Transfer of 137Cs to rice plants from various paddy soils contaminated under flooded conditions at different growth stages

Transfer factor of 137Cs and 90Sr to various crops in semi-arid environment

This study focuses on evaluating the transfer factor (F_v) of ¹³⁷Cs and ⁹⁰Sr from two basic soil types in the country, i.e. Aridisol and Inceptisol, to 18 common crops belong to six groups, i.e. cereals, leafy, non-leafy vegetables, tubers, leguminous fodder and leguminous vegetables. In addition, the variation of F_vs of ¹³⁷Cs and ⁹⁰Sr with crop components, growth stages of plants and the influence of mineral fertilisation were investigated. The experiments were performed in an open field and the results were expressed as geometric means. The data revealed that F_vs of both radionuclides were higher in Aridisol than Inceptisol for all crops by about 1.03-4.86 fold. F_vs of ⁹⁰Sr were more enhanced than those of ¹³⁷Cs by one or two orders of magnitude despite plant group and soil type, e.g. F_vs ranged 0.12-5.2 for ⁹⁰Sr and 0.0035-0.26 for ¹³⁷Cs in the vegetative portion of the crops. Among the six crop groups investigated, cereals gave the lowest F_vs for both radionuclides, which is compatible with the data reported worldwide. The average F_vs observed in cereal grains reached 0.001 for ¹³⁷Cs and 0.017 for ⁹⁰Sr, in Inceptisol. However, Jew-mallow (one of the major leafy vegetables in the country that is consumed throughout the year) reflected the highest F_vs for ¹³⁷Cs and ⁹⁰Sr, i.e. 0.11 and 2.44 in Inceptisol, respectively. Comparing F_vs of the radionuclides through the growing stages of the plants indicated enhanced values at the mid-season than harvest as a consequence of the decrease of the physiological activity of the plants towards maturation and dilution made by the increase of plant biomass; e.g. F_vs dropped to about 3.0 fold for ¹³⁷Cs and 2.2 for ⁹⁰Sr, in Aridisol. Mineral fertilisation of soil (for four crops, i.e. sorghum, barley, spinach and alfalfa) reduced F_vs for both radionuclides to an extent of 30% probably because of the competing action of their stable nutrient analogues NH₄⁺, K⁺ or Ca²⁺ or because of growth dilution. The data presented herein would form a baseline when decision of land-investment or phytoremediation is the preferable countermeasure for the management of ¹³⁷Cs and ⁹⁰Sr-contaminated soil in semi-arid environment.

Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region

Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium ((137)Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of (137)Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the (137)Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10(-1) and 1.8 × 10(-1) for (137)Cs and stable Cs, respectively. The Fm of (137)Cs had geometric mean values of 1.9 × 10(-2) d L(-1) and 4.6 × 10(-2) d L(-1), respectively, for adopted Cows 1 and 2; 1.7 × 10(-2) d L(-1) for the cows of local farmers, and 4.0 × 10(-3) d L(-1) for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of (137)Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for (137)Cs and stable Cs and their dependence on the potassium content ((40)K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of (137)Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 μSv y(-1) and 0.04 μSv y(-1),while that to an adult were 0.39 μSv y(-1) and 0.05 μSv y(-1), respectively.

Soil to rice transfer factors for (226)Ra, (228)Ra, (210)Pb, (40)K and (137)Cs: a study on rice grown in India

India is the second largest producer of rice (Oryza sativa L.) in the world and rice is an essential component of the diet for a majority of the population in India. However, detailed studies aimed at the evaluation of radionuclide transfer factors (F(v)) for the rice grown in India are almost non-existent. This paper presents the soil to rice transfer factors for natural ((226)Ra, (228)Ra, (40)K, and (210)Pb) and artificial ((137)Cs) radionuclides for rice grown in natural field conditions on the West Coast of India. A rice field was developed very close to the Kaiga nuclear power plant and the water required for this field was drawn from the cooling water discharge canal of the power plant. For a comparative study of the radionuclide transfer factors, rice samples were also collected from the rice fields of nearby villages. The study showed that the (226)Ra and (228)Ra activity concentrations were below detection levels in different organs of the rice plant. The soil to un-hulled rice grain (40)K transfer factor varied in the range of 6.5 × 10(-1) to 2.9 with a mean of 0.15 × 10(1), and of (210)Pb varied in the range of <1.2 × 10(-2) to 8.1 × 10(-1) with a mean of 1.4 × 10(-1), and of (137)Cs varied in the range of 6.6 × 10(-2) to 3.4 × 10(-1) with a mean of 2.1 × 10(-1). The mean values of un-hulled grain to white rice processing retention factors (F(r)) were 0.12 for (40)K, 0.03 for (210)Pb, and 0.14 for (137)Cs. Using these processing retention factors, the soil to white rice transfer factors were estimated and these were found to have mean values of 1.8 × 10(-1), 4.2 × 10(-3), and 3.0 × 10(-2) for (40)K, (210)Pb, and (137)Cs, respectively. The study has shown that the transfer of (40)K was higher for above the ground organs than for the root, but (210)Pb and (137)Cs were retained in the root and their transfer to above the ground organs of the rice plant is significantly lower.

Paddy-field contamination with 134Cs and 137Cs due to Fukushima Dai-ichi Nuclear Power Plant accident and soil-to-rice transfer coefficients

The transfer coefficient (TF) from soil to rice plants of (134)Cs and (137)Cs in the form of radioactive deposition from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011 was investigated in three rice paddy fields in Minami-Soma City. Rice crops were planted in the following May and harvested at the end of September. Soil cores of 30-cm depth were sampled from rice-planted paddy fields to measure (134)Cs and (137)Cs radioactivity at 5-cm intervals. (134)Cs and (137)Cs radioactivity was also measured in rice ears (rice with chaff), straws and roots. The rice ears were subdivided into chaff, brown rice, polished rice and rice bran, and the (134)Cs and (137)Cs radioactivity concentration of each plant part was measured to calculate the respective TF from the soil. The TF of roots was highest at 0.48 ± 0.10 in the field where the (40)K concentration in the soil core was relatively low, in comparison with TF values of 0.31 and 0.38 in other fields. Similar trends could be found for the TF of whole rice plants, excluding roots. The TF of rice ears was relatively low at 0.019-0.026. The TF of chaff, rice bran, brown rice and polished rice was estimated to be 0.049, 0.10-0.16, 0.013-0.017 and 0.005-0.013, respectively.

Transport behavior and rice uptake of radiostrontium and radiocesium in flooded paddy soils contaminated in two contrasting ways

In order to investigate the transport behavior and rice uptake of radiostrontium and radiocesium in flooded rice fields, lysimeter experiments with two paddy soils were performed in a greenhouse. A solution containing (85)Sr and (137)Cs was applied in two different ways - being mixed with the top soil 27 d before transplanting or being dropped to the surface water 1d after transplanting. Rice uptake was quantified with two kinds of transfer factor - TF(m) (dimensionless) and TF(a) (m(2)kg(-1)-dry) for the pre- and post-transplanting depositions, respectively. For brown rice, the TF(m) values of (85)Sr and (137)Cs differed between the soils by factors of 2 (1.6×10(-2) and 2.5×10(-2)) and 7 (2.2×10(-2) and 1.5×10(-1)), respectively. Corresponding factors by the TF(a) values were 2 (2.5×10(-4) and 4.4×10(-4)) for (85)Sr and 3 (1.1×10(-3) and 2.9×10(-3)) for (137)Cs. Straws had several times higher TF(m) and TF(a) values of (85)Sr than of (137)Cs. The surface-water concentrations were substantially higher for the TF(a) than for the TF(m), indicating the possibility of a much higher plant-base uptake for the TF(a). In the TF(a) soils, (137)Cs and, to a lesser degree, (85)Sr were severely localized towards the soil surface, probably leading to an increased root uptake. The activity loss due to plant uptake and water percolation was generally inconsiderable. Time-dependent K(d) values of (85)Sr measured in a parallel experiment ranged from 20 to 170, whereas (137)Cs had much higher K(d) values. The use of TF(a) values instead of TF(m) values turned out to be a reasonable approach to the evaluation of a vegetation-period deposition.

Influence of plant activity and phosphates on thorium bioavailability in soils from Baotou area, Inner Mongolia

Harm of thorium to living organisms is governed by its bioavailability. Thorium bioavailability in the soil-plant system of Baotou rare earth industrial area was studied using pot experiments of wheat and single extraction methods. The effects of wheat growth stage and phosphate on thorium bioavailability were also investigated. Based on extractabilities of various extraction methods (CaCl(2), NH(4)NO(3), EDTA, HOAc) and correlation analysis of thorium uptake by wheat plant and extractable thorium, a mixture of 0.02M EDTA+0.5M NH(4)OAc (pH 4.6) was found suitable for evaluation of thorium bioavailability in Baotou soil, which could be predicted quantitatively by multiple regression models. Because of differences of wheat root activities, thorium bioavailability in rhizosphere soil was higher than in bulk soil at tillering stage, but the reverse occurred at jointing stage. Phosphate addition induced the mineralization of soluble thorium by forming stable thorium phosphate compounds, and reduced thorium bioavailability in soil.

Root uptake of radionuclides following their acute soil depositions during the growth of selected food crops

Greenhouse experiments were performed to investigate the root uptake of radionuclides following their acute soil deposition during the growth of several food crops. For this purpose, the soil under the standing plants was contaminated without any direct contamination of their stems or leaves. The intention of this design was to differentiate foilar uptake and root uptake subsequent to a radionuclide deposition during the vegetation period. Soil-to-plant transfer of a radionuclide was quantified with its aggregated transfer factors specified for the time periods from deposition until harvest (T(ag)(a), m(2)kg(-1)). Deposition time-dependent T(ag)(a) values of Mn, Co, Sr and Cs for selected crop species were measured in an acid sandy soil. For rice and Chinese cabbage, HTO experiments were also carried out using this soil. Particularly for rice, experiments with various paddy soils were also performed for (90)Sr and (137)Cs. The obtained T(ag)(a) values varied considerably with the radionuclides, plant species, and times of deposition. Recommendations about, and limitations in, the use of the T(ag)(a) values were discussed.

Proteomic analysis of mature soybean seeds from the Chernobyl area suggests plant adaptation to the contaminated environment

The explosion in one of the four reactors of the Chernobyl Nuclear Power Plant (CNPP, Chernobyl) caused the worst nuclear environmental disaster ever seen. Currently, 23 years after the accident, the soil in the close vicinity of CNPP is still significantly contaminated with long-living radioisotopes, such as (137)Cs. Despite this contamination, the plants growing in Chernobyl area were able to adapt to the radioactivity, and survive. The aim of this study was to investigate plant adaptation mechanisms toward permanently increased level of radiation using a quantitative high-throughput proteomics approach. Soybeans of a local variety (Soniachna) were sown in contaminated and control fields in the Chernobyl region. Mature seeds were harvested and the extracted proteins were subjected to two-dimensional gel electrophoresis (2-DE). In total, 9.2% of 698 quantified protein spots on 2-D gel were found to be differentially expressed with a p-value Collapse

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MESH Headings

• Adaptation, Physiological
• Cesium Isotopes/toxicity
• Chernobyl Nuclear Accident
• Electrophoresis, Gel, Two-Dimensional
• Gene Expression/drug effects
• Geography
• Models, Biological
• Plant Proteins/metabolism
• Proteomics
• Seeds/growth & development
• Seeds/metabolism
• Seeds/physiology
• Seeds/radiation effects
• Soil Pollutants, Radioactive/toxicity
• Glycine max/metabolism
• Glycine max/physiology
• Glycine max/radiation effects
• Stress, Physiological
• Tandem Mass Spectrometry
• Time Factors
• Ukraine

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Affiliation(s)

Maksym Danchenko Department of Reproduction and Developmental Biology, Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Nitra, Slovakia
Ludovit Skultety
Namik M Rashydov
Valentyna V Berezhna
L'ubomír Mátel
Terézia Salaj
Anna Pret'ová
Martin Hajduch

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Effects of the simultaneous application of potassium and calcium on the soil-to-Chinese cabbage transfer of radiocesium and radiostrontium

Pot experiments were carried out in a greenhouse to investigate how effectively the transfer of radiocesium and radiostrontium from soil to Chinese cabbage could be reduced by applying K and Ca simultaneously to the soil. The sources of these elements were KCl and Ca(OH)(2) at agrochemical grades. Varying dosages of K and Ca were tested for an acid loamy soil treated with a mixed solution of (137)Cs and (85)Sr at two different times - 3 d before sowing and 32 d after sowing. For the pre-sowing deposition, the soil-to-plant transfer of (137)Cs decreased sharply with increasing dosages of K and Ca (K/Ca, g m(-2)) from 4.8/46 up to 22.4/215 but the (85)Sr transfer had the greatest reduction at a dosage of 12.8/123. At this dosage, an about 60% reduction occurred for each radionuclide. Plant growth was inhibited from the dosage of 22.4/215, above which all the plants died young. Both dosages of 4.8/46 and 12.8/123 tested following the growing-time deposition produced around 95% reductions for (137)Cs and 50% reductions for (85)Sr. In the second year after the 12.8/123 applications, the effects for (85)Sr were almost the same as in the first year, whereas those for (137)Cs were diminished slightly for the pre-sowing deposition and markedly for the growing-time deposition. Considerably (K) or slightly (Ca) higher doses than 12.8/123 would be allowable for the maximum TF reductions achievable without a growth inhibition.

Transfer of 90Sr to rice plants after its acute deposition onto flooded paddy soils

The transfer of 90Sr to rice plants following its acute ground deposition was examined experimentally in a greenhouse. Lysimeters were flooded after being filled with the soil monoliths from 12 paddy fields. A solution of 90Sr was applied to the standing water in the flooded lysimeters at the pre-transplanting stage or booting stage. Applied 90Sr was mixed with the topsoil only after the pre-transplanting application (PTA). The transfer was quantified with the areal transfer factor (TF(a), m2 kg(-1)-dry) defined as the ratio of the plant concentration to the initial ground deposition. In the PTA, the first-year TF(a) values in the 12 soils were in the range of 8.2 x 10(-3) -2.1 x 10(-2) and 1.7 x 10(-4) -3.6 x 10(-4) for the straws and hulled seeds, respectively. The TF(a) values from the booting-stage application (BSA) were higher than those from the PTA by a factor of up to four. The ratios of the seed TF(a) to the straw TF(a) were, on the whole, higher in the BSA. The 90Sr TF(a) in the PTA was negatively correlated with the soil pH and, to a lesser degree, the exchangeable Ca content. In the second year, the TF(a) in the PTA reduced to 53-90% of that in the first year. A more significant reduction, in general, occurred in a sandier soil. Based on the four consecutive years' transfer data, an overall half-time of the 90Sr TF(a) was estimated to be 2.2 years.

Predicting the transfer of 137Cs to rice plants by a dynamic compartment model with a consideration of the soil properties

This paper describes the predictions of the transfer of 137Cs to rice plants following soil deposition during a non-growth season of rice by a dynamic compartment model considering the soil properties, and their comparison with experimental results. Major processes considered in the model were percolation, soil mixing by plowing, plant uptake, leaching to deep soil, fixation to clay mineral, and time-dependent growth of a plant. To consider the effects of the soil properties (pH, clay mineral, organic matter content, and exchangeable K) on plant uptake and the leaching rates of 137Cs in a root zone soil, the Absalom model was used for the present model. The 137Cs aggregated transfer factors (TFa, m2kg-1 dry plant) of rice plants for two consecutive cultivation years were obtained as a result of simulated 137Cs soil deposition experiments with 17 paddy soils of different properties, all of which were performed before transplanting of the rice. Observed 137Cs TFa values of the rice plants did not show an evident trend for the pH and clay content of the soil properties, while they increased with an increasing organic matter content and a decreasing exchangeable K concentration. Predicted 137Cs TFa values of the rice plants were found to be comparable with those observed.

The investigation of 137Cs and 90Sr background radiation levels in soil and plant around Tianwan NPP, China

(137)Cs and (90)Sr background levels in soil and plant around Tianwan Nuclear Power Plant (NPP) are reported. Eighty-four soil samples and 44 plant samples were collected from March 2000 to April 2002. The samples were analyzed by gamma spectrometry and radiochemical separation procedure to quantify (137)Cs and (90)Sr radioactivities. The concentrations (Bqkg(-1) dry weight) have been observed in the range of 0.6-1.6 for (90)Sr and 1.4-6.9 for (137)Cs in soils, their average values are 1.0+/-0.3 and 4.6+/-1.6, respectively, which are relatively lower than the reported values in neighboring countries. The mean concentrations (in Bqkg(-1) fresh weight except for tea and grass which is expressed in Bqkg(-1) dry weight) of (137)Cs and (90)Sr are 0.1+/-0.03 and 7.7+/-4.1 in pine needle, 0.27+/-0.05 and 3.0+/-1.1 in tea, 0.65+/-0.19 and 2.1+/-0.3 in grass, 0.033+/-0.021 and 0.084+/-0.045 in wheat, 0.019+/-0.01 and 0.23+/-0.06 in China cabbage, and 0.009+/-0.007 and 0.024+/-0.084 in rice, respectively. The pine needle and tea can be regarded as indicator species for (90)Sr and (137)Cs. The soil-to-plant transfer factor (TF) values of (90)Sr and (137)Cs are, respectively, 0.022 and 0.031 for rice, 0.066 and 3.83 for China cabbage, 0.0088 and 0.089 for wheat, and 0.037 and 0.56 for grass.