Plutonium in the Ozyorsk population

Results of the long-term autopsy studies on plutonium body burden in the population of Ozyorsk situated in the vicinity of the radiochemical plant of the Mayak Production Association (Russia) have been presented. The data were obtained from radiochemical analysis of the soft tissue and bone samples collected at the autopsy of 239 non-occupational individuals for the period 1975-2003. The dynamics of plutonium accumulation in the Ozyorsk population is associated with the environmental contamination due to radioactive releases from the Mayak Production Association. Plutonium body burden and its distribution between the respiratory tract and extrapulmonary organs depend on the residence time of individuals in the city. Since the early 1950s, plutonium body burden in the Ozyorsk population was linearly increasing at the almost constant rate of accumulation and amounted to 5.8 Bq at 35 y after the beginning of residence in the city that was several tens of times higher than background levels of fallout plutonium. Distribution of plutonium in the body was also studied in Ozyorsk population. Plutonium deposition fraction in the respiratory tract did not exceed 11% of the body burden in individuals with short residence times (1-9 y) and is halved for increasing residence times more than 10 y. The average skeleton:liver ratio was 65:20 = 3.25.     

Plutonium in Lake Sediments of the Taimyr Peninsula

A radiochemical study is made of five cores of lake sediments collected from the Taimyr Peninsula. For the first time quantitative data are reported on the content and vertical distribution of ^239,240Pu and ²³⁸Pu in lake sediments of this region. The plutonium content was found to range from 0.89 Bq/kg in the surface layers to 0.02 Bq/kg in the lower horizons (5-10 cm) of the sediment cores studied. The observed variations in the Pu vertical distribution are interpreted in terms of bioturbation and specific features of water catchment for the lakes studied. The 239,240Pu and ²³⁸Pu contents and the ²³⁸Pu/^239,240Pu activity ratios obtained in this work (0.02-0.10) correspond to the global level for the North hemisphere, although the region studied is not far from the principal nuclear weapons test site of the former Soviet Union in the Novaya Zemlya Archipelago.     

Stereochemistry of Plutonium in Oxygen-Containing Compounds

The coordination of 122 crystallographically nonequivalent Pu(III, IV, V, VI, VII) atoms in the crystal structures of all the oxygen-containing compounds characterized with the R-factor lower than 0.1 was analyzed with the aid of Voronoi–Dirichlet polyhedra (VDPs). The Pu atoms form PuO _n coordination polyhedra (6 ≤ n ≤ 12) of 14 types. At a fixed oxidation state of the Pu atoms, the plutonium VDP volume in PuO _n complexes is virtually independent of the coordination number n. The rule of 14 neighbors is fulfilled in sublattices consisting of Pu atoms (Pu sublattices). Analysis of the PVD characteristics in Pu sublattices revealed compounds in which the occurrence of bonding Pu–Pu 5f interactions can be assumed. As demonstrated by the example of Pu(III), the VDP parameters can be successfully used for finding the most adequate 4f surrogates for highly radioactive transuranium elements.     

Isolation of Plutonium in the Course of REE/TPE Separation by Displacement Complexing Chromatography

Radiochemistry - Isolation of Pu from a TPE/REE mixture by displacement complexing chromatography on KU-2 cation-exchange resin was studied. To stabilize Pu in the trivalent state, the sorption of...     

Intravital Multiphoton Imaging of the Selective Uptake of Water‐Dispersible Quantum Dots into Sinusoidal Liver Cells

Although many studies reporting the organ‐level biodistribution of nanoparticles (NPs) in animals, very few have addressed the fate of NPs in organs at the cellular level. The liver appears to be the main organ for accumulation of NPs after intravenous injection. In this study, for the first time, the in vivo spatiotemporal disposition of recently developed mercaptosuccinic acid (MSA)‐capped cadmium telluride/cadmium sulfide (CdTe/CdS) quantum dots (QDs) is explored in rat liver using multiphoton microscopy (MPM) coupled with fluorescence lifetime imaging (FLIM), with subcellular resolution (～1 μm). With high fluorescence efficiency and largely improved stability in the biological environment, these QDs show a distinct distribution pattern in the liver compared to organic dyes, rhodamine 123 and fluorescein. After intravenous injection, fluorescent molecules are taken up by hepatocytes and excreted into the bile, while negatively charged QDs are retained in the sinusoids and selectively taken up by sinusoidal cells (Kupffer cells and liver sinusoidal endothelial cells), but not by hepatocytes within 3 h. The results could help design NPs targeting the specific types of liver cells and choose the fluorescent markers for appropriate cellular imaging.     

Radiochemical Determination of Plutonium in Natural Water

A procedure was developed for radiochemical determination of plutonium in natural waters of various salinity; it includes concentration of plutonium on iron hydroxide with addition of ²⁴²Pu tracer and radiochemical analysis of the resulting concentrate with -spectrometric measurement of plutonium isotopes.     

Uptake of silica-coated nanoparticles by HeLa cells

Nanoparticles have seen wide applications in cellular research and development. One major issue that is unclear is the uptake of nanoparticles by cells. In this study, we have investigated the uptake of silica-coated nanoparticles by HeLa cells, employing rhoadime 6G isothiocyanate (RITC)-doped nanoparticles as a synchronous fluorescent signal indicator. These nanoparticles were synthesized with reverse microemulsion. A few factors, such as nanoparticle concentration, incubation time and temperature, and serum and inhibitors in culture medium were assessed on the nanoparticle's cellular uptake. The experimental results demonstrated that uptake was maximum after a 6 h incubation and was higher at 37 degrees C than that at 4 degrees C. Nanoparticle uptake depended on the nanoparticle concentration and was inhibited by hyperosmolarity, K+ depletion. In addition, serum in culture medium decreased the cellular uptake of nanoparticles. The results indicated that the uptake of silica-coated nanoparticles by HeLa cells was a concentration-, time-, and energy-dependent endocytic process. Silica-coated nanoparticles could be transported into HeLa cells in part through adsorptive endocytosis and in part through fluid-phase endocytosis.     

Effect of Intense Self-Irradiation on the Phase Composition of Metallic Plutonium

The crystal structure of film samples of "high-level" (based on ²³⁸Pu) and low-level (based on ²³⁹Pu) metallic plutonium during their prolonged (up to 343 days) storage (self-irradiation) at room temperature was studied by X-ray diffraction. In the samples of high-level plutonium, the -Pu and -Pu lattices coexist. In the period of 40-60 days, the other known crystal modifications of plutonium (-Pu, -Pu, -Pu, and -Pu) are also present. Low-level plutonium had only the -Pu lattice. A possible origin of this phenomenon is discussed.     

Effect of Bacteria on Plutonium Behavior in Seawater

Heterotrophic bacteria are demonstrated to assimilate effectively plutonium in seawater, from time to time changing its content and speciation.