Influence of Organic Amendments on the Accumulation of 137Cs and 90Sr from Contaminated Soil by Three Grass Species

Bahia grass (Paspalum notatum), johnson grass (Sorghum halpense) and switchgrass (Panicum virginatum) werecompared for their ability to accumulate ¹³⁷Csand ⁹⁰Sr from three different contaminated soilsin the presence and absence of either sphagnum peator poultry litter amendments. Above-ground plantbiomass did not differ between plants that were notexposed to these radionuclides and those that wereexposed to soil containing ¹³⁷Cs or ⁹⁰Sr.After three harvests, bahia, johnson and switchgrassplants accumulated from 17.2 to 67.3% of the¹³⁷Cs and from 25.1 to 61.7% of the ⁹⁰Sradded to the soil. Poultry litter and peat mossamendments increased aboveground plant biomass,activity of ¹³⁷Cs or ⁹⁰Sr in plant tissue, %accumulation of ¹³⁷Cs or ⁹⁰Sr from soil andthe plant bioconcentration ratio at each harvestcompared to the control (no amendment) treatment. Thegreatest increases in plant biomass, and radionuclideaccumulation were observed with poultry litter foreach of the three grass species. Johnson grass hadgreater aboveground plant biomass, activity of¹³⁷Cs and ⁹⁰Sr in plant tissue, %accumulation of ¹³⁷Cs or ⁹⁰Sr from soil andbioconcentration ratio in each soil amendment, at eachharvest compared to bahia and switchgrass. Thegreatest accumulation of ¹³⁷Cs and ⁹⁰Sr wasmeasured in johnson grass grown in soil that wasamended with poultry litter. These results suggestthat plant species selection and agronomic practicesmay need to be considered to maximize phytoremediationof radionuclide contaminated soils.     

Migration and Chemical Availability of 137Cs and 90Sr in SwedishLong-Term Experimental Pastures

Migration and chemical availability of ¹³⁷Cs and⁹⁰Sr in the long-term was studied on a36-yr-old deposition experiment on pastureconsisting of a sandy soil and a clay soil,contaminated in 1961 with radionuclides in aqueoussolution. Comparisons were made with a study of thesame soils in 1967. Soil samples to 55 cm depth wereanalysed for ¹³⁷Cs and ⁹⁰Sr to establish thevertical distribution. Chemical availability wasstudied using sequential extractions with H₂O,NH₄Ac, NH₂OH·HCl, H₂O₂ andHNO₃. Both ¹³⁷Cs and ⁹⁰Sr were found atall depths in both soil types. Cs-137 waspredominantly retained within the upper 10 cm (70%)in both soils. For ⁹⁰Sr, the soils differedsignificantly, retention within the upper 10 cm was27% in sandy soil and 47% in clay soil. Migrationsince 1967 was faster in the sandy soil for bothnuclides. More than 95% of ¹³⁷Cs was bound inthe acid-digestible and residual fractions in bothsoils. The residual fraction was larger in clay soil.⁹⁰Sr was highly available in both soils. Noresidual fraction was found, and the easilyexchangeable fraction was 63–75%.     

West Valley-derived radionuclides in the Niagara river area of Lake Ontario

The presence of West Valley-derived radionuclides in the densely-populated Niagara River/Lake Ontario region is demonstrated through measurements on water and sediment samples. The ¹³⁷Cs profile in a ²¹⁰Pb-dated Lake Ontario sediment core is consistent with the pattern of West Valley discharges to the local aquatic environment in that the observed ¹³⁷Cs activity maximum corresponds to the 1970 peak discharge and not the 1963 fallout peak activity. Preliminary mass balance estimate, based on a ¹³⁷Cs/⁹⁰Sr activity ratio of 1.5 and on the assumption that the dominant regional flow of Lake Erie transports most of the radionuclides to Lake Ontario va the Niagara River, shows that nearly all of the West Valley-delivered ¹³⁷Cs is deposited in the bottom sediments of Lake Ontario. It is suggested that any accidental releases of radioactivity from the site are likely to provide additional radiation dose to the area residents using municipal water supplies.     

Die Aufnahme von137Cs und 90Sr durch verschiedene sommerrapsgenotypen aus dem Boden*

Die Aufnahme von ¹³⁷Cs und ⁹⁰Sr durch verschiedene Sommerrapsgenotypen aus kontaminiertem Boden wurde geprüft. Statistisch gesicherte Unterschiede bei der Aufnahme von Radionukliden zwischen den Genotypen konnten festgestellt werden. Die Aufnahme von ¹³⁷Cs und ⁹⁰Sr ist bei den einzelnen Sorten nicht gleichsinnig. Nur ein geprüfter Genotyp nahm sowohl geringe Mengen von ¹³⁷Cs, als auch von ⁹⁰Sr auf. Die mittleren jährlichen Schwankungen in der Radionuklidaufnahme waren größer, als die Unterschiede zwischen den Genotypen.     

Role of plants in the spatial differentiation of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr statuses on the aggregate level

The increased concentration of an element in plant biomass compared to the soil mass is an essential condition for the differentiated spatial distribution and status of the element on the aggregate level. Two forms of this differentiation have been revealed for ¹³⁷Cs and ⁹⁰Sr. Transfer of ¹³⁷Cs from plant roots and concentration on the surface of soil aggregates have been established experimentally. Indirect data also point to the potential localization of ¹³⁷Cs on the surface of intraaggregate pores. The effect of radionuclide concentrating on the outer and inner surfaces of aggregates is due to the rapid and strong fixation of cesium microamounts by mineral soil components. ¹³⁷Cs from the surface of aggregates is more available for the repeated uptake by plant roots than from the intraped mass. The distortion of this spatial differentiation mainly occurs during the reaggregation of soil mass, which in turn decreases the availability of the radionuclide to plants. For ⁹⁰Sr, its elevated concentration in the form of organic residues has been revealed in the inter- and intraaggregate pore space. However, due to the high diffusion rate, ⁹⁰Sr is relatively rapidly (during several months under pot experimental conditions) redistributed throughout the entire volume of soil aggregates and its major part gradually passes into the phase of humic compounds, to which the radionuclide is bound by exchange sorption. The high level of the next root uptake (higher than for ¹³⁷Cs by one to two orders of magnitude) favors the permanent renewal of loci with increased ⁹⁰Sr concentrations in the inter- and intraaggregate pore space in the form of plant residues.     

Sources and behavior of anthropogenic radionuclides in the Ottawa river waters

Multiphase radionuclide measurements on Ottawa River waters are reported for the period October 1984 to March 1986. Numerous radionuclides are present in detectable amounts in raw, drinking and centrifuged waters as well as in suspended sediment and water filtration plant floc samples. The sediment/water partitioning behavior of these radionuclides is also reported. The prevailing low particle flux allows rapid migration of radionuclides through the system. Most of the ⁹⁰Sr in the river derives from its fallout inventory in the watershed rather than from the Chalk River Nuclear Laboratories (CRNL). On the other hand, fallout and CRNL-derived ¹³⁷Cs appear to contribute equally to the prevailing levels of this radionuclide in the river. The data also suggest that the prevailing levels of the naturally-occurring ²²⁶Ra impart more dose than ⁹⁰Sr insofar as the radiological quality of the drinking water is concerned. Many of the radionuclides are removed by the floc during filtration of the receiving waters. Though their removal efficiencies cannot be precisely defined from the currently available measurements, the results show that processes other than simple association with suspended sediments may also play significant role in the retention of some radionuclides by the floc.     

Artificial radionuclides in waters of the lower section of the river Ebro (Northeast Spain)

The river Ebro, in Northeast Spain,discharges into the Mediterranean Sea after flowingthrough several large cities and agricultural, miningand industrial areas. The Ascó nuclear power plant(NPP) is located in the lower river section andcomprises two pressurised-water reactor (PWR) units,from which low-level liquid radioactive waste isreleased to river waters under authority control.During the period 1989 to 1993, we carried out 29sampling campaigns in order to determine ³H,⁹⁰Sr, ¹³⁴Cs, ¹³⁷Cs, ²³⁸Pu and^239,240Pu in Ebro river waters at differentlocations, both upstream and downstream from theAscó NPP. ³H, ¹³⁴Cs and ¹³⁷Csactivities showed large variability as they rangedfrom <1.4 to 117±3 Bq L^-1, <0.27 to22±1 mBq L^-1 and <0.36 to 35±1mBq L^-1, respectively. This behaviour, especiallyremarkable for tritium, was due to the detection oftank releases travelling downstream. Thecharacteristic NPP ¹³⁴Cs/¹³⁷Cs ratio wasfound to be 0.61±0.02 (N = 22). In the estuarinearea, ¹³⁷Cs traces from Mediterranean waters wereobserved and relatively enhanced tritium activitiesmight possibly be present due to the accumulation ofactivity in the estuary. ⁹⁰Sr and ^239,240Puactivities were homogeneous both in respect to timeand space, showing mean activities 6.9±0.2 mBq L^-1 (N = 10) and 1.36±0.10 mBq m^-3 (N = 3), respectively. These levels couldonly be attributed to nuclear weapons fallout leachedby continental waters, as the impact from the plantappears to be negligible and no other sources arepresent in the area.     

Contamination of terrestrial ecosystem components with <Superscript>90</Superscript>Sr, <Superscript>137</Superscript>Cs,and <Superscript>226</Superscript>Ra caused by the deterioration of the multibarrier protection of radioactive waste storages

The spatial-temporal features of the radioactive contamination of terrestrial ecosystem components caused by the deterioration of the multibarrier protection of regional radioactive waste storages of the State Research Center of the Russian Federation-Leipunskii Institute of Physics and Power Engineering at the input of radionuclides into the soil and ground water were studied. The composition of the radioactive contamination was determined, and the hydrological and geochemical processes resulting in the formation of large radioactive sources were described. The natural features of the radioactive waste storage areas favoring the entry of ⁹⁰Sr, ¹³⁷Cs, and ²²⁶Ra into the soils and their inclusion in the biological turnover were characterized. The directions of the horizontal migration of ⁹⁰Sr, ¹³⁷Cs, and ²²⁶Ra and the sites of their accumulation within the superaquatic and aquatic landscapes of a near-terrace depression were studied; the factors of the ⁹⁰Sr accumulation in plants and cockles were calculated. The results of the studies expand the theoretical concepts of the mechanisms, processes, and factors controlling the behavior of radionuclides at the deterioration of the multibarrier protection of radioactive waste storages. The presented experimental data can be used for solving practical problems related to environmental protection in the areas of industrial nuclear complexes.     

Growth and cadmium accumulation in selected switchgrass cultivars

Abstract

Switchgrass (Panicum virgatum L.) has potential as a sustainable biofuel crop. Utilizing alternative sources of fertilizer nutrients could enhance production of switchgrass. However, alternative sources of fertilizer such as sewage sludge sometimes contain heavy metals such as cadmium (Cd) and the response of switchgrass to Cd is not known. Four switchgrass cultivars (Alamo, Blackwell, Cave‐in‐Rock, and Trailblazer) grown in sand culture were watered twice weekly with a nutrient solution containing Cd. Cadmium levels in solution were 0, 1, 2, 4, 8, and 16 mg Cd L^‐1. Plants were harvested 63 d after planting and separated into leaf blade, stem (culm + leaf sheath), and root components. Tissue Cd concentrations were determined using atomic absorption spectrophotometry. Cultivars differed (P<0.05) by less than 15% for biomass accumulation and allocation among plant parts. Cadmium levels of 16 mg L^‐1 reduced biomass yields by 31% for roots, 39% for leaf blades, and 47% for stems as compared to no added Cd. At 16 mg Cd L^‐1, Cd concentration in leaf blades was 9.9 mg kg^‐1. The highest levels of Cd (329 mg kg^‐1) were found in roots of Blackwell and Trailblazer grown at the highest Cd level. Cadmium at 16 mg Cd L^‐1 is phytotoxic to switchgrass and accumulates in all plant parts. The cultivars tested in this study did not differ in biomass accumulation in response to Cd; however, Cd accumulation in plant parts differed among cultivars. Consideration of Cd uptake should be a part of switchgrass cultivar selection when grown in the presence of Cd.     

Artificial and natural radionuclides in soils of the southern and middle taiga zones of Komi Republic

Specific activities of artificial (¹³⁷Cs, ⁹⁰Sr) and natural (⁴⁰К, ²³²Th, ²²⁶Ra) radionuclides in background soils of southern and middle taiga of Komi Republic have been estimated with consideration for the landscape-geochemical features of the territory. It has been shown that their accumulation and migration in soils are determined by the following factors: position in relief, texture, and organic matter content. No anomalous zones with increased contents of radionuclides in soils have been revealed.     

Radioactive contamination of permafrost-affected soils with 137Cs and 90Sr, the products of an accidental underground nuclear explosion

The specificity of contamination of permafrost-affected soils with radionuclides derived from an accidental underground nuclear explosion at the Kraton-3 polygon located in the northern taiga subzone has been studied in northwestern Yakutia. It is shown that the high density of the radioactive contamination is preserved in the soils 23 years after the nuclear accident. The concentrations of ¹³⁷Cs and ⁹⁰Sr vary from 34 to 1025 and from 57 to 781 kBq/m², respectively, which is 30–1000 times higher than the global fallout of these radionuclides.     

Investigations on Interception and Translocation of Airborne 85Sr, 131I, 137Cs in Beans, Spinach and Radish Plants

The work reported here deals with the study of interception/deposition and translocation of ⁸⁵Sr, ¹³¹I, and¹³⁷ Cs in three different types of vegetables i.e. beans (Phasoolus vulgaris), spinach (Spinicia olericia) and radish (Raphanous sative) following redionuclides release to the environment. Activity was injected in the experimental chamber in the form of aerosols having a size distribution of 0.3–1.0 µm (AMAD). Plant samples were collected soon after the injection for the evaluation of interception/deposition factors (IF/DF) for the different parts of the plants, as well as for the whole plant and the washable fraction of the deposited activity and its variation with time. The evaluated IF/DF shows a minimum value of 0.12 m³ kg^-1 for ⁸⁵Sr in case of spinach whole plant and maximum value of 1.93 m³ kg^-1 for ¹³¹I in case of beans whole plant. Translocation factors (TF) have also been evaluated for the activity that migrates from the above soil plant parts to the root and its variation with time. The evaluated TF shows a range of 7.27 × 10^-3 to 136 × 10^-3.     

Adaptive Capability of the VERT_MIG Algorithm to Simulate Vertical Migration of Radionuclides in Soils

The possibility of using the VERT_MIG algorithm in simulation models of the vertical migration of radionuclides in soil is discussed. The algorithm was successfully used to develop models of ¹³⁷Cs and ⁹⁰Sr migration for radioactive contamination of different soils as a result of the accidents at the Chernobyl and Fukushima-1 nuclear power plants. The modeling results are given. Prospects for further use of this algorithm and some aspects of using imitation modeling in this area are discussed.     

The modern radioecological situation at the Globus-1 site

This article is dedicated to analysis of the modern radioecological situation at the site of the Globus-1 peaceful nuclear explosion in the Ivanovo region. The variability of the ionizing radiation background, specific activity of ¹³⁷Cs and ⁹⁰Sr in the 0–20 cm soil layer, and dominant species of meadow vegetation near the site of the explosion are presented. Higher levels of ⁹⁰Sr contamination of plants in this territory and water from a research well were determined. The indices of contamination of the meadow biogeocoenosis components according to ¹³⁷Cs did not exceed the established norms.     

Agroecological optimums concerning saturation with calcium of soils contaminated by <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr

A close negative correlation between the biological availability of ⁹⁰Sr and ¹³⁷Cs for agricultural crops and the content of exchangeable calcium in soils has been revealed in a field experiment performed for soddy-podzolic loamy sandy soil. The efficiency of soil saturation with exchangeable calcium regarding ⁹⁰Sr discrimination is much higher in soils with a low supply of plants with this nutrient. For the bulk of the studied crops, the minimal biological availability of ⁹⁰Sr is registered at 1200–1400 mg/kg (6.0–7.0 mg-equiv./100 g) of the exchangeable calcium content in the soil and that of ¹³⁷Cs is registered at 1000–1100 mg/kg (5.0–5.5 mg-equiv./100 g). The crop productivity varies significantly depending on the exchangeable calcium content in the soil.     

Transfer of radiocesium from hydroponic medium to potherb mustard and tomato plants

Abstract

Potherb mustard (Brassica rapa var. nipposinica) and tomato plants (scion, ‘CF Momotaro haruka’; rootstock, ‘Dokutar K’; Solanum lycopersicum) were cultured in hydroponic medium containing cesium-137 (¹³⁷Cs) at three different concentrations (0.03, 0.13 and 1.03 Bq L^?1), and uptake of ¹³⁷C into the plants was determined. When the ¹³⁷Cs radioactivity concentration in the medium was 1.03 Bq L^?1, the ¹³⁷Cs radioactivity concentrations in the edible portions of the plants were 4.80 Bq kg^?1 fresh weight for the potherb mustard plants and 3.60 Bq kg^?1 fresh weight for the tomato plants. In both species, the ¹³⁷Cs radioactivity concentration in the edible portions decreased with decreasing ¹³⁷Cs radioactivity concentration in the culture medium. When the ¹³⁷Cs radioactivity concentration in the medium was 0.03 Bq L^?1, a concentration observed in many streams and in tap water in Fukushima Prefecture after the accident at the Fukushima Daiichi Nuclear Power Plant, the ¹³⁷Cs radioactivity concentrations in the edible portions of the plants were 0.50 and 0.15 Bq kg^?1 fresh weight for potherb mustard and tomato plants, respectively. These values are less than the Japanese allowable limit for radiocesium in food. For both species, the transfer factors for ¹³⁷Cs uptake from the culture media to the edible portions and the average transfer rates over the cultivation period were calculated.     

Impact of Chemical Substances on 137Cs Accumulation in Spring Wheat Seedlings and Their Cell Nuclei Reactions

The aim of the present work was to determine peculiarities of accumulation of ionic state ¹³⁷Cs in model experiments with seedlings of spring wheat (Triticum aestivum L., ??Nandu??) using laboratory experiments and to evaluate the complex effect of ¹³⁷Cs ionizing radiation and geochemical factors on the growth of this plant. ¹³⁷Cs accumulation in seedlings is influenced by the presence of mineral substances in the nutritional medium and by the conditions of illumination. Mineral substances (K⁺, Ca²⁺, Mg²⁺, Cu²⁺, NH ₄ ⁺ , P⁵⁺, Fe³⁺) reduced the ¹³⁷Cs accumulation coefficient of seedlings approximately three times. Addition of heavy metals as well as anionic group NO ₃ ^? to the growth medium caused insignificant changes in the level of radionuclide accumulation. In the model systems of RNA synthesis with wheat seedling cells nuclei isolated after complex treatment (in vivo) by ¹³⁷Cs and HM showed clear inhibition of the RNA-polymerase II. This inhibition manifested itself as a complex effect of ¹³⁷Cs ionizing radiation and heavy metals.     

Accumulation of radioactive cesium in sorghum (Sorghum bicolor (L.) Moench) accessions cultivated in Fukushima in 2011 and 2012

ABSTRACT

The accident at Fukushima 1 Nuclear Power Plant in 2011 caused contamination by radioactive cesium (¹³⁴Cs and ¹³⁷Cs) in surrounding areas. After this accident, concerns about Cs contamination, including food safety, have limited industrial activities and reconstruction in Fukushima. Sorghum (Sorghum bicolor (L.) Moench) is an annual C₄ crop that can be used as biofuel feedstock due to its high biomass. Use of Cs-contaminated fields to produce biofuel feedstock would be more acceptable than use for food or feed crops due to the lower risk of human internal exposure to radioactive Cs. In addition, high-biomass sorghum might be suitable for removal of Cs from fields (phytoremediation). For both applications, it is important to use accessions showing the appropriate level of accumulation of radioactive Cs (low for biofuel feedstock, high for phytoremediation). Here, we examined the accumulation of radioactive Cs in the aerial parts of 56 sorghum accessions grown in Fukushima. Accessions were cultivated in a low-level-contaminated field in 2011 and in a highly contaminated field in a planned evacuation zone in 2012. After cultivation, activity concentrations from ¹³⁴Cs and ¹³⁷Cs were measured in the aerial plant parts. In 2011, the activity concentrations of ¹³⁴Cs and ¹³⁷Cs were 58.2–350 and 58.6–450 Bq kg^?1 dry weight, respectively. In 2012, the concentrations of ¹³⁴Cs and ¹³⁷Cs were 54.2–1320 and 57.1–1960 Bq kg^?1 dry weight, respectively. Relative to the median values of the accessions grown each year, 3 showed lower activity concentrations and 2 showed higher activity concentrations of radioactive Cs under both cultivation conditions. In contrast to a previous report, there was no significant correlation between biomass and Cs activity concentration. Because both biomass and Cs concentration are important in classifying accessions for use in phytoremediation, we also calculated the Cs accumulation index (single-plant biomass × Cs activity concentration) for each accession. The accession AKLMOI WHITE showed the highest values in both years, suggesting that this accession has the high per-plant accumulation capacity for radioactive Cs. Our data collected from actual contaminated fields is irreplaceable for choosing sorghum accessions for cultivation in Cs-polluted sites such as Fukushima.     

Influence of plowing on the depth distribution of various radionuclides in the soil

The present work deals with a comparison of the vertical distribution of ¹³⁷Cs, ¹³⁴Cs, ¹⁰⁶Ru, ¹²⁵Sb, and ⁹⁰Sr at two agricultural sites in Styria (Austria) in the first two years after the Chernobyl fallout. Three months after deposition the Chernobyl derived radionuclides had their maximum concentrations in the first cm. Detectable amounts, however, had penetrated down to a depth of 12 cm (Stagno-Dystric Gleysol, site A) and 20 cm (Dystric Cambisol, site B). Significant differences between the two sites were observed after the first plowing. At site A a new concentration maximum at 15 to 18 cm depth was observed due to an extreme turnover effect. Even the second plowing in 1988 did not yield a homogeneous radionuclide distribution over the tillage depth. At site B the furrow slice was twisted only 60° against the slope gradient. This resulted in a slight mixing in the first 12 cm. From this it may be concluded that plowing does not lead to a thorough mixing in any case. At least two or three plowing steps may be needed to obtain an uniform nuclide distribution at certain sites.     

Is It Possible to Use 90Sr and 137Cs As Tracers for the Aeolian Dust Transport?

A noble approach for the estimation of the deposition of the Asian dust over Japan by using atmospheric anthropogenic radioactivity, ⁹⁰Sr and ¹³⁷Cs, is proposed. Those radioactivities once deposited globally onto the ground by the past nuclear test, etc. are resuspended along with the surface soil particles in the air by the storm and deposited again on the ground. The difference in ¹³⁷Cs/⁹⁰Sr activity ratios in the surface soil between dry and wet climatic conditions gives a clue to know about the source of the dust. It was found that the average activity ratio in the deposited material (average: 2.1, n=82) at MRI, Tsukuba in the 1990s is not close to that of the surface soil taken in neighborhood (median: 6.8, n=8), which had been considered as the primary source. While, it is close to that of the soil samples taken in the arid area in the Asian continent (median: 2.0, n=4), which is the one of the source regions of the aeolian dust. Thus we can reasonably assume that deposited dust in Tsukuba is brought not only from the neighboring fields, etc. but also from the arid area in the continent. Using a simple two-component model it was estimated that the Asian dust may transport about 90% of ⁹⁰Sr and 70% of ¹³⁷Cs depositions observed in Tsukuba in the 1990s. Also, Asian dust may transport about 2/3 of the dust deposited in Tsukuba.