Bolete mushroom Boletus bainiugan from Yunnan as a reflection of the geographical distribution of 210Po, 210Pb and uranium (234U, 235U, 238U) radionuclides, their intake rates and effective exposure doses.

This pioneering study aimed to determine the activity concentrations of 210Po, 210Pb and uranium (234U, 235U, 238U) radionuclides in fruit bodies of wild bolete Boletus bainiugan Dentinger and to estimate its edible safety, which may give scientific evidence for the consumption of this species. The analyses were performed using alpha spectrometer after digestion, exchange resins separation and deposition. Measurement data were analysed and interpolation maps reflecting 210Po, 210Pb and uranium (234U, 235U, 238U) geographical distribution in Yunnan province (China) were presented. In addition, from the perspective of food safety, the possible related effective radiation dose to mushrooms consumers were estimated. The results indicated that 210Po, 210Pb and uranium (234U, 235U, 238U) radionuclides contents in B. bainiugan were significantly different with respect to geographical distribution, and their possible intake in a part of the region was considerably higher. A very interesting observation was done according to the values of 235U/238U activity ratio indicating the occurrence of uranium faction from the global fallout of nuclear weapon tests.

Uranium accumulation and its phytotoxicity symptoms in Pisum sativum L.

Environmental contamination by uranium (U) and other radionuclides is a serious problem worldwide, especially due to, e.g. mining activities. Ultimate accumulation of released U in aquatic systems and soils represent an escalating problem for all living organisms. In order to investigate U uptake and its toxic effects on Pisum sativum L., pea plantlets were hydroponically grown and treated with different concentrations of U. Five days after exposure to 25 and 50 µM U, P. sativum roots accumulated 2327.5 and 5559.16 mg kg-1 of U, respectively, while in shoots concentrations were 11.16 and 12.16 mg kg-1, respectively. Plants exposed to both U concentrations showed reduced biomass of shoots and reduced content of photosynthetic pigments (total chlorophyll and carotenoids) relative to control. As a biomarker of oxidative stress, lipid peroxidation (LPO) levels were determined, while antioxidative response was determined by catalase (CAT) and glutathione reductase (GR) activities as well as cysteine (Cys) and non-protein thiol (NP-SH) concentrations, both in roots and shoots. Both U treatments significantly increased LPO levels in roots and shoots, with the highest level recorded at 50 µM U, 50.38% in shoots and 59.9% in roots relative to control. U treatment reduced GR activity in shoots, while CAT activity was increased only in roots upon treatment with 25 µM U. In pea roots, cysteine content was significantly increased upon treatment with both U concentrations, for 19.8 and 25.5%, respectively, compared to control plants, while NP-SH content was not affected by the applied U. This study showed significant impact of U on biomass production and biochemical markers of phytotoxicity in P. sativum, indicating presence of oxidative stress and cellular redox imbalance in roots and shoots. Obtained tissue-specific response to U treatment showed higher sensitivity of shoots compared to roots. Much higher accumulation of U in pea roots compared to shoots implies potential role of this species in phytoremediation process.

Enhanced phytoremediation of uranium contaminated soil by artificially constructed plant community plots.

In order to develop an artificially constructed plant community plot for the enhanced phytoremediation of uranium contaminated soils, three uranium accumulators including Bamboo-willow (Salix sp.), Paspalum scrobiculatum linn and Macleaya cordata were used to construct four artificial plant community plots, and greenhouse experiments were conducted to investigate the bioaccumulation of uranium by the plants and the organic acid content, enzyme activity, and the change of microbial community structure in their rhizosphere soils. The transfer factor (TF) and the total bioaccumulation amount (TBA) of uranium were used to describe remediation efficiencies in this paper. It was found that their remediation efficiencies were in the order Bamboo-willow (Salix sp.)-Paspalum scrobiculatum linn-Macleaya cordata > Bamboo-willow (Salix sp.)-Macleaya cordata > Paspalum scrobiculatum linn-Macleaya cordata > Bamboo-willow (Salix sp.)-Paspalum scrobiculatum linn. The bioaccumulation amount of uranium by each plant in the Bamboo-willow (Salix sp.)-Paspalum scrobiculatum linn-Macleaya cordata community plot was significantly (P < 0.05) higher than that by its single population, the bioaccumulation amounts of uranium by Bamboo-willow (Salix sp.), Paspalum scrobiculatum linn and Macleaya cordata were 0.29, 0.32 and 2.19 mg/plant, respectively, and they were increased by 31.82%, 77.78% and 146.07%, respectively, and the transfer efficiencies by the plants were increased by 150%, 110% and 52.17%, respectively. The interaction between the plants' roots and the microorganisms in the rhizosphere soil of the Bamboo-willow (Salix sp.)-Paspalum scrobiculatum linn-Macleaya cordata community plot resulted in the high content of organic acids such as oxalic acid in the rhizosphere soil of the plant community plot, which was significantly (P < 0.05) higher than that of its single population. The chelation of the organic acids with uranium led to an increase in the proportion of exchangeable uranium in soil solution. In addition, Burkholderia, which is an iron-producing carrier bacterium and can increase the uptake and accumulation of uranium by plants, and Leptolyngbya, which is a plant growth promoting rhizobacteria and can increase the biomass of plants, emerged in the rhizosphere soil of the plant community plot. These may be the mechanisms by which the phytoremediation of the uranium contaminated soils was enhanced by the plant community plot.

Uranium sequestration in sediment at an iron-rich contaminated site at Oak Ridge, Tennessee via. bioreduction followed by reoxidation.

This study evaluated uranium sequestration performance in iron-rich (30 g/kg) sediment via bioreduction followed by reoxidation. Field tests (1383 days) at Oak Ridge, Tennessee demonstrated that uranium contents in sediments increased after bioreduced sediments were re-exposed to nitrate and oxygen in contaminated groundwater. Bioreduction of contaminated sediments (1200 mg/kg U) with ethanol in microcosm reduced aqueous U from 0.37 to 0.023 mg/L. Aliquots of the bioreduced sediment were reoxidized with O2, H2O2, and NaNO3, respectively, over 285 days, resulting in aqueous U of 0.024, 1.58 and 14.4 mg/L at pH 6.30, 6.63 and 7.62, respectively. The source- and the three reoxidized sediments showed different desorption and adsorption behaviors of U, but all fit a Freundlich model. The adsorption capacities increased sharply at pH 4.5 to 5.5, plateaued at pH 5.5 to 7.0, then decreased sharply as pH increased from 7.0 to 8.0. The O2-reoxidized sediment retained a lower desorption efficiency at pH over 6.0. The NO3--reoxidized sediment exhibited higher adsorption capacity at pH 5.5 to 6.0. The pH-dependent adsorption onto Fe(III) oxides and formation of U coated particles and precipitates resulted in U sequestration, and bioreduction followed by reoxidation can enhance the U sequestration in sediment.

Potassium supply reduces cesium uptake in Konara oak not by an alteration of uptake mechanism, but by the uptake competition between the ions.

Radiocesium contamination of forests has been a severe problem after the Fukushima Daiichi Nuclear Power Plant accident in 2011. Bed logs of Konara oak (Quercus serrata Murray), used for mushroom cultivation, were an economically important product from the forests prior to their contamination. One of the potential countermeasures to reduce radiocesium content in trees is potassium fertilization, but the evidence for the effect of K+ in reducing Cs+ uptake has not been obtained yet in the woody plant. Therefore, we investigated the ability of rhizospheric K+ to suppress uptake and translocation of Cs+ in Konara oak seedlings through hydroponic experiments in order to clarify the effect of K+. Elemental analysis showed that the seedlings cultivated for 4 weeks under low-K (K+ = 50 µM) contained higher amount of Cs comparing to the seedlings cultivated under high-K (K+ = 3 mM). Then, the uptake rate of Cs+ and K+ in the seedlings from the solution having 50 µM K+ and 0.1 µM Cs+ was calculated using radioactive 137Cs+ and 42K+ to evaluate the effect of growth condition on the ion uptake mechanism. The interference between Cs+ and K+ at the site of root uptake was also evaluated based on the Cs+ and K+ uptake rates at K+ concentrations of 50 µM, 200 µM, and 3 mM in the seedlings grown under the medium-K (K+ = 200 µM) condition. As a result, the Cs+ uptake rate at 50 µM K+ was not influenced by the growth condition, whereas Cs+ uptake decreased when the uptake solution itself was supplemented with 3 mM K+. In addition, the Cs/K ratio in the seedlings was found to rise to exceed the Cs/K ratio in the culture solution as the rhizospheric K+ concentration increased, which was in contrast with previous findings in herbaceous plants. Our experiments demonstrated the first direct evidence for woody plants that a high K+ concentration can suppress Cs accumulation in Konara oak and that it was derived from competition for uptake between K+ and Cs+ in the rhizosphere, not from the growth K+ condition.

Microbial communities in a former pilot-scale uranium mine in Eastern Finland - Association with radium immobilization.

The bacterial, fungal and archaeal communities were characterized in 17 top soil organic and mineral layer samples and in top sediment samples of the Paukkajanvaara area, a former pilot-scale uranium mine, located in Eno, Eastern Finland, using amplicon sequencing and qPCR. Soil and sediment samples were in addition analyzed for radium (226Ra), sulfate (SO42-), nitrate (NO3-) and phosphate (PO43-) concentrations. New bacterial strains, representing Pseudomonas spp., were isolated from the mine and reference area and used in laboratory experiments on uptake and leaching of radium (Ra). The effect of these strains on the sulfate leaching from the soil samples was also tested in vitro. Between 6 × 106 and 5 × 108 copies g-1 DW (dry weight) of bacterial 16S rRNA genes, 5 × 105-1 × 108 copies g-1 DW archaeal 16S rRNA genes and 1 × 105-1 × 108 copies g-1 DW fungal 5.8S rRNA genes were detected in the samples. A total of 814, 54 and 167 bacterial, archaeal and fungal genera, respectively, were identified. Proteobacteria, Euryarchaeota and Mortiriella were the dominant bacterial, archaeal and fungal phyla, respectively. All tested Pseudomonas spp. strains isolates from Paukkajanvaara removed Ra from the solution, but the amount of removed Ra depended on incubation conditions (temperature, time and nutrient broth). The highest removal of Ra (5320 L/kg DW) was observed by the Pseudomonas sp. strain T5-6-I at 37 °C. All Pseudomonas spp. strains decreased the release of Ra from soil with an average of 23% while simultaneously increasing the concentration of SO42- in the solution by 11%. As Pseudomonas spp. were frequent in both the sequence data and the cultures, these bacteria may play an important role in the immobilization of Ra in the Paukkajanvaara mine area.

Soil-to-cassava plant transfer factor of natural radionuclides on a mining impacted soil in a tropical ecosystem of Nigeria.

The transfer factors (TFs) of naturally occurring radionuclides, 238U and 232Th from soil to different cassava plant compartments were calculated. Cassava is widely cultivated in Nigeria and contributes significantly to the food supply of the nation. There is sparsity of data on the TFs in Nigeria, and no TF data from any African country were included in the International Atomic Energy Agency's compilation of TFs for the tropical ecosystem. Samples of tin tailings and soil samples from virgin land were used to formulate three soil groups; group-A (soil from virgin land only), group-B (tailings only) and group-C (equal dry mass combination of tailings and soil from virgin land). Pot experiments were set up to determine the TFs of 238U and 232Th. The activity concentrations of 238U and 232Th in the dried samples of the soil and plant compartments were determined using a sodium iodide detector. The TF of 238U ranged from below detection limit (BDL) to 0.01 in the tuber samples, BDL to 0.23 in the stem samples and BDL to 0.90 in the leaf samples, while the TF of 232Th ranged between 0.006 and 0.49 for tuber samples, 0.03 and 0.65 in stem samples and 0.03 and 1.54 in the leaf samples. There were significant difference in the TF of 238U and 232Th between the soil groups. The leaf compartment generally had most of the highest TF values while the tuber samples had most of the lowest TF values for both radionuclides.

Enhancement of repeated applications of chelates on phytoremediation of uranium contaminated soil by Macleaya cordata.

A greenhouse pot experiment was performed to investigate the enhancement of repeated applications of citric acid (CA), ethylenediamine disuccinic acid (EDDS), and Oxalic acid (OA) on phytoremediation of uranium (U) contaminated soil by Macleaya Cordata. The chelates followed the order CA > EDDS > OA in terms of the enhancement on uranium uptake by M. cordata. The repeated applications of the chelates were found to be more effective than the one time application at the equal dose as the U concentration of soil solution increased significantly from the 8th to 14th day. The repeated applications of 10 mmol kg-1 CA promoted the solubilization of U in the U-contaminated soil by significantly decreasing the pH of soil solution, achieved the maximum U concentration of soil solution (1463.6 µg L-1), bioconcentration factors (BCFs, 11.4), bioaccumulation factors (BAFs, 21.4) and transfer factors (TFs, 1.9), which were 215.2, 5.7, 30.6 and 16.3 times as compared with the control group, respectively. The three applied chelates significantly affected the activities of the antioxidant enzymes in the leaves. Repeated applications of CA further enhanced the activities of the antioxidant enzymes in the leaves of M. cordata as compared with the control, EDDS and OA, mitigated the oxidative stress induced by uranium and chelates, and maximized the enhancement on the uranium uptake, which will be beneficial for the enhancement on the phytoremediation of uranium contaminated soil by U hyperaccumulating plants. These results indicated that the phytoavailability of uranium in soil solution as well as the accumulation of U by M. cordata were both significantly increased after repeated applications of CA, and that the repeated applications of 10 mmol kg-1 CA increased the activities of the antioxidant enzymes and promoted U accumulation by M. cordata. The study provided an environmentally friendly alternative for the enhancement on the phytoremediation of uranium contaminated soil using M. cordata.

The influence of humic substances on uranium biomineralization induced by Bacillus sp. dwc-2.

In this paper, the influence of humic acid (HA) and fulvic acid (FA) on biomineralization behaviour was evaluated. The results showed HA and FA did not obviously inhabit or promote the precipitation of U-phosphate minerals. The data from molecular dynamic simulation indicated that the free energy for the dissociation of uranyl the PO43- -uranyl was 202.49 kJ/mol, which was much larger than that form HA-uranyl (88.3 kJ/mol). These simulated results revealed the less competitiveness of HA and FA with PO43- for uranyl and explained why HA and FA had less impacted on the formation of U-phosphate minerals. However, the influence of HA/FA on the morphology was obvious, the microstructure of the bio-minerals changed from small particles to lamellar stacking structure with the addition of HA or FA. The findings of this study are helpful for us to gain a better understanding natural U-phosphate biomineralization behaviour.

Multiple environmental factors influence 238U, 232Th and 226Ra bioaccumulation in arbuscular mycorrhizal-associated plants.

Ecological consequences of low-dose radioactivity from natural sources or radioactive waste are important to understand but knowledge gaps still remain. In particular, the soil transfer and bioaccumulation of radionuclides into plant roots is poorly studied. Furthermore, better knowledge of arbuscular mycorrhizal (AM) fungi association may help understand the complexities of radionuclide bioaccumulation within the rhizosphere. Plant bioaccumulation of uranium, thorium and radium was demonstrated at two field sites, where plant tissue concentrations reached up to 46.93 µg g-1 238U, 0.67 µg g-1 232Th and 18.27 kBq kg-1 226Ra. High root retention of uranium was consistent in all plant species studied. In contrast, most plants showed greater bioaccumulation of thorium and radium into above-ground tissues. The influence of specific soil parameters on root radionuclide bioaccumulation was examined. Total organic carbon significantly explained the variation in root uranium concentration, while other soil factors including copper concentration, magnesium concentration and pH significantly correlated with root concentrations of uranium, radium and thorium, respectively. All four orders of Glomeromycota were associated with root samples from both sites and all plant species studied showed varying association with AM fungi, ranging from zero to >60% root colonisation by fungal arbuscules. Previous laboratory studies using single plant-fungal species association had found a positive role of AM fungi in root uranium transfer, but no significant correlation between the amount of fungal infection and root uranium content in the field samples was found here. However, there was a significant negative correlation between AM fungal infection and radium accumulation. This study is the first to examine the role of AM fungi in radionuclide soil-plant transfer at a community level within the natural environment. We conclude that biotic factors alongside various abiotic factors influence the soil-plant transfer of radionuclides and future mechanistic studies are needed to explain these interactions in more detail.

Accumulation of U(VI) on the Pantoea sp. TW18 isolated from radionuclide-contaminated soils.

Pantoea sp. TW18 isolated from radionuclide-contaminated soils was used for the bioremediation of radionuclides pollution. Accumulation mechanism of U(VI) on Pantoea sp. TW18 was investigated by batch experiments and characterization techniques. The batch experiments revealed that Pantoea sp. TW18 rapidly reached accumulation equilibrium at approximately 4 h with a high accumulation capacity (79.87 mg g-1 at pH 4.1 and T = 310 K) for U(VI). The accumulation data of U(VI) onto Pantoea sp. TW18 can be satisfactorily fitted by pseudo-second-order model. The accumulation of U(VI) on Pantoea sp. TW18 was affected by pH levels, not independent of ionic strength. Analysis of the FT-IR and XPS spectra demonstrated that accumulated U(VI) ions were primarily bound to nitrogen- and oxygen-containing functional groups (i.e., carboxyl, amide and phosphoryl groups) on the Pantoea sp. TW18 surface. This study showed that Pantoea sp. TW18 can be considered as a promising sorbent for remediation of radionuclides in environmental cleanup.

Ramie (Boehmeria nivea)'s uranium bioconcentration and tolerance attributes.

The authors sampled and analyzed 15 species of dominant wild plants in Huanan uranium tailings pond in China, whose tailings' uranium contents were 3.21-120.52 µg/g. Among the 15 species of wild plants, ramie (Boehmeria nivea) had the strongest uranium bioconcentration and transfer capacities. In order to study the uranium bioconcentration and tolerance attributes of ramie in detail, and provide a reference for the screening remediation plants to phytoremedy on a large scale in uranium tailings pond, a ramie cultivar Xiangzhu No. 7 pot experiment was carried out. We found that both wild ramie and Xiangzhu No. 7 could bioconcentrate uranium, but there were two differences. One was wild ramie's shoots bioconcentrated uranium up to 20 µg/g (which can be regarded as the critical content value of the shoot of uranium hyperaccumulator) even the soil uranium content was as low as 5.874 µg/g while Xiangzhu No. 7's shoots could reach 20 µg/g only when the uranium treatment concentrations were 275 µg/g or more; the other was that all the transfer factors of 3 wild samples were >1, and the transfer factors of 27 out of 28 pot experiment samples were <1. Probably wild ramie was a uranium hyperaccumulator. Xiangzhu No. 7 satisfied the needs of uranium hyperaccumulator on accumulation capability, tolerance capability, bioconcentration factor, but not transfer capability, so Xiangzhu No. 7 was not a uranium hyperaccumulator. We analyzed the possible reasons why there were differences in the uranium bioconcentration and transfer attributes between wild ramie and Xiangzhu No. 7., and proposed the direction for further research. In our opinion, both the plants which bioconcentrate contaminants in the shoots and roots can act as phytoextractors. Although Xiangzhu No. 7's biomass and accumulation of uranium were concentrated on the roots, the roots were small in volume and easy to harvest. And Xiangzhu No. 7's cultivating skills and protection measures had been developed very well. Xiangzhu No. 7's whole bioconcentration factors and the roots' bioconcentration factors, which were 1.200-1.834 and 1.460-2.341, respectively, increased with the increases of uranium contents of pot soil when the soil's uranium contents are 25-175 µg/g, so it can act as a potential phytoextractor when Huanan uranium tailings pond is phytoremediated.

Uptake of Plutonium-238 into Solanum tuberosum L. (potato plants) in presence of complexing agent EDTA.

Bioavailability and plant uptake of radionuclides depend on various factors. Transfer into different plant parts depends on chemical and physical processes, which need to be known for realistic ingestion dose modelling when these plants are used for food. Within the scope of the present work, the plutonium uptake by potato plants (Solanum tuberosum L.) was investigated in hydroponic solution of low concentration [Pu] = 10-9 mol L-1. Particular attention was paid to the speciation of radionuclides in the solution which was modelled by the speciation code PHREEQC. The speciation, the solubility and therefore the plant availability of radionuclides mainly depend on the pH value and the redox potential of the solution. During the contamination period, the redox potential did not change significantly. In contrast, the pH value showed characteristic changes depending on exudates excreted by the plants. Plant roots took up high amounts of plutonium (37%-50% of the added total amount). In addition to the uptake into the roots, the radionuclides can also adsorb to the exterior root surface. The solution-to-plant transfer factor showed values between 0.03 and 0.80 (Bq kg-1/ Bq L-1) for the potato tubers. By addition of the complexing agent EDTA (10-4 mol L-1), the plutonium uptake from solution increased by 58% in tubers and by 155% in shoots/leaves. The results showed that excreted substances by plants affect bioavailability of radionuclides at low concentration, on the one hand. On the other hand, the uptake of plutonium by roots and the accumulation in different plant parts can lead to non-negligible ingestion doses, even at low concentration. We are aware of the limited transferability of data obtained in hydroponic solutions to plants growing in soil. However, the aim of this study is twofold: First we want to investigate the influence of Pu speciation on plant uptake in a rather well defined system which can be modelled using available thermodynamic data. Second, techniques developed here shall be applied to the investigation of plants growing in soil in the future. The present work contributes to the basic understanding how plant induced effects on nutrient solution influence bioavailability of radionuclides and fosters the need for more detailed investigations of the complex uptake and accumulation processes of radionuclides into plants.

Assessment of the bioavailability and depuration of uranium, cesium and thorium in snails (Cantareus aspersus) using kinetics models.

Uranium ore waste has led to soil contamination that may affect both environmental and soil health. To analyze the risk of metal transfer, metal bioavailability must be estimated by measuring biological parameters. Kinetic studies allow taking into account the dynamic mechanisms of bioavailability, as well as the steady state concentration in organisms necessary to take into account for relevant risk assessment. In this way, this work aims to model the snail accumulation and excretion kinetics of uranium (U), cesium (Cs) and thorium (Th). Results indicate an absence of Cs and Th accumulation showing the low bioavailability of these two elements and a strong uranium accumulation in snails related to the levels of soil contamination. During the depuration phase, most of the uranium ingested was excreted by the snails. After removing the source of uranium by soil remediation, continued snails excretion of accumulated uranium would lead to the return of their initial internal concentration, thus the potential trophic transfer of this hazardous element would stop.

Plant uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K from a coal ash and slag disposal site and control soil under field conditions: A preliminary study.

The aim of this study was to investigate the uptake of 238U, 235U, 232Th, 226Ra, 210Pb and 40K by plants that grow on a coal ash and slag disposal site known for its higher content of naturally occurring radionuclides. Plant species that were sampled are common for the Mediterranean flora and can be divided as follows: grasses & herbs, shrubs and trees. To compare the activity concentrations and the resultant concentration ratios of the disposal site with those in natural conditions, we used control data specific for the research area, obtained for plants growing on untreated natural soil. Radionuclide activity concentrations were determined by high resolution gamma-ray spectrometry. Media parameters (pH, electrical conductivity and organic matter content) were also analysed. We confirmed significantly higher activity concentrations of 238U, 235U, 226Ra and 210Pb in ash and slag compared to control soil. However, a significant increase in the radionuclide activity concentration in the disposal site's vegetation was observed only for 226Ra. On the contrary, a significantly smaller activity concentration of 40K in ash and slag had no impact on its activity concentration in plant samples. The calculated plant uptake of 238U, 235U, 226Ra and 210Pb is significantly smaller in comparison with the uptake at the control site, while it is vice versa for 40K. No significant difference was observed between the disposal site and the control site's plant uptake of 232Th. These results can be the foundation for further radioecological assessment of this disposal site but also, globally, they can contribute to a better understanding of nature and long-term management of such disposal sites.

Bacterial endophytes enhance phytostabilization in soils contaminated with uranium and lead.

The combined use of plants and bacteria is a promising approach for the remediation of polluted soil. In the current study, the potential of bacterial endophytes in partnership with Leptochloa fusca (L.) Kunth was evaluated for the remediation of uranium (U)- and lead (Pb)-contaminated soil. L. fusca was vegetated in contaminated soil and inoculated with three different endophytic bacterial strains, Pantoea stewartii ASI11, Enterobacter sp. HU38, and Microbacterium arborescens HU33, individually as well as in combination. The results showed that the L. fusca can grow in the contaminated soil. Bacterial inoculation improved plant growth and phytoremediation capacity: this manifested in the form of a 22-51% increase in root length, 25-62% increase in shoot height, 10-21% increase in chlorophyll content, and 17-59% more plant biomass in U- and Pb-contaminated soils as compared to plants without bacterial inoculation. Although L. fusca plants showed potential to accumulate U and Pb in their root and shoot on their own, bacterial consortia further enhanced metal uptake capacity by 53-88% for U and 58-97% for Pb. Our results indicate that the combination of L. fusca and endophytic bacterial consortia can effectively be used for the phytostabilization of both U- and Pb-contaminated soils.

A Highly Expressed High-Molecular-Weight S-Layer Complex of Pelosinus sp. Strain UFO1 Binds Uranium.

Cell suspensions of Pelosinus sp. strain UFO1 were previously shown, using spectroscopic analysis, to sequester uranium as U(IV) complexed with carboxyl and phosphoryl group ligands on proteins. The goal of our present study was to characterize the proteins involved in uranium binding. Virtually all of the uranium in UFO1 cells was associated with a heterodimeric protein, which was termed the uranium-binding complex (UBC). The UBC was composed of two S-layer domain proteins encoded by UFO1_4202 and UFO1_4203. Samples of UBC purified from the membrane fraction contained 3.3 U atoms/heterodimer, but significant amounts of phosphate were not detected. The UBC had an estimated molecular mass by gel filtration chromatography of 15 MDa, and it was proposed to contain 150 heterodimers (UFO1_4203 and UFO1_4202) and about 500 uranium atoms. The UBC was also the dominant extracellular protein, but when purified from the growth medium, it contained only 0.3 U atoms/heterodimer. The two genes encoding the UBC were among the most highly expressed genes within the UFO1 genome, and their expressions were unchanged by the presence or absence of uranium. Therefore, the UBC appears to be constitutively expressed and is the first line of defense against uranium, including by secretion into the extracellular medium. Although S-layer proteins were previously shown to bind U(VI), here we showed that U(IV) binds to S-layer proteins, we identified the proteins involved, and we quantitated the amount of uranium bound. IMPORTANCE: Widespread uranium contamination from industrial sources poses hazards to human health and to the environment. Herein, we identified a highly abundant uranium-binding complex (UBC) from Pelosinus sp. strain UFO1. The complex makes up the primary protein component of the S-layer of strain UFO1 and binds 3.3 atoms of U(IV) per heterodimer. While other bacteria have been shown to bind U(VI) on their S-layer, we demonstrate here an example of U(IV) bound by an S-layer complex. The UBC provides a potential tool for the microbiological sequestration of uranium for the cleaning of contaminated environments.

Influence of soil structure on the "Fv approach" applied to 238U and 226Ra.

The soil-to-plant transfer factors were determined in a granitic area for the two long-lived uranium series radionuclides 238U and 226Ra. With the aim to identify a physical fraction of soil whose concentration correlates linearly with the plant concentration, the soil compartment was analyzed in various stages. An initial study identified the soil compartments as being either bulk soil or its labile fraction. The bulk soil was subsequently divided into three granulometric fractions consisting of: coarse sand, fine sand, and silt and clay. The soil-to-plant transfer of radionuclides for each of these three texture fractions was analyzed. Lastly, the labile fraction was extracted from each textural part, and the activity concentration of the radionuclides 238U and 226Ra was measured. In order to assess the influence of soil texture on the soil-to-plant transfer process, we sought to identify possible correlations between the activity concentration in the plant compartment and those found in the different fractions within each soil compartment. The results showed that the soil-to-plant transfer process for uranium and radium depends on soil grain size, where the results for uranium showed a linear relationship between the activity concentration of uranium in the plant and the fine soil fraction. In contrast, a linear relation between the activity concentration of radium in the plant and the soil coarse-sand fraction was observed. Additionally, the presence of phosphate and calcium in the soil of all of the compartments studied affected the soil-to-plant transfer of uranium and radium, respectively.

Biogeochemistry of uranium in the soil-plant and water-plant systems in an old uranium mine.

The present study highlights the uranium (U) concentrations in water-soil-plant matrices and the efficiency considering a heterogeneous assemblage of terrestrial and aquatic native plant species to act as the biomonitor and phytoremediator for environmental U-contamination in the Sevilha mine (uraniferous region of Beiras, Central Portugal). A total of 53 plant species belonging to 22 families was collected from 24 study sites along with ambient soil and/or water samples. The concentration of U showed wide range of variations in the ambient medium: 7.5 to 557mgkg(-1) for soil and 0.4 to 113µgL(-1) for water. The maximum potential of U accumulation was recorded in roots of the following terrestrial plants: Juncus squarrosus (450mgkg(-1) DW), Carlina corymbosa (181mgkg(-1) DW) and Juncus bufonius (39.9mgkg(-1) DW), followed by the aquatic macrophytes, namely Callitriche stagnalis (55.6mgkg(-1) DW) Lemna minor (53.0mgkg(-1) DW) and Riccia fluitans (50.6mgkg(-1) DW). Accumulation of U in plant tissues exhibited the following decreasing trend: root>leaves>stem>flowers/fruits and this confirms the unique efficiency of roots in accumulating this radionuclide from host soil/sediment (phytostabilization). Overall, the accumulation pattern in the studied aquatic plants (L. minor, R. fluitans, C. stagnalis and Lythrum portula) dominated over most of the terrestrial counterpart. Among terrestrial plants, the higher mean bioconcentration factor (≈1 in roots/rhizomes of C. corymbosa and J. squarrosus) and translocation factor (31 in Andryala integrifolia) were encountered in the representing families Asteraceae and Juncaceae. Hence, these terrestrial plants can be treated as the promising candidates for the development of the phytostabilization or phytoextraction methodologies based on the accumulation, abundance and biomass production.

Time series changes in radiocaesium distribution in tea plants (Camellia sinensis (L.)) after the Fukushima Dai-ichi Nuclear Power Plant accident.

Radiocaesium ((134)Cs and (137)Cs) release following the accident at the Fukushima Dai-ichi Nuclear Power Plant, belonging to the Tokyo Electric Power Company caused severe contamination of new tea plant (Camellia sinensis (L.)) shoots by radiocaesium in many prefectures in eastern Japan. Because tea plants are perennial crops, there is the fear that the contamination might last for a long time. The objectives of this study were to reveal time series changes in the distribution of radiocaesium in tea plants after radioactive fallout and to evaluate the effect of pruning on reduction of radiocaesium concentrations in new shoots growing next year. The experimental tea field was located in Shizuoka, Japan, approximately 400 km away from the Fukushima Dai-ichi Nuclear Power Plant in a southwest direction. Time series changes in radiocaesium concentrations in unrefined tea, a tea product primarily produced for making Japanese green tea, from May 2011 to June 2013 and distribution of radiocaesium in tea plants from May 2011 to May 2012 were monitored. The radiocaesium concentrations in unrefined tea exponentially decreased; the effective half-lives for (134)Cs and (137)Cs were 0.30 and 0.36 y during the first 2 y after the accident, respectively. With time, the highest concentrations of (137)Cs moved from the upper to the lower parts of plants. Medium pruning 2-3 months after the accident reduced the concentration of (137)Cs in new shoots harvested in the first crop season of the following year by 56% compared with unpruned tea plants; thus, pruning is an effective measure for reducing radiocaesium concentration in tea.