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1.
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   

2.
We investigated the distribution of radiocesium (134Cs and 137Cs) in three orchards in Tsukuba, 170 km southwest from the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Plant 9 months after the accident. The radiocesium was distributed mainly in the surface soil. The distribution of radiocesium differed between deciduous and evergreen plants. In deciduous blueberry (Vaccinium virgatum Aiton), the concentration was high in the old branches because the bushes had no leaves at the time of the accident. Therefore, the concentration per bush was greater in unpruned than in pruned bushes. More radiocesium was present in the trunk and rootstock of each bush, although the concentration was low. In evergreen Satsuma mandarin (Citrus unshiu Marcow), the concentration was high in the leaves, and it was higher in old leaves that expanded before the accident than in new leaves that expanded after the accident, because the old leaves were contaminated by direct deposition of the fallout. However, the total radiocesium was higher in the new leaves than in the old leaves because of the greater amount of new leaves. The radiocesium concentration in fruits was higher in trees with fewer fruits than in trees with many fruits, but the total radiocesium in fruits was higher in trees with many fruits.  相似文献   

3.
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   

4.
Following the accident at the Tokyo Electric Power Company, Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium (134Cs + 137Cs) concentrations in deciduous mature fruits were determined in orchards in the northern area of Fukushima Prefecture. At the time of the nuclear accident, most deciduous fruit trees were in the dormant stage prior to bud burst. To evaluate the relationship between radiocesium deposition in the soil and fruit contamination, radiocesium concentrations were measured from the 5-cm topsoil and from six fruit species across 17 orchards in 2011. The vertical distribution of radiocesium in the topsoil (0–30 cm in depth) and its spatial distribution in the 5-cm topsoil underlying the tree canopy of a peach, Prunus persica (L.) Batsh, orchard (“Akatsuki” cultivar) were also investigated. Significant correlations between the radiocesium concentration in the mature fruit and that in the 5-cm topsoil layer were observed for the 17 orchards as well as for the trees of the peach orchard. However, 93% of the 137Cs found in the 30-cm soil core was retained within the top 3 cm of the soil in the peach orchard. Considering the profile of the root of this deciduous fruit tree, we assumed a negligible level of radiocesium uptake via the roots. However, the possibility of inward migration via the bark was undeniable, because some radiocesium adhered to the tree canopy before bud burst while depositing on the soil surface. Additionally, transfer factors for peach and grape, hybrid of Vitis labrusca L. and Vitis vinifera L., from young, uncontaminated trees cultivated with contaminated soil were lower than those previously reported.  相似文献   

5.
Abstract

Radioactive 137Cs concentrations of forage corn (Zea mays L.) and Italian ryegrass (Lolium multiflorum Lam.) in a double cropping system under continuous cattle farmyard manure (FYM) application were observed for more than 2 years after the Fukushima Daiichi Nuclear Power Station accident in 2011. The experiment field is located 110 km southwest of the Fukushima Daiichi Nuclear Power Station, and the soil contains 137Cs of 920 Bq kg?1 on average. For crop cultivation, nitrogen fertilizer was applied in addition to FYM. The 137Cs concentrations in corn decreased significantly between 2011 and 2012, but only differed significantly between 2012 and 2013 for the plot with no FYM application. For Italian ryegrass, no significant differences were observed between the harvest in 2012 and 2013 despite the FYM application rate. To minimize corn 137Cs concentrations, the FYM application rate should be more than and equal to 30 Mg ha?1 when FYM is used as the major nutrient source. Exchangeable potassium oxide (K2O) greater than around 0.3 g kg?1 was mostly maintained with the FYM application rates. Corn 137Cs concentration appeared to increase at exchangeable K2O levels below 0.15 g kg?1. These results suggest that continuous FYM application can maintain soil nutrients including K2O and thereby control radioactive Cs transfer from the soil. FYM application rate of 30 Mg ha?1 is within the levels recommended by the prefectural governments around Fukushima Prefecture for crop production before the accident. These levels are sufficient to decrease the radioactive Cs concentrations for corn. However, unlike corn, differences in soil chemical properties by FYM application did not affect 137Cs concentrations in Italian ryegrass in this study, although low exchangeable K2O seemed to increase concentrations of stable 133Cs. Further experiments should be conducted to understand the observed differences between corn and Italian ryegrass.  相似文献   

6.
ABSTRACT

Radiocesium (RCs) discharged by the Fukushima Daiichi Nuclear Power Plant (Tokyo Electric Power Co., Inc.) accident has extensively contaminated agricultural land in Fukushima Prefecture and its neighboring areas. Many studies have demonstrated that Cs (RCs and 133Cs) uptake of plants is affected by the exchangeable K (Ex-K) concentration in soil. However, the precise plant–soil interaction in relation to Cs uptake is still unclear. The aim of this study was to investigate Cs uptake of plant in field by focusing on xylem exudate and roots because nutrients in xylem exudate reflect medium (soil) conditions and affect nutrient accumulation in shoots. Two varieties of amaranth, K4 (Amaranthus caudatus L.) and Mexico type (A. hypochondriacus L.), which have different Cs uptake abilities, were grown in four fields and in pots (750 to 3440 Bq kg?1 of RCs) in Fukushima Prefecture. Cs concentrations in xylem exudate, shoot, and soil; Ex-K concentration in soil; and root distribution in soil were determined. RCs concentration in xylem exudate varied from 0.04 to 164 Bq kg?1 and 133Cs concentration in xylem exudate ranged from 0.01 to 33.7 μg kg?1. The Cs concentrations were decreased by the high Ex-K concentration and the large amount of 2:1 type clay minerals in soil. The average of the ratios of Cs concentration in shoot to Cs concentration in xylem exudate for all samples was 127 ± 112 (mean ± standard deviation), although no clear correlation was found between them. The correlations betwee\n RCs and 133Cs concentrations in xylem exudate and shoot were strong in pot and in the field with low Ex-K concentration. Eighty-five percent of the total root length was distributed in the topsoil (0–20 cm soil layer). The positions where roots take up Cs were estimated from the differences in the vertical distribution of RCs and 133Cs concentrations in soil. The estimated Cs uptake ratios of topsoil to total soil layer ranged from 7% to 91% and varied with the concentration and the vertical distribution of Ex-K in soil.  相似文献   

7.
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   

8.
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   

9.
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   

10.
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   

11.
We investigated changes in the radiocesium concentration in a blueberry (Vaccinium virgatum Aiton) orchard in Fukushima prefecture to clarify the radiocesium contamination for 3 years after the Tokyo Electric Power Company’s Fukushima Daiichi nuclear power plant accident occurred in mid-March 2011. In the aboveground part of blueberry bushes, the concentrations of radiocesium in branches that were directly affected by radioactive fallout were the highest among the samples investigated, and the concentrations in fruits were the lowest. The concentration of radiocesium decreased exponentially in the fruits and leaves over 3 years. The radiocesium concentrations in soils were higher in the surface layer. The amount of radiocesium in organic matter on the soil surface under the canopy greatly decreased from 2011 to 2012. The transfer factor of the radiocesium from soil to blueberry fruits decreased annually. These results suggest that radiocesium adhered directly to the aboveground organs of blueberry bushes in March 2011, and it is possible that the accumulation of radiocesium in fruits is mainly due to radiocesium transfer from the branches and trunk to fruits for several years after the nuclear power plant accident.  相似文献   

12.
The 137Cs and 40K activities and transfer factors from soil to vegetables, grass, and milk from villages located around Tarapur Atomic Power Station (TAPS) were determined using high-resolution gamma spectrometry. A total of 32 soil, 21 vegetable, 23 dry paddy grass, and 23 milk samples were collected from 23 different agricultural farms from various villages around TAPS to determine transfer factors for natural environment. The mean concentration values for 137Cs and 40K in soil, grass, and milk were 2.39?±?0.86 Bq kg?1, 0.31?±?0.23 Bq kg?1, and 12.4?±?5.7 mBq L?1 and 179?±?31 Bq kg?1, 412?±?138 Bq kg?1, and 37.6?±?9.3 Bq L?1, respectively, for soil?Cgrass?Cmilk pathway. In the soil?Cvegetation pathway, the mean concentrations values for 137Cs and 40K were 2.15?±?1.04 Bq kg?1, 16.5?±?7.5 mBq kg?1, and 185?±?24, 89?±?50 Bq kg?1, respectively. The evaluated mean transfer factors from soil?Cgrass, grass?Cmilk, and soil?Cvegetation for 137Cs were 0.14, 0.0044, and 0.0073 and that of 40K were 2.42, 0.0053, and 0.49, respectively. Only 15 out of total 44 milk and vegetable samples were detected positive for 137Cs, indicating a very low level of bioavailability.  相似文献   

13.
ABSTRACT

Following the Fukushima Daiichi Nuclear Power Plant accident of 2011, the potential for radiocesium transfer from contaminated soils, such as Andosols, to agricultural crops became a significant concern. Andosols account for up to 70％ of paddy soils in the northern and northwest areas of Tochigi Prefecture, where the radiocesium concentration is 1000 Bq kg?1 or greater in the soil of some fields. The present study was carried out in order to determine the phytoavailability of radiocesium in Andosols by comparing it with that of gray lowland soils in the first 3 years following the accident. The transfer factor (TF) tended to be higher in Andosols than in gray lowland soils, leading to higher radiocesium concentrations in brown rice grown in Andosols. The exchangeable potassium (Ex-K2O) in Andosols was highly and negatively correlated with TF, followed by clay. The Ex-K2O value was positively correlated with the clay/total carbon (T-C) value, suggesting that a high T–C ratio could weaken K2O adsorption on clay mineral sites; hence, the low clay/T-C values can partially explain the relatively large TF values of Andosols. Samples with Ex-K2O contents less than 200 mg kg?1 and with low clay/T-C values showed striking decreases in TF values from 2011 to 2012. However, the decrease from 2012 to 2013 was quite small; radiocesium in these samples was potentially available for rice uptake for a long time, likely due to the reversible adsorption and fixation characteristics of allophane. Most gray lowland soil samples showed very low TF values over the 3 years of the study, except for those with TF values greater than 0.1 due to low Ex-K2O and clay contents; the geometric mean (GM) value of TF was below 0.01 in 2012. The extraction of exchangeable radiocesium (Ex-Cs) with a 1 mol L?1 ammonium acetate solution may not be an appropriate method for explaining the variability in radiocesium TF in Andosols. This is because the Ex-Cs value was significantly correlated with Ex-K2O in Andosols, but not in gray lowland soils, indicating that Ex-K2O explained this variability in relation to Ex-Cs.  相似文献   

14.
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   

15.
We investigated radiocesium distribution in tea plants (Camellia sinensis L. var. sinensis) of Saitama Prefecture, located approximately 200–250 km away from Tokyo Electric Power Company’s Fukushima Daiichi nuclear power plant. In 2012, more than 2500 samples of tea plants were analyzed. We found differences in radiocesium concentration among tea plant cultivars, which appeared to be attributable mainly to the leaf morphology and depth of the leaf layer in tea plants. Furthermore, the radiocesium concentration in the first tea crop showed a strong correlation with that in spring skiffing.  相似文献   

16.
Abstract

Leaf composting is an essential technique in organic farming; it improves the physicochemical properties of soil such as texture, structure, water-holding capacity, and nutrient content. However, the use of leaf compost is prohibited in the Fukushima and Ibaraki prefectures because large areas of the Fukushima and Ibaraki forests were contaminated by radiocesium (134Cs and 137Cs) after the Fukushima Daiichi nuclear power plant (FDNPP) accident. We examined the changes in radio Cs concentration and other physicochemical properties in leaf compost made from Ibaraki and Fukushima forest leaves. At the beginning of the composting process, rice bran-treated compost showed 25%–32% lower radio Cs concentration than the leaf-only compost; however, 2?years after composting, the difference in concentration between these treatments had increased to 35%–63%. Moreover, the incorporation of rice bran significantly increased the compost temperature, moisture, electrical conductivity, bulk density, and total nitrogen during the composting process. Plant uptake of radio Cs was significantly lower in rice bran-treated compost than the leaf-only compost at each level of application; furthermore, the levels of soil radio Cs showed a similar trend. Potassium application combined with leaf compost resulted in a significant reduction of radio Cs plant uptake. Our data revealed that adding rice bran to leaves positively affects radio Cs reduction in leaf compost and also reduces its uptake by plants. Our findings may improve the management of leaf composting after the FDNPP accident.  相似文献   

17.
Pits of sandy alluvial soils were studied in different parts of the floodplains of the Iput River and its tributary the Buldynka River near the settlement of Starye Bobovichi (Bryansk oblast). The 137Cs content in the soil horizons varied from 0.01 to 31.2 Bq/g reaching the maximum in the initially polluted layers buried at depths of 6 to 40 cm. Radiocesium was found in all the particle-size fractions with its predominate concentration in the finest fractions. The specific 137Cs activity in the fractions of <1, 1–5, 5–10, and >10 μm comprised 44.1 ± 11.5; 33.3 ± 7.6, 20.9 ± 4.9, and 2.4 ± 0.6 Bq/g of soil. However, the contribution of the coarse (>10 μm) fractions to the total radiocesium pool in the soils (19–60%, or 34 ± 2% on the average) was comparable with that of the clay fraction (16–71%, or 38 ± 3% on the average), because of the predominance of the sand-size fractions in the soils. The highest coefficient of variation with respect to the relative contribution of particular fractions to the total soil pool of 137Cs was characteristic of the fraction of 5–10 μm; in the other fractions, it varied from 31 to 41%. The portion of 137Cs bound with the finest fractions increased in the deeper layers. The total 137Cs activity in the polluted horizons of the soils was mainly determined by its concentration in the clay fraction (Spearman’s coefficient of rank correlation (r) for the moderately polluted horizons comprised 0.926 at n = 14). It was experimentally proved that clay particles, upon the destruction of organic films on their surface, could readsorb the released radiocesium for a second time.  相似文献   

18.
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   

19.
The vertical distribution and bioavailability of 137Cs in Histosols and mineral soils with different physicochemical properties from the southeast of Bavaria (Germany) more than ten years after the Chernobyl accident were the focus of this study. The vertical distribution of 137Cs was low in the investigated soils. About 85–98 % of the total 137Cs was located in the upper 10 cm of the mineral soils. Slightly higher 137Cs percentages were observed in deeper soil layers of the peat soils. Although the organic matter is assumed to enhance 137Cs mobility in soils, 137Cs was also located in the upper 10 cm of the peat soils (73–85 %). The highest 137Cs‐activities were found in the humus layers of forest soils, where 45–93 % of the total 137Cs soil inventories were observed. To determine the bioavailability of radiocesium, the soil‐to‐plant transfer of 137Cs and additionally added 134Cs was investigated under controlled conditions. The results revealed that the 134+137Cs soil‐to‐plant transfer factors as well as the percentages of NH4‐exchangeable 134+137Cs were much higher for the peat soils and humus layers than for the mineral soils. Nevertheless, the migration of 137Cs from the humus layers to the underlying soils was low. Considering the high bioavailability and low migration of radiocesium in the humus layers, it is suggested that radiocesium is involved in a shortcut element cycle in the system humus layer‐plant uptake‐litter. Furthermore, the organic matter has to be taken into account for radiocesium immobilization.  相似文献   

20.
Environmental samples of soil, plant and air dust collected after the Fukushima Daiichi Nuclear Power Plant accident were analyzed by autoradiograph, and significant amounts of radioactive particles containing higher cesium-134 (134Cs) and cesium-137 (137Cs) were found. Most of the radioactive soil particles were clay sized. The main part of the radioactivity and radioactive particles of air dust was detected from the 1.1–2.0μm fraction of an Andersen sampler filter. A considerable part of the radioactive particles on the air dust filter were not water soluble. Radioactive particles attached to outdoor plant leaves persisted for nearly 1 year. Thus, soil, leaf and air dust similarly contained sparingly water-soluble, micron-sized radioactive particles each with comparable ranges of elevated radio-Cs. A sheet dilution method was proposed and used to select and purify these radioactive particles. Using selected radioactive particles, the relation between area × gray value on autoradiograph and radioactivity was estimated. Radioactivity per particle was up to a few Bq and the geometrical average radioactivity of detected particles was around 0.1 Bq per particle or less. The configuration, chemical composition, origin and formation mechanisms of the radioactive particles require clarification.  相似文献   

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