Soluble salt sources in medieval porous limestone sculptures: a multi-isotope (N, O, S) approach.

The sources and mechanisms of soluble salt uptake by porous limestone and the associated degradation patterns were investigated for the life-sized 15th century "entombment of Christ" sculpture group located in Pont-à-Mousson, France, using a multi-isotope approach on sulphates (δ(34)S and δ(18)O) and nitrates (δ(15)N and δ(18)O). The sculpture group, near the border of the Moselle River, is within the potential reach of capillary rise from the alluvial aquifer. Chemical analyses show a vertical zonation of soluble salts with a predominance of sulphates in the lower parts of the statues where crumbling and blistering prevail, and higher concentrations of nitrates and chloride in the high parts affected by powdering and efflorescence. Isotope fingerprints of sulphates suggest a triple origin: (1) the lower parts are dominated by capillary rise of dissolved sulphate from the Moselle water with characteristic Keuper evaporite signatures that progressively decreases with height; (2) in the higher parts affected by powdering the impact of atmospheric sulphur becomes detectable; and (3) locally, plaster reparations impact the neighbouring limestone through dissolution and re-precipitation of gypsum. Nitrogen and oxygen isotopes suggest an organic origin of nitrates in all samples. N isotope signatures are compatible with those measured in the alluvial aquifer of the Moselle River further downstream. This indicates contamination by sewage or organic fertilisers. Significant isotopic contrasts are observed between the different degradation features depending on the height and suggest historical changes of nitrate sources.

Assessing methane oxidation under landfill covers and its contribution to the above atmospheric CO2 levels: the added value of the isotope (δ¹³C and δ¹8O CO2; δ¹³C and δD CH4) approach.

We are presenting here a multi-isotope approach (δ¹³C and δ¹8O of CO2; δ¹³C and δD of CH4) to assess (i) the level(s) of methane oxidation during waste biodegradation and its migration through a landfill cover in Sonzay (France), and (ii) its contribution to the atmospheric CO2 levels above the surface. The isotope approach is compared to the more conventional mass balance approach. Results from the two techniques are comparable and show that the CH4 oxidation under the landfill cover is heterogenous, with low oxidation percentages in samples showing high biogas fluxes, which was expected in clay covers presenting fissures, through which CH4 is rapidly transported. At shallow depth, more immobile biogas pockets show a higher level of CH4 oxidation by the methanotrophic bacteria. δ¹³C of CO2 samples taken at different heights (from below the cover up to 8m above the ground level) were also used to identify and assess the relative contributions of its main sources both under the landfill cover and in the surrounding atmosphere.

[A comparative study of the in vitro biocompatibility of 2 root canal sealing cements]. / Etude comparative de la biocompatibilité in vitro de deux ciments de scellement canalaire.

The aim of this study was to evaluate the biocompatibility of radicular sealing cements with agarose cell culture. The two cements studied were Sealite and Pulp Canal Sealer with different mixing times. In the experimental conditions used the cytocompatibility of Sealite was better than that of Pulp Canal Sealer. The cytotoxicity of both products was not negligible and corresponded to those of other studies with Pulp Canal Sealer and a cement with amount similar composition to Sealite. Because theses cements are currently used with success in humans, the results of this test raise the question of extrapolation to man.