A combined DGT - DET approach for an in situ investigation of uranium resupply from large soil profiles in a wetland impacted by former mining activities.

An in situ methodology combining DET and DGT probes was applied in a wetland soil, downstream of a former uranium mine (Rophin), to evaluate metal resupply by calculating the R ratio (R = [U]/[U]) from a high resolution and large (75 cm) soil profile. Our study confirms its applicability in soil layers with varying properties; only soil layers with low water content or coarse texture appear to be limiting factors. For soil profiles, DET provides new insights of the distribution of Uranium as soluble species (free ions, small inorganic complexes, …) along the pore water profile, whereas DGT highlights the presence of other "DGT labile" species.

Flow period influence on uranium and trace elements release in water from the waste rock pile of the former La Commanderie uranium mine (France).

Uranium mining activities expose uranium ore and mine tailings to the surface environment, where the release of radionuclides is facilitated by weathering at rates exceeding those typically found in nature. Therefore, close to former uranium mining sites, radionuclides and especially uranium concentrations in water may surpass local background levels. The methodology proposed herein, entails coupling, gamma-ray mapping, water sampling and chemical analyses including DGT (Diffusive Gradient in Thin Film) measurements, provides new insights into describing the environment of the La Commanderie site (France).

Alteration of vitrified intermediate level nuclear waste in alkaline media: effects of cementitious materials, pH and temperature.

Alteration experiments involving intermediate level nuclear waste (ILW) glass in contact with hardened cement paste (HCP) were performed to assess its behavior under simulated repository conditions. Batch experiments were conducted at 20 °C and 50 °C in several artificial cement pore water (ACW) samples (pH from 10 to 13), in the presence of HCP (CEM-I, CEM-V and low pH), with a ratio of glass surface to volume of solution of 8000 m and a ratio of mass of HCP to volume of solution of 10 g L. Glass alteration rates increase up to ∼4 × 10 g m d with pH in contact with HCP, notably with CEM-I.

Towards speciation of organically bound tritium and deuterium: Quantification of non-exchangeable forms in carbohydrate molecules.

An original methodology to quantitatively explore exchangeability of hydrogen isotopes in carbohydrate molecules is proposed. To access the speciation of organically bound hydrogen isotopes, isotopic exchanges were carried out under a soft path regime in the vapor phase at 20 °C with set (D,T/H) vapor pressure ratios. When steady states were reached, the fraction of exchangeable hydrogen of microcrystalline cellulose, alpha-cellulose and wheat grains were obtained and ranged from 13 to 31% (versus a theoretical value of 30%).

Adsorption and transport of polymaleic acid on Callovo-Oxfordian clay stone: batch and transport experiments.

Dissolved Organic Matter (DOM) can affect the mobility of radionuclides in pore water of clay-rich geological formations, such as those intended to be used for nuclear waste disposal. The present work studies the adsorption and transport properties of a polycarboxylic acid, polymaleic acid (PMA, Mw=1.9kDa), on Callovo-Oxfordian argillite samples (COx).

Evaluation of the anthropogenic influx of metal and metalloid contaminants into the Moulay Bousselham lagoon, Morocco, using chemometric methods coupled to geographical information systems.

Superficial and cored sediment samples from the Moulay Bousselham lagoon and sub-watershed were analyzed for Al, Fe, Cu, Zn, Pb, Mn, Ni, Cr, As, Hg, and Cd. The temporal and spatial distributions of the main contamination sources of heavy metals were identified and described using chemometric and geographic information system (GIS) methods. Sediments from coastal lagoons near urban and agricultural areas are commonly contaminated with heavy metals, and the concentrations found in surface sediments are significantly higher than those from 50-100 years ago.

Non-disturbing characterization of natural organic matter (NOM) contained in clay rock pore water by mass spectrometry using electrospray and atmospheric pressure chemical ionization modes.

We have investigated the composition of the mobile natural organic matter (NOM) present in Callovo-Oxfodian pore water using electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and emission-excitation matrix (EEM) spectroscopy. The generation of knowledge of the composition, structure and size of mobile NOM is necessary if one wants to understand the interactions of these compounds with heavy metals/radionuclides, in the context of environmental studies, and particularly how the mobility of these trace elements is affected by mobile NOM. The proposed methodology is very sensitive in unambiguously identifying the in situ composition of dissolved NOM in water even at very low NOM concentration, due to innovative non-disturbing water sampling and ionization (ESI/APCI-MS) techniques.

Strontium binding by calcium silicate hydrates.

In the present study the binding of strontium with pure calcium silicate hydrates (C-S-H) has been investigated using batch-type experiments. Synthetic C-S-H phases with varying CaO:SiO(2) (C:S) mol ratios, relevant to non-degraded and degraded hardened cement paste, were prepared in the absence of alkalis (Na(I), K(I)) and in an alkali-rich artificial cement pore water (ACW). Two types of experimental approaches have been employed, investigating sorption and co-precipitation processes, respectively.

Measurement and modeling of the surface potential evolution of hydrated cement pastes as a function of degradation.

Hydrated cement pastes (HCP) have a high affinity with a lot of (radio)toxic products and can be used as waste confining materials. In cementitious media, elements are removed from solution via (co)precipitation reactions or via sorption/diffusion mechanisms as surface complexation equilibria. In this study, to improve the knowledge of the surface charge evolution vs the degradation of the HCP particles, two cements have been studied: CEM-I (ordinary Portland cement, OPC) and CEM-V (blast furnace slag and fly ash added to OPC).

Subcellular and intranuclear localization of neptunium-237 (V) in rat liver.

The present investigation was aimed at establishing the distribution of 237Np within the different structures of hepatocytes. Rats were contaminated experimentally by intravenous injection of 237Np (V) and the subcellular structures of the liver were separated by ultracentrifugation. Twenty-four hours after contamination, the nuclear and cytosolic fractions bound 54 and 32%, respectively, of the total radionuclide.