species vary between 1.73 ± 0.12 (Lepista nebularis) and 2.16 ± 0.26 (Russula cyanoxantha). By comparing these ratios, information on the major mycelium location can be gained. In the dynamic approach, the change with time of the 137Cs134Cs ratio in 14 fungal species and in different layers of forest soil is compared. At the investigated site, both approaches yield similar results. The advantages of both methods are discussed.
Caesium-134 and 137Cs measurements in about 250 samples from L-, Of-, Oh-, Ah- and B-horizons of a Bavarian forest from 1987 to 1994 are analysed with respect to migration by using a compartment model. The derived ecological half-lives are 2.8 years, 3.8 years, 4.4 years and 7.7 years, respectively. By using these results, caesium behaviour can be predicted for about 25 years. The resulting profile is similar to that found nowadays for weapons fallout caesium, migrating within about 25 years in the same forest. Therefore, the model is suitable for the estimation of future behaviour of radiocaesium in the forest investigated for a period of about 25 years after deposition.
The reproducibility, the small scale as well as the large scale variability of137Cs extracted sequentially from the soil by using a modified Tessier procedure was investigated at several grassland sites in Bavaria/Germany and in the Chemobyl area. Because undisturbed grassland soils are never homogeneous with respect to their soil properties, all sequential extractions at the German sites were carried out at each plot separately for different soil layers (e.g., 0–2, 2–5, 5–10, 10–15, 15–20 and 20–30 cm). The results show that the coefficients of variation (CV) for the reproducibility of the extraction procedure for137Cs was (with some exceptions) around 10–20% for all fractions. For the small scale variability of137Cs (samples within an area of 10×10m2) the values for theCV were (again with a few exceptions) in the same range. Compared to that, the large scale variability of extractable137Cs (random soil samples within an area of 100×200 km2) was higher for all fractions, even though only moderately. The implications of these results with respect to a sampling design are discussed.
A review of the published literature describing transfer to fungi was carried out, summarising the collated data to determine factors controlling transfer and identify an appropriate modelling approach to predict future contamination. transfer ratios (TR) are derived for fungi species collected within Europe and the CIS. Considerable variability in TRs is demonstrated, with TRs varying between <0.001 and >10 m2 kg−1 across all species and over three orders of magnitude for individual species (e.g. Boletus badius). Generally, meta-information (such as habitat and soil attributes) is poorly reported in the literature so that classification of the TR is limited to the effect of nutritional type (P<0.025) in the order mycorrhizal>saprophytic≈parasitic. Analysis of the literature data set (a heterogeneous source) suggests that there is no statistical evidence to indicate a decrease in TRs for 10 years after the Chernobyl accident. Spatial analysis of a data set for Belgium indicates variability in transfer within a sampling location, such that fruitbodies collected over a scale of approximately 5 km would show activities as variable as those collected over a much larger scale (≈ or>50 km). Therefore, it is proposed that the collated data sets for individual species can be used to derive “best estimates” for the parameters describing the distribution of TRs. These can then be used to estimate an “effective” TR, which, when combined with local soil deposition level and frequency and effect of culinary practices, can give an estimate of the activity of fungi consumed by the general population.
Soil samples were collected in various forest stands, located about 40 km north-west from Uppsala. The various stands were: (1) Clear cut area made in 1987, (2) Normal forest with 50–100 old Norway spruce and Scots pine and with a thick humic layer of about 10 cm; (3) Raised bog with 50-year-old Scots pine and Sphagnum moss layer over peat soil. (4) Rocky area with old Scots pine, growing on a shallow soil, mainly of organic origin. (5) Normal forest with nearly 100-year-old spruce and pine, growing a shallow humic layer over sandy soil. Soil blocks of about 20×20 cm and down to a depth of 10–15 cm were collected on each site. The soil samples were mechanically separated into various fractions: bulk, rhizosphere and soil–root interface. The results showed that was unevenly distributed between the three soil fractions. The highest activity concentrations — 3–4 times higher than in the other two fractions — as well as the highest organic content — usually more than 95% — were found in the soil–root interface fraction. Of the total activity in the soil, 18% as a mean value was found in the soil–root interface fraction. The results thus show that a substantial fraction of the in the soils in some way associated with the biological part of the soil, probably with the fungal component.
The migration potentials for 134Cs in spruce soil columns (undisturbed profile) following a surface contamination and also the redistribution of the radionuclide through the profile have been investigated. The radiocaesium bioavailability in the different horizons was estimated by activity measurements in the soil solution and from extractions made of the solid phase. The calculation of a Kd ratio indicates that retention mechanisms increase very rapidly with depth. 134Cs speciation reveals the high affinity of the radionuclide for specific sites on mineral components. In spite of its organic nature, the O Ah horizon has a great efficiency for Cs accumulation; the role of humic clay components and/or microflora is unforeseen.
Decomposition rates of pine litter and cotton were measured in the litter (AoL) and fermentation (AoF) horizons of two forests in Ireland (Pinus contorta) and the Ukraine (Pinus sylvestris). The extent of decomposition was similar in spite of seasonal climatic differences between the two sites. The amounts of 137Cs and K in litter bags were determined at different stages of decomposition. During the first 2–4 months of decomposition, the K content of litter bags decreased by up to 80%; maximum weight loss in this time was 18%. At both sites decomposition of the litter was accompanied by an increase in 137Cs content of the litter bags. It is suggested that the increase in 137Cs content is due to importation of 137Cs by invading decomposer fungi. Fungus-mediated translocation of 137Cs to fresh litter is proposed to explain the persistence of Chernobyl radiocaesium in the upper horizons of forest soils.
Fruitbodies of Suillus variegatus and Lactarius rufus and, at a maximum distance of 50 cm, the corresponding mycorrhizae, were collected on a rocky area in a coniferous forest. The tuberculate mycorrhizae collected close to S. variegatus fruitbodies were identified by the RFLP pattern to be S. variegatus mycorrhizae. In contrast the smooth brown mycorrhizae collected close to fruitbodies of L. rufus were found to be of various species — L. rufus, but also Russula sp. The 137Cs activity concentrations in fruitbodies and the fungal part of the tuberculate mycorrhizae of S. variegatus were about the same. A local enrichment of 137Cs within fruit-bodies was studied by collecting fruitbodies growing in clusters. Between 13 and 64% of the mean ground 137Cs deposition of the cluster area (400 or 625 cm2) was found in the fruitbodies. This indicates that there might be an important fungal redistribution of 137Cs in the forest floor during the production of fruitbodies. The distribution of 137Cs within the fruitbodies was heterogenous. For example in Cortinarious armillatus, the 137Cs level in the cap was 2.7 times higher compared to in the stripe.
Short-term radiocaesium influx into fungal hyphae was measured for eighteen fungal species by experiments in which hyphal mats were incubated in 137Cs-labelled medium. The fungal species investigated included saprotrophic and mycorrhizal basidiomycete fungi, together with examples of non-basidiomycete mycorrhizal species. When results were expressed on a dry weight basis the range of influx values was 85 to 276 nmol Cs g−1 dry weight h−1, with saprotrophic species tending to have the highest values, and non-basidiomycete mycorrhizal species the lowest. When results were expressed on a surface area basis, however, the relationship between species type and Cs influx was less obvious. Influx was measured both in fungi which had had no Cs pre-treatment before the experiment, and in replicate samples which were given a 24 h pre-treatment period in medium containing 5 μm-CsCl. No significant differences were found between values of Cs influx measured in the two sets. The wide range of observed Cs influx values obtained here may help to explain the large differences in radiocaesium levels observed in fruiting bodies of different fungal species collected in field surveys after the Chernobyl reactor accident.
The distribution of 137Cs in the soil profile and in plants was studied in a forest located 35 km northwest of Uppsala. More than 85% of the total 137 Cs activity was found in the upper 5 cm of the soil profile, implying that nearly all 137 Cs activity is found in the raw humic layer that extends to a depth of about 10 cm in a normal Swedish coniferous forest. The 137Cs activity concentrations in some plants (birch, Scots pine, bilberry, lingonberry, and heather) are presented for the period from 1986 until 1991. Levels of 137 Cs activity in bilberry and lingonberry have decreased since 1986, but in the other plants, the level of activity seems to be relatively constant from 1986 to 1991. This means that the normal level of 137Cs activity found in heather is about 12000 Bg/kg (dry wt.).
Reports of high concentrations of fallout radiocaesium in basidiomycete fruit bodies after the Chernobyl nuclear reactor accident and speculation that fungi could be long-term 137Cs accumulators led us to ask if fungi could be long-term 137Cs accumulators. We used six common upland grassland species to try to estimate their importance in the immobilization of 137Cs. Uptake of Cs by these species ranged from 44 to 235 nmol Cs g−1d.w. h−1. Efflux studies indicate that more than 40% of the Cs taken up is bound within the hyphae. We estimate that the fungal component of the soil could immobilize the total radiocaesium fallout received in upland grasslands following the Chernobyl accident.
A variety of mushrooms, plants and soils collected in Japanese forests were analyzed for 137Cs, 134Cs and 40K. The 137Cs concentrations in forest soils ranged from <0.6–175 Bq/kg on a dry weight basis. The highest 137Cs concentrations in the soil profiles were observed mostly in the surface soil layer (0–5 cm). Litter layers contained significantly less 137Cs than the surface soil layer. Concentrations of 137Cs in plants were in general much lower than those in mushrooms. The levels of 137Cs in 81 mushroom species collected in 1989 and 1990 varied very widely, ranging from <4 to 16300 Bq/kg (dry wt.), while those of 40K were relatively constant. The median concentrations of 137Cs and 40K were 45 and 1110 Bq/kg (dry wt.), respectively. The 137Cs concentrations in mycorrhizal fungi tended to be higher than those in saprophytes, although the concentration range of each type varied widely. High concentrations of 137Cs in several Hebeloma species, ammonia fungi, were observed. In addition to the species-specific accumulation, the concentrations in many mushrooms reflected the layers in which their mycelia were growing.
Caesium (137Cs and 134Cs) concentrations in higher fungi (Basidiomycetes) from Slovenia, north-west Yugoslavia, are reported following the Chernobyl accident. Special attention was paid to the Cortinariaceae, already known as Cs accumulators. The highest levels were found in Cortinarius armillatus, C. traganus (both inedible species) and Rozites caperata. The median concentration of 137,134Cs in R. caperata from over 40 sampling sites was about 22 kBq/kg dry weight. High levels were also found in Xerocomus badius and Laccaria amethystina.From the 137Cs/134Cs ratios, which reflect the depth of the mycelium and the excess 137Cs from historic pre-Chernobyl fallout, it may be surmised that radiocaesium levels in certain species will probably increase further next year and subsequently as Cs migrates down the soil profile.In addition, 110mAg was found at concentrations up to 500 Bq/kg dry weight in certain species known to be Ag accumulators, particularly Agaricaceae and Lycoperdaceae.
Sequential extraction procedure (SEP) was applied for fractionation of Chernobyl fallout 137Cs bound onto soils of a coniferous forest ecosystem located in central Sweden. Results of sequentially extracted 137Cs fractions demonstrated that 8% (mean value) of the total deposited 137Cs was water soluble (F1) and 13% was NH4OAc extractable (F2). Oxidation of F2 residuals by H2O2 led to a release of 15% of soil-bound 137Cs (F3). Acid digestion of F3 residuals showed a possibility of releasing an extra amount of soil-bound 137Cs, 22% of the total soil 137Cs inventory (F4). These two fractions (F3 and F4) include strongly bound 137Cs that seems to require longer biodegradation processes by soil microflora and microfauna before becoming available for uptake by plants and fungi. More than 37% of the total soil 137Cs inventory was bound onto soil residuals in a non-extractable form that includes slowly degradable organic matter and other soil residual compartments. The distribution coefficient (Kd) was rather low and shows an inverse relation with the increase of percentage of soil organic matter, which indicates a week binding of 137Cs onto forest soil. In contrast, chemical fractionation of soil bound 137Cs showed a substantial fraction of 137Cs was strongly bound onto soil as organically bound 137Cs. Apparently, the binding processes of radiocaesium onto forest soil seems to be time dependent.
The transfer of cesium-137 from organic soil horizons to understorey vegetation has been studied on two coniferous tree sites. In total, 14 different plants preferably taking up their nutrients from organic soil layers were taken into account. A relatively good correlation was found to exist between the transfer factor (Bq/kg plant dry wt./Bq/kg O-horizons dry wt.) for dicotyledons (r = 0.51) and berry plants (r = 0.63), but there was no correlation for monocotyledons (r= −0.15). The correlations could not be improved by additionally taking potassium in plant and soil into account. These results are discussed in respect to different parameters influencing the amount of cesium-137 uptake, including plants supported by mycorrhizal fungi.
Since summer 1987, the distribution of radiocaesium in three different coniferous forest soils in South Bavaria and the radiocaesium concentration in mushrooms has been investigated. A total of 364 samples from 83 different fungal species, distinguishable according to their living habits into the three groups of symbionts, saprophytes and parasites were taken and analyzed. The 137Cs activity concentration in the fruiting bodies ranges between 2 and 15 000 Bq/kg fresh weight, depending on the living habits and the species of mushroom, indicating a species-specific accumulation rate. Therefore, Xerocomus badius, which is the most frequent species on the authors' sampling sites, was taken as a standard, and the radiocaesium content of the other species relative to this mushroom was calculated. Most fungi show a stable ratio, independent of the year and location of sampling. To describe these uptake rates, a transfer factor soil-fungi, defined as caesium activity concentration in the fruiting body of fungi to that in the organic soil horizon, is suggested. This is because mushrooms take up most of their nutrients from these layers and most of the radiocaesium from the Chernobyl accident is still present in the organic horizons. Also the 137Cs/134Cs ratio in mushrooms and O-horizons is very similar. During the last five years, no significant decrease of the 137Cs activity in the fruiting bodies studied has been observed.
Studies carried out inside the 30-km restriction zone of the Chernobyl Nuclear Power Plant (ChNPP) and in other contaminated regions of Ukraine, Belarus and Russia have shown that much of the 137Cs and 90Sr deposited by the accident in 1986 has been retained in the superficial layers of the soil and is likely to remain there for a long time. However, in wet organic soils, there has been considerable downward movement.Between 1987 and 1993, laboratory and field experiments were carried out in order to determine the vertical distribution profiles of 137Cs and 90Sr in undisturbed soils at various locations and in various soil types. The data from these experiments were then used to calculate the vertical migration rates of the two radionuclides by two types of model.The experimental results showed that the type of soil and its water content had a significant influence on the radionuclide distribution pattern in the soil profile. In undisturbed well-drained sandy and sandy loamy soils, the radionuclides were retained in the upper soil layers. However, in peaty boggy soils and flooded meadows, there was a greater downward migration. In tilled soils, the radionuclides were distributed more or less homogeneously within the cultivated soil layer: the depth and homogeneity of the nuclide distribution depended on the soil texture and the way that the soil had been managed. The vertical migration rates of the 90Sr were always higher than that of 137Cs. In a comparison of migration rates between 137Cs and 90Sr in different types of soils, 90Sr appeared to migrate fastest in sandy loam and sandy soils, and 137Cs migrated fastest in peaty, boggy soils. The limitations in usage of the models are discussed, and predictions are made for the next years.
Metabolically-active fungal biomass, as determined with fluorescein diacetate (FDA) staining, was studied during a 27-month period (21 samplings) in three horizons of a podzolized pine-forest soil. Recurrent definite biomass peaks were registered in autumn and early spring. Biomass increase was also noted during the winter with soil temperatures below 0°C. Only a minor fraction (2.4-4.3%) of the total fungal biomass was found to be active. The FDA-active biomass m-2 was equally distributed between the organic (5 cm) and mineral (15 cm) soil horizons, and varied between 0.5 and 2.4 g d.w. m-2. The amount of FDA-active biomass was correlated with soil moisture content.
The 137Cs content of 118 species (668 samples) of higher fungi collected in the period from August 1984 to October 1989 at three different locations in Styria, Austria, was determined by gamma-spectrometry. The Cs-content of most mushrooms has been increasing since September 1986. In order to find out which factors determine the 137Cs-contamination of mushrooms and the transfer-value soil to mushroom, the concentration of total and plant-available radiocesium in soils as well as the pH-value, the content of humus, clay, silt, sand, exchangeable cations, the composition of the clay minerals, and the particle size distribution of the soils of two different locations were examined. The higher the 137Cs contamination of the soil, the thicker the layer of humus and the higher the content of humus, the lower the pH-value, and the lower the amount of essential cations, especially of K+, the higher the amount of 137Cs plant-available will be. Therefore, the contamination of the mushrooms in the coniferous forest of Koralpenblick (1000 m) is higher than in the mixed forest at the Rosenberg around Graz at approx. 500 m height. Of 26 different species of mushrooms measured at both sites, only 61% show the highest TF-values soil to mushrooms also at the Koralpenblick. In the spruce forest at Koralpenblick there are many species of mushrooms with high 137Cs-contamination which were not found at the Rosenberg. However, the properties of the species to which a mushroom belongs are more important than environmental conditions and soil properties. The transfer values of 40K stay within narrow bounds, whereas those of 137Cs differ widely.
In an attempt to understand the mechanisms governing the transfer and retention of radiocaesium in the understorey vegetation, 39 macromycetes species and 33 plant species, together with humus samples, were systematically collected from the undercover vegetation in a boreal coniferous forest. The results indicate that the main factors determining interspecific differences in contamination level are the rooting depth in plants, the depth of mycelium in fungi, and the ecophysiological behaviour of fungi, mycotrophism or plant parasitism. A comparison between the investigated species and the same species growing in similar ecosystems, albeit under different climatic conditions, resulted in an almost identical ranking in terms of radiocaesium contamination levels; the contamination ratios between species were also relatively constant. From an experiment involving humus samples, it was shown that up to 40% of the radiocaesium could be retained by the microflora, particularly by mycelia.
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Soil fungi and the fate of radiocaesium in the soil ecosystem—a discussion of possible mechanisms involv in the radiocaesium accumulation in fungi and the role of fungi as a Cs-sink in the soil
- Olsen
Mechanisms of 137Cs migration in coniferous forest soils
- Rafferty
Biological pathways of radionuclides originating from the Chernobyl fallout in a boreal forest ecosystem
- Guillitte