An estimation of 137Cs accumulation in forest fungi by the soil properties

A method of calculation of radiocaesium uptake by forest mushrooms as a function of soil properties is presented. Calculated value of 137Cs transfer factor for Xerocomus badius in the contaminated area of Bryansk Province of Russia is in a good agreement with experimental data.     

Modelling of radiocaesium soil-plant transfer

Existing methods of predicting of radiocaesium transfer from soil to plants was critcally reviewed. The analysis of radiocaesium behavior in the system "soil solid phase/pore solution/plant" was carried out. Equations for calculation of radiocaesium uptake by plants as a function of soil properties were obtained and tested using the reported experimental data. Key soil parameters which natural variability and estimation difficulty are the main sources of prediction uncertainty were identified.     

Plant uptake of radiocaesium: a review of mechanisms, regulation and application

Soil contamination with radiocaesium (Cs) has a long-term radiological impact because it is readily transferred through food chains to human beings. Plant uptake is the major pathway for the migration of radiocaesium from soil to human diet. The plant-related factors that control the uptake of radiocaesium are reviewed. Of these, K supply exerts the greatest influence on Cs uptake from solution. It appears that the uptake of radiocaesium is operated mainly by two transport pathways on plant root cell membranes, namely the K(+) transporter and the K(+) channel pathway. Cationic interactions between K and Cs on isolated K-channels or K transporters are in agreement with studies using intact plants. The K(+) transporter functioning at low external potassium concentration (often <0.3 mM) shows little discrimination against Cs(+), while the K(+) channel is dominant at high external potassium concentration with high discrimination against Cs(+). Caesium has a high mobility within plants. Although radiocaesium is most likely taken up by the K transport systems within the plant, the Cs:K ratio is not uniform within the plant. Difference in internal Cs concentration (when expressed on a dry mass basis) may vary by a factor of 20 between different plant species grown under similar conditions. Phytoremediation may be a possible option to decontaminate radiocaesium-contaminated soils, but its major limitation is that it takes an excessively long time (tens of years) and produces large volumes of waste.     

Proximate composition and biological activity of food plants gathered by chilean Amerindians

The proximate composition and biological activity of food plants and mushrooms gathered by Chilean Amerindians were assessed. The gathered plants served primarily as sources of carbohydrates with highest values for Dioscorea tubers, Prosopis alba pods meal and Bromus catharticus seeds. The mushrooms Clavaria coralloides and Boletus loyus proved to be the best protein sources in our survey, but deficient in the amino acids methionine and cysteine. Some extracts of the plants and mushrooms under study showed biological activity as free radical scavengers, enzyme inhibitors, hypotensive or DNA binding effect. Free radical scavenging activity was detected in Cryptocarya alba fruit extract, while Typha angustifolia showed a strong DNA binding effect at 0.50 mg/ml. Methanolic extracts of the Apiaceae species Sanicula graveolens and Apium australe were moderately active as β-glucuronidase inhibitors at 50 fig/ml.     

Absorption,retention and tissue distribution of radiocaesium in reindeer: effects of diet and radiocaesium source

Radiocaesium absorption and retention in reindeer (Rangifer tarandus) calves was compared in groups fed diets containing different proportions of lichen and concentrates, and different chemical forms of radiocaesium ((134)CsCl in solution or fallout from the Chernobyl accident). Daily intakes of fallout radiocaesium were 15-23 kBq, while daily intakes of (134)CsCl ranged from 70 kBq to 1,160 kBq. The half-life for radiocaesium in red blood cells (RBC) in animals fed with a pure lichen diet exceeded that in animals fed with a combined diet of lichen and concentrates by 40% (17.8+/-0.7 days vs. 12.7+/-0.4 days). Corresponding differences in the half-lives for urinary and faecal excretion were about 60% and 40%, respectively. Transfer coefficients (F(f)) to reindeer meat were estimated to be 0.25+/-0.01 days kg(-1) for fallout radiocaesium and 1.04+/-0.03 days kg(-1) for (134)CsCl, reflecting differences in both radiocaesium bioavailability and retention. The bioavailability of the Chernobyl radiocaesium in lichen in 1988 was estimated at ca. 35% compared to (134)CsCl.     

Sorption and release of radiocaesium from particulate matter of the Baltic coastal zone

Laboratory expriments have demonstrated that radiocaesium can be released in different proportions from Baltic sediments, depending on the type and origin of sediment, contact time and solid-to-liquid phase ratio. Rapidly accumulating sediments in areas affected by river discharge have much higher percentage of exchangeable radiocaesium than slowly accumulating marine sediments. The latter have been shown to {uptake radiocaesium from overlying sea water at high suspended loads. Pronounced radiocaesium gradients at sediment-water interface in Gda\'nsk Bay can be explained by either diffusion from pore water or desorption from sediment particles uprised by waves and/or bottom currents, or a combination of both. Desorption is likely to decrease with age of the sediment.     

Extraradical mycelium of the arbuscular mycorrhizal fungus Glomus lamellosum can take up,accumulate and translocate radiocaesium under root-organ culture conditions

Radiocaesium enters the food chain when plants absorb it from soil, in a process that is strongly dependent on soil properties and plant and microbial species. Among the microbial species, arbuscular mycorrhizal (AM) fungi are obligate symbionts that colonize the root cortex of many plants and develop an extraradical mycelial (ERM) network that ramifies in the soil. Despite the well-known involvement of this ERM network in mineral nutrition and uptake of some heavy metals, only limited data are available on its role in radiocaesium transport in plants. We used root-organ culture to demonstrate that the ERM of the AM fungus Glomus lamellosum can take up, possibly accumulate and unambiguously translocate radiocaesium from a 137Cs-labelled synthetic root-free compartment to a root compartment and within the roots. The accumulation of 137Cs by hyphae in the root-free compartment may be explained by sequestration in the hyphae or by a bottleneck effect resulting from a limited number of hyphae crossing the partition between the two compartments. Uptake and translocation resulted from the incorporation of 137Cs into the fungal hyphae, as no 137Cs was detected in mycorrhizal roots treated with formaldehyde. The importance of the translocation process was indicated by the correlation between 137Cs measured in the roots and the total hyphal length connecting the roots with the labelled compartment. 137Cs may be translocated via a tubular vacuolar system or by cytoplasmic streaming per se.     

Temporal and spatial prediction of radiocaesium transfer to food products

A recently developed semi-mechanistic temporal model is used to predict food product radiocaesium activity concentrations using soil characteristics available from spatial soil databases (exchangeable K, pH, percentage clay and percentage organic matter content). A raster database of soil characteristics, radiocaesium deposition, and crop production data has been developed for England and Wales and used to predict the spatial and temporal pattern of food product radiocaesium activity concentrations (Bq/kg). By combining these predictions with spatial data for agricultural production, an area’s output of radiocaesium can also be estimated, we term this flux (Bq/year per unit area). Model predictions have been compared to observed data for radiocaesium contamination of cow milk in regions of England and Wales which received relatively high levels of fallout from the 1986 Chernobyl accident (Gwynedd and Cumbria). The model accounts for 56% and 80% of the observed variation in cow milk activity concentration for Gwynedd and Cumbria, respectively. Illustrative spatial results are presented and suggest that in terms of food product contamination areas in the North and West of England and Wales are those most vulnerable to radiocaesium deposition. When vulnerability is assessed using flux the spatial pattern is more complex and depends upon food product. Received: 26 March 2001 / Accepted: 11 July 2001     

Effects of External Potassium Supply on Compartmentation and Flux Characteristics of Radiocaesium in Intact Spring Wheat Roots

Short term experiments investigated the effects of potassiumsupply on radiocaesium influx/efflux and the radiocaesium compartmentationin intact spring wheat roots. Short term (24–72 h) influxanalysis showed that net influxes of radiocaesium to both rootand xylem were reduced approximately ten-times by increasingexternal potassium concentration from 50 µM to 200 µM.Efflux analysis distinguished three components for radiocaesium(namely cell wall+free space, cytoplasm and vacuole) and showedthat the rates of Cs⁺efflux at an external potassium concentrationof 100 µM (19.16 and 1.70 Bq g^-1min^-1for     

Monte-Carlo prediction of changes in areas of west Cumbria requiring restrictions on sheep following the Chernobyl accident

Following the 1986 Chernobyl accident radiocaesium levels in sheep meat in some upland areas of the United Kingdom were above the national intervention limit. West Cumbria was one of these areas and restrictions are currently still in place. In addition to deposition from the Chernobyl accident, Cumbria has been subject to radiocaesium deposition from atmospheric nuclear weapons tests, the 1957 Windscale accident and routine releases from the Sellafield nuclear reprocessing plant. A Monte-Carlo approach has been used to try to predict areas in west Cumbria where radiocaesium activity concentrations in lamb meat would require the imposition of restrictions at different times after the Chernobyl accident. The approach models the transfer of radiocaesium from soil to vegetation, based upon soil organic matter, and from vegetation to lamb meat. Spatial inputs are soil organic matter and total post-Chernobyl (137)Cs and (134)Cs deposition; a ratio of Chernobyl (137)Cs to (134)Cs deposition has been used to differentiate Chernobyl and pre-Chernobyl (137)Cs deposition. Comparisons of predicted radiocaesium transfer from soil-vegetation and the spatial variation in lamb (137)Cs activity concentrations are good and predicted restricted areas with time after Chernobyl compare well to the restricted areas set by UK government. We predict that restrictions may be required until 2024 and that in some areas the contribution of pre-Chernobyl (137)Cs to predicted lamb radiocaesium activity concentrations is significant, such that restrictions may only have been required until 1994 as a consequence of Chernobyl radiocaesium deposition alone. This work represents a novel implementation of a spatial radioecological model using a Monte-Carlo approach.     

The use of an in vitro technique to predict the absorption of dietary radiocaesium by sheep

The validity of an in vitro extraction technique to predict the availability for absorption of radiocaesium in the sheep gut has been assessed. The technique (a 2-h extraction with caesium chloride) was found to be valid for sources with a low availability for transfer across the gut, but inappropriate for ionic radiocaesium or radiocaesium incorporated internally within herbage. For such radiocaesium sources, which have a high in vitro availability, no correlation was found between in vitro extraction and true absorption measurements. A true absorption value of 0.80 is recommended for these sources, although values for individual sheep in the range 0.60 to 1.00 should be expected.     

Physiological parameters that affect the transfer of radiocaesium to ruminants

Recently there has been a renewed interest in biological scaling relationships between parameters, such as those between, for example, body mass, dry matter intake and biological half-times of radionuclides that are useful in predicting the transfer of radiocaesium to different animal species, particularly to wild animals. However, there is still a considerable unexplained variability in transfer coefficient estimates between individuals of the same species. This paper discusses the physiological parameters that affect the transfer of radiocaesium to ruminants, and it shows how a better understanding of these parameters may help to reduce the within-species variability in radiocaesium transfer coefficients. In light of the improved understanding during the past 10-15 years of the importance of source-dependent bioavailability on absorption of radiocaesium from the gastrointestinal tract, it is concluded that further studies are required on the effects of feed digestibility and physiological factors on absorption and endogenous faecal excretion of radiocaesium to better understand the variability in transfer coefficients.     

Fluvial transport and redistribution of Chernobyl fallout radionuclides

Fallout of Chernobyl-derived radionuclides over the UK evidenced marked spatial variation. Relatively high levels were recorded in central Wales, but they declined rapidly to the east and southeast. As a result, the headwaters of the River Severn received substantial inputs of fallout, whereas only low levels were recorded over the middle and lower reaches of its drainage basin. This situation afforded a valuable opportunity to investigate the sediment-associated transport of Chernobyl-derived radiocaesium through the 10 000 km² drainage basin and its redistribution by fluvial processes.Information on the fallout inputs of radiocaesium has been obtained from the sampling of soil inventories across the basin. Measurements of the radiocaesium content of suspended sediment have been made at several sites on the main river over a period extending from before the Chernobyl disaster through to 1988. Concentrations of caesium-137 in the suspended sediment increased by two orders of magnitude immediately after the accident up to 1450 mBq g ^–1, declined rapidly subsequently, but remained almost an order of magnitude greater than the pre-Chernobyl levels throughout the remainder of the period (1986–1988). Downstream redistribution of radiocaesium has occurred as a result of deposition of sediment-associated radiocaesium in channel and floodplain sinks. It is estimated that 0.6% of the total fallout input of Chernobyl-derived caesium-134 has been transported out of the basin during the period 1986–1990. Estimates of channel and floodplain storage of sediment-associated caesium-134 at the time of sampling in 1988 and 1989 account for 0.01% and 0.2% of the total fallout input to the basin respectively.     

Genotypic effects in phytoavailability of radiocaesium are pronounced at low K intensities in soil

The differences in radiocaesium uptake between species were analysed in a series of solution culture and pot trials. Since radiocaesium uptake is very sensitive to the solution potassium (K) concentration, it was hypothesised that species depleting K in the rhizosphere to a larger extent, will have a higher radiocaesium uptake. Five species (bean, lettuce, winter barley, ryegrass and bentgrass) were grown for 18–21 days in nutrient solution spiked with ¹³⁷Cs and at 4 K concentrations between 0.025 and 1.0 mM. Shoot ¹³⁷Cs activities all decreased between 17- and 81-fold with increasing K supply. Shoot ¹³⁷Cs activities were 4-fold different between species at the lowest K supply and 3.4-fold different at high K supply. The same five species were grown in two ¹³⁴Cs spiked soils with contrasting exchangeable K but similar clay content. Shoot ¹³⁴Cs activities were up to 19-fold higher in the soil with lowest exchangeable K. Differences in shoot activity concentrations between the species were only 4.5-fold in the high K soil, but were 15-fold in the low K soil. Bulk soil solution ¹³⁴Cs and K concentration data were combined with radiocaesium uptake characteristics measured in solution culture to predict radiocaesium uptake from soil. Predictions were within 1.6-fold of observations in the high K soil but largely underestimated ¹³⁴Cs uptake in lettuce, ryegrass and barley in the low K soil. A solute transport model was used to estimate K and radiocaesium concentrations in the rhizosphere. These calculations confirmed the assumption that higher radiocaesium uptake is found for species that deplete K in the rhizosphere to a larger extent.     

Variation in the metabolism of radiocaesium between individual sheep

Considerable variability has been recorded in the radiocaesium activity concentration of muscle between individual sheep in the same flocks in upland areas that received fallout from the Chernobyl accident. In a previous paper we demonstrated that there is a propensity for certain sheep within a flock to be always amongst the most contaminated and others to be consistently the least contaminated. Here we report a study to determine the extent to which variation in the metabolism of radiocaesium by individual sheep may contribute to the observed variability within sheep flocks. The transfer coefficient and biological half-life of orally administered ionic radiocaesium in muscle were determined under controlled conditions in 22 ewes from an upland farm in an area of the UK which received comparatively high levels of Chernobyl fallout. There was considerable variation between individuals in both the transfer coefficient (0.19–0.56 day⋅kg^–1; mean 0.34 day⋅kg^–1) and biological half-life in muscle (5.2– 18.7 days; mean 9.8 days). Changes in liveweight during the study and feed intake together accounted for 72% of the variation in the derived transfer coefficients; liveweight change also accounted for 56% of the observed variation in biological half-life. In a subsequent study, the true absorption coefficient of radiocaesium was determined in 12 of the ewes. There was a positive correlation between transfer and true absorption coefficients (R=0.57). We conclude that differences in the metabolism of radiocaesium will contribute to the observed variability in radiocaesium activity concentrations within sheep flocks in areas which were contaminated by Chernobyl fallout. We also suggest that for growing animals, the influence of liveweight change and feed intake on radiocaesium transfer may be greater than observed here. Similarly, in dairy cattle, for which feed intake changes considerably during the course of a lactation, large temporal variation in radiocaesium transfer to milk could be expected. Received: 10 August 1998 / Accepted in revised form: 20 October 1998     

Predicting rarity and decline in animals,plants, and mushrooms based on species attributes and indicator groups

In decisions on nature conservation measures, we depend largely on knowledge of the relationship between threats and environmental factors for a very limited number of species groups, with relevant environmental factors often being deduced from the relationship between threat and species traits. But can relationships between traits and levels of threats be identified across species from completely different taxonomic groups; and how accurately do well-known taxonomic groups indicate levels of threat in other species groups? To answer these questions, we first made a list of 152 species attributes of morphological and demographic traits and habitat requirements. Based on these attributes we then grew random forests of decision trees for 1183 species in the 18 different taxonomic groups for which we had Red Lists available in the Netherlands, using these to classify animals, plants, and mushrooms according to their rarity and decline. Finally, we grew random forests for four species groups often used as indicator groups to study how well the relationship between attribute and decline within these groups reflected that relationship within the larger taxonomic group to which these groups belong. Correct classification of rarity based on all attributes was as high as 88% in animals, 85% in plants, and 94% in mushrooms and correct classification of decline was 78% in animals, 69% in plants, and 70% in mushrooms. Vertebrates indicated decline in all animals well, as did birds for all vertebrates and vascular plants for all plants. However, butterflies poorly indicated decline in all insects. Random forests are a useful tool to relate rarity and decline to species attributes thereby making it possible to generalize rarity and decline to a wider set of species groups. Random forests can be used to estimate the level of threat to complete faunas and floras of countries or regions. In regions like the Netherlands, conservation policy based on attributes known to be relevant for the decline to birds, vertebrates or plants will probably also impact all aboveground terrestrial and freshwater macrofauna or macrophytes.     

Radiocaesium in lynx in relation to ground deposition and diet

The european lynx (Lynx lynx) might be expected to have a high intake of radiocaesium in the parts of Sweden where the main prey of the lynx, namely reindeer and roe deer have high activity concentrations of radiocaesium because of high ground deposition. We have measured ¹³⁷Cs in muscle samples from 733 lynx during 1996–2003. The aim was to quantify the extent to which radiocaesium is transferred from fallout deposition to lynx, to test whether the transfer was higher in areas where there are reindeer present, to see if there was any decline in radiocaesium over time, and to calculate the radiation dose to lynx. Most samples were collected in central and northern Sweden during January–April. Activity concentrations in lynx varied from 13 Bq kg^–1 to about 15 kBq kg^–1 fresh weight, with the highest value corresponding to a radiation dose at 18 mGy/year. Aggregated transfer coefficients (Tag), calculated by dividing the ¹³⁷Cs activity concentration in lynx muscle by the average ground deposition (total from Chernobyl and nuclear weapon tests) within a 50 km radius around the location of the lynx, varied from 0.004 to 1.3 m² kg^–1 and were significantly higher within the reindeer herding area than outside. The concentration ratio (CR) for lynx/reindeer was 2.6 on average, whilst the average for lynx/roe deer outside the reindeer herding area was lower at 1.3. Based on these results, a CR of around 2 could be considered representative for the general ratio between predator and prey. A long-term decline of radiocaesium in prey species was reflected in lynx, with an effective half-life of 7 years from 1996 to 2003. The study shows that the accumulation of radiocaesium in predators, especially predators of reindeer, makes them more vulnerable to high radiocaesium deposition than most other wild species.     

食用菌栽培种类野生种质的评价

我国是食用菌野生种质资源丰富的国家,目前已查明自然分布可栽培野生种类93种,分布于担子菌的33个属。我国人工栽培种类近70种（变种）,不同规模栽培有50种,商业规模栽培33种,分布于5目,12科,18属。与绿色植物的自养型光合作用合成有机物质相反,食用菌将植物光合作用合成的有机物分解,以体壁吸收方式摄取营养建造自身。这种生理特点的不同,导致其种质资源评价要求的不同。由于子实体形态相对于绿色植物简单,且易受环境条件的影响,常常导致以形态特征为主要依据进行分类鉴定陷入困境。另一方面,形态相似的多个可栽培近缘种在侧耳（Pleurotus）、木耳（Auricularia）、蜜环菌（Armillaria）等中广泛存在,完全靠形态特征进行分类鉴定就更加困难。因此,在食用菌可栽培种类野生种质评价中,ITS测序等成为获得菌种生物学种的常用鉴定技术。菌种的分离培养中常受到菌落形态相似真菌的污染,RAPD、ISSR或ITS测序等常用来进行菌种符合性鉴定。食用菌孢子传播的特点,使其分布地理区域广泛,地理区域的隔离产生种内的个体或群体间的差异,形成种群的多样性,常用拮抗反应进行营养亲和群（个体、菌株）的鉴定。不同区域气候和生态条件下的个体,长期的进化和对环境条件适应性的形成,导致可栽培利用的特点不同。栽培性状要通过栽培试验进行评价。栽培性状主要包括菌丝长速、温度反应、结实性、丰产性、抗性、商品形态和耐贮运性等。为了充分利用远缘优势,对于具可利用栽培性状的种质还需要与栽培菌株间的遗传距离分析,通常用生物化学和分子生物学方法进行。     

Use of the true absorption coefficient as a measure of bioavailability of radiocaesium in ruminants

Limitations of existing methods to describe the bioavailability of dietary radionuclides to ruminants (the transfer coefficient and apparent absorption coefficient) have led to the alternative suggestion of using the true absorption coefficient (A _t). Various approaches to estimatingA _t for radiocaesium, involving the intravenous administration of a second isotope, are presented and discussed with reference to results from studies in which a range of radiocaesium sources were examined in sheep. Although estimates ofA _t differed between the sources, they were reasonably consistent between measurement techniques. Those methods which involved the estimation of endogenous faecal excretion of radiocaesium could be used with previously contaminated animals and did not require continuous administrations of radiocaesium isotopes, but gave unreliable results for sources of low bioavailability. Methods based on estimating the turnover rate of dietary radiocaesium through blood plasma were sufficiently sensitive to measureA _t for the range of sources studied. However, they require previously uncontaminated animals and continuous administration of both isotopes for approximately 7 days. Bioavailability is more effectively measured asA _t than as the transfer or apparent absorption coefficients sinceA _t does not incorporate factors relating to the metabolism of radiocaesium in the tissues of the animal. The results of these studies show that differences in transfer coefficients between sheep and cattle and between sheep of differing ages are not due to variation in absorption across the gut. The potential for applying these approaches to other radioactive elements is discussed.