Pu Uptake Research Articles

Accelerated Analyte Uptake on Single Beads in Microliter-Scale Batch Separations Using Acoustic Streaming: Plutonium Uptake by Anion Exchange for Analysis by Mass Spectrometry

The use of acoustic streaming as a noncontact mixing platform to accelerate mass-transport-limited diffusion processes in small-volume heterogeneous reactions has been investigated. Single-bead anion exchange of plutonium at nanomolar and subpicomolar concentrations in 20 microL liquid volumes was used to demonstrate the effect of acoustic mixing. Pu uptake rates on individual approximately 760 microm diameter AG 1 x 4 anion-exchange resin beads were determined using acoustic mixing and compared with Pu uptake rates achieved by static diffusion alone. An 82 MHz surface acoustic wave (SAW) device was placed in contact with the underside of a 384-well microplate containing flat-bottomed semiconical wells. Acoustic energy was coupled into the solution in the well, inducing acoustic streaming. Pu uptake rates were determined by the plutonium remaining in solution after specific elapsed time intervals using liquid scintillation counting (LSC) for nanomolar concentrations and thermal ionization mass spectrometry (TIMS) analysis for the subpicomolar concentration experiments. It was found that this small batch uptake reaction could be accelerated by a factor of about 5-fold or more, depending on the acoustic power applied.

A comparison between intact fruit and fruit explants to study the effect of polyamines and aminoethoxyvinylglycine (AVG) on fruit ripening in peach and nectarine ( Prunus persica L. Batch)

In order to establish whether in vitro model systems are suitable to study the reciprocal relationships between ethylene and polyamines (PAs) in peach fruit, whole detached fruit and fruit explants from “Redhaven” peaches and “Stark Red Gold” nectarines at two different ripening stages were subjected to in vitro treatments with 10 mM putrescine (Pu), 1 mM spermidine (Sd) or 0.32 mM aminoethoxyvinylglycine (AVG) in the presence or in the absence of labelled Pu or methionine. Labelled Pu uptake studies showed that, in the short-term, much more label was recovered in intact nectarines than in peaches. In fact, in the former, ethylene production was strongly impaired by Pu and Sd at both stages, while it was substantially unaffected in the latter. In treated fruit, flesh firmness, soluble solids content and fresh weight were only sporadically affected. Under the same experimental conditions, AVG almost totally inhibited ethylene production although fruit quality was practically unaltered. In explants obtained from fruit at the firmer ripening stage, Pu and Sd did not alter and even enhanced methionine incorporation into ethylene, while in those from softer fruit only Sd was able to counteract ethylene biosynthesis. Also in this case, AVG dramatically reduced ethylene biosynthesis. Short-term treatments of fruit explants showed that only Sd and AVG counteracted ripening. Comparing results from intact fruit and fruit explants indicates that Pu and Sd exert a differential effect on ethylene and fruit quality, depending upon ripening stage and cultivar.

239Pu sorption by suspended matter from Hueznar reservoir (southern Spain): Experimental and modelling study

Kinetic transfer coefficients are important parameters to understand and reliably model the behaviour of non-conservative radionuclides in aquatic environments. This report pertains to a series of radiotracer experiments on 239 Pu uptake in natural unfiltered waters from the Hueznar reservoir (southern Spain). The experimental procedure ensures the preservation of environmental conditions and the dissolved Pu activity was measured by liquid scintillation technique. The data suggest that the main pathways for Pu uptake consist of two parallel and reversible reactions. We studied the effects of suspended matter concentrations and the specific surface area on the kinetic transfer coefficients.

Comparative uptake of plutonium from soils by Brassica juncea and Helianthus annuus

Plutonium uptake by Brassica juncea (Indian mustard) and Helianthus annuus (sunflower) from soils with varying chemical composition and contaminated with Pu complexes (Pu–nitrate [239Pu(NO3)4], Pu–citrate [239Pu(C6H5O7)+], and Pu–diethylenetriaminepentaacetic acid (Pu–DTPA [239Pu–C14H23O10N3]) was investigated. Sequential extraction of soils incubated with applied Pu was used to determine the distribution of Pu in the various soil fractions. The initial Pu activity levels in soils were 44.40–231.25 Bq g−1 as Pu–nitrate, Pu–citrate, or Pu–DTPA. A difference in Pu uptake between treatments of Pu–nitrate and Pu–citrate without chelating agent was observed only with Indian mustard in acidic Crowley soil. The uptake of Pu by plants was increased with increasing DTPA rates, however, the Pu concentration of plants was not proportionally increased with increasing application rate of Pu to soil. Plutonium uptake from Pu–DTPA was significantly higher from the acid Crowley soil than from the calcareous Weswood soil. The uptake of Pu from the soils was higher in Indian mustard than in sunflower. Sequential extraction of Pu showed that the ion-exchangeable Pu fraction in soils was dramatically increased with DTPA treatment and decreased with time of incubation. Extractability of Pu in all fractions was not different when Pu–nitrate and Pu–citrate were applied to the same soil. More Pu was associated with the residual Pu fraction without DTPA application. Consistent trends with time of incubation for other fractions were not apparent. The ion-exchangeable fraction, assumed as plant-available Pu, was significantly higher in acid soil compared with calcareous soil with or without DTPA treatment. When the calcareous soil was treated with DTPA, the ion-exchangeable Pu was comparatively less influenced. This fraction in the soil was more affected with time of incubation. The lowest extractable Pu was from a pH 6.55 Crockett soil that contained the highest clay compared to the other two soils. Extractable soil Pu was largely affected by soil pH and the amounts of clay, salt, metal oxide, and carbonate.

Solubility and sorption of redox-sensitive radionuclides (Np, Pu) in J-13 water from the Yucca Mountain site: comparison between experiment and theory

This study presents the characterization of Pu-bearing precipitates and the results from uptake studies of Np and Pu on inorganic colloidal particulates in J-13 water from the Yucca Mountain site. Plutonium solubilities determined experimentally at pH values of 6, 7, and 8.5 are about two orders of magnitude higher than those calculated using the existing thermodynamic database indicating the influence of colloidal Pu(IV) species. Solid phase characterization using X-ray diffraction revealed primarily Pu(IV) in all precipitates formed at pH 6, 7, and 8.5. The solubility controlling Pu-bearing solids precipitated at ambient temperature consisted of amorphous Pu(OH) 4(s) with several Pu–O distances between 2.3 and 2.7 Å that are characteristic for Pu(IV) colloids. High temperature (90 °C) increased solid phase crystallinity and produced Pu(IV) solids that contained Pu oxidation state impurities. X-ray absorption spectroscopic studies revealed diminished Pu–O and Pu–Pu distances that were slightly different from those in crystalline PuO 2(s). A Pu–O bond of 1.86 Å was identified that is consistent with the plutonyl(V) distance of 1.81 Å in PuO 2 +(aq). Hematite, montmorillonite, and silica colloids were used for uptake experiments with 239Pu(V) and 237Np(V). The capacity of hematite to sorb Pu significantly exceeded that of montmorillonite and silica. A low desorption rate was indicative of highly stable Pu-hematite colloids, which may facilitate Pu transport to the accessible environment. Neptunium uptake on all mineral phases was far less than Pu(V) uptake suggesting that a potential Pu(V)–Pu(IV) reductive sorption process was involved. The temperature effect on Pu solubility and pseudocolloid formation is also discussed.

Uptake and translocation of plutonium in two plant species using hydroponics

This study presents determinations of the uptake and translocation of Pu in Indian mustard ( Brassica juncea) and sunflower ( Helianthus annuus) from Pu contaminated solution media. The initial activity levels of Pu were 18.50 and 37.00 Bq ml −1 for Pu-nitrate [ 239Pu(NO 3) 4] and for Pu-citrate [ 239Pu(C 6H 5O 7) +] in nutrient solution. Plutonium-diethylenetriaminepentaacetic acid (DTPA; [ 239Pu-C 14H 23O 10N 3] solution was prepared by adding 0, 5, 10, and 50 μg of DTPA ml −1 with 239Pu(NO 3) 4 in nutrient solution. Concentration ratios (CR, Pu concentration in dry plant material/Pu concentration in nutrient solution) and transport indices (TI, Pu content in the shoot/Pu content in the whole plant) were calculated to evaluate Pu uptake and translocation. All experiments were conducted in hydroponic solution in an environmental growth chamber. Plutonium concentration in the plant tissue was increased with increased Pu contamination. Plant tissue Pu concentration for Pu-nitrate and Pu-citrate application was not correlated and may be dependent on plant species. For plants receiving Pu-DTPA, the Pu concentration was increased in the shoots but decreased in the roots resulting in a negative correlation between the Pu concentrations in the plant shoots and roots. The Pu concentration in shoots of Indian mustard was increased for application rates up to 10 μg DTPA ml −1 and up to 5 μg DTPA ml −1 for sunflower. Similar trends were observed for the CR of plants compared to the Pu concentration in the shoots and roots, whereas the TI was increased with increasing DTPA concentration. Plutonium in shoots of Indian mustard was up to 10 times higher than that in shoots of sunflower. The Pu concentration in the apparent free space (AFS) of plant root tissue of sunflower was more affected by concentration of DTPA than that of Indian mustard.

Experimental and modelling study of Plutonium uptake by suspended matter in aquatic environments from southern Spain

Kinetic transfer coefficients are important parameters to understand and reliably model the behaviour of non-conservative radionuclides in aquatic environments. This report pertains to a series of five radiotracer experiments on Pu uptake in natural aqueous suspensions of unfiltered waters from three aquatic systems in the south of Spain (Gergal reservoir, the Guadalquivir river, and the estuary of the Tinto river). The experimental procedure ensured the simulation of environmental conditions. Pu activity was measured by a liquid scintillation technique. The uptake curves, covering a period up to one week, are discussed with respect to numerical uptake kinetics models. The data suggest that in our experimental setting the main pathways for Pu uptake consist of two parallel and reversible reactions followed by a consecutive non-reversible reaction. Kinetic transfer coefficients were estimated by a fitting procedure and a comparative study was followed.

Siderophore mediated plutonium accumulation by Microbacterium flavescens (JG-9).

Uptake of plutonium and uranium mediated by the siderophore desferrioxamine-B (DFOB) has been studied for the common soil aerobe Microbacterium flavescens(JG-9). M. flavescens does not bind or take up nitrilotriacetic acid (NTA) complexes of U(VI), Fe(III), or Pu(IV) or U(VI)-DFOB but does take up Fe(III)-DFOB and Pu(IV)-DFOB. Pu(IV)-DFOB and Fe(III)-DFOB accumulations are similar: only living and metabolically active bacteria take up these metal-siderophore complexes. The Fe(III)-DFOB and Pu(IV)-DFOB complexes mutually inhibit uptake of the other, indicating that they compete for shared binding sites or uptake proteins. However, Pu uptake is much slower than Fe uptake, and cumulative Pu uptake is less than Fe, 1.0 nmol of Fe vs 0.25 nmol of Pu per mg of dry weight bacteria. The Pu(IV)-DFOB interactions with M. flavescens suggest that Pu-siderophore complexes could generally be recognized by Fe-siderophore uptake systems of many bacteria, fungi, or plants, thereby affecting Pu environmental mobility and distribution. The results also suggest that the siderophore complexes of tetravalent metals can be recognized by Fe-siderophore uptake proteins.

Plutonium in tree rings from France and Japan

Plutonium, along with other radionuclide concentrations, was measured in evergreen tree rings from two different locations. This was used as an information source for the past two centuries. Tree rings are a product of annual layers and thus chronological information is clearly visible. Three trees were harvested in 1988–1990: a French white fir (137 years old) and a spruce tree (177 years old) from the France-Germany border near Nancy, France and a sugi (78 years old) from Nagasaki, Japan. The uniform branchless part of the trunks from the harvested trees were immediately separated into a set of tree ring samples each of which contained 3–20 years of growth. The separated samples were mechanically powdered, dried at 105°C to obtain the dry weight, ashed at 350°C to measure 40K, 134Cs and 137Cs and ashed again at 600°C to determine 239+240Pu. The highest 239+240 Pu concentration of 30.0 mBq/kg of dry wood was obtained from the tree rings from Nagasaki, located at the centre of the local fallout of the Pu A-bomb detonated in 1945. This concentration peak was, however, observed in tree rings of 1965–1967. The concentration was only 2.9 mBq/kg for the tree rings of 1944–1946. The contribution of the local fallout on the surface soils from the A-bomb was 181 mBq/cm 2 at the harvested area of the tree, while the contribution of global fallout by many weapons testing was 5.9 mBq/cm 2 (or 3.3% total fallout in the region). The reason for the over 20 year time lag of 239+240Pu uptake by the tree rings is unknown because many factors influence the routes of Pu into the tree rings. Also the chemical form of Pu in surface soils may have been changed by the surrounding environment. The highest concentration in the tree rings from France was 9.4 mBq/kg which is about 31% of Nagasaki 239 + 240Pu concentration. The harvested area did not have any recorded Pu sources other than global fallout. An interesting result was that that distribution of 134Cs and 137Cs concentrations in the French white fir was different from Nagasaki. Data suggested that these new radionuclide inputs were from the Chernobyl accident. The mobility (or diffusion coefficient) of cesium is 2–8 cm 2/yr in the portion of heart-wood tree rings (1870–1955). Although tree rings can record chronological inputs of various trace elements, some elements cannot be used. These exceptions would be elements that: (1) are mobile within tree rings; (2) have little understood entry routes to the tree rings (via roots, leaves or barks); and (3) have unknown biogeochemical behaviour in the surrounding environment. Further investigation is warranted to use tree rings as a tool to record past environmental history.

Interactions and Transport of Plutonium-Humic Acid Particles in Groundwater Environments

ABSTRACTPu adsorption on pure γ-alumina and heterogeneous mineral phases was investigated as a function of pH and humic acid (HA) concentration. Information on surface speciation was obtained by using various actinides as valence analogues for Pu. Surface redox transformations of Pu(V) appeared to control Pu uptake onto electron exchanging minerals. A one-dimensional transport experiment of high molecular weight HA in water saturated clayey sand column was performed under reducing conditions (Eh <-200 mV). This showed that HA particles larger than 600 nm were retained in the column. The HA breakthrough curve was characterized by extended tailing. Physico-chemical interactions at the mineral surface and particle straining in smaller pore spaces appeared to control HA transport through the soil. The chemical association of Pu with moving HA was investigated by leaching of 238-Pu-doped borosilicate glasses. Enhancement in Pu release rate was observed in HA solutions compared with organic-free groundwater.

Pu and other trace elements in/on plants

Most Pu from nuclear fallout is currently found in surface soils from which it is distributed by migration, resuspension and uptake by the roots of plants. This paper investigates the sites of localization of Pu in plants and examines which parameters determine its uptake. Different species of trees were studied, special attention being directed towards seasonal variations of Pu uptake in different parts of the plants. To differentiate between Pu adsorption and absorption, the plant parts were washed with CHCl 3. Most of the Pu was found in the bark, being adsorbed on the plant surface. Comparison of Pu concentrations in plants over several years shows a constant decrease similar to that observed in air.

Plutonium uptake by marine phytoplankton in culture1

At environmentally realistic atom conscentrations 237Pu tracer was used to examine Pu uptake by unialgal cultures of Thalassiosira pseudonana (live and dead), Thalassiosira sp., and Platymonas sp., as well as by glass particles. Live or dead cells and glass particles accumulated Pu at similar rates, indicating that initial uptake was a passive phenomenon. Uptake was strongly affected by the nature of particle surfaces, but much less by composition of the media. Cells from rapidly growing cultures took up more Pu than did those from late log or senescent cultures. Acid‐washed glass took up more Pu, faster, than did unwashed glass. Cells accumulated more Pu from UV‐treated seawater than from seawater untreated or enriched with f/50‐level EDTA or f/50 vitamins; from complete f/50 medium uptake was even less, as with f/50 trace metals + EDTA. After a short uptake Pu was 25% removable in tracer‐free media, but after 3 days of uptake none was removable in seawater or exometabolite media, and only 15% in f/50‐level EDTA. The data support the hypothesis that Pu in marine environments associates with suspended particles that could act as vertical vectors for this element.

Influence of cadmium and copper on the distribution pattern of plutonium in the rat.

The results of pilot experiments on metal interactions in vivo are presented. In rats pretreated with a single injection of Cd, substantially less Pu accumulated in the liver, while significantly more was found after pretreatment with Cu. In bone, somewhat more Pu was detected after Cd and less after Cu administration. Both metals increased the retention of Pu in the kidneys and spleen. The changes were similar with 238Pu and 239Pu and were still present 1 wk after Pu administration; in the case of Cu they were dependent on the amount administered. All the changes described concern solely the tissue distribution pattern of Pu; the total amount of Pu retained in the organs studied remained the same. The possible relation of Pu uptake to induced synthesis of Cd-thionein and Cu-chelatin is discussed.

Plutonium uptake by Scenedesmus obliquus as a function of isotope and oxidation state

Uptake of 238Pu 4+, 238Pu 6+, 239Pu 4+ and 239Pu 6+ by the green alga Scenedesmus obliquus (Türp) Kütz was studied to determine whether isotope or oxidation state differences affect Pu uptake from aqueous medium by algal cells. At equivalent 238Pu and 239Pu concentrations, even when initial oxidation states differed, accumulations of these isotopes by S. obliquus were not significantly ( p>0.05) different. Plutonium accumulation by S. obliquus was log-linear.