Joint Project: Migration of Actinides in the System Clay, Humic Substance, Aquifer - Migration Behavior of Actinides (Uranium, Neptunium) in Clays: Characterization and Quantification of the Influence of Humic Substances (Final Report BMWi Project No.: 02 E 9673)

Objective of this project was the study of interaction processes between humic substances, U(VI), Np(V) and kaolinite KGa-1b. It contributed to the attainment of a better process understanding, the improvement of the knowledge on the interaction of humic substances and metal ions and the enhancement of the thermodynamic database. With a synthetic humic acid (HA), N-containing functional groups of HA were characterized by 15N-NMR spectroscopy. Based on these results, model studies of the influence of amino groups on the complexation behavior of HA were performed. Spectroscopic studies with amino acids show that the amino group do not contribute to the U(VI) complexation at pH 4. The impact of kaolinite on the formation of HA and humic substance-kaolinite-sorbates was studied in model syntheses. The results exhibit that the presence of kaolinite during the syntheses mainly influences the yields on HA and their elemental compositions. Synthetic humic substance-kaolinite-sorbates were isolated. Under exclusion of CO2, the U(VI) complexation by HA was investigated at pH 7 by means of the conventional time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses. Complexation parameters for the ternary complex UO2(OH)HA(I) were determined. Studies of the Np(V) reduction in presence of HA with different functionalities under anaerobic conditions have shown that Np(V) is reduced to Np(IV) by HA. The redox capacity depends on the HA functionality. Applying a modified HA it was verified that phenolic/acidic OH groups play a dominating role in the Np(V) reduction. The influence of HA on the U(VI) and Np(V) sorption onto kaolinite was investigated in batch experiments. In dependence on the experimental conditions, HA effects the sorption and consequently the mobility of U(VI) and Np(V). From studies of the U(VI) sorption onto synthetic humic substance-kaolinite-sorbates it was concluded that the structure and functionality of sorbed/associated humic substances considerably influence the sorption behavior of U(VI). The structure of U(VI)-kaolinite-surface complexes in presence of HA was studied by means of X-ray absorption spectroscopy and TRLFS and compared to those of U(VI)-kaolinite-complexes. Investigations of the migration of HA and U(VI) in the laboratory system kaolinite-water were carried out in diffusion experiments. The migration of HA in compacted clay is governed by diffusion and influenced by its colloidal properties. Humic substances exert an immobilizing effect on the U(VI) transport in compacted kaolinite

Effect of U(VI) aqueous speciation on the binding of uranium by the cell surface of Rhodotorula mucilaginosa, a natural yeast isolate from bentonites

This study presents the effect of aqueous uranium speciation (U-hydroxides and U-hydroxo-carbonates) on the interaction of this radionuclide with the cells of the yeast Rhodotorula mucigilanosa BII-R8. This strain was isolated from Spanish bentonites considered as reference materials for the engineered barrier components of the future deep geological repository of radioactive waste. X-ray absorption and infrared spectroscopy showed that the aqueous uranium speciation has no effect on the uranium binding process by this yeast strain. The cells bind mobile uranium species (U-hydroxides and U-hydroxo-carbonates) from solution via a time-dependent process initiated by the adsorption of uranium species to carboxyl groups. This leads to the subsequent involvement of organic phosphate groups forming uranium complexes with a local coordination similar to that of the uranyl mineral phase meta-autunite. Scanning transmission electron microscopy with high angle annular dark field analysis showed uranium accumulations at the cell surface associated with phosphorus containing ligands. Moreover, the effect of uranium mobile species on the cell viability and metabolic activity was examined by means of flow cytometry techniques, revealing that the cell metabolism is more affected by higher concentrations of uranium than the cell viability. The results obtained in this work provide new insights on the interaction of uranium with bentonite natural yeast from genus Rhodotorula under deep geological repository relevant conditions

Joint Project: Migration of Actinides in the System Clay, Humic Substance, Aquifer - Migration Behavior of Actinides (Uranium, Neptunium) in Clays: Characterization and Quantification of the Influence of Humic Substances (Final Report BMWi Project No.: 02 E 9673)

Objective of this project was the study of interaction processes between humic substances, U(VI), Np(V) and kaolinite KGa-1b. It contributed to the attainment of a better process understanding, the improvement of the knowledge on the interaction of humic substances and metal ions and the enhancement of the thermodynamic database. With a synthetic humic acid (HA), N-containing functional groups of HA were characterized by 15N-NMR spectroscopy. Based on these results, model studies of the influence of amino groups on the complexation behavior of HA were performed. Spectroscopic studies with amino acids show that the amino group do not contribute to the U(VI) complexation at pH 4. The impact of kaolinite on the formation of HA and humic substance-kaolinite-sorbates was studied in model syntheses. The results exhibit that the presence of kaolinite during the syntheses mainly influences the yields on HA and their elemental compositions. Synthetic humic substance-kaolinite-sorbates were isolated. Under exclusion of CO2, the U(VI) complexation by HA was investigated at pH 7 by means of the conventional time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses. Complexation parameters for the ternary complex UO2(OH)HA(I) were determined. Studies of the Np(V) reduction in presence of HA with different functionalities under anaerobic conditions have shown that Np(V) is reduced to Np(IV) by HA. The redox capacity depends on the HA functionality. Applying a modified HA it was verified that phenolic/acidic OH groups play a dominating role in the Np(V) reduction. The influence of HA on the U(VI) and Np(V) sorption onto kaolinite was investigated in batch experiments. In dependence on the experimental conditions, HA effects the sorption and consequently the mobility of U(VI) and Np(V). From studies of the U(VI) sorption onto synthetic humic substance-kaolinite-sorbates it was concluded that the structure and functionality of sorbed/associated humic substances considerably influence the sorption behavior of U(VI). The structure of U(VI)-kaolinite-surface complexes in presence of HA was studied by means of X-ray absorption spectroscopy and TRLFS and compared to those of U(VI)-kaolinite-complexes. Investigations of the migration of HA and U(VI) in the laboratory system kaolinite-water were carried out in diffusion experiments. The migration of HA in compacted clay is governed by diffusion and influenced by its colloidal properties. Humic substances exert an immobilizing effect on the U(VI) transport in compacted kaolinite

Joint Project: Migration of Actinides in the System Clay, Humic Substance, Aquifer - Migration Behavior of Actinides (Uranium, Neptunium) in Clays: Characterization and Quantification of the Influence of Humic Substances (Final Report BMWi Project No.: 02 E 9673)

Objective of this project was the study of interaction processes between humic substances, U(VI), Np(V) and kaolinite KGa-1b. It contributed to the attainment of a better process understanding, the improvement of the knowledge on the interaction of humic substances and metal ions and the enhancement of the thermodynamic database. With a synthetic humic acid (HA), N-containing functional groups of HA were characterized by 15N-NMR spectroscopy. Based on these results, model studies of the influence of amino groups on the complexation behavior of HA were performed. Spectroscopic studies with amino acids show that the amino group do not contribute to the U(VI) complexation at pH 4. The impact of kaolinite on the formation of HA and humic substance-kaolinite-sorbates was studied in model syntheses. The results exhibit that the presence of kaolinite during the syntheses mainly influences the yields on HA and their elemental compositions. Synthetic humic substance-kaolinite-sorbates were isolated. Under exclusion of CO2, the U(VI) complexation by HA was investigated at pH 7 by means of the conventional time-resolved laser-induced fluorescence spectroscopy (TRLFS) and TRLFS with ultrafast pulses. Complexation parameters for the ternary complex UO2(OH)HA(I) were determined. Studies of the Np(V) reduction in presence of HA with different functionalities under anaerobic conditions have shown that Np(V) is reduced to Np(IV) by HA. The redox capacity depends on the HA functionality. Applying a modified HA it was verified that phenolic/acidic OH groups play a dominating role in the Np(V) reduction. The influence of HA on the U(VI) and Np(V) sorption onto kaolinite was investigated in batch experiments. In dependence on the experimental conditions, HA effects the sorption and consequently the mobility of U(VI) and Np(V). From studies of the U(VI) sorption onto synthetic humic substance-kaolinite-sorbates it was concluded that the structure and functionality of sorbed/associated humic substances considerably influence the sorption behavior of U(VI). The structure of U(VI)-kaolinite-surface complexes in presence of HA was studied by means of X-ray absorption spectroscopy and TRLFS and compared to those of U(VI)-kaolinite-complexes. Investigations of the migration of HA and U(VI) in the laboratory system kaolinite-water were carried out in diffusion experiments. The migration of HA in compacted clay is governed by diffusion and influenced by its colloidal properties. Humic substances exert an immobilizing effect on the U(VI) transport in compacted kaolinite

A highly virulent variant of HIV-1 circulating in the Netherlands

We discovered a highly virulent variant of subtype-B HIV-1 in the Netherlands. One hundred nine individuals with this variant had a 0.54 to 0.74 log10 increase (i.e., a ~3.5-fold to 5.5-fold increase) in viral load compared with, and exhibited CD4 cell decline twice as fast as, 6604 individuals with other subtype-B strains. Without treatment, advanced HIV-CD4 cell counts below 350 cells per cubic millimeter, with long-term clinical consequences-is expected to be reached, on average, 9 months after diagnosis for individuals in their thirties with this variant. Age, sex, suspected mode of transmission, and place of birth for the aforementioned 109 individuals were typical for HIV-positive people in the Netherlands, which suggests that the increased virulence is attributable to the viral strain. Genetic sequence analysis suggests that this variant arose in the 1990s from de novo mutation, not recombination, with increased transmissibility and an unfamiliar molecular mechanism of virulence