The implications of selenium deficiency for wild herbivore conservation: a review

Selenium (Se) is required at a fundamental physiological level in all animals. Adequate levels of Se are necessary for proper bone metabolism, iodine metabolism, immune function, reproductive success, and recruitment. Selenium is a component of enzymes which scavenge oxidative free radicals that would otherwise degrade cell membranes. Severe deficiency results in obvious symptoms such as white muscle disease in ungulates. However, more frequently, deficiency may be chronic and subclinical. Individuals then display no obvious signs of malady, yet performance suffers until their populations decline without apparent cause or through proximate factors which obscure underlying primary factors. Although well known in domestic stock, the link between population performance and Se deficiency in wild populations has been difficult to firmly establish. Confounding factors include the role of vitamin E, which also acts as an antioxidant to mitigate the need for Se under some circumstances; changing Se requirements at changing times in animal life history; changing Se requirements in relation to pollution levels and other factors causing oxidative stress; and the non-uniform distribution of Se in its various chemical forms in the environment. The latter point is especially important to wild populations that have been reduced to remnant portions of their previous range. Here, we have reviewed the literature of Se in wildlife as well as provided an introduction to Se in physiology and Se behavior in the environment for the wildlife researcher and manager. We conclude that unrecognized Se deficiency may often impede optimal population performance, and we provide recommendations for habitat analysis with regard to Se which can be used in future research. Finally, evidence that the amount of available Se in the environment is decreasing from anthropogenic causes is show

The implications of selenium deficiency for wild herbivore conservation: A review

Selenium (Se) is required at a fundamental physiological level in all animals. Adequate levels of Se are necessary for proper bone metabolism, iodine metabolism, immune function, reproductive success, and recruitment. Selenium is a component of enzymes which scavenge oxidative free radicals that would otherwise degrade cell membranes. Severe deficiency results in obvious symptoms such as white muscle disease in ungulates. However, more frequently, deficiency may be chronic and subclinical. Individuals then display no obvious signs of malady, yet performance suffers until their populations decline without apparent cause or through proximate factors which obscure underlying primary factors. Although well known in domestic stock, the link between population performance and Se deficiency in wild populations has been difficult to firmly establish. Confounding factors include the role of vitamin E, which also acts as an antioxidant to mitigate the need for Se under some circumstances; changing Se requirements at changing times in animal life history; changing Se requirements in relation to pollution levels and other factors causing oxidative stress; and the non-uniform distribution of Se in its various chemical forms in the environment. The latter point is especially important to wild populations that have been reduced to remnant portions of their previous range. Here, we have reviewed the literature of Se in wildlife as well as provided an introduction to Se in physiology and Se behavior in the environment for the wildlife researcher and manager. We conclude that unrecognized Se deficiency may often impede optimal population performance, and we provide recommendations for habitat analysis with regard to Se which can be used in future research. Finally, evidence that the amount of available Se in the environment is decreasing from anthropogenic causes is shown.Fil: Fluck, Werner Thomas. Universidad Atlantida Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Smith Flueck, J. M.. Universidad Atlantida Argentina; ArgentinaFil: Mionczynski, J.. No especifíca;Fil: Mincher, B. J.. No especifíca

Supercritical Fluid Extraction of Plutonium and Americium from Soil

Supercritical fluid extraction (SFE) of plutonium and americium from soil was successfully demonstrated using supercritical fluid carbon dioxide solvent augmented with organophosphorus and beta-diketone complexants. Spiked Idaho soils were chemically and radiologically characterized, then extracted with supercritical fluid carbon dioxide at 2,900 psi and 65 C containing varying concentrations of tributyl phosphate (TBP) and thenoyltrifluoroacetone (TTA). A single 45 minute SFE with 2.7 mol% TBP and 3.2 mol% TTA provided as much as 88% {+-} 6.0 extraction of americium and 69% {+-} 5.0 extraction of plutonium. Use of 5.3 mol% TBP with 6.8 mol% of the more acidic beta-diketone hexafluoroacetylacetone (HFA) provided 95% {+-} 3.0 extraction of americium and 83% {+-} 5.0 extraction of plutonium in a single 45 minute SFE at 3,750 psi and 95 C. Sequential chemical extraction techniques were used to chemically characterize soil partitioning of plutonium and americium in pre-SFE soil samples. Sequential chemical extraction techniques demonstrated that spiked plutonium resides primarily (76.6%) in the sesquioxide fraction with minor amounts being absorbed by the oxidizable fraction (10.6%) and residual fractions (12.8%). Post-SFE soils subjected to sequential chemical extraction characterization demonstrated that 97% of the oxidizable, 78% of the sesquioxide and 80% of the residual plutonium could be removed using SFE. These preliminary results show that SFE may be an effective solvent extraction technique for removal of actinide contaminants from soil

Decomposition of PCBs in oils using gamma radiolysis: A treatability study. Final report

This report presents the results of a treatability study of radiologically and PCB contaminated waste hydraulic oils at the Idaho National Engineering Laboratory (INEL). The goal of the study was to demonstrate that PCBs could be selectively removed from the contaminated oils. The PCBs were selectively decomposed in an in-situ fashion via gamma-ray radiolysis. The gamma-ray source was spent nuclear fuel at the Advanced Test Reactor (ATR) canal at the Test Reactor Area (TRA), of the INEL. Exposure to gamma-rays does not induce radioactivity in the exposed solutions. The treatability study was the culmination of five years of research concerning PCB radiolysis conducted at INEL which investigated the mechanism and kinetics of the reaction in several solvents. The major findings of this research are summarized here. Based upon these findings three INEL waste streams were selected for testing of the process. The Environmental Protection Agency (EPA) treatment standard of 2 mg/kg was successfully achieved in all waste streams. The interference of contaminants other than PCBs is discussed

Gamma Ray Radiolysis of the FPEX Solvent

Slide presentation. FPEX contains a calixarene for Cs extraction, a crown ether for Sr extraction, Cs7SB modifier, and TOA to aid in stripping, in Isopar L diluent. The radiation stability FPEX must be evaluated prior to process use. Radiolytic degradation of species in solution are due to reaction with the direct radiolysis products of the diluent. In Isopar L, the reactive species produced include e-, •H and alkane radicals, resulting in a reducing environment. However, in nitric acid, oxidizing hydroxyl (•OH) and nitro (•NO2) radicals dominate system chemistry. Thus, the nature of diluent and the presence of radical scavengers affect the results of irradiation. We report the preliminary results of a new program to investigate the radiolysis of FPEX using the 60Co irradiation of FPEX neat solvent, acid pre-equilibrated solvent and mixed aerated phases. The Cs and Sr distribution ratios were used as metrics

Gamma and pulsed electron radiolysis studies of CyMe4BTBP and CyMe4BTPhen: Identification of radiolysis products and effects on the hydrometallurgical separation of trivalent actinides and lanthanides

The radiolytic stability of the highly selective ligands CyMe4BTBP and CyMe4BTPhen against ionizing gamma radiation was studied in 1-octanol solution. CyMe4BTBP and CyMe4BTPhen are important extractants for a potential treatment of used nuclear fuel. They were studied under identical experimental conditions to directly compare the effects of gamma and pulsed electron radiolysis on the ligands and systematically study the influence of structural changes in the ligand backbone. Distribution ratios of Am3+, Cm3+ and Eu3+, the residual concentration of CyMe4BTBP and CyMe4BTPhen in solution, and the formation of radiolysis products were studied as a function of absorbed gamma dose and presence of an acidic aqueous phase during irradiation. Quantitative and semi-quantitative analyses were used to elucidate the radiolysis mechanism for both ligands. Addition products of alpha-hydroxyoctyl radicals formed through radiolysis of the 1-octanol diluent to the ligand molecules were identified as the predominant radiolysis products. These addition products also extract trivalent metal ions, as distribution ratios remained high although the parent molecule concentrations decreased. Therefore, the utilization time of a solvent using these extractants under the harsh conditions of used nuclear fuel treatment could be considerably longer than expected. Understanding the radiolysis mechanism is crucial for designing more radiation resistant extractants

Remediation of soil at nuclear sites

As the major nuclear waste and decontamination and decommissioning projects progress, one of the remaining problems that faces the nuclear industry is that of site remediation. The range of contamination levels and contaminants is wide and varied and there is likely to be a significant volume of soil contaminated with transuranics and hazardous organic materials that could qualify as mixed TRU waste. There are many technologies that offer the potential for remediating this waste but few that tackle all or most of the contaminants and even fewer that have been deployed with confidence. This paper outlines the progress made in proving the ability of Supercritical Fluid Extraction as a method of remediating soil, classified as mixed (TRU) transuranic wast

Complexation of lanthanides, actinides and transition metal cations with a 6-(1,2,4-triazin-3-yl)-2,2’:6’,2’’-terpyridine ligand: implications for actinide(III) /lanthanide(III) partitioning

The quadridentate N-heterocyclic ligand 6-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-1,2,4-benzotriazin-3-yl)-2,2’:6’,2’’-terpyridine (CyMe4-hemi-BTBP) has been synthesized and its interactions with Am(III), U(VI), Ln(III) and some transition metal cations have been evaluated by X-ray crystallographic analysis, Am(III)/Eu(III) solvent extraction experiments, UV absorption spectrophotometry, NMR studies and ESI-MS. Structures of the 1:1 complexes with Eu(III), Ce(III) and the linear uranyl (UO22+) ion were obtained by X-ray crystallographic analysis, and showed similar coordination behavior to related BTBP complexes. In methanol, the stability constants of the Ln(III) complexes are slightly lower than those of the analogous quadridentate bis-triazine BTBP ligands, while the stability constant for the Yb(III) complex is higher. 1H NMR titrations and ESI-MS with lanthanide nitrates showed that the ligand forms only 1:1 complexes with Eu(III), Ce(III) and Yb(III), while both 1:1 and 1:2 complexes were formed with La(III) and Y(III) in acetonitrile. A mixture of isomeric chiral 2:2 helical complexes was formed with Cu(I), with a slight preference (1.4:1) for a single directional isomer. In contrast, a 1:1 complex was observed with the larger Ag(I) ion. The ligand was unable to extract Am(III) or Eu(III) from nitric acid solutions into 1-octanol, except in the presence of a synergist at low acidity. The results show that the presence of two outer 1,2,4-triazine rings is required for the efficient extraction and separation of An(III) from Ln(III) by quadridentate N-donor ligand

Supercritical Fluid Extraction of Plutonium and Americium from Soil

Supercritical fluid extraction (SFE) of plutonium and americium from soil was successfully demonstrated using supercritical fluid carbon dioxide solvent augmented with organophosphorus and beta-diketone complexants. Spiked Idaho soils were chemically and radiologically characterized, then extracted with supercritical fluid carbon dioxide at 2,900 psi and 65 C containing varying concentrations of tributyl phosphate (TBP) and thenoyltrifluoroacetone (TTA). A single 45 minute SFE with 2.7 mol% TBP and 3.2 mol% TTA provided as much as 88% {+-} 6.0 extraction of americium and 69% {+-} 5.0 extraction of plutonium. Use of 5.3 mol% TBP with 6.8 mol% of the more acidic beta-diketone hexafluoroacetylacetone (HFA) provided 95% {+-} 3.0 extraction of americium and 83% {+-} 5.0 extraction of plutonium in a single 45 minute SFE at 3,750 psi and 95 C. Sequential chemical extraction techniques were used to chemically characterize soil partitioning of plutonium and americium in pre-SFE soil samples. Sequential chemical extraction techniques demonstrated that spiked plutonium resides primarily (76.6%) in the sesquioxide fraction with minor amounts being absorbed by the oxidizable fraction (10.6%) and residual fractions (12.8%). Post-SFE soils subjected to sequential chemical extraction characterization demonstrated that 97% of the oxidizable, 78% of the sesquioxide and 80% of the residual plutonium could be removed using SFE. These preliminary results show that SFE may be an effective solvent extraction technique for removal of actinide contaminants from soil

High energy decomposition of halogenated hydrocarbons. FY 1992 final report

This program is the INEL component of a joint collaborative effort with Lawrence Livermore National Laboratory (LLNL). Purpose is to demonstrate a viable process for breaking down hazardous halogenated organic wastes to simpler, nonhazardous wastes using high energy ionizing radiation. The INEL effort focuses on the use of spent reactor fuel gamma radiation sources to decompose complex wastes such as PCBS. Work in FY92 expanded upon that reported for FY91. During FY91 it was reported that PCBs were susceptible to radiolytic decomposition in alcoholic solution, but that only a small percentage of decomposition products could be accounted for. It was shown that decomposition was more efficient in methanol than in isopropanol and that the presence of a copper-zinc couple catalyst did not affect the reaction rate. Major goals of FY92 work were to determine the reaction mechanism, to identify further reaction products, and to select a more appropriate catalyst. Described in this report are results of mechanism specific experiments, mass balance studies, transformer oil irradiations, the use of hydrogen peroxide as a potential catalyst, and the irradiation of pure PCB crystals in the absence of diluent