Yields of CO2CO_2 formation and scissions at ether bonds along nuclear tracks in CR-39

Yields of $CO_2$ gas formation and the scissions at ether bonds have been determined along ion tracks in CR-39 plastics. Thin CR-39 films with 15 \mum thickness were irradiated by 130 MeV C-13 ions at 45\degres incidence up to $10{13}$ ions/cm$^2$, and then IR spectra were obtained without removing the samples from the vacuum chamber. The absorption band for $CO_2$ was observed clearly around 2338 cm$^{-1}$, whose absorbance increased proportional to the fluence up to $3\times10^{12}$ ions/cm$^2$ and then saturated. Using a mole absorption coefficient for gaseous $CO_2$, the yield along the track was determined to be 7200 $CO_2$ molecules/\mum. This means that the $G$-value of $CO_2$ formation in CR-39 was about 3.6 molecules/100 eV. The scission yield of ether bonds was found to be 11,000 scissions/\mum. This corresponds to a $G$-value of about 5.5 scissions/100 eV. These values suggest that the parts between the two carbonate ester bonds in each repeat unit of CR-39 can be segmented into two $CO_2$ and other small molecules along the nuclear tracks

Caractérisation structurelle et optique des couches épaisses et complexes par interférométrie polychromatique

National audienc

Sensors and related devices for IoT, medicine and s mart-living

International audienceThe evolutions of medicine covering genome to exposome (i.e. all types of environmental exposures) [1] opened new paths of development for electronics including low power sensors. Additionally, the frontiers for new generations of sensors between smart-living, environment and health are fading. In this paper, we will give examples based on our developments in emerging autonomous sensors and medical devices, and show how they can be included in our daily lif

Investigation of Sodium Sulfate Additions into Cryolite-Alumina Melts

In the Hall-Héroult process, sulfur impurities may not only emit harmful gases but also reduce current efficiency. To better understand this process, the behaviour of sulfur compounds in a cryolite-alumina melt at 1253 K (980 °C) was investigated in a laboratory cell. Sodium sulfate (Na2SO4) was added into the molten bath as a sulfur source. Furnace off-gases were passed through a mass spectrometer for qualitative assessment. The stability of sodium sulfate in the cryolite melt was found to depend on the presence of carbon (t1/2 = 116 min) and carbon aluminium (t1/2 = 29 min). It changed dramatically during electrolysis (t1/2 = 5-8 min). Detected sulfurous gases included SO2, COS, CS2, and H2S.submittedVersio

Diagnostiquer et réduire à la source les micropolluants -Retour d'expérience du projet Regard (Bordeaux Métropole)

Micropollutants (MPs) represent an important environmental and health issue. Identifying their sources and then reducing their discharges is the strategy used in France to fight against water pollution. This is also the approach implemented in the Regard project (Reduction and management of micropollutants in the Bordeaux metropolis). The first phase of the project aimed to carry out a territorial, global and integrated diagnosis combining both chemical and biological analyses of the natural environment and the sewerage network from the discharge points (wastewater treatment plant, separate stormwater overflow, by-pass) to the emission sources (domestic, industrial, hospital and stormwater). In addition, a social characterization of the sources was carried out in order to understand the practices, products and uses at the origin of MP discharges and to identify decisive actions to reduce these discharges. The strengths of this diagnostic assessment are the complementary of various approaches (engineering and social sciences, chemical and biological analyses, wastewater and stormwater studies) and the large number of sampling sites. The second phase of the project was to ensure the implementation of reduction actions to test and evaluate their impacts from the environmental (effectiveness in reducing the quantity, diversity and effect of MPs), social (appropriation and satisfaction of solutions) and economic (to guide public action) points of view. The best results have been achieved with (i) the “water families challenge” action on the domestic source, (ii) mechanical rat control actions, defoaming of tennis courts and grassing of cemeteries for the community source, and (iii) the treatment action of separate stormwater in real conditions on a pilot scale. This feedback on what has been achieved to date should help communities interested to implement such an approach in order to avoid the same “mistakes” and, on the contrary, to directly implement actions that give significant reduction results.Les micropolluants (MP) représentent un enjeu environnemental et sanitaire important. Identifier leurs sources pour ensuite réduire leurs rejets est la stratégie privilégiée au niveau français pour lutter contre cette pollution. C’est aussi la démarche qui a été mise en oeuvre dans le projet Regard (réduction et gestion des micropolluants sur la métropole bordelaise). La première phase du projet correspondait ainsi à la réalisation d’un diagnostic territorial, global et intégré couplant à la fois des analyses chimiques et biologiques du milieu naturel et du réseau d’assainissement depuis les points de rejets (station de traitement des eaux usées, exutoires pluviaux, by-pass) jusqu’aux sources d’émission (domestique, industrielle, hospitalière et pluviale). En complément, une caractérisation sociale dessources a été faite afin de comprendre les pratiques, les produits et les usages à l’origine des rejets de MP et d’identifier des leviers d’action pour réduire ces rejets. Les points forts de ce diagnostic sont la complémentarité des approches (sciences de l’ingénieur et sciences sociales, analyses chimiques et biologiques, étude des eaux usées et pluviales) et le nombre important de sites d’étude. La seconde phase du projet correspondait à la mise en oeuvre d’actions de réduction pour les tester et les évaluer du point de vue environnemental (efficacité pour réduire la quantité, la diversité et l’effet des MP), social (appropriation et satisfaction vis-à-vis des solutions) et économique (aide à l’orientation de l’action publique). Les actions ayant eu les meilleurs résultats sont (i) l’action « Familles EAU Défi » sur la source domestique, (ii) les actions de dératisation mécanique, de démoussage des terrains de tennis et d’enherbement des cimetières pour la source collectivité et (iii) l’action de traitement des eaux pluviales strictes en conditions réelles à l’échelle d’un pilote. Le présent retour d’expérience sur ce qui a été fait doit aider les collectivités qui souhaiteraient effectuer une telle démarche à ne pas commettre les mêmes « erreurs » et, au contraire, à mettre en oeuvre directement les actions qui donnent des résultats satisfaisants