Development of quantitative detection method for mass spectrometry coupled to an infrared laser spectroscope (Picarro) to monitor in nitrogen matrix a complex gas mixture of H2 , He, CO, N2 , Ne, O2 , Ar, CO2 , H2 S, CH4 , C2 H4 , C2 H6 , C3 H6 , C3 H8 , i-C4 H10 , n-C4 H10 , and C5 H12.

RATIONALE: The deep geological repository is considered the international reference for radioactive waste management. All gas exchanges must be understood in the context of the feasibility of such a repository. The technological challenge is to continuously monitor a wide range of gaseous molecules at low concentrations in confined spaces. METHODS: A gas monitoring station, composed of two complementary analyzers, was developed: an electron impact quadrupole mass spectrometer (HPR-20 R&D Hiden Analytical) and an infrared laser spectroscope (Picarro). The spectrometer was calibrated using simple mixtures (i.e., C2 H6 in N2 ) and multiple mixtures (i.e., H2 , He, CO2 , CH4 , and O2 in N2 ) at different concentrations to correct interferences. A matrix calculation is proposed to calculate the relative concentrations. RESULTS: The method developed allows the measurement of gaseous species: light hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, and nitrogen in the same mixture. For each gas, the SDs and the limits of detection and quantification were calculated. The method was validated by comparing the concentrations of the measured gas species with the reference values of two standard gas cylinders. CONCLUSIONS: Calibration of a complex gas mixture remains a challenge because fragmentation of molecules, especially hydrocarbons, reduces the sensitivity of the method. The method developed is suitable for continuous gas monitoring in a confined environment and can be implemented to perform experiments in underground structures: galleries, microtunnels (cells), and boreholes.

The design and fabrication of beta sensor system for in situ diffusion tests in mudstone in France.

Long term in situ diffusion experiments in the Callovian-Oxfordian mudstone (France) are designed in the context of nuclear waste management. ß-emitters HTO and 36Cl radiotracers are representative of neutral and anionic species in these experiments. Studies have been carried out to design an in situ beta monitoring system in order to quantify tracer migration in the rock pore water over time. The development, design and calibration of ß-emitter radiation sensors were performed. An optimised geometry was calculated for the detection chamber of 36Cl in solution (Ø×L=30×2mm2) via Monte-Carlo N-Particle transport simulation tools. A better SNR (Signal to Noise Ratio) was obtained with YSO cylindrical crystal (Ø×L=6.5×0.5mm2). A sensitivity of 0.21cpm/Bq/mL was measured using 36Cl standards. The 36Cl detection limits were 18Bq/mL and 14.2Bq/mL after 1h and 24h of accumulation time respectively. Such beta sensors, placed 350mm from the radiotracer injection borehole, could successfully discriminate 36Cl anisotropic diffusion in various directions within 4 years. It will be tested in situ and can be adapted to other in situ experience.

Desulfosporosinus burensis sp. nov., a spore-forming, mesophilic, sulfate-reducing bacterium isolated from a deep clay environment.

A novel anaerobic, gram-positive, spore-forming, curved rod-shaped, mesophilic and sulfate-reducing bacterium was isolated from pore water collected in a borehole at -490 m in Bure (France). This strain, designated BSREI1(T), grew at temperatures between 5 °C and 30 °C (optimum 25 °C) and at a pH between 6 and 8 (optimum 7). It did not require NaCl for growth, but tolerated it up to 1.5 % NaCl. Sulfate, thiosulfate and elemental sulfur were used as terminal electron acceptors. Strain BSREI1(T) used crotonate, formate, lactate, pyruvate, fructose, glycerol and yeast extract as electron donors in the presence of sulfate. The sole quinone was MK-7. The G+C content of the genomic DNA was 43.3 mol%. Strain BSREI1(T) had the type strains of Desulfosporosinus lacus (16S rRNA gene sequence similarity of 96.83 %), Desulfosporosinus meridiei (96.31 %) and Desulfosporosinus hippei (96.16 %) as its closest phylogenetic relatives. On the basis of phylogenetic and physiological properties, strain BSREI1(T) is proposed as a representative of a novel species of the genus Desulfosporosinus, Desulfosporosinus burensis sp. nov.; the type strain is BSREI1(T) ( = DSM 24089(T) = JCM 17380(T)).

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. It was possible to analyze a quite exhaustive inventory of the small organic compounds of clay pore water without proceeding to any chemical treatment at naturally occurring concentration levels. The structural features observed were mainly acidic compounds and fatty acids as well as aldehydes and amino acids.