Geomagnetic, cosmogenic and climatic changes across the last geomagnetic reversal from Equatorial Indian Ocean sediments

cited By 13International audienceno abstrac

Revised phosphate-water fractionation equation reassessing paleotemperatures derived from biogenic apatite.

8 pagesInternational audienceOxygen isotopes of biogenic apatite have been widely used to reassess anomalous temperatures inferred from oxygen isotope ratios of ancient biogenic calcite, more prone to diagenetic alteration. However, recent studies have highlighted that oxygen isotope ratios of biogenic apatite differ dependent on used analytical techniques. This questions the applicability of the phosphate–water fractionation equations established over 25 years ago using earlier analytical techniques to more recently acquired data. In this work we present a new phosphate–water oxygen isotope fractionation equation based on oxygen isotopes determined on fish raised in aquariums at controlled temperature and with monitored water oxygen isotope composition. The new equation reveals a similar slope, but an offset of about +2‰ to the earlier published equations. This work has major implications for paleoclimatic reconstructions using oxygen isotopes of biogenic apatite since calculated temperatures have been underestimated by about 4 to 8 °C depending on applied techniques and standardization of the analyses

Reply on Comment by Longinelli (2013) on a revised phosphate-water fractionation equation.

3 pagesInternational audienc

Characterisation of CIME, an experimental chamber for simulating interactions between materials of the cultural heritage and the environment

International audienceAn approach consisting in combining in situ and laboratory experiments is often favoured for investigating the mechanisms involved in the weathering of the materials of the cultural heritage. However, the realistic simulation in the laboratory of the environmental conditions ruling the interactions of atmospheric compounds with materials is a very complex task. The aim of this work is to characterise CIME, a new chamber specially built to simulate the interactions between materials of the cultural heritage and the environment. The originality of this instrument is that beside the usual climatic parameters (temperature, relative humidity, solar radiation) and gaseous pollutants, it also allows the controlled injection of different types of particulate matter such as terrigenous, marine and anthropogenic. Therefore, varied realistic atmospheric environments (marine or urban) can be easily simulated within CIME. In addition to the technical description of CIME, this paper shows the first results obtained by the impact of gaseous pollutants on non-durable glass, bronze and limestone. The first experiments for the deposition of different particles (calcite, clays, soot and halite) are also presented

Airborne Release Fraction of Dissolved Materials During the Combustion of Liquids Representative of Nuclear Waste Treatment Process

International audienceExperimental results are reported on the airborne release, under fire conditions, of hazardous materials dissolved in mixture of organic solvents (tributylphosphate TBP and hydrogenated tetrapropylene HTP) representatives of the nuclear fuel recycling process. Cerium and ruthenium have been considered respectively as stable and volatile fission products and which could be eventually released as airborne particles during thermal degradation of contaminated and inflammable liquids. Airborne release fractions (ARF) and their experimental uncertainties have been determined. Considering fire involving contaminated organic solvents, higher ARF are reported for ruthenium Ru(+III) (0.99 +/-1.20 %) in comparison with cerium (0.22 +/-0.31 % and 0.20 +/-0.28 % for Ce(+III) and Ce(+IV), respectively). This discrepancy is partially due to the volatility of ruthenium formed under these conditions. Considering configurations involving an aqueous nitric acid phase placed below contaminated solvents, boiling of this phase enhances the release of contaminant materials, 1.78 +/-1.06 % and 1.01 +/-1.31 % for Ce(+III) and Ce(+IV), respectively and 12.41 +/-29.45 % for Ru(+III). Analysis of size distribution, morphology and chemical composition of released particles and droplets emitted during HTP/TBP bubble collapse are reported, highlighting the contribution of bubble bursting at the solvent surface to airborne release