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137Cs in the fungal compartment of Swedish forest soils
Abstract
The (137)Cs activities in soil profiles and in the mycelia of four ectomycorrhizal fungi were studied in a Swedish forest in an attempt to understand the mechanisms governing the transfer and retention of (137)Cs in forest soil. The biomass of four species of fungi was determined and estimated to be 16 g m(-2) in a peat soil and 47-189 g m(-2) in non-peat soil to the depth of 10 cm. The vertical distribution was rather homogeneous for two species (Tylospora spp. and Piloderma fallax) and very superficial for Hydnellum peckii. Most of the (137)Cs activity in mycelium of non-peat soils was found in the upper 5 cm. Transfer factors were quite high even for those species producing resupinate sporocarps. In the peat soil only approximately 0.3% of the total (137)Cs inventory in soil was found in the fungal mycelium. The corresponding values for non-peat soil were 1.3, 1.8 and 1.9%.
... In forest ecosystems soil organisms, can be important for immobilization, translocation and recycling of radionuclides. For example, the presence of soil organisms, such as fungi, in the upper organic rich forest soil layers enhances retention of 137 Cs within the soil profile and makes it available for uptake (Vinichuk et al., 2004). However, our understanding of the processes involved in the radionuclide interactions with living components of soil systems in forest is limited. ...
... Weather data is measured at weather station in Gävle (close to Hille) with a normal mean for 30 years 1961-1990, Alexandersson and Eggertsson-Karlström (2001. The areas around the Hille Lake were heavily contaminated after fallout from the Chernobyl accident in 1986 and have been investigated in several studies concerning the transport of radionuclides in soils and plants (Rosén et al., 1999;Vinichuk et al., 2004;Matisoff et al., 2011). Other studies performed in the area are on redistribution of radionuclides in wetland areas (Stark et al., 2006) and radiation doses to frogs (Stark et al., 2004;Stark and Pettersson, 2008). ...
... These result are within the range of what has been found in other studies in the study area. For example, Rosén et al. (1999) found a deposition maximum of 174,000 Bq m −2 and Vinichuk et al. (2004) found the ground deposition of 137 Cs to be between 30,000 and 100,000 Bq m −2 and Matisoff et al. (2011) found a mean deposition of 111,400 Bq m −2 . It can be assumed that the deposition at site A1 is similar to location A2 as they were very close (about 10 m) to each other. ...
In forest ecosystems soil organisms are important for immobilization, translocation and recycling of radionuclides. Still, there is a lack of studies on the role of insects such as ants in the turnover of radionuclides and how radioactivity affects an ant community. In this study seven anthills were sampled in an area that was heavily contaminated after the fallout from the Chernobyl accident. Samples of ant and anthill materials were taken from different depths of the anthills as well as from the surrounding soil and the activity concentrations of 137Cs were determined. In addition, a radiation dose assessment was performed for ants and anthills using the ERICA tool. The deposition of 137Cs in 1986 in the study area was calculated back to be on average 110,500 Bq m-2. The averaged data for all the seven locations investigated indicate that the level of 137Cs activity concentrations in the anthill's material increased with depth of the anthill being highest at the depth 50-65 cm. The concentration in the upper layers (0-2 cm) and of the ants showed significant correlations with the deposition upon multivariate analysis. The concentration ratio (CR) defined as the ratio between the mass activity for 137Cs density in ants (Bq kg-1 d.w.) and mass activity density in soil (Bq kg-1 d.w.) was determined to be in the range of 0.04-0.14. Also, the transfer factor (TF) defined as the ratio between the mass activity for 137Cs density in ant (Bq kg-1 d.w.) and to the unit area activity density (in Bq m-2 d.w.) was determined for 137Cs to be 0.0015 m2 kg-1 d.w. The assessed radiation doses were found to be a 4.9 μGy h-1 which is below international reference levels for non-human biota.
... 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). 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 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).
... Substantial research in this area has been conducted in Sweden after the fallout from nuclear weapons tests and the Chernobyl accident. Some results are published in a series of several articles in collaboration with Profs K.J. Johanson, H. Rydin and Dr. A. Taylor (Vinichuk et al., 2004; 2010a; 2010b;). This chapter aims to summarize the acquired knowledge from studies in Sweden and to place them in a larger context. ...
... Rubidium concentrations in sporocarps were more than one order of magnitude higher than those in mycelium extracted from soil of the same plots where fungal sporocarps were sampled. The ability of fungi to accumulate Rb is documented: mushrooms accumulate at least one order of magnitude higher concentrations of Rb than plants growing in the same forest (Yoshida & Muramatsu, 1998)Vinichuk & Johanson, 2003; Vinichuk et al., 2004). The differences between fungal species in their preferences for uptake of 137 Cs or stable 133 Cs appear to reflect the location of the fungal mycelium relative to that of cesium within the soil profile (Rühm et al., 1997). ...
... In soils with high clay content, there is low bioavailability and low vertical migration rate of radiocesium due to binding to some clay minerals (Cornell, 1993 ). In nutrientpoor but organic-matter-rich forest soils, the vertical migration rate of 137 Cs is also low, but bioavailability is often high, particularly for mycorrhizal fungi (Olsen et al., 1990; Vinichuk & Johansson, 2003; Vinichuk et al., 2004;). In forests and pastures, extensive fungal mycelium counteracts the downward transport of 137 Cs by an upward translocation flux (Rafferty et al., 2000); this results in a slow net downward transport of 137 Cs in the soil profile. ...
... Substantial research in this area has been conducted in Sweden after the fallout from nuclear weapons tests and the Chernobyl accident. Some results are published in a series of several articles in collaboration with Profs K.J. Johanson, H. Rydin and Dr. A. Taylor (Vinichuk et al., 2004; 2010a; 2010b;). This chapter aims to summarize the acquired knowledge from studies in Sweden and to place them in a larger context. ...
... Rubidium concentrations in sporocarps were more than one order of magnitude higher than those in mycelium extracted from soil of the same plots where fungal sporocarps were sampled. The ability of fungi to accumulate Rb is documented: mushrooms accumulate at least one order of magnitude higher concentrations of Rb than plants growing in the same forest (Yoshida & Muramatsu, 1998)Vinichuk & Johanson, 2003; Vinichuk et al., 2004). The differences between fungal species in their preferences for uptake of 137 Cs or stable 133 Cs appear to reflect the location of the fungal mycelium relative to that of cesium within the soil profile (Rühm et al., 1997). ...
... In soils with high clay content, there is low bioavailability and low vertical migration rate of radiocesium due to binding to some clay minerals (Cornell, 1993 ). In nutrientpoor but organic-matter-rich forest soils, the vertical migration rate of 137 Cs is also low, but bioavailability is often high, particularly for mycorrhizal fungi (Olsen et al., 1990; Vinichuk & Johansson, 2003; Vinichuk et al., 2004;). In forests and pastures, extensive fungal mycelium counteracts the downward transport of 137 Cs by an upward translocation flux (Rafferty et al., 2000); this results in a slow net downward transport of 137 Cs in the soil profile. ...
... The net vertical migration depends on the balance between downward and upward migration. In forest soils upward migration seems to be performed by the fungal mycelium (Melin & Wallberg, 1991;Fawaris & Johansson, 1995;Nylén, 1996;Forsberg & Strandmark, 2000;Vinichuk , 2004;Brückmann & Wolters, 1994;Wirth et al., 1994;Rafferty et a., 1997). In a raised bog, there is a rather small amount of fungal mycelium. ...
... Different plant species have specific 137 Cs uptake characteristics and this phenomenon has been extensively studied (Rosén, 1991 & Johanson, 1995;Vinichuk et al. 2004), which showed a high 137 Cs activity concentration in heather and in some other ericoid plants and lower values for most other plants. Heather has an ericoid mycorrhiza which may explain the very high 137 Cs levels. ...
... Differences in 137 Cs activity concentrations found in mushrooms growing at different locations were probably due to different species of mushrooms being collected. According to many previous studies (Fawaris & Johanson, 1995;;McGee et al. 2000: Vinichuk et al. et al. 2004) mushrooms generally have very high 137 Cs activity concentrations. ...
Vertical migration of 137Cs and 137Cs activity concentrations in plants growing on a raised bog in Central Sweden were investigated. Raised bogs are among the most nutrient poor ecosystems. Blocks of soil (peat) and samples of plants were collected from two sites on the bog, the open bog site where no trees were growing and the low pine site with slowly growing Scots pine. The peat at both sites was composed of living Sphagnum mosses in the upper 5 cm layer and dead and more or less decomposed Sphagnum material in deeper layers. Samples were also collected from a forest on mineral soil close to the bog. The soil blocks from the bog were cut in 2 cm layers down to a depth of about 40 cm. The 137Cs activity concentrations (Bq kg-1 dw) in plant samples and the 137Cs activity per m-2 in each peat layer were determined and the migration centers and the migration rates were calculated.
In 2005, the migration center at the open bog site was 13.42 cm and the migration rate was
0.70 cm y-1, at the low pine site the migration center was 15.53 cm and the migration rate
0.81 cm y-1. The corresponding values in the forest soil were 7.47 cm and 0.39 cm y-1. At
the open bog site about 35 % of the total 137Cs activity in the soil profile was found in the upper 5 cm (living part). The corresponding percentage at the low pine site was 20 % and 50% at the forest site. The results from 2005 were compared with results from 1989. In
1989, the migration center was 5.0 cm and the migration rate was 1.67 cm y-1 at the open
bog site. Obviously, the migration rate was higher in 1989 compared to 2005.
In 2005, the highest 137Cs activity concentrations in plants collected from the open bog site were found in heather – about 20 000 Bq kg-1. The corresponding value in heather
collected from the low pine site was about 10 000 Bq kg-1 and at the forest site 5 000 Bq
kg -1. A much lower level, 418 Bq kg-1, was found in crowberry growing at the forest site.
In 1989, the 137Cs activity concentration in heather growing at the open bog site was
44 000 Bq kg-1. The 137Cs activity concentrations thus seem to have decreased by about 50
% from 1989 to 2005.
... Более 19 % площади Ненецкого автономного округа занято болотами (~ 3,4 млн га) [1]. Преобладающим типом являются бедные питательными веществами верховые болота, основным источником питания которых являются аэрозоли, воздушная пыль и атмосферные осадки [2]. В связи с преимущественным атмосферным питанием, верховые торфяники представляют собой огромный архив атмосферных загрязнителей, ведущую роль среди которых играют радиоактивные элементы, поскольку арктические территории, к которым относится Ненецкий автономный округ, с момента начала атомной эры подверглись существенному воздействию техногенной радиоак- ADVANCES IN CURRENT NATURAL SCIENCES № 11, 2021 EARTH SCIENCES (25.00.00) тивности [3,4]. ...
... Similarly, Suomela et al. (1999) found that a majority of the 137 Cs from the Chernobyl fallout could be observed in the top 5 cm soil layer 11 years after the accident. Thus, there seem to be a wide array of studies indicating that the vertical migration of 137 Cs in forest soils is slow (Fawaris and Johanson, 1994;Nylen and Grip, 1997;Tikhomirov and Shcheglov, 1994;Vinichuk et al., 2004). Almgren and Isaksson (2006) have estimated the downward migration of 137 Cs to 3.5 mm y −1 in Sweden. ...
Wildfires are expected to increase with warmer climate, which can contribute to the mobility and the resuspension of long-lived and potentially hazardous radionuclides. The release of ¹³⁷Cs during combustion of dried litter, forest floor organic soil, and peat was investigated in a small-scale experimental set-up. Combustion conditions were varied to simulate different wildfire scenarios, and the fuels was dried organic material collected in a boreal environment of Sweden that was contaminated following the Chernobyl accident in 1986. The combustion-related release of ¹³⁷Cs to the air was on average 29% of the initial fuel content, while 71% of the initial ¹³⁷Cs remained in the ashes after the combustion. Peat and forest soil had the highest releases (39% and 37%, respectively), although these numbers should be viewed as potential releases since authentic wildfire combustion of these fuels are usually less effective than observed in these experiments. These results indicates that the ¹³⁷Cs has migrated downwards in the organic material, which imply potentially significantly more ¹³⁷Cs emissions in severe wildfires with intense combustion of the organic vertical profile in peatbogs and forests. More ¹³⁷Cs tended to be released during intense and efficient combustion processes, although no significant differences among combustion intensities were observed.
The generated experimental data was used in an emission scenario to investigate the possible range in ¹³⁷Cs emissions from a wildfire. Our study shows that a severe wildfire in a contaminated area of 10 000 ha could potentially release up to 7 TBq of ¹³⁷Cs. This is the first laboratory study to investigate ¹³⁷Cs release upon varying combustion conditions using real fallout contaminated organic material obtained from a boreal environment.
... In this region of the subarctic, the main types of marsh are nutrient-poor (ombrotrophic) bogs, whose main sources of nutrition are aerosols, air dust, and precipitation, in which mosses (sphagnums) predominate (Selyanina et al. 2013). Therefore, peatlands are a vast archive of atmospheric pollutants, among which radioactive elements play a leading role because the Arctic territories have undergone significant radioactive contamination since the beginning of the atomic age (Hallstadius et al. 1982;Smith et al. 2000;Gwynn et al. 2004;Strand et al. 2002;Dowdall et al. 2005;Karcher et al. 2010; Responsible editor: Georg Steinhauser * Evgeny Yakovlev evgeny.yakovlev@fciarctic.ru 2013; Lokas et al. 2013;Matishov et al. 2014;Vinichuk et al. 2004). ...
This article presents the results of studies of the activity of radionuclides in peat-bog profiles of the European subarctic of Russia. Two peat profiles were collected in different areas of the Arkhangelsk region. The peat cores were used to determine 210Pb, 137Cs, 241Am, 239Pu, 240Pu, 238U, and 234U content. To estimate the relationship between radionuclide activity and physicochemical parameters of peat, the content of organic matter, water-soluble salts, carbonates and ash, and the pH of aqueous and salt extracts were studied. Radionuclide activity concentrations in peat samples were measured using inductively coupled plasma mass spectrometry (ICP-MS), low-background semiconductor gamma spectrometry with a high-purity germanium (HPGe) detector, and alpha spectrometry. The 210Pb chronology of peat cores was studied using a constant flow model based on the Monte Carlo simulation method. Comparison of 210Pb dating data showed that the position of the maximum activity peaks of anthropogenic radionuclides shifted along the peat profile. This is probably due to the relative mobility of different radionuclides in the peat massif. Measurement of the atomic ratio 240Pu/239Pu showed that the main sources of pollution in the peatlands of the European subarctic of Russia are global fallout from atmospheric tests from the 1950s through 1980 and fallout from the Chernobyl nuclear accident in 1986. This study shows that a complex of radioactive isotopes in peat deposits can provide valuable information on the environmental pollution loads of subarctic territories.
... Several works have found independently that in soils with high clay content, there is low bioavailability and low vertical migration rate of 137 Cs because cesium binds to specific clay minerals (Cremers et al. 1988;Cornell 1993;Wauters et al. 1996). Particularly, in organic matter-rich soils, as peatlands, some papers have also reported that the vertical migration rate of 137 Cs is also low, despite the relatively low clay content, probably due to the relatively high bioavailability, particularly due to the mycorrhizal fungi activity (Olsen et al. 1990;Steiner et al. 2002;Vinichuk and Johanson 2003;Vinichuk et al. 2004;Rosén et al. 2009). Fiałkiewicz-Kozieł et al. (2014 studied chronologies of peat sequences by measuring the 14 C, 210 Pb and 137 Cs profile activities (0-20-cm depth) in a Polish peat bog. ...
To help understand the dynamics of peatlands forming on the Southern Serra do Espinhaço, Brazil, the occurring natural (²²⁶Ra, ²³²Th, ⁴⁰K) and anthropogenic (¹³⁷Cs) activity of gamma-ray emitters located at three sites, namely the localities of São João da Chapada (CH), Pinheiro (PIN) and Pau de Fruta (PDF), was studied. The iron compounds were characterized by ⁵⁷Fe Mössbauer spectroscopy. Differences on natural radionuclide levels and distributions were found among the peatland sites, indicating differences on mineral composition, hydric regimes and living. Significant correlation was found only for ²³²Th–²²⁶Ra activity values (Pearson correlation coefficient of − 0.5), which is different from other South American soils, where significant positive correlations among all radionuclides were determined. In PDF and CH, the dose rate results are lower than the worldwide mean value, but in PIN, they are higher because of the relatively high ²²⁶Ra concentration. The only anthropogenic radionuclide is ¹³⁷Cs. The convection–diffusion model fits the CH and PDF activity profiles, although the PIN profile is likely affected by other soil mechanisms as well. Mössbauer spectra reveal Fe³⁺ in two different local environments and the occurrence of hematite in the upper samples of the CH site. The iron concentration decreases with depth. Contrary to soils of other regions, no significant correlation was found between iron species and the natural radioactivity. The studied peatlands exhibit clear differences between their natural and anthropogenic radionuclide distributions to those of mineral soils.
... Враховуючи те, що отримані величини біомаси міцелію у верхніх шарах досліджуваних лісових ґрунтів швидше недооцінені, ніж переоцінені, та враховуючи показник щільності ґрунту 0,4 г см -3 , приймаємо, що питомий вміст міцелію у цьому шарі ґрунту становитиме від 3 до 6 об'ємних відсотків. Наведені значення досить добре узгоджуються з оцінками, наведеними у наших попередніх роботах [13,14]. Оцінюючи біомасу тонких (≤ 2 мм у діаметрі) коренів у ґрунті, використовували дані (400 г/м 2 до глибини 90 см) для ґрунтів хвойних лісів Бельгії, де у насадженнях переважає сосна звичайна віком 70 років [7]. ...
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.
... 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.
... Thus, Cs concentrations in sporocarps were nearly one order of magnitude higher than those in mycelium. Similar behaviour of 137 Cs was observed in our previous studies (Vinichuk and Johanson, 2003;Vinichuk et al., 2004), where 137 Cs activity increased in the order: soil b mycelium b fungal sporocarps. The differences between fungal species in their preferences for uptake of 137 Cs or stable Cs seem to reflect the location of the fungal mycelium relative to that of caesium within the soil profile (Rühm et al., 1997). ...
Radiocaesium ((137)Cs) was widely deposited over large areas of forest in Sweden as a result of the Chernobyl accident in 1986 and many people in Sweden eat wild fungi and game obtained from these contaminated forests. In terms of radioisotope accumulation in the food chain, it is well known that fungal sporocarps efficiently accumulate radiocaesium ((137)Cs), as well as the alkali metals potassium (K), rubidium (Rb) and caesium (Cs). The fungi then enhance uptake of these elements into host plants. This study compared the accumulation of these three alkali metals in bulk soil, rhizosphere, soil-root interface, fungal mycelium and sporocarps of mycorrhizal fungi in a Swedish forest. The soil-root interface was found to be distinctly enriched in K and Rb compared with the bulk soil. Potassium concentrations increased in the order: bulk soil<rhizosphere<fungal mycelium<soil-root interface<fungal sporocarps; and Rb concentration in the order: bulk soil<rhizosphere<soil-root interface<fungal mycelium<fungal sporocarps. Caesium was more or less evenly distributed within the bulk soil, rhizosphere and soil-root interface fractions, but was actively accumulated by fungi. Fungi showed a greater preference for Rb and K than Cs, so the uptake of (137)Cs could be prevented by providing additional Rb or K at contaminated sites. The levels of K, Rb, and Cs found in sporocarps were at least one order of magnitude higher than those in fungal mycelium. These results provide new insights into the use of transfer factors or concentration ratios. The final step, the transfer of alkali metals from fungal mycelium to sporocarps, raised some specific questions about possible mechanisms.
... In soils with high clay content, there is low bioavailability and low vertical migration rate of radiocaesium due to its binding to certain clay minerals (Cremers et al., 1990;Cornell, 1993;Wauters et al., 1996). In nutrient-poor but organic matter-rich forest soils, the vertical migration rate of 137 Cs is also low but the bioavailability is often high, particularly for mycorrhizal fungi (Olsen et al., 1990;Steiner et al., 2002;Vinichuk and Johanson, 2003;Vinichuk et al., 2004). In forests and pastures, extensive fungal mycelium counteracts the downward transport of 137 Cs by an upward translocation flux (Rafferty et al., 1997(Rafferty et al., , 2000. ...
The vertical distribution of (137)Cs activity in peat soil profiles and (137)Cs activity concentration in plants of various species was studied in samples collected at two sites on a raised bog in central Sweden. One site (open bog) was in an area with no trees and only a few sparsely growing plant species, while the other (low pine) was less than 100 m from the open bog site and had slowly growing Scots pine, a field layer dominated by some ericaceous plants and ground well-covered by plants. The plant samples were collected in 2004-2007 and were compared with samples collected in 1989 from the same open bog and low pine sites. Ground deposition of (137)Cs in 2005 was similar at both sites, 23,000 Bq m(-2). In the open bog peat profile it seems to be an upward transport of caesium since a clear peak of (137)Cs activity was found in the uppermost 1-4 cm of Sphagnum layers, whereas at the low pine site (137)Cs was mainly found in deeper (10-12 cm) layers. The migration rate was 0.57 cm yr(-1) at the open bog site and the migration centre of (137)Cs was at a depth of 10.7, while the rate at the low pine site was 0.78 cm yr(-1) and the migration centre was at 14.9 cm. Heather (Calluna vulgaris) was the plant species with the highest (137)Cs activity concentrations at both sites, 43.5 k Bq(-1) DM in 1989 decreasing to 20.4 in 2004-2007 on open bog and 22.3 k Bq kg(-1) DM in 1989 decreasing to 11.2 k Bq(-1) DM by the period 2004-2007 on the low pine site. (137)Cs transfer factors in plants varied between 0.88 and 1.35 on the open bog and between 0.48 and 0.69 m(2)kg(-1) DM at the low pine site.
The dating of young peatlands with 210Pb method is a difficult task. Standard 210Pb dating models require an exponential decrease in activity down the peat profile. In Arctic peatlands, we note a significant migratory capacity of lead, therefore, for accurate dating of peat, it is necessary to improve the existing dating models to eliminate the effect of migration and their verification using independent isotope chronometers, for example, 137Cs. We applied several models CA, CFCS, PF, CF together with the Monte Carlo method for peat core samples taken within the European Subarctic of Russia (Arkhangelsk region). Comparison with the specific activities of 137Cs, determined at a depth of 19—21 cm, associated with the global fallout in 1963, showed that the closest age to the specified reference point is given by the CFCS and CF models (1965 and 1962, respectively). Among these two options, CF using the Monte Carlo method turned out to be preferable, since it provided, taking into account the error, a slightly better agreement with the specific activities of 137Cs in the reference horizon. Despite the difficulties associated with the complex distribution of 210Pb over the peat section due to migration, the dating methods used were successful and, in the future, can be applied to dating other peat deposits.
210 Pb-датирование, применяемое во временном диапазоне 100-150 лет. Моделирование по методу Монте-Карло использовано для оценки погрешности 210 Pb-датирования. Подход реализован в формате электронных таблиц MS Excel, в которых расчетными параметра-ми являются диаметр керна, период полураспада 210 Pb, глубина слоя, сухая масса слоя, общее содержание 210 Pb и концентрация 226 Ra. Метод апробирован при датировании торфяных кернов, отобранных в Приморском и Мезенском районах Архангельской области, с последующим расчетом темпов осадконакопления.
IntroductionClassification, Structure, and Color MeasurementsLegislation and RegulationsAlternative Decolorization Treatment TechnologiesFungal Decolorization and Degradation of DyesYeast Decolorization and Degradation of DyesWhite-Rot Fungal Decolorization and Degradation of DyesMechanisms of Fungal Decolorization and Degradation of DyesMetabolic Products and PathwaysFactors Affecting Fungal Decolorization and Degradation of DyesFungal Dye Decolorization and Degradation BioreactorsDecolorization and Degradation of Dyes by Fungal EnzymesDecolorization of Artificial Textile EffluentSequential Dye DecolorizationConclusions and Future PerspectivesReferences
Fertilization of soils contaminated by radionuclides with potassium (K) and its effect on 137Cs transfer from soil to crops is well studied in field conditions; however experiments over many years are few.
The effects of potassium fertilization on cesium-137 (137Cs) transfer to hay, pasture grass, and barley growing on organic rich soils and mineral sand and loam soils in a number of field experimental sites situated in different environments in Sweden are summarized and discussed. The basic experimental treatments were control (no K fertilizers were applied), 50, 100, and 200 kg K ha−1. In the experiment, which lasted over 3–6 years, 137Cs transfer factors in control treatments ranged between 0.0004 m2 kg−1 (barley grain on sand soil) and 0.07 m2 kg−1 (pasture grass on organic rich soil). Potassium application on soils with low clay content i.e. mineral sand and organic rich soils was effective at the 50–100 kg ha−1 level. Application of 200 kg K ha−1 resulted in a five-fold reduction in 137Cs transfer for hay and up to four-fold for barley grain. The effects of potassium application were generally greater on sand than organic rich soil and were observed already in the first cut. After K application, the reduction in 137Cs transfer to crops was correlated with 137Cs:K ratios in plant material. Additional application of zeolite caused a 1.4 reduction of 137Cs transfer to hay on sand and 1.8-fold reduction on organic rich soil; whereas, application of potash-magnesia and CaO had no effect.
We record the distribution of (137)Cs, K, Rb and Cs within individual Sphagnum plants (down to 20cm depth) as well as (137)Cs in vascular plants growing on a peatland in eastern central Sweden. In Calluna vulgaris(137)Cs was mainly located within the green parts, whereas Andromeda polifolia, Eriophorum vaginatum and Vaccinium oxycoccos showed higher (137)Cs activity in roots. Carex rostrata and Menyanthes trifoliata showed variable distribution of (137)Cs within the plants. The patterns of (137)Cs activity concentration distribution as well as K, Rb and Cs concentrations within individual Sphagnum plants were rather similar and were usually highest in the capitula and/or in the subapical segments and lowest in the lower dead segments, which suggests continuous relocation of those elements to the actively growing apical part. The (137)Cs and K showed relatively weak correlations, especially in capitula and living green segments (0-10cm) of the plant (r=0.50). The strongest correlations were revealed between (137)Cs and Rb (r=0.89), and between (137)Cs and stable Cs (r=0.84). This suggests similarities between (137)Cs and Rb in uptake and relocation within the Sphagnum, but that (137)Cs differs from K.
Cenococcum geophilum Fr. is one of the most frequently encountered ECM fungi in nature. This genus is cosmopolitan and is well recognized for its extremely wide host and habitat range. C. geophilum was originally described from its black sclerotia by J. Sowerby in 1800 under the name Lycoperdon graniforme Sow. Elias Fries introduced the genus Cenococcum and the species C. geophilum in 1825, and considered Sowerby’s L. graniforme to be a synonym of C. geophilum Fr. (Fries 1825). In their monographic study of Cenococcum Fr., Ferdinandsen and Winge (1925) made the new combination C. graniforme (Sow.) Ferd. and Winge. The isolation of a “jet-black mycelium” that formed ECM was first identified by Hatch (1934) and provisionally named Mycelium radicus nigrostrigosum Hatch. The connection of these black ECM to C. geophilum was made by Linhell (1942). This black ECM was subsequently reported by many researchers on a wide variety of tree species in different parts of the world (Mikola 1948). C. geophilum Fr. is the sanctioned name.
Mushrooms and substrata collected from a coastal pine forest in Rokkasho-mura, Aomori Prefecture, Japan were measured for radiocaesium and stable Cs. The ranges of 137Cs and stable Cs concentrations in mushrooms were ND-570 Bq kg-1 fresh weight and 0·005–1·6 mg kg-1 fresh weight, respectively. Both 137Cs and stable Cs concentrations in mushrooms were higher than those in common agricultural plants. The concentrations of 137Cs and stable Cs in the substrata were 37–261 Bq kg-1dry weight and 0·29–0·98 mg kg-1 dry weight, respectively. The specific activities of 137Cs in mushrooms were several times higher than those in the substrata. The substratum-to-mushroom transfer factors of 134Cs, 137Cs and stable Cs were in the range of 0·1–3·5, 0·03–3·3 and 0·01–1·7, respectively. These transfer factors were 1–3 orders of magnitudes higher than those for plants. The transfer factors of 137Cs were equivalent to those of 134Cs and were also significantly correlated to those of stable Cs.
Since 1987, 134Cs and 137Cs measurements have been carried out on about 350 samples of different fungal species which have grown in a coniferous Bavarian forest. It was established, through these measurements, that different fungal species have their mycelia in different soil horizons. Since the radiocaesium activity in these soil horizons changes with time, the activities of radiocaesium in different fungal species are also expected to behave differently over time. The time-dependent behaviour of the radiocaesium activity in mushrooms was therefore compared with the time-dependent behaviour of radiocaesium activity in certain soil horizons where mycelia of these species are located, for 14 species gathered in at least four different years. By means of least-squares regressions, non-time-dependent transfer factors with standard error levels of less than 20% were derived. Fungal species were identified in which radiocaesium contamination was decreasing, constant, or increasing. In the future, the mean radiocaesium activity will decrease giving ecological half-lives of between 3 and 8 years for all species. These results are useful for describing radiocaesium contamination of mushrooms in terms of generic models currently being developed for forest ecosystems.
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.
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.
Autoradiography and quantitative image analysis were used to measure 137Cs distribution and translocation through mycelia of A. gallica Marxmuller & Romagn. and A. ostoyae (Romagn.) Herink growing in small microcosms in the laboratory. Rhizomorphs of A. gallica were labelled with 134Cs in the field, and the translation of radiolabel measured after excavation and destructive harvesting. The flux of radiocaesium through rhizomorphs was estimated to be greater than through undifferentiated hyphae, and greater through rhizomorphs growing in the field than through rhizomorphs grown across homogeneous media in the laboratory'. Differentiation within mycelia resulting in melanization or rhizomorph formation cave rise to increased heterogeneity in the 137Cs distribution through laboratory microcosms compared with that through microcosms containing undifferentiated mycelia. Radiocaesium leaked from undifferentiated hyphae into the surrounding medium, but melanized regions of the mycelium appeared to be conservative for radiocaesium. These findings provide further evidence for the importance of filamentous fungi in determining the distribution and rate of release of radiocaesium currently present in the environment as a result of weapons testing and the accident at the Chernobyl nuclear reactor.
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.
SUMMARYA new technique, autoradiography followed by quantitative image analysis, provides a powerful, non-destructive method for measurement of radiolabel distribution and translocation throughout: fungal mycelia. Using this technique radio caesium was found to be translocated by bulk flow in actively expanding mycelium of S. commune but by diffusion in established mycelium in microcosms. Differentiation of hyphae to form primordia in preparation for basidiocarp production was found to introduce heterogeneity into the distribution of radio caesium in mycelia which could later be reversed by diffusion. Mycelium of S. commune was not conservative for radiocaesium, losing significant amounts to the medium; it is suggested that binding to soil particles may be more significant in terms of long-term retention of this radionuclide in the environment. These processes may account in part for the high and variable concentrations of radiocaesium found in mushrooms in the environment.
• The asexual ectomycorrhizal fungus Cenococcum geophilum , known for its wide host and habitat range, has been suggested to provide isolate‐dependant drought protection to fine roots. However, little is known about its genetic structure at the fine scale.
• Genetic diversity and population structure of C. geophilum at the regional and stand scales was surveyed in five beech ( Fagus silvatica ) forests in northeastern France. The stands were selected for their contrasting climatic and edaphic features to assess the effect of environmental factors on population structure.
• The genetic diversity of C. geophilum was estimated using RAPD, PCR/RFLP of the rDNA internal transcribed spacer (ITS) and PCR/RFLP and sequencing of an anonymous sequence characterized amplified region (SCAR) on ectomycorrhizas and sclerotia‐derived mycelial cultures.
• A high degree of genetic diversity was observed between and within beech stands in C. geophilum populations. These results suggest the occurrence of a high rate of mitotic or meiotic recombination and an effect of stand features on population structure.
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.
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.
Fungi are one of the most important components of forest ecosystems, since they determine to a large extent the fate and transport processes of radionuclides in forests. They play a key role in the mobilization, uptake and translocation of nutrients and are likely to contribute substantially to the long-term retention of radiocesium in organic horizons of forest soil. This paper gives an overview of the role of fungi regarding the transfer and cycling of nutrients and radionuclides, with special emphasis on mycorrhizal symbiosis. Common definitions of transfer factors, soil–fungus and soil–green plant, including their advantages and limitations, are reviewed. Experimental approaches to quantify the bioavailability of radionuclides in soil and potential long-term change are discussed.
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.
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.
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.
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.
Resupinate thelephoroid fungi (hereafter called tomentelloid fungi) have a world-wide distribution and comprise approximately 70 basidiomycete species with inconspicuous, resupinate sporocarps. It is only recently that their ability to form ectomycorrhizas (EM) has been realized, so their distribution, abundance and significance as mycobionts in forest ecosystems is still largely unexplored. In order to provide baseline data for future ecological studies of tomentelloid fungi, we explored their presence and abundance in nine Swedish boreal forests in which the EM communities had been analysed. Phylogenetic analyses were used to compare the internal transcribed spacer of nuclear ribosomal DNA (ITS rDNA) sequence data obtained from mycobionts on single ectomycorrhizal tips with that obtained from sporocarps of identified tomentelloid fungi. Five species of Tomentella and one species of Pseudotomentella were identified as ectomycorrhizal fungi. The symbiotic nature of Tomentella bryophila, T. stuposa, T. badia and T. atramentaria is demonstrated for the first time. T. stuposa and Pseudotomentella tristis were the most commonly encountered tomentelloid fungi, with the other species, including T. sublilacina, only being recorded from single stands. Overall, tomentelloid fungi were found in five of the studies, colonizing between 1 and 8% of the mycorrhizal root tips. Two of the five sites supported several tomentelloid species. Tomentelloid fungi appear to be relatively common ectomycorrhizal symbionts with a wide distribution in Swedish coniferous forests. The results are in accordance with accumulating data that fungal species which lack conspicuous sporocarps may be of considerable importance in EM communities.
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%.
Soil fungi and the fate of radiocaesium in the soil ecosystem-a discussion of possible mechanisms involved in the radiocaesium accumulation in fungi, and the role of fungi as a Cs-sink in the soil
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