Soil fertilisation with 137Cs-contaminated and uncontaminated wood ash as a countermeasure to reduce 137Cs uptake by forest plants

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 T_ag 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.

Response of spring wheat and potato to foliar application of Zn, Mn and EDTA fertilizers on 137Cs uptake

The impact of foliar fertilization with zinc (ZnSO₄) and manganese (MnSO₄ on ¹³⁷Cs uptake by spring wheat and potato was studied. The experiments were conducted during 3 years (2014-2016) in a¹³⁷Cs-contaminated area, Zhytomyr region of Ukraine. The fertilization was carried out on podzolic loamy sand soil, poor in most of the microelements. Both crops were fertilized at four successive stages of growth. Foliar application of fertilizers caused higher yield of wheat grain/straw and potato tubers yield in 2014-2015 years but had no effect in 2016. Thus, the overall effect of fertilization between 2014 and 2016 was less pronounced and generally insignificant. Application of Zn, Mn and EDTA reduced ¹³⁷Cs uptake by wheat grain and potato tubers, when fertilized at earlier stages of growth and development in years 2014 and 2015 by factor 1.5-2.0, while in 2016 the effect was generally statistically insignificant. It is suggested, that reduction of ¹³⁷Cs uptake by spring wheat and potato, at least partly, was caused by an effect of radionuclide dilution due to the higher biomass of the plants. A foliar spray of EDTA at earlier stages of plant growth and development may be considered as a potential countermeasure aiming reducing ¹³⁷Cs uptake from soil to plants, even if such effect appeared to be conditional.

Transfer of radionuclides and dose assessment to ants and anthills in a Swedish forest ecosystem

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.

Response to omalizumab using patient enrichment criteria from trials of novel biologics in asthma

Background

Recent efficacy studies of asthma biologics have included highly enriched patient populations. Using a similar approach, we examined factors that predict response to omalizumab to facilitate selection of patients most likely to derive the greatest clinical benefit from therapy.

Methods

Data from two phase III clinical trials of omalizumab in patients with allergic asthma were examined. Differences in rates of asthma exacerbations between omalizumab and placebo groups during the 16‐week inhaled corticosteroid (ICS) dose‐stable phase were evaluated with respect to baseline blood eosinophil counts (eosinophils <300/μL [low] vs ≥300/μL [high]) and baseline markers of asthma severity (emergency asthma treatment in prior year, asthma hospitalization in prior year, forced expiratory volume in 1 second [FEV₁; FEV₁ <65% vs ≥65% predicted], inhaled beclomethasone dipropionate dose [<600 vs ≥600 μg/day], and long‐acting beta‐agonist [LABA] use [yes/no]).

Results

Adults/adolescents (N = 1071) were randomized to receive either omalizumab (n = 542) or placebo (n = 529). In the 16‐week ICS dose‐stable phase, rates of exacerbations requiring ≥3 days of systemic corticosteroid treatment were 0.066 and 0.147 with omalizumab and placebo, respectively, representing a relative rate reduction in omalizumab‐treated patients of 55% (95% CI, 32%‐70%; P = .002). For patients with eosinophils ≥300/μL or with more severe asthma, this rate reduction was significantly more pronounced.

Conclusion

In patients with allergic asthma, baseline blood eosinophil levels and/or clinical markers of asthma severity predict response to omalizumab.

Rapid gamma spectrometric analysis of soil samples after radioactive fallout using a "conjugate view" technique

A method for fast determination of the activity in soil samples by measuring a fresh soil core sample from both ends with an HPGe-detector is proposed. The method was tested by simulations, as well as by measurements on spiked soil samples. Both simulations and measurements showed that the geometrical mean of the count rates when the sample is measured twice, with the bottom and the top end, respectively, facing the detector closely resembles the count rate from a measurement on a homogenized sample. Therefore, an efficiency calibration for homogenized samples could be used even if the activity is highly inhomogeneous in the soil core, as is the case with fresh fallout. It was also shown that by studying the ratio between the two measurements, a rough estimation of the extent of penetration of the radionuclide in the soil can be found. This will enhance the possibility to make rapid estimations of the soil inventory by field gamma spectrometry.

The grain storage of wet-deposited caesium and strontium by spring wheat - A modelling study based on a field experiment

The aims of this study were to extend the Tracey model in order to quantify and to analyse spring wheat's grain storage dynamics of wet-deposited radionuclides. Tracey, a dynamic model of trace element cycling in terrestrial ecosystems, was extended with descriptions of wet-deposition, interception, foliar uptake and radioactive decay. Radionuclide fluxes were set proportional to corresponding water or carbon fluxes, simulated with CoupModel. The extended Tracey was calibrated against experimental data, where ¹³⁴Cs and ⁸⁵Sr were deposited on spring wheat at six growth stages in 2010 and 2011. Sensitivities of grain storage to wheat's and radionuclide properties were assessed, using the Eikos software, by 1000 Monte Carlo simulations for each of the 48 scenarios (combination of 2 radionuclides, 1 foliar uptake, 2 root uptake approaches, 6 deposition treatments and 2years). Simulations were accepted if simulated grain storage values were within 95% confidence intervals (CI) of measurements. We found that 15% of ¹³⁴Cs and ⁸⁵Sr simulations for 2011, and 6% of the 2010 simulations met the CI-criterion. Foliar uptake accounted for 99% and 90% of total plant uptake of ¹³⁴Cs and ⁸⁵Sr, respectively. Mean simulated grain storage at harvest increased with lateness of deposition, as the stored proportion of radionuclide deposited was 0.02% when deposition was before flowering, 2% between flowering and ripening, and 5% (2010) or 10% (2011, late harvest) after ripening, respectively. Similarly, the property that governed grain storage depended on the growth stage at time of deposition; stem and leaf fixation rates (deposition before flowering), grain fixation rates (between flowering and ripening) and grains' interception capacity (after ripening). We conclude that grains' interception capacities can be used to predict grain storage of radionuclides deposited in the riskiest period, i.e. close to harvest.

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

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

Interception and transfer of wet-deposited (134)Cs to potato foliage and tubers

Contamination levels on potato foliage and tubers were investigated by repeated sampling after multiple foliar contaminations of wet-deposited (134)Cs at five different growth stages in a micro-plot field experiment in three successive years. Application of the radionuclide early in the growing season (deposition date 19-27 June, growth stage II = plant establishment) resulted in low (134)Cs activity concentration in potato tubers across sampling occasions (mean 60, 25 and 115 Bq kg(-1) dry weight (D.W.) for years 1, 2 and 3, respectively). Following radionuclide deposition in the middle of the growing season (15-24 July, growth stage III = tuber initiation), (134)Cs activity concentration in tubers across sampling occasions was found to be highest (mean 150, 850 and 660 Bq kg(-1) D.W. for years 1, 2 and 3, respectively). When the radionuclide was sprayed on at later stages (5-7 August, growth stage IV = tuber bulking), (134)Cs activity concentrations in tubers across sampling dates decreased (mean 75, 310 and 395 Bq kg(-1) D.W. for years 1, 2 and 3, respectively). Deposition in the second half of August (15-28 August, late growth stage IV and beginning of growth stage V = tuber maturation) resulted in yet lower (134)Cs activity concentration in tubers. Potato tubers may concentrate as much as up to 2 times more (134)Cs than foliage depending on deposition date of radionuclide.

Interception and retention of wet-deposited radiocaesium and radiostrontium on a ley mixture of grass and clover

The aims of this study were to assess the potential radioactive contamination of fodder in the case of accidental radionuclide fallout, and to analyse the relationship between interception and retention of radionuclides as a function of biomass and Leaf Area Index (LAI). The interception and the retention of wet deposited (134)Cs and (85)Sr in ley (a mixture of grass and clover) were measured after artificial wet deposition in a field trial in Uppsala (eastern central Sweden). The field trial had a randomised block design with three replicates. (134)Cs and (85)Sr were deposited at six different growth stages during two growing seasons (2010 and 2011) using a rainfall simulator. The biomass was sampled in the center of each parcel 2 to 3h after deposition and at later growth stages (1 to 5) during the growing season. The above ground biomass and LAI were measured as well. The interception of radionuclides by the ley was largest at the late growth stages; the spike and tassel/flowering (code 5:6) in the 1(st) year, and at flowering/initial flowering (code 6:5) in the 2(nd) year. There was a correlation between radionuclide interception and above ground plant biomass, as well as with LAI, for both radionuclides in both years. The highest activity concentrations of both radionuclides were measured after deposition at the late growth stages and were found to be higher in the 2(nd) year. The weathering half-lives were shorter at the earlier growth stages than at the later growth stages for both radionuclides. For the magnitude of deposition chosen in our experiment, it can be concluded that the above ground biomass is a good predictor and the LAI a more uncertain predictor of the interception of radiocaesium and radiostrontium by ley grass and clover.

Potassium fertilization and (137)Cs transfer from soil to grass and barley in Sweden after the Chernobyl fallout

Fertilization of soils contaminated by radionuclides with potassium (K) and its effect on (137)Cs 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 ((137)Cs) 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, (137)Cs transfer factors in control treatments ranged between 0.0004 m(2) kg(-1) (barley grain on sand soil) and 0.07 m(2) 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 (137)Cs 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 (137)Cs transfer to crops was correlated with (137)Cs:K ratios in plant material. Additional application of zeolite caused a 1.4 reduction of (137)Cs transfer to hay on sand and 1.8-fold reduction on organic rich soil; whereas, application of potash-magnesia and CaO had no effect.

Inoculation with arbuscular mycorrhizae does not improve 137Cs uptake in crops grown in the Chernobyl region

Methods for cleaning up radioactive contaminated soils are urgently needed. In this study we investigated whether the use of arbuscular mycorrhizal (AM) fungi can improve (137)Cs uptake by crops. Barley, cucumber, perennial ryegrass, and sunflower were inoculated with AM fungi and grown in low-level radionuclide contaminated soils in a field experiment 70 km southwest of Chernobyl, Ukraine, during two successive years (2009-2010). Roots of barley, cucumber and sunflower plants were slightly or moderately infected with AM fungus and root infection frequency was negatively or non-correlated with (137)Cs uptake by plants. Roots of ryegrass were moderately infected with AM fungus and infection frequency was moderately correlated with (137)Cs uptake by ryegrass. The application of AM fungi to soil in situ did not enhance radionuclide plant uptake or biomass. The responsiveness of host plants and AM fungus combination to (137)Cs uptake varied depending on the soil, although mycorrhization of soil in the field was conditional and did not facilitate the uptake of radiocesium. The total amount of (137)Cs uptake by plants growing on inoculated soil was equal to amounts in plant cultivated on non-inoculated soil. Thus, the use of AM fungi in situ for bioremediation of soil contaminated with a low concentration of (137)Cs could not be recommended.

Accumulation of wet-deposited radiocaesium and radiostrontium by spring oilseed rape (Brássica napus L.) and spring wheat (Tríticum aestívum L.)

The accumulation of (134)Cs and (85)Sr within different parts of spring oilseed rape and spring wheat plants was investigated, with a particular focus on transfer to seeds after artificial wet deposition at different growth stages during a two-year field trial. In general, the accumulation of radionuclides in plant parts increased when deposition was closer to harvest. The seed of spring oilseed rape had lower concentrations of (85)Sr than spring wheat grain. The plants accumulated more (134)Cs than (85)Sr. We conclude that radionuclides can be transferred into human food chain at all growing stages, especially at the later stages. The variation in transfer factors during the investigation, and in comparison to previous results, implies the estimation of the risk for possible transfer of radionuclides to seeds in the event of future fallout during a growing season is still subject to considerable uncertainty.

Downward migration of radiocaesium in organic soils across a transect in Scotland

Following the accident at the Chernobyl nuclear power plant in 1986, radioactive materials including (137)Cs were distributed over large parts of the former Soviet Union and Europe. Due to the relatively long physical half-life of (137)Cs (30.1 y) measurable activity concentrations can still be observed in the natural environment. We have determined the depth distribution of (137)Cs from the testing of nuclear weapons in the atmosphere and Chernobyl, in eight highly-organic soils along an approximately east to west transect across the Central Highlands of Scotland. The (137)Cs activity concentrations in the soil profiles, corrected for radioactive decay to May 1986, were between 2.8 and 14.4 kBq m(-2). There were differences in the pattern of distribution of (137)Cs in the soil profiles. The mean migration depth of (137)Cs in the soil profiles was 12.2 cm with a range between 8.2 and 17.4 cm. Quantitative mineralogical analysis of the ash obtained after heating the soil to 400 °C indicated that clay minerals alone did not have a prime role in controlling the migration of (137)Cs down the profile.

Effect of arbuscular mycorrhizal (AM) fungi on 137Cs uptake by plants grown on different soils

The potential use of mycorrhiza as a bioremediation agent for soils contaminated by radiocesium was evaluated in a greenhouse experiment. The uptake of (137)Cs by cucumber, perennial ryegrass, and sunflower after inoculation with a commercial arbuscular mycorrhizal (AM) product in soils contaminated with (137)Cs was investigated, with non-mycorrhizal quinoa included as a "reference" plant. The effect of cucumber and ryegrass inoculation with AM fungi on (137)Cs uptake was inconsistent. The effect of AM fungi was most pronounced in sunflower: both plant biomass and (137)Cs uptake increased on loamy sand and loamy soils. The total (137)Cs activity accumulated within AM host sunflower on loamy sand and loamy soils was 2.4 and 3.2-fold higher than in non-inoculated plants. Although the enhanced uptake of (137)Cs by quinoa plants on loamy soil inoculated by the AM fungi was observed, the infection of the fungi to the plants was not confirmed.

137Cs in fungal sporocarps in relation to vegetation in a bog, pine swamp and forest along a transect

In this study, we estimated the relative importance of vegetation and fungi for radiocesium uptake and biological retention in adjacent bog, pine swamp, and forest. The measurements for (137)Cs activity concentration in sporocarps (i.e. fruitbodies of fungi) and vegetation along a bog to forest transect were combined with complementary published data to calculate estimates. Aboveground vegetation comprised 17.7% of the total fallout-derived radiocesium in the system in bog, 16.5% in pine swamp, and 40.6% in forest. In fungal sporocarps grown along a gradient, (137)Cs activity comprised <0.001% of the total radiocesium for peat bog, <0.02% for pine swamp, and 0.11% for forest. Total (137)Cs activity in sporocarps increased along the gradient due to increased production of sporocarps in the presence of trees from 0.006 (bog), 0.097 (pine swamp) and 0.67 (forest) g dwt m(-2). Based on calculation of the total vegetation biomass and through relationships between fungal biomass in sporocarps and as mycelia in soil, the total (137)Cs activity located in fungi was estimated as 0.1% in bog, 2% in pine swamp, and 11% in forest. An analysis of the time-dependency of (137)Cs in the sporocarps in forest between 1990 and 2011 suggested an ecological half-life for (137)Cs between 8 and 13 years. Although fungi comprised a relatively small fraction of the total radiocesium in the systems, its activity decreased slowly with time, and ecological residence time for (137)Cs in sporocarps of fungi was long, suggesting they will continue to contribute to the accumulation and cycling of this radionuclide in forest.

Uptake and translocation of 109Cd and stable Cd within tobacco plants (Nicotiana sylvestris)

The availability, uptake, and translocation of recently added ((109)Cd) and naturally occurring (stable) soil Cd within tobacco plants were compared. (109)Cd was added to soil in two treatments, A (0.25 MBq kg soil(-1) DW) and B (eight-fold dose): stable Cd was measured in both treatments. Both the added and the stable Cd were higher in leaves and reproductive structures of the plant than in stalks and roots. The uptake of (109)Cd was 5.3 kBq plant(-1) for treatment A and 36.7 kBq plant(-1) for treatment B, and about 26 μg plant(-1) for stable Cd. Leaves of the tobacco plants accumulated 40-45% of the total (109)Cd and about 50% of total stable Cd taken up by the plant. Cadmium concentration in the plant was three times higher than in roots and two times higher than the concentration in soil: the concentration in roots was lower than in the soil.

Correlations between potassium, rubidium and cesium ((133)Cs and (137)Cs) in sporocarps of Suillus variegatus in a Swedish boreal forest

An analysis of sporocarps of ectomycorrhizal fungi Suillus variegatus assessed whether cesium ((133)Cs and (137)Cs) uptake was correlated with potassium (K) or rubidium (Rb) uptake. The question was whether intraspecific correlations of Rb, K and (133)Cs mass concentrations with (137)Cs activity concentrations in sporocarps were higher within, rather than among, different fungal species, and if genotypic origin of sporocarps within a population affected uptake and correlation. Sporocarps (n = 51) from a Swedish forest population affected by the fallout after the Chernobyl accident were studied. The concentrations were 31.9 ± 6.79 g kg(-1) for K (mean ± SD, dwt), 0.40 ± 0.09 g kg(-1) for Rb, 8.7 ± 4.36 mg kg(-1) for (133)Cs and 63.7 ± 24.2 kBq kg(-1) for (137)Cs. The mass concentrations of (133)Cs correlated with (137)Cs activity concentrations (r = 0.61). There was correlation between both (133)Cs concentrations (r = 0.75) and (137)Cs activity concentrations (r = 0.44) and Rb, but the (137)Cs/(133)Cs isotopic ratio negatively correlated with Rb concentration. Concentrations of K and Rb were weakly correlated (r = 0.51). The (133)Cs mass concentrations, (137)Cs activity concentrations and (137)Cs/(133)Cs isotopic ratios did not correlate with K concentrations. No differences between, within or, among genotypes in S. variegatus were found. This suggested the relationships between K, Rb, (133)Cs and (137)Cs in sporocarps of S. variegatus is similar to other fungal species.

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

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

Accumulation of potassium, rubidium and caesium (133Cs and 137Cs in various fractions of soil and fungi in a Swedish forest

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.

The distribution of (137)Cs, K, Rb and Cs in plants in a Sphagnum-dominated peatland in eastern central Sweden

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.

137Cs in a raised bog in central Sweden

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.

Effects of ageing and microbial component on chemical availability of (137)Cs in a long-term experimental site

A loamy soil contaminated with (137)CsCl 40 years ago was investigated by a sequential extraction technique to determine the effect of ageing on chemical availability of (137)Cs. The soil samples were sequentially extracted with H(2)O, NH(4)Ac, NH(2)OH x HCl, H(2)O(2), and HNO(3). Extractability of (137)Cs decreased in the order: HNO(3) > Residual > H(2)O(2) > NH(4)Ac > NH(2)OH x HCl > H(2)O. Only 0.94% in labile fractions (H(2)O and NH(4)Ac), while more than 96% was found in the strongly bound fraction (HNO(3) and residual). However, the activity percentage in labile fractions was increased to 1.34% after autoclaving treatment, while those in the other fractions did not significantly differ. This indicates that the microbial activity played a role in the (137)Cs retention. In the subsequent pot experiments with ryegrass and leek, specific activities in both plants were significantly higher in autoclaved soil than in non-autoclaved soil, and uptake of (137)Cs in the five cuts by ryegrass was 25% of the labile (137)Cs in the soil. In addition, a positive correlation was found between the amount of (137)Cs in labile fractions and that by plant uptake.

Effect of clay content and wetting-and-drying on radiocaesium behaviour in a peat and a peaty podzol

The interaction of radiocaesium with peat under two moisture regimes was studied in laboratory experiments and by growing ryegrass in pot experiments to simulate changing field moisture conditions. A peat untreated and treated with 5% by weight of clay containing 46% illitic minerals, and a peaty podzol naturally containing 4.5% mineral matter on a dry weight basis were contaminated with (134)Cs and incubated. The soils were exposed to 8 wetting-and-drying cycles or kept constantly wet during 40 days. Extraction of the peat with 1 M CH(3)COONH(4) (pH 7) repeated after each wetting-and-drying cycle indicated increasing (134)Cs fixation with time of incubation. The peat treated with clay showed a much higher (134)Cs fixation than that without clay. The pot experiment with the incubated soils showed a (134)Cs transfer to ryegrass of the same order for the peaty podzol as for the peat treated with clay. For the peat untreated with clay the (134)Cs transfer to ryegrass was much greater. Wetting-and-drying the peat, with or without clay, increased the overall yield of grass and the concentration and uptake of (134)Cs over 5 consecutive harvests. K-fertilisation increased the yield of plant material (except for the peat with added clay), decreased the concentration of (134)Cs, but had no significant effect (p=0.05) on the resultant uptake of (134)Cs. Mixing clay with the surface layer of organic soils appears to be an effective means of decreasing radiocaesium transfer to field crops in fallout situations.

Arbuscular mycorrhizal fungi mediated uptake of 137Cs in leek and ryegrass

In a first experiment of soil contaminated with 137Cs, inoculation with a mixture of arbuscular mycorrhizae enhanced the uptake of 137Cs by leek under greenhouse conditions, while no effect on the uptake by ryegrass was observed. The mycorrhizal infection frequency in leek was independent of whether the 137Cs-contaminated soil was inoculated with mycorrhizal spores or not. The lack of mycorrhizae-mediated uptake of 137Cs in ryegrass could be due to the high root density, which was about four times that of leek, or due to a less well functioning mycorrhizal symbiosis than of leek. In a second experiment, ryegrass was grown for a period of four cuts. Additions of fungi enhanced 137Cs uptake of all harvests, improved dry weight production in the first cut, and also improved the mycorrhizal infection frequencies in the roots. No differences were obtained between the two fungal inoculums investigated with respect to biomass production or 137Cs uptake, but root colonization differed. We conclude that, under certain circumstances, mycorrhizae affect plant uptake of 137Cs. There may be a potential for selecting fungal strains that stimulate 137Cs accumulation in crops. The use of ryegrass seems to be rather ineffective for remediation of 137Cs-contaminated soil.

Role of the fungal mycelium in the retention of radiocaesium in forest soils

The aim of this work was to study possible binding of 137Cs to various organic components in the soil and fungi, by using various sequential extraction procedures. The retention and binding of 137Cs has been studied in two horizons Of/Oh and Ah/B of a Ukrainian forest soil. The exchangeable fractions 137Cs from soil (sum of H2O and 1 M NH4OAc fraction) were found to be 12% in the organic-rich layer (range 11-14%) and 23% in the organic-poor (range 20-29%). The hydrolysis with 10% H2SO4 resulted in an additional release of 30% of 137Cs from the organic-rich soil (range 30-35%) and 38% from the organic-poor soil horizon (range 27-53%). Extraction with 30% H2O2 released 11 and 15% of the 137Cs activity from organic-rich and organic-poor soil horizons. The corresponding values for treatment with 98.8% NaOCl were about 27% in both types of soil. About 11% of the total 137Cs activity was found in the humic acid fraction, about 5% in the fulvic fraction and 46% in the residue fraction. Relatively high level of 137Cs activity in soil (ca. 50%) was thus still left unsolved in the residue fraction. About 29% of 137Cs activity concentration in fungal mycelia was found as water soluble with a range of 11 to 41%. Additionally 24% of the 137Cs activity from mycelia was released by 1 M ammonium acetate extraction. Together, water and 1 M ammonium acetate extraction released about 53% of the total 137Cs activity in the mycelia. In fruit bodies of mycorrhizal fungi, 68% of the total 137Cs inventory was found to be water soluble at room temperature and 93% at 80 degrees C.

Uptake and distribution of 137Cs and 90Sr in salix viminalis plants

Agricultural areas in middle and northern parts of Sweden were contaminated with radionuclides after the Chernobyl accident in 1986. Alternative crops in these areas are biomass plantations with fast-growing Salix clones for energy purposes. The uptake and internal distribution of 137Cs and 90Sr in Salix viminalis were studied. Plants were grown in microplots under field conditions. The soils in the experimental site had been contaminated in 1961 with 35.7 and 13.4 MBq m(-2) of 137Cs and 90Sr, respectively. The experiment was carried out during three years. The plots were fertilised with 60 kg N ha(-1) and three treatments of K, consisting of 0, 80 and 240 kg K ha(-1) during the first two years. The activity concentration of 137Cs in the different plant parts varied between 140 and 20,000 Bq kg(-1) and was ranked in the following order: lowest in stems < cuttings < leaves < roots. The fine roots (0-1 mm) had the highest 137Cs activity concentration. One-year-old stems had higher 137Cs activity concentrations than two-year-old stems. The activity concentration of 137Cs in the plants was significantly affected by K-supply and was higher in the 0 kg K treatment than in the 80 or 240kg K treatment. Leaves contained more 90Sr than stems and cuttings.

Chemical availability of 137Cs and 90Sr in undisturbed lysimeter soils maintained under controlled and close-to-real conditions

Chemical availability of 137Cs and 90Sr was determined in four undisturbed soils in a lysimeter study three and four years after deposition to the soil surface. The study was part of a larger project on radionuclide soil-plant interactions under well-defined conditions. The soil types were loam, silt loam, sandy loam and loamy sand, and were representatives of important European soil and climatic conditions. The lysimeters were installed in greenhouses with climatic and hydrological control, and were contaminated with 137Cs and 90Sr in an aerosol mixture simulating fallout from a nuclear accident. Soil samples were taken from several depths in each soil in 1997 and 1998 and the samples were sequentially extracted with H2O, NH4Ac, NH2OH.HCl, H2O2 and HNO3. Extractability of 137Cs decreased in the order: HNO3 > R-esidual > or = NH4Ac > H2O2 > or = NH2OH.HCl > or = H2O. More than 80% was found in the acid digestible or residual fractions, and 11-17% in labile fractions. Soil type differences were small. Extractability of 90Sr decreased in the order: NH4Ac > NH2OH.HCl > HNO3 > H2O2 approximately H2O. 31-58% was found in easily available fractions. Differences between soil types were quite small. The results suggest that availability of 137Cs for plant uptake and migration is low, whereas availability of 90Sr is rather high.

Long-term studies on transfer of 137Cs from soil to vegetation and to grazing lambs in a mountain area in northern Sweden

Studies were made during 1990-1997 on the transfer of 137Cs from soil to vegetation (herbage) and to grazing lambs on a mountain farm with an uncultivated grazing area of about 10 km2. The farm is situated in an area in Northern Sweden which was contaminated by the Chernobyl fallout in 1986. The mean concentration of 137Cs in the soil to a depth of 10 cm for eight sampling sites observed in the 8-year period was 14.51 kBq/m2, while in the cut herbage the average concentration was 859 Bq/kg d.w. and in lamb meat 682 Bq/kg w.w. A slow vertical migration of 137Cs in the 0-10 cm soil layer was indicated. Although the 137Cs concentration in herbage gradually decreased, the concentration in lamb meat varied from year to year. Soil ingestion by the lambs as a pathway for activity transfer was shown to be negligible, while ingestion of fungi with high concentrations of 137Cs was demonstrated to occur, as large numbers of fungi spores were counted in samples of the lambs' faeces. Fungi ingestion might therefore partly explain the varying mean yearly 137Cs concentrations in lamb muscle. The mean transfer parameters were as follows: for "soil to herbage" 61.3 Bq/kg d.w. herbage per kBq/m2 soil, for "herbage to lamb meat" 0.81 Bq/kg w.w. meat per Bq/kg d.w. herbage, and for "soil to lamb meat" 47.1 Bq/kg w.w. meat per kBq/m2 soil. A trend of decreasing values of the transfer parameter for "soil to herbage" indicated that 137Cs was becoming less available for root-uptake with time. The effective ecological half-life of 137Cs in soil, herbage and lamb meat was calculated to be 19, 7 and 16 years, respectively. It can be concluded that natural areas are vulnerable to 137Cs contamination, resulting in high concentrations in plants, fungi and lamb meat for a long time.

Transfer of radiocaesium in sensitive agricultural environments after the Chernobyl fallout in Sweden: III. County of Västernorrland

In 1986 a large number of farms in the Chernobyl-affected area in the county of Västernorrland in northern Sweden were investigated for radiocaesium transfer to grass and cereal grain. The soil surface layer (0-5 cm) in 1986 and the crop products in 1986-1996 were analysed. The aim was to study the impact of soil and crop rotation on sensitivity of 137Cs transfer in a short and long term perspective. In the fallout year 1986 the transfer to grass was usually much higher than to cereal grain. In this year the transfer to grass was usually much higher in the first cut rather than the second cut. The reduction in transfer with year was large but variable with site and with crop sequence. Ploughing was effective in decreasing the transfer of 137Cs to crops. On arable sites in 1986 the transfer to cereal straw was larger at late stem elongation (LSE) than at the maturing stage. Unexpectedly, there was no clear relationship between transfer of 137Cs to the crops and any of the soil characteristics. In 1986 the transfer of 131I to grass and cereals was also investigated on some of the farms. The results are compared with the transfer of 137Cs, 2 months after the Chernobyl fallout.

Fusarium infection with unusual skin lesions in a patient with acute lymphocytic leukemia

A 27-year-old woman with acute lymphocytic leukemia developed red painful skin lesions, asymmetrically distributed over the face and extremities. They gradually increased in size and number, and in the center of each lesion blisters appeared followed by central necrosis with surrounding erythema. In several lesions the central necrosis was covered with a white powder shown to be fungal mycelium. Cultures from skin lesions and blood showed a Fusarium species. The skin lesions are helpful in recognizing this deep fungal infection in an immunocompromised host.

Thyroid function in patients with pustulosis palmoplantaris

Fifty consecutive patients (45 women and 5 men) with pustulosis palmoplantaris were evaluated for thyroid disease. Five women had previously had thyroid disorders for which they were receiving thyroxine substitution therapy. Of the other 40 women three had a raised serum concentration of thyroid-stimulating hormone and nine had high concentrations of antibodies against thyroid "microsomal antigen." During a 4-year follow-up hypothyroidism developed in two women with initially raised thyroid-stimulating hormone, and laboratory test results for one woman indicated subclinical hyperthyroidism. Four of nine patients with thyroid abnormality also had evidence of gastric autoimmunity. Of the patients 94% smoked at the onset of pustulosis palmoplantaris compared with 33% in age- and sex-matched healthy controls. The prevalence of thyroid disease in women with pustulosis palmoplantaris was significantly higher than in a comparable population sample of women from the same geographic region. We conclude that patients with pustulosis palmoplantaris should be screened for thyroid disease.

PUVA, etretinate, and PUVA-etretinate therapy for pustulosis palmoplantaris. A placebo-controlled comparative trial

Thirty patients with severe pustulosis palmoplantaris completed a placebo-controlled comparative trial. Patients were randomly allocated to placebo or etretinate therapy; after two weeks, psoralen plus long-wave ultraviolet light (PUVA) treatment was instituted on one hand or foot, while the other hand or foot served as an untreated control. Fourteen of 18 hands or feet cleared with the combined treatment, compared with three of 18 with etretinate treatment and three of 12 with PUVA treatment. Follow-up showed a high relapse rate. Treatment of severe pustulosis palmoplantaris must be individualized to minimize short- and long-term side effects.

Oral psoralen photochemotherapy (PUVA) of hyperkeratotic dermatitis of the palms

Oral psoralen photochemotherapy (PUVA) was found to be effective in five patients with chronic hyperkeratotic dermatitis of the palms. Relapses may occur but they respond well to retreatment.