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1.
Abstract

The accident at Fukushima Dai-Ichi Nuclear Power Station (NPS) extensively contaminated the agricultural land in the Tohoku region of Japan with radioactive cesium [sum of cesium-134 (134Cs) and cesium-137 (137Cs)]. We evaluated the status of radioactive cesium (Cs) contamination in soil and plants at the Field Science Center of Tohoku University, northern Miyagi prefecture, 150 km north of the NPS. In seven pastures with different management, we examined: (1) the distribution of radioactive Cs in soil, (2) the concentration of radioactive Cs in various herbaceous plant species and (3) the change in radioactive Cs content of plants as they matured. We collected samples of litter, root mat layer (root mat soil and plant roots), and subsurface soil (0–5 cm beneath the root mat) at two to three locations in each pasture in December 2011 and May 2012. The aboveground parts of herbaceous plants (four grasses, two legumes, and one forb species) were collected from May 9 to June 20, 2012, at 14-d intervals, from one to five fixed sampling locations in each pasture. The distribution of radioactive Cs in soil differed among pastures to some degree: a large proportion of radioactive Cs was distributed in the root mat layer. Pasture management greatly influenced the radioactive Cs content of herbaceous plants (p < 0.001); plant species had less influence. Radioactive Cs content was highest (> 3 kBq kg?1 dry weight) on May 9 and significantly decreased with maturity (p < 0.001) for most of the pastures, whereas it remained low (0.04–0.18 kBq kg?1 dry weight) throughout the measurement period in the pasture where composted cattle manure was applied. The soil-to-plant transfer factor was negatively correlated to pH(H2O) (R2 = 0.783, p < 0.001) and exchangeable K content (R2 = 0.971, p < 0.001) of root mat soils, which suggests that surface application of composted cattle manure reduces plant uptake of radioactive Cs by increasing the exchangeable K content of the soil. The radioactive Cs content of plants decreased with plant maturity; its degree of decrease (May 9 to June 6) was smaller in legumes (80.6%) than grasses (55.5%) and the forb (58.6%). Radioactive Cs content decreased with plant maturity; also, the proportion remaining in the aboveground plant was higher in legumes (80.6%) than grasses (55.5%) and the forb (58.6%).  相似文献   

2.
Abstract

Radioactive cesium (Cs) deposited after the Fukushima Daiichi Nuclear Power Station accident contaminated farmyard manure (FYM) in the wide area surrounding the plant. We conducted a field trial to determine the transfer factor of radioactive Cs to forage corn (Zea mays L.) from soil to which the contaminated FYM had been applied. The main purpose of this experiment was to examine the behavior of the radioactive Cs from contaminated FYM that was incorporated in agricultural fields. Application of FYM containing 3900 Bq kg?1 dry matter (DM) of cesium-137 (137Cs) at a rate of 4.3 kg m?2 increased the 137Cs concentration in the soil by 64 Bq kg?1 dry soil, and in the forage corn by 9.2 Bq kg?1 DM. Therefore, we calculated the transfer factor to corn plants from the soil after application of contaminated FYM to be 0.14. This value is lower than that observed for soil to which uncontaminated FYM had been applied as a control, and it is within the range of reported soil-to-plant transfer factors of 0.003–0.49 listed in the recent parameter handbook by International Atomic Energy Agency. The increase in the radioactive Cs concentration in the corn plants, expressed as the sum of 137Cs and cesium-134 (134Cs), was only 3% of the 2012 provisional tolerance level for cattle roughage in Japan. Even though the application of contaminated FYM did not cause a large change in the radioactive Cs concentration in the corn plants in this trial, such application should be carefully controlled because it increased radioactive Cs concentrations in both soil and forage corn.  相似文献   

3.
Pot and field experiments were conducted to clarify the effect of soil exchangeable potassium (K) and cesium-137 (137Cs) on 137Cs accumulation and to establish soil index in rice (Oryza sativa L.). Four paddy soils in Fukushima Prefecture, Japan, showing different transfer factors for radioactive Cs derived from the accident of Fukushima Daiichi Nuclear Power Station in the field were compared in terms of 137Cs accumulation in rice in a pot experiment. 137Cs accumulation in shoots and brown rice widely varied among soils with the transfer factor ranging from 0.018 to 0.068 for shoots and 0.004 to 0.065 for brown rice. 137Cs concentration in brown rice and shoots tended to decrease with higher levels of soil exchangeable K, and they were more closely related to the exchangeable Cs/K ratio. Similar relationships between the Cs/K ratio and Cs accumulation in plants were obtained for the stable isotope cesium-133 (133Cs). The distributions of 137Cs and 133Cs in grains were also similar and variable among soils. The transfer factors obtained in pot experiments mostly agreed with field observations. The results imply that the exchangeable 137Cs/K can be a potential soil index to estimate 137Cs accumulation in rice.  相似文献   

4.
The levels of radioactive contamination by artificial radiocesium (137Cs) were evaluated in sediments and the commonest species of water plants. Specimens were collected from a range of biotopes along the Pinios River and its tributaries, during the years 1998 and 2010. The 137Cs concentrations within the above period clearly indicate that this radionuclide still decrease in the River Pinios. A marked decrease is also observed in comparison to our previous results in 1993. 137Cs concentration activities in the sediment are higher than in the plant material. In general, roots showed greater 137Cs concentration than leaves, while stems showed the lowest concentration. Significant differences in 137Cs concentrations were found among different species growing under similar environmental conditions. 137Cs content in collected aquatic plants was in the descending order: Ceratophyllum demersum L. > Myriophyllum spicatum L. > Paspalum pasalodes Scribner > Cladophora glomerata L. > Cyperus longus L. > Potamogeton nodosus Poiret. A comparison of the studied stations indicated that the southwest side of Thessalia plain, where the first two initial sampling stations of the Pinios River and the tributaries Enipeas and Kalentzis are situated, was highly contaminated. Low 137Cs concentrations were observed in the Titarisios tributary, originated from the northeast part of Thessalia plain, behind Mt. Olympus and the last sampling stations of the Pinios River.  相似文献   

5.
The features of cesium-137 (137Cs) root uptake by spring oat (Avena sativa L.) and lettuce (Lactuca sativa L.) plants have been studied in a model experiment with simulation of radionuclide fallout into undisturbed monoliths of arable chernozems from the Plavsk radioactive spot. An integrated approach using digital autoradiography and γ-spectrometry methods has revealed a uniform pattern of vertical and lateral 137Cs distribution in the soil profile and low bioavailability of the radionuclide or root uptake by plants. Certain biological features of the test crops with respect to root uptake of 137Cs have been demonstrated: limited translocation of the element into shoots via its relative accumulation in roots for oats and limitation of general root uptake of 137Cs into plants, given its uniform distribution between roots and shoots for lettuce.  相似文献   

6.
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.  相似文献   

7.
Agricultural land use in the area of the post-Chernobyl Plavsk radioactive hotspot (Tula region, Central Russia) has raised a problem of radioecological safety of obtained plant foodstuff. Verification of 137Cs activities and inventories in components of “soil-plant” systems of the territory has been conducted in 2014–2017 in 10 agrosystems and 2 semi-natural meadows. It was revealed that density of 137Cs contamination of arable chernozems and alluvial calcareous soils nowadays varies in a range 140–220 kBq/m2 and exceeds radiation safety standard by ˜ 3.5–6 times. Deep plowing of the arable soils up to 30-cm in 1986–1987 resulted in decreasing of 137Cs inventories in rooting zone by ≈ 70% for crops cultivated with shallow disk plowing (wheat, barley), and by ≈ 35% for crops cultivated with middle plowing (buckwheat, amaranth, white mustard). The investigated plants and their compartments can be grouped on the basis of transfer factor values as follows: maize (stems and leaves) > amaranth > bromegrass > vegetation of dry meadow, galega, sunflower (seeds), vegetation of wet meadow > maize (grain), soybean (pods), barley (grain), buckwheat (grain), potatoes (tubers) > white mustard (seeds), wheat (grain). It is noticeable that generative plant compartments are characterized by less 137Cs activities in comparison with stems and leaves; and that 137Cs root uptake is not coincide with total flux of mineral nutrients in “soil-plant” systems. In sum, 137Cs soil-to-plant transfer in the area of the Plavsk radioactive hotspot is characterized by considerable discrimination, so 137Cs activities in plants are completely in accordance with national standards.  相似文献   

8.
Abstract

Radioactivity levels of cesium (Cs)-134 and 137Cs in bamboo [Phyllostachys reticulata (Rupr) K. Koch] sprouts grown from April to June 2011 over a wide area (including Fukushima Prefecture) were elevated (max. 3100 Bq kg?1 fresh weight) after the Tokyo Electric Power Company, Inc. (TEPCO) Fukushima Daiichi Nuclear Power Plant disaster in March 2011. Bamboo sprouts in 2012 also contained high radioactivity levels. Radioactivity imaging analysis of bamboo sprouts harvested in 2012 showed increasing concentration gradients of radioactivity from the lower parts to the top of the sprouts. The peels were individually separated from the sprouts, and the inner edible part (trunk) was cross-sectioned at the internodal sections from the top to the lower parts. Each segmented trunk and its corresponding peel were analyzed for radioactive cesium (134Cs and 137Cs) and stable cesium (133Cs). The concentrations of 134Cs and 137Cs showed significant increases from the lower part to the top, whereas 133Cs showed an almost constant value in the trunk and peel except in the peel of the top node. We speculated that 134Cs and 137Cs in newly emerging bamboo sprouts in 2012 were translocated mainly from various plant tissues (where the fallout was layered on the bamboo tissues) in older bamboo, while 133Cs was translocated from the soil through the roots of the new bamboo sprouts and was present in the roots and stems.  相似文献   

9.
Radioactive substances were released into the environment after the nuclear accident at the Fukushima Daiichi Nuclear Power Station; this led to the contamination of the soil at Fukushima Prefecture. Mixing of organic matter with soil during plowing is known to influence radiocesium (134Cs and 137Cs) absorption by crops. However, the effect of mixing organic matter polluted by radioactive substances during plowing on radiocesium absorption by plants is not yet known. The aim of this study was to investigate the effect on the radiocesium absorption by komatsuna (Brassica rapa L. var. perviridis) cultivated in a 45-L container containing Andosol (14,300 Bq kg?1) or Gray Lowland soil (33,500 Bq kg?1) mixed with polluted wheat (Triticum aestivum L. Thell.) straw (2080 Bq kg?1). The radiocesium concentration of the plants and the soil and the amount of exchangeable radiocesium in the soil were determined using a germanium semiconductor. The transfer of radiocesium from the soil to plants decreased by 53 and 27% in Andosol and Gray Lowland soil, respectively, after the application of 10 t ha?1 polluted wheat straw. This reduction in the level of radiocesium transfer might be attributed to potassium contained in the wheat straw, which might compete with cesium during membrane transport and thereby block the transport of cesium from the soil solution to the roots and from the roots to the shoots. Alternatively, the applied wheat straw probably absorbed radiocesium and decreased the amount of exchangeable radiocesium in the soil. Our findings suggest that the mixing of polluted wheat straw with contaminated soil might influence the absorption of radiocesium content by agricultural products. Further studies are warranted to determine the long-term effects of the application of polluted wheat straw on the rate of radiocesium transfer to crops.  相似文献   

10.
The role of mineralization of soil organic matter (SOM) in the mobilization of 137Cs was estimated on the basis of data on the biokinetic fractionation of the organic matter of soddy-podzolic sandy-loam and peat bog soils and on the coefficients of the soil-to-plant transfer of radiocesium under field conditions. The peat bog soils were richer than the soddy-podzolic soils in the total organic carbon (by 7.9–23.8 times), the potentially mineralizable carbon (by 2.4–6.5 times), and the carbon of the microbial biomass (by 2.9–4.6 times). The agricultural use of the soddy-podzolic and peat bog soils led to a decrease in the SOM mineralization capacity by 1.1–1.8 and 1.4–2.0 times, respectively. Simultaneously, the portions of the easily, moderately, and difficultly mineralizable fraction of the SOM active pool changed. The coefficients of the 137Cs transfer from the peat bog soils to plants were 3.3–17.6 times higher than those for the soddy-podzolic soils. The content of 137Cs in plants grown on the peat bog soils was 2–65 times higher than that in the mobile (salt-extractable) soil pool by the beginning of the growing season. Strong positive linear correlations were found between the coefficients of the soil-to-plant transfer of 137Cs and the total content of the SOM, the content of the microbial biomass, the content of the potentially mineralizable carbon, and the intensity of its mineralization. It was concluded that the decisive factors controlling the intensity of the 137Cs transfer from mineral and organic soils into plants are the SOM content and its mineralization potential. The mineralization of the SOM is accompanied by the release of both 137Cs and mineral nitrogen; the latter facilitates the transfer of radiocesium into plants.  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
River floodplains have been recognised as important sinks for storing suspended sediment and associated contaminants mobilised from the upstream catchment. However, information on contemporary rates of overbank sedimentation is difficult to obtain using conventional methods. Measurements of the 137Cs content of floodplain sediments provide an alternative approach to obtaining; estimates of medium-term rates (ca. 40 years) of overbank sediment deposition. The 137Cs approach requires only a single site visit and minimum sample preparation. Furthermore, it is capable of providing information on spatial patterns of sediment deposition on floodplains, which is needed to improve our understanding of the processes involved in overbank flow and sediment deposition. This paper reviews the basis for using 137Cs measurements in floodplain sedimentation studies and presents improved procedures for interpreting 137Cs profiles in floodplain sediments and for obtaining estimates of sedimentation rates from single measurements of the total. 137Cs inventories of bulk sediment cores. The results obtained from a case study undertaken on the floodplain of the River Stour, Dorset, UK, are presented.  相似文献   

16.
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17.
ABSTRACT

An incubation experiment was conducted to clarify how soil flooding influences the mobility of radioactive cesium (RCs: 134Cs and 137Cs) in paddy soil after aging, focusing on the effects of ammonium increase and soil reduction. We used two contaminated paddy soils (A and B, both Gleyic Fluvisols) aged for 26 months after the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Plant accidents, and analyzed both the RCs and stable cesium (133Cs). The soils were incubated in a flooded condition, with or without the addition of ammonium fertilizer, for 1, 15 and 30 d, and in an unflooded condition for 30 d. After the incubation periods, we quantified 133Cs concentration in the soil solution, 133Cs and RCs released from soil in 0.01 mol L–1 calcium chloride solution as parameters of release intensity, and 133Cs and RCs extracted with 1 mol L?1 ammonium acetate solution as exchangeable quantities, and analyzed their relationship with ammonium content and redox condition in soil. The increase of ammonium by both ammonification and fertilizer application promoted release of exchangeable 133Cs and RCs to the soil solution and calcium solution. When ammonium content became low during unflooded incubation, exchangeable 133Cs and RCs themselves decreased. When soil reduction progressed with flooded incubation, however, exchangeable 133Cs and RCs decreased, despite high ammonium content. To estimate the influence of soil reduction on the exchangeability of RCs, soil A was sequentially extracted with sodium hydrosulfite (a reducing agent) and ammonium acetate solutions. Compared with a control treatment using sodium sulfate instead of sodium hydrosulfite, the total RCs extracted by the reducing treatment was 42% lower, indicating that soil reduction decreases RCs exchangeability. Through these analyses of 133Cs and RCs, we conclude that soil flooding influences the mobility of aged RCs through two opposite effects: the release of exchangeable RCs into soil solution is enhanced with increased ammonium, while the exchangeable RCs itself decreases due to soil reduction.  相似文献   

18.
Measurements of 137Cs, 239/240Pu and 241Am contamination in substrate and vegetation on a tide washed pasture in the Mersey Estuary have enabled the dynamic response of vegetation contamination resulting from individual inundation events to be observed. Vegetation contamination is almost entirely due to external contamination by sediment, although there is some evidence for a small contribution from root uptake for 137Cs, with a transfer factor from substrate to internal plant of about 0.003. Marked temporal variation is consistent with contamination by deposition of suspended sediments during tidal inundations, subsequently decreasing with a halflife of 20–30 days. Overall accumulation factors (total plant:substrate) are lower than those observed for the few pastures and saltmarshes studies further north in Cumbria, and consistent with the lower inundation frequency of the Mersey Estuary site.  相似文献   

19.
The role of the mineralogy of the clay fraction and the physicochemical properties of alluvial soils in the floodplain of the Iput River and its tributary the Buldynka River (in the region of the settlement of Starye Bobovichi in Bryansk oblast) in the distribution and immobilization of radioactive isotope 137Cs from the atmospheric fallout after the Chernobyl accident was studied. The soils had a sandy texture; a significant variation in the content of amorphous iron oxides (0.1–0.77%) and labile manganese (11.2–193 mg/kg), the cation exchange capacity (6.1–54.2 meq/100 g soil), and the base saturation (29–100%) was common; an appreciable content of X-ray amorphous mineral substances in the clay fraction (<1 μm) enriched with organic carbon (7.7–13.1%); the predominance of trioctahedral hydromicas (Me=50%) in the clay fraction; and the presence of fine-disperse quartz and lepidocrocite. The specific activity of the 137Cs in the clay fraction of the moderately and strongly contaminated layers increased with the increasing portion of smectite formations and (or) hydromicas. On the whole, the presence of the clay fraction favored a decrease in the 137Cs mobility (the correlation between its content and that of exchangeable cesium was r=?0.608, n=17). However, the portion of exchangeable radiocesium (extracted with 1 M CH3COONH4, 1:10) had a tendency toward an increase with increasing content of hydromicas in the clay fraction. Thus, the minerals of this group were a potential source of exchangeable 137Cs in the soils. The significant role of amorphous and mobile iron forms in the immobilization and migration of radiocesium in the secondary contaminated horizons of the alluvial soils was revealed.  相似文献   

20.
A study was made to determine if infection with vesicular-arbuscular mycorrhizal (VAM) fungi would increase the uptake of 137Cs and 60Co by Yellow sweetclover [Melilolus officinalis (L.) Lam] and Sudan grass [Sorghum sudanense (Piper) Stapf.]. Plants were inoculated by germinating and growing plants in small volumes of soil containing one of three inoculum sources. Control plants were grown in steam-sterilized inoculum to which sieved (38 μm) inoculum washings had been added. Infected and control plants, with the accompanying soil volume, were subsequently transplanted into pots containing autoclaved field soil which 7 yr previously had been contaminated with 137Cs and 60Co. The clover was harvested at 65 and 93 days; Cs content was 2.0 and 1.7 times that of the control respectively, on these dates, while Co was not significantly different. The grass was harvested at 85 and 119 days; Cs content was greater in the treated than the control grass, but not significantly; however, Co content was increased 2.5 times that of the control at the first harvest data, but was not significant at the second.  相似文献   

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