Membrane luminescence determination of technogenic actinides and their speciation in environmental objects

Researchers of the Vernadsky Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences created a luminescence photometer of a new generation for the determination of trace amounts of uranium and transuranium elements (TUE). The limits of detection for actinides vary from 0.3 pg for uranium and neptunium to 2.0 pg for plutonium. For ²³⁷Np, the relative limit of detection is 0.008 Bq/L. The photometer was tested in the radioecological monitoring of a number of polluted zones in Russia. The dynamics of actinide migration in all of the studied zones enhanced in the series ²³⁹Pu < ²⁴¹Am < ²³⁷Np. In this series, concentrations of radionuclides in water-soluble and exchange forms that are most mobile and determine the migration mobility of chemical elements increased in all of the studied soil types. In the group of fulvic acids, concentrations of radionuclides decreased in the series ²³⁷Np > ²⁴¹Am > ²³⁹Pu irrespectively of the soil. In the group of humic acids, concentrations of radionuclides increased in the series ²³⁷Np < ²³⁹Pu < ²⁴¹Am. The sorption coefficients of radionuclides by bottom sediments of the Markha River (Kraton-3 underground nuclear explosion site) and Lake Kyzyltash (East Urals Radioactive Trace) were calculated. Bioaccumulation factors of radionuclides by different plants in the impact area of the Kraton underground nuclear explosion were determined depending on the plant type.     

REE distribution in zircon from reference rocks of the Arctic region: Evidence from study by the LA-ICP-MS method

The results of the LA-ICP-MS analysis of the concentrations of REEs, U, Th, and Hf in zircon from Paleo- and Neoarchean reference rocks of the Kola region (garnet–amphibole gneiss, basic and acid granulites, and granite pegmatite) are reported. A new methodology of the study of accessory zircons has been validated and modified. The accuracy of the results is confirmed by analysis of standard zircons Temora 1 and 91 500 and by comparison with the data obtained in other laboratories.     

High-gradient metamorphism and anatexis in the Teletsk–Chulyshman metamorphic belt (Gornyi Altai): New data on the age and estimate of <Emphasis Type="Italic">P–T</Emphasis> parameters

Estimates of the P–T parameters of metamorphism, the first results of U–Pb dating of zircons from migmatites of the Teletsk–Chulyshman metamorphic belt, are reported. The age of migmatites from the southern block of the Teletsk–Chulyshman belt is 483.9 ± 5.7 Ma. As is evident from the pressure estimate (≤3–4 kbar), the Chulyshman migmatite–gneiss complex could be an apical part of the thermal–dome structure formed during the Early Ordovician thermal impact of a shallow magmatic basic thermal source, later displaced to the appropriate depth along the thrust at the collisional stage.     

Physical parameters of the continuum radiating layer of the star L2 Pup

Data from spectrophotometric observations in the 485-1105 nm range at different times are used to determine the basic physical parameters of the continuum radiating layer of L₂ Pup: spectrophotometric temperatures, radii, and velocities of recession from the star's center. The phase dependences of these parameters over a cycle, during which the temperature varied from 2300 to 2900 K and the variations in radius were as high as 60%, are determined. The radius of the radiating layer is seen to vary irregularly, the radius of the layer is found to depend on wavelength, and the variations in the expansion velocity are evaluated. Translated from Astrofizika, Vol. 52, No. 1, pp. 99–115 (February 2009).     

Kinetics and mechanism of transformations in iron-rich pyrrhotites and in troilite-pyrrhotite metastable assemblages

Iron-rich pyrrhotites proved to be metastable and to decompose at 70–140° C to troilite and pyrrhotite with less iron content as shown by nuclear gamma-resonance (Mössbauer) studies at high temperatures. Coherence of decomposition product lattices was established by studying powder samples textured in a magnetic field. Detailed X-ray powder diffraction and Mössbauer investigations revealed two different mechanisms of transformation in metastable associations. Kinetic phenomena are discussed in terms of a thermodynamic model of two-phase assemblage.     

Evaluative Zoning of Seawater Areas Based on Environmental and Fishery Characteristics

The principles and methods of comprehensive evaluative mapping of seawater areas are considered using the Barents Sea as an example. The areas are classified using a digital map database represented by a series of electronic thematic maps. The digital thematic maps are based on a raster version of a geographic information system (GIS).     

Ion exchange properties of oceanic ferromanganese nodules and enclosing pelagic sediments

Results of the experimental study of ion exchange properties of deep-sea pelagic sediments and related ferromanganese nodules (FMN) are considered. The exchange complex of sediments and nodules includes Na⁺, K⁺, Ca²⁺, and Mg²⁺ cations. The FMNs also include Mn²⁺ cations. Series of reactivity of metal cations during exchange reactions in different types of pelagic clayey sediments and diagenetic-sedimentary FMN are compiled. Series of exchange capacity of the sediments and FMN for alkali and heavy metal cations are also presented. The exchange capacity of FMN is always higher than that of enclosing sediments. Sediments are characterized by reversible equivalent sorption of cations of both alkali and heavy metals. Irrespective of the mineral composition, the FMNs are characterized by the reversible equivalent sorption of alkali metal cations, whereas sorption of heavy metal cations is only partly reversible. More over, alkali metal cations do not replace heavy metal cations. The results obtained refine the role of ion exchange processes in the redistribution of heavy metal cations at the water-bottom sediment interface during the diagenetic-sedimentary formation of ferromanganese nodules.     

Observations of cosmic gamma-ray bursts with the main detector of the SIGMA telescope onboard the Granat Observatory

We present the observations of cosmic gamma-ray bursts (GRBs) with the main detector of the SIGMA telescope onboard the Granat Observatory from January 1990 through September 1994. The observations were carried out in the energy range 35–1300 keV. We detected 36 GRBs and 31 high-energy solar flares during this period. No GRB fell within the main field of view; they were all recorded by the “secondary optics” of the telescope. The SIGMA telescope recorded relatively bright bursts with peak fluxes of 10^?6–10^?4 erg s^?1 cm^?2 in the 100–500-keV energy band. Stable detector background allows the long-term variability of GRB sources on a time scale of ～1000 s to be studied. The results of our search for early afterglows of GRBs are presented. The flux averaged over all bursts in the interval 100–800 s after the main event is 0.36±0.14 counts s^?(35–300 keV), suggesting that there is soft gamma-ray emission on this time scale after a considerable number of GRBs.     

The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory

The Spin-X wide-field X-ray monitor of the Spectrum-X-Gamma astrophysical observatory, which is based on the principle of a coded-aperture telescope, is designed to detect and localize cosmic gammaray-burst (GRB) sources; to survey large areas of the sky in search of new transients; and to carry out long-term observations of bright Galactic sources, including X-ray bursters. The monitor consists of two noncoaxial identical modules, Spin-X1 and Spin-X2, which together cover 6.8% of the sky. The high-apogee, four-day orbit of the Spectrum-XG satellite allows the instrument to be in observing mode more than 50% of the time. Having simulated the rate of GRB detection by Spin-X, we show that extrapolating BATSE 50–300-keV average data on the number of GRBs, their duration, and their mean energy spectrum to the X-ray energy band leads to disagreement with the observed detection rate of GRBs in the X-ray band. The number of GRBs that can be detected and localized with an accuracy r≤3′ (3σ) (the error-circle radius) by Spin-X is estimated to be ten bursts per year. We present data on the Spin-X sensitivity achievable during long-term observations of persistent and transient sources and on its sensitivity to X-ray bursts from Galactic sources in the 2–30-keV energy band.