No abstract

SummaryX-ray absorption spectroscopy has been used to establish polymer formation of Tc(IV) in aqueous solutions of NaAs the molybdenum chemistry show similarities to that of technetium, we used MoOIn aqueous solution, some polymers are formed regardless to the nature of the media composition: Tc-Tc=2.50 ± 0.02 Å. The general structure is in agreement with a first coordination shell containing 6 O. The modelling shows that, in the first coordination shell, there is no chloride ligand. The observed geometries are close to those found for TcOCombination of these results with XANES led to attribute Tc

SummaryThe substitution of the Cl

SummaryTo study the interaction between Tc and subsurface bacteria, we conducted batch experiments with soil and groundwater or sterilized deionized water. The system water/soil was amended with lactate and phosphate for bacterial growth. Nitrate and sulfate were added to stimulate the growth of indigenous denitrifying and sulfate-reducing bacteria. During denitrification Tc-concentration did not change with time. In the presence of sulfate-reducing bacteria, Tc-concentrations decreased in reacted waters which could be attributed to Tc(VII) reduction and precipitation of TcO

Isotopic fractionation of tritium is a highly relevant issue in radiation protection and requires certain radioecological considerations. Sound evaluation of this factor is indeed necessary to determine whether environmental compartments are enriched/depleted in tritium or if tritium is, on the contrary, isotopically well-distributed in a given system. The ubiquity of tritium and the standard analytical methods used to assay it may induce biases in both the measurement and the signification that is accorded to the so-called fractionation: based on an exhaustive review of the literature, we show how, sometimes large deviations may appear. It is shown that when comparing the non-exchangeable fraction of organically bound tritium (neOBT) to another fraction of tritium (e.g. tritiated water) the preparation of samples and the measurement of neOBT reported frequently led to underestimation of the ratio of tritium to hydrogen (T/H) in the non-exchangeable compartment by a factor of 5% to 50%. In the present study, corrections are proposed for most of the biological matrices studied so far. Nevertheless, the values of isotopic fractionation reported in the literature remain difficult to compare with each other, especially since the physical quantities and units often vary between authors. Some improvements are proposed to better define what should encompass the concepts of exchangeable and non-exchangeable fractions.