Monitoring of trace metals and pharmaceuticals as anthropogenic and socio-economic indicators of urban and industrial impact on surface waters

International audienc

Micro- and macro-scale investigation of fractionation and matrix effects in LA-ICP-MS at 1064 nm and 266 nm on glassy materials.

Fundamental processes taking place in UV and IR laser ablation and their significance for LA-ICP-MS measurements were investigated with synthetic glassy materials. LA-ICP-MS experiments were conducted on several vitreous and crystallized matrices with different composition using two NdYAG laser ablation systems operating at 1064 nm and 266 nm. Macro-scale effects of the laser factors and matrix properties were evaluated with ICP-MS detection. In-situ investigation of the laser ablation process was carried out at the micro-scale to assess physical and chemical transformations of the original material, based on electron probe microanalysis of ablation products collected on filters and laser impacts. Fragments and beads in the 1–10 µm range enriched in refractory elements (Ca, Al) were characteristic of IR laser ablation, whereas sub-microscopic particles with similar composition to the original matrix were found for UV laser ablation. LA-ICP-MS response factors for matrix and minor elements appeared to be dependent on both the chemical composition and structure of the matrix (up to 30% and 60% for the UV and IR laser, respectively) and were also different for the two lasers by a factor 10. The use of La, a refractory matrix element, as an internal standard could compensate for differences in the ablation yield and thus limit matrix effects. However, fractionation effects were observed for the IR laser and also, to a lesser extent, with the UV one for volatile elements (e.g., Pb, As, B, Cs). Elemental fractionation effects were correlated with the oxide melting point of the elements as the LA-ICP-MS response factors for the IR laser normalized by the UV ones showed a linear relation with this parameter. At the micro-scale, the samples underwent physical and chemical differentiation that could be explained in terms of fusion, vaporization and fragmentation, resulting in the recombination of the analytes in the ablation products

Hydrochemical and hydrodynamical investigations to characterize flow modes in hard rock aquifers. Application to the Ursuya massif (France)

International audienc

Real time alteration of a nuclear waste glass and remobilization of lanthanide into an interphase.

The development of predictive models for the long term evolution of nuclear waste glass requires the complete knowledge of the glass dissolution at the laboratory scale. A new approach was developed to determine the initial reaction during the first steps of experience, a new concept was developed, based on the combination of dynamic leaching test and the characterization of the altered materials. With this experimental set-up it is possible to follow in real time the glass alteration process at a fine temporal scale. The results put in evidence a singular behaviour of the lanthanide, shown by a concentration peak of La, Nd and Ce after 2 h and a quick decrease of their concentration measured on line in the solution during the leaching test. This fact is directly linked to the development of an interphase (altered layer which differs from the initial solid by its texture, structure and chemical composition) at the interface of the glass surface and the leaching solution. This work is an attempt to integrate the formation of the alteration products (here the interphase) during leaching into the dissolution mechanisms of a nuclear waste glass. A model is proposed and discussed

Synthesis and characterization of low-temperature precursors of thorium–uranium (IV) phosphate–diphosphate solid solutions

RADIOCHIMIESeveral compositions of new precursor of thorium–uranium (IV) phosphate–diphosphate solid solutions (Th4−xUx(PO4)4P2O7, called β-TUPD) were synthesized in closed PTFE containers either in autoclave (160 °C) or on sand bath (90–160 °C). All the samples appeared to be single phase. From XRD data and TEM observations, the diffraction lines matched well with that of pure thorium phosphate–hydrogenphosphate hydrate (TPHPH), Th2(PO4)2(HPO4) · H2O, which confirmed the preparation of a complete solid solution between pure thorium and uranium (IV) compounds. TGA/DTA experiments showed that samples of thorium–uranium (IV) phosphate–hydrogenphosphate hydrate (TUPHPH) prepared at 150–160 °C were monohydrated leading to the proposed formula Th2−x/2Ux/2(PO4)2(HPO4) · H2O. The variation of the XRD diagrams versus the heating temperature showed that TUPHPH remained crystallized and single phase from room temperature to 200 °C. After heating between 200 °C and 800 °C, the presence of diphosphate groups in the solid was evidenced. In this range of temperature, the solid was transformed into the low-temperature monoclinic form of thorium–uranium (IV) phosphate–diphosphate (α-TUPD). This latter compound finally turned into well-crystallized, homogeneous and single-phase β-TUPD (orthorhombic form) above 930–950 °C for x values lower than 2.80. For higher x values, a mixture of β-TUPD, α-Th1−zUzP2O7 and U2−wThwO(PO4)2 was obtained. By this new chemical route of preparation of β-TUPD solid solutions, the homogeneity of the samples is significantly improved, especially considering the distribution of thorium and uranium