Effect of the application of polluted wheat (Triticum aestivum L. Thell.) straw during plowing on the transfer of radiocesium from the soil to komatsuna (Brassica rapa L. var. perviridis)

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.     

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.     

Contamination of agricultural products and soils with radiocesium derived from the accident at TEPCO Fukushima Daiichi Nuclear Power Station: monitoring,case studies and countermeasures

Five years have passed since the accident at Tokyo Electric Power Company Fukushima Daiichi Nuclear Power Station that was triggered by the Great East Japan Earthquake on 11 March 2011. Severe damage to agriculture and the environment is still of great concern in Japanese society. We review the contamination status of agricultural products and soils, decontamination efforts and countermeasures to reduce radiocesium concentration in soil and crops, as well as the responses of Japanese ministries. Since rice is an important staple food for Japanese, the impact of radiocesium on rice (Oryza sativa L.) and paddy fields has been extensively investigated since the accident, and, therefore, issues concerning rice receive considerable attention in this review.     

Changes in radiocesium concentration in a blueberry (Vaccinium virgatum Aiton) orchard resulting from radioactive fallout

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.     

Differences in the distribution of radiocesium in deciduous and evergreen fruit trees: A case study

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.     

Vertical distribution and bioavailability of 137Cs in organic and mineral soils

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.     

Effect of the Fukushima Daiichi nuclear power plant accident on radiocesium distribution in tea fields in Saitama Prefecture: Intercultivar differences

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.     

Genotype x environment interaction in the uptake of Cs and Sr from soils by plants

The soil‐plant transfer factors for Cs and Sr were analyzed in relationship to soil properties, crops, and varieties of crops. Two crops and two varieties of each crop: lettuce (Lactuca sativa L.), cv. Salad Bowl Green and cv. Lobjoits Green Cos, and radish (Raphanus sativus L.), cv. French Breakfast 3 and cv. Scarlet Globe, were grown on five different soils amended with Cs and Sr to give concentrations of 1 mg kg^–1 and 50 mg kg^–1 of each element. Soil‐plant transfer coefficients ranged between 0.12–19.10 (Cs) and 1.48–146.10 (Sr) for lettuce and 0.09–13.24 (Cs) and 2.99–93.00 (Sr) for radish. Uptake of Cs and Sr by plants depended on both plant and soil properties. There were significant (P ≤ 0.05) differences between soil‐plant transfer factors for each plant type at the two soil concentrations. At each soil concentration about 60 % of the variance in the uptake of the Cs and Sr was due to soil properties. For a given concentration of Cs or Sr in soil, the most important factor effecting soil‐plant transfer of these elements was the soil properties rather than the crops or varieties of crops. Therefore, for the varieties considered here, soil‐plant transfer of Cs and Sr would be best regulated through the management of soil properties. At each concentration of Cs and Sr, the main soil properties effecting the uptake of Cs and Sr by lettuce and radish were the concentrations of K and Ca, pH and CEC. Together with the concentrations of contaminants in soils, they explained about 80 % of total data variance, and were the best predictors for soil‐plant transfer. The different varieties of lettuce and radish gave different responses in soil‐plant transfer of Cs and Sr in different soil conditions, i.e. genotype x environment interaction caused about 30 % of the variability in the uptake of Cs and Sr by plants. This means that a plant variety with a low soil‐plant transfer of Cs and Sr in one soil could have an increased soil‐plant transfer factor in other soils. The broad implications of this work are that in contaminated agricultural lands still used for plant growing, contaminant‐excluding crop varieties may not be a reliable method for decreasing contaminant transfer to foodstuffs. Modification of soil properties would be a more reliable technique. This is particularly relevant to agricultural soils in the former USSR still affected by fallout from the Chernobyl disaster.     

非饱和土壤热质运移的数学模型

A system atic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non-equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynam ic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.     

Radiocesium transfer from Andosols to brown rice in the northern and northwest areas of Tochigi Prefecture,in the first 3 years following the 2011 Fukushima Daiichi nuclear power plant accident

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.     

Occurrence of vesicular-arbuscular mycorrhizae with Amaranthaceae in soils of the Indian semi-arid region

Summary Some members of the family Amaranthaceae, which has mostly been reported as non-mycorrhizal, were examined for a symbiotic association with mycorrhizae in the semiarid and arid zones. Ten species belonging to five genera, Achyranthes, Aerva, Alternanthera, Amaranthus, and Celosia were examined, using 1.0-cm long root standards. Intercellular hyphae, vesicles and arbuscules were observed in the root cortex. The number of different types of spores in the rhizosphere soil of different plants ranged from one to three. The spores isolated represented nine species belonging to four genera, Glomus, Gigaspora, Sclerocystis, and Scutellospora. No correlation could be established between spore counts and either soil pH or soil moisture.     

Varietal difference in vitamin C content in the fruit of kiwifruit and other actinidia species

Vitamin C content in the fruit of various cultivars of kiwifruit and other Actinidia species was estimated by determination of L-ascorbic acid and L-dehydroascorbic acid using ion-pair reversed-phase high-performance liquid chromatography. Fruit of A. deliciosa cv. Hayward, the most common commercially available cultivar, contained 65.5 mg/100 g fresh weight (FW) vitamin C. Vitamin C content in A. deliciosa fruit varied from 29 mg/100 g FW to 80 mg/100 g FW. In most cultivars of A. chinensis, vitamin C content in fruit was higher than that of Hayward. In particular, vitamin C content in cv. Sanuki Gold fruit reached more than 3-fold that of Hayward on a weight for weight basis. In A. argutafruit, there was wide variation in vitamin C content, with concentrations ranging from 37 to 185 mg/100 g FW. In cv. Gassan, Issai, and Mitsuko, vitamin C content of the fruit was much higher than that of Hayward. In A. arguta fruit, the ratio of L-ascorbic acid to total ascorbic acid tended to be higher than that of other species.     

Factors affecting transfer of degradative plasmids between bacteria in soils

Horizontal gene transfer is useful for enhancing bioremediation through gene bioaugmentation. However, factors affecting transfer of degradative plasmids have not been systematically addressed. To this end, plasmid transfer experiments were performed using a TOL-like plasmid carrying the gene encoding for catechol 2,3-dioxygenase (C23O) between two soil bacteria under different conditions. Transfer frequency increased with air temperature in the range of 10–35 °C and reached 6 × 10⁻⁴ transconjugants per donor cell at 35 °C. The transfer frequency detected at soil depth 5–10 cm was significantly higher (p < 0.05) compared with other depths. Addition of 5–75% LB in the microbial inoculum promoted plasmid transfer frequencies. Addition of phenol to the experimental system resulted in significantly higher transfer frequency (p < 0.05) compared with no addition. Transfer frequency heat-moisture in loam was significantly higher (p < 0.05) than in other soils. The highest transfer frequency was found in the experiment containing tomato seedlings, with up to about 1.3 × 10⁻³ transconjugants per donor cell. Corn and wheat seedlings also led to significantly higher transfer frequencies (p < 0.05) compared with no plants. Furthermore, C23O activities of transconjugants formed under different conditions were measured, as a surrogate measure of the activity of transconjugant. Transfer temperature, soil and plant types had a minor influence on activities of transconjugants. Topsoil (0–5 cm) transconjugants expressed C23O more efficiently under normal incubation condition, but less efficiently when soils incubated with excessive LB medium concentrations, and in the absence of phenol in soil. These results suggested that transfer temperature, soil depth, dilutions of LB broth, phenol content, and soil and plant types had important effects on transfer of the TOL-like plasmid in soil, and some factors also affected activities of transconjugants.     

Aspects of phosphorus transfer from soils in Europe

Imbalanced nutrient management has caused soil phosphorus (P) to become an environmental rather an agronomic problem in more economically developed countries. This subject has been the topic of numerous journal special issues, conferences, and reviews but we consider yet another review of this subject is necessary with the main target of providing a point of view on nonpoint transfer from soils and control strategies for an improved environmental management of P. This review considers the causes of the excessive P transfer from soil to surface water in Europe and the scientific knowledge necessary to develop control strategies.     

城郊菜地土壤重金属浓度及芦蒿吸收特征

A total of 222 surface soil samples and 40 plant samples were collected to investigate the spatial distribution and possible sources of soil heavy metals and to know the uptake and translocation of heavy metals from roots to different plant parts in a representative vegetable production area in the Baguazhou Island, a suburb of Nanjing City, East China. The arithmetic mean values of total Cd, Cr, Cu, Ni, Pb, and Zn concentrations in the soils were 0.314, 133, 41.0, 58.0, 31.8, and 114 mg kg^-1, respectively. All of these values were above the topsoil background values in the Nanjing area. Multivariate and geostatistical analyses showed that soil Cd contamination was derived mainly from agricultural practices. In contrast, Cu and Zn were derived mainly from soil parent materials and Pb from atmospheric deposition from highway gasoline stations. Artemisia selengensis, a locally important specialty vegetable, accumulated heavy metals primarily in the edible leaves. The general distribution of heavy metal concentrations in this plant species showed that the highest occurred in the leaves, intermediate in the stems and lowest in the roots. Cd had the highest concentration factor (root-to-soil ratio) and may pose increased health risks in the future to the local population through the consumption of contaminated vegetables.     

降雨非饱和入渗对土壤热量运移变化的影响

高温季节土壤表层温度非常高,土壤内部含水率较低,突发性降雨对于土壤温度动态变化和水热交换运移影响极大。为了揭示降雨非饱和入渗对土壤热量运移变化的影响,该研究建立了反映降雨入渗过程的土壤热量运移数学模型,编制了有限元数值计算程序,针对南京雨花台区典型土壤,开展了降雨非饱和入渗对土壤热量运移影响的数值计算与分析研究。结果表明:不考虑降雨入渗情况下,土壤温度变化与热量运移主要是表层土壤与环境之间的热交换作用引起,热量运移影响深度约0.2 m;降雨强度45 mm/h作用下,随降雨历时增加,雨水全部自由入渗到土壤内部,土壤内部基质吸力呈线性递减趋势,湿润锋面逐渐下移,土壤体积含水率快速增加;湿润锋过后的土壤体积含水率逐渐接近于饱和体积含水率,土壤入渗能力逐渐下降,直至趋于饱和入渗率;在降雨非饱和入渗影响下,入渗到土壤孔隙中的低温雨水与土壤颗粒发生热量交换,进而改变了原有土壤温度场分布,并随着降雨入渗深度的持续增加,降雨入渗过程对土壤热量运移的影响呈现逐渐减弱趋势。经过现场实测数据与模拟计算结果验证,随着降雨历时增加,土壤体积含水率实测值和数值计算值相对误差保持在±3.99%以内,均方根误差RMS...     

施用污泥后石灰性土壤中铜、锌、镉的植物有效性

The toxicity of trace elements (TEs), such as copper (Cu), zinc (Zn), and cadmium (Cd), often restrict land application of sewage sludge (SS) and there was little information about soil-plant transfer of TEs in SS from field experiments in China. In this study pot and field experiments were carried out for 2 years to investigate the phytoavailability of TEs in calcareous soils amended with SS. The results of the pot experiment showed that the phytoavailability of Zn and Cu in the SS was equal to 53.4%-80.9% and 54.8%-91.1% of corresponding water-soluble metal salts, respectively. The results from the field experiment showed that the contents of total Zn, Cu, and Cd in the soils increased linearly with SS application rates. With increasing SS application rates, the contents of Zn and Cu in the wheat grains initially increased and then reached a plateau, while there was no significant change of Cd content in the maize grains. The bioconcentration factors of the metals in the grains of wheat and maize were found to be in the order of Zn > Cu > Cd, but for the straw the order was Cd > Cu > Zn. It was also found that wheat grains could accumulate more metals compared with maize grains. The results will be helpful in developing the critical loads of sewage sludge applied to calcareous soils.     

The solubility and plant uptake of chromium from heated soils

Abstract

The effects of heating on the solubility and plant uptake of Cr from three soils variously influenced by ultramafic parent materials were evaluated. Chromium extracted by 2 M HNO₃ and by M KCl increased with degree of serpentine influence and with temperature of ignition in air. In contrast, solubility of the element was only slightly influenced by ignition in a N₂ atmosphere. Heating enhanced the solubility of soil Cr by at least two oxidative reactions: (1) the destruction of a relatively heat‐stable, probably organic, complex with the release of Cr(III), and (2) the oxidation of free Cr(III) to Cr(VI).

Corn (Zea mays L.) grew poorly in the ignited soils, but normally in ignited and leached soils. Growth depression from ignition was related to shoot Cr levels (r² = 0.494) and is attributed to the readily absorbed and translocated chromate formed at elevated temperatures. Under more usual soil conditions, as in the untreated and ignited then leached soils, the less readily soluble forms of the element are the principal contributors to available Cr.     

基于小白菜Cd吸收推算土壤Cd安全阈值

Cadmium(Cd), a common toxic heavy metal in soil, has relatively high bioavailability, which seriously threatens agricultural products. In this study, 8 different soils with contrasting soil properties were collected from different regions in China to investigate the Cd transfer coefficient from soil to Chinese cabbage(Brassica chinensis L.) and the threshold levels of Cd in soils for production of Chinese cabbage according to the food safety standard for Cd. Exogenous Cd(0–4 mg kg~(-1)) was added to the soils and equilibrated for 2 weeks before Chinese cabbage was grown under greenhouse conditions. The influence of soil properties on the relationship between soil and cabbage Cd concentrations was investigated. The results showed that Cd concentration in the edible part of Chinese cabbage increased linearly with soil Cd concentration in 5 soils, but showed a curvilinear pattern with a plateau at the highest dose of exogenous Cd in the other 3 soils. The Cd transfer coefficient from soil to plant varied significantly among the different soils and decreased with increasing soil p H from 4.7 to 7.5. However, further increase in soil pH to 8.0 resulted in a significant decrease in the Cd transfer coefficient. According to the measured Cd transfer coefficient and by reference to the National Food Safety Standards of China, the safety threshold of Cd concentration in soil was predicted to be between 0.12 and 1.7 mg kg~(-1) for the tested soils. The predicted threshold values were higher than the current soil quality standard for Cd in 5 soils, but lower than the standard in the other 3 soils. Regression analysis showed a significant positive relationship between the predicted soil Cd safety threshold value and soil p H in combination with soil organic matter or clay content.     

季节性冻融土壤水盐动态预测BP网络模型研究

冻融土壤水盐运移模拟预测一直是冻土物理学和土壤水科学研究的热点和难点,而冻土水盐运动的特殊规律与分配特性是影响河套灌区土壤盐渍化发生、发展和演变的重要因素。该文基于内蒙古河套灌区5个冻融期（1994～1999）的水分、盐分和温度的田间实测资料,利用人工神经网络对冻融土壤水盐耦合运移进行了联合预测。结果表明：初冻期地下水埋深、初冻期含水率、初冻期含盐量、秋浇水量、11月到翌年4月的月平均地温等10个影响因子可以有效表征冻融土壤水分和盐分之间的强烈耦合关系,神经网络预测模型具有较好的精度。该研究为冻融条件下土壤水盐动态预报和灌区灌溉管理的研究开辟了新的途径。