Influence of the thermophoresis on aerosol deposition on warm urban surfaces

International audienceIn the case of an accidental or chronic atmospheric pollution by a nuclear plant, aerosols' deposition transfer coefficients must be known. A major issue is to determine the impact of aerosols contained in the radioactive plume on urban areas with the smallest uncertainties

Kimasomaso : a weekly radio programme about sexual health

Contents: Transcript in English; audio in mp3 format and in Swahili languageKimasomaso is co-produced and broadcast by the BBC Swahili Service. The programme is recorded, mixed and edited in Nairobi weekly.Medical experts from the East Africa region are in the studio to answer questions sent in by Kimasomaso listeners. The questions touch on issues like ectopic pregnancies and masturbation

Influence of the thermophoresis on aerosol deposition on warm urban surfaces

International audienceIn the case of an accidental or chronic atmospheric pollution by a nuclear plant, aerosols' deposition transfer coefficients must be known. A major issue is to determine the impact of aerosols contained in the radioactive plume on urban areas with the smallest uncertainties

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

Développement de nouvelles méthodes d’analyse de l’iode 129 à bas niveau appliquées à la compréhension des mécanismes de transfert de l’iode dans l’environnement

National audienceL’iode est un halogène volatil [1] possédant 37 isotopes, dont l’iode 129, le radio-isotope ayant la période la plus longue (16,1 millions d’années). Ce radionucléide est rejeté de façon chronique et réglementée par les usines de retraitement du combustible nucléaire usé, comme Orano La Hague, dans l’atmosphère et dans environnement marin. L’iode étant facilement absorbé par la thyroïde [2], il est important de le quantifier et donc d’évaluer la réémission de l’iode de l’environnement marin vers le littoral par émission de gaz ou d’aérosol. L’iode 129 est souvent analysé par spectrométrie gamma mais les limites de détections obtenues avec cette technique sont supérieures aux activités potentiellement mesurables dans l’environnement. La spectrométrie de masse permettrait d’atteindre les niveaux environnementaux et de mesurer le rapport isotopique 129I/127I, contrairement à la spectrométrie gamma. La spectrométrie de masse par accélérateur (AMS) présente une excellente sensibilité et sélectivité [3]. Cependant, cette technique est trop coûteuse pour être mise en place dans des laboratoires pour des analyses de routine, il n’existe d’ailleurs que 22 AMS dans le monde qui permettent la mesure de 129I. La spectrométrie de masse couplée à un plasma inductif (ICP-MS) [4] est une excellente alternative à cette technique, et plus spécifiquement l’ICP-MS/MS. Cette technique présente de nombreux avantages notamment sa rapidité, son principe de fonctionnement indépendant de l’énergie d’émission et la possibilité de quantifier le rapport isotopique 129I/127I.Cependant, les mesures peuvent être compliquées due aux interférences spectrales et non spectrales. La première contrainte est liée aux effets mémoires [5], accentués par l’extrême volatilité de l’iode et ses nombreuses formes. Pour y remédier, différents milieux de mesure et de rinçage du système d’introduction ont été comparés et un milieu optimal a été retenu. La seconde contrainte est liée à la présence d’interférents. Ces interférents peuvent être isobariques, essentiellement le 129Xe+ qui est présent comme impureté dans l’argon. Ils peuvent également être moléculaires dû par exemple à 127IH2+. Grâce à un traitement chimique avant la mesure, les interférents polyatomiques ont pu être éliminés grâce à une séparation en phase solide (SPE).L’interférence isobarique due au xénon a pu être supprimée lors de l’étape de mesure en injectant de l’oxygène dans la cellule de collision/réaction. La nouvelle méthode mise en place permet donc la mesure de l’iode 129 en direct ou après un traitement chimique. La durée du traitement chimique a été diminuée à 40 min, et une prise d’essai jusqu’à 1 L d’échantillon peut être traitée. Un gain en sensibilité jusqu’à un facteur 200 a été observé et a permis d’estimer la limite de détection à 8 mBq.L-1 et à 0,15 mBq.L-1 après traitement chimique, ce qui est 100 fois inférieur à certaines méthodes actuelles basées sur le comptage nucléaire.Références[1]T. Kaiho in Iodine Chemistry and Applications, John Wiley & Sons, Ltd, 2014, 7–14.[2]K. Markou, N. Georgopoulos, V. Kyriazopoulou, A. g. Vagenakis, Thyroid, 11 (2001) 501–510.[3]M. Arnold, G. Aumaître, D.L. Bourlès, K. Keddadouche, R. Braucher, R. Finkel, E. Nottoli, L. Benedetti, S. Merchel, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 294 (2013) 24–28.[4]G. Yang, H. Tazoe, M. Yamada, Analytica Chimica Acta, 1008 (2018) 66–73.[5]Y.-K. Hsieh, T. Wang, L.-W. Jian, W.-H. Chen, T. Tsuey-Lin, C.-F. Wang, Radiochimica Acta, 102 (2014)

Measurement and modelling of gaseous elemental iodine (I2) dry deposition velocity on grass in the environment

International audienceAssessing the impact of radioactive iodine on humans subsequent to a nuclear accident requires a better understanding of its behaviour in the environment. An original approach aimed at developing a model constrained by data collected during experimental campaigns has been developed. These experimental campaigns, named MIOSEC 2 and MIOSEC 3 respectively, were conducted in the middle of grassland. They are based on emissions of gaseous elemental iodine (I2) into the atmosphere above the grassland to determine the dry deposition velocities of iodine on the grass and to model these velocities as a function of the environmental conditions, particularly wind friction velocity, sensible heat flux, and stomatal resistance. The measured dry deposition velocities were between 0.02 and 0.49 cm s-1 during MIOSEC 2, varying by more than one order of magnitude, and between 0.48 and 1.25 cm s−1 during MIOSEC 3. The dry deposition model for iodine developed as a result of these experiments relies on the micrometeorological characteristics of the atmospheric surface layer, the pertinent physical and chemical properties of the iodine and the surface properties of the grass; all these parameters were measured at the time of the experiments. Given the experimental conditions, the modelled dry deposition velocities varied between 0.11 and 0.51 cm s−1 during MIOSEC 2 and between 0.31 and 1.6 cm s−1 during MIOSEC 3. The dry deposition model for iodine indicates that the variations in deposition velocity are induced by the mechanical turbulence, since there is significant correlation between the dry deposition velocities of iodine and the wind friction velocities on grass. The model also shows that the higher deposition velocity values during MIOSEC 3 are due to the fact that the stomata were more open during the experiments. There is also significant correlation between the experimental results and modelled values both for MIOSEC 2 (R2 = 0.61) and for MIOSEC 3 (R2 = 0.71)

Dispersion and deposition of gas and aerosol particles in urban environment: examples of in situ experiments for predictive model validation

International audienceIn terms of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric gas and particle dispersion, as well as particle-bound radionuclide deposition flux on ground surfaces is essential to assess risks on both populations and environments. Protecting urban environments and populations living in the vicinity is a major issue. However, urban areas are among the least studied environments due to their complexity in terms of dynamics, thermal properties and spatial heterogeneity. Our work focus on how in situ experiments help constraining predictive models of atmospheric gas and particle dispersion, and particle-bound radionuclide deposition flux on various spatiotemporal scales in urban environments. Examples of past and ongoing studies will be presented. Our in situ experiments use tracing gas (SF6 and He), tracing particles (fluorescein) or natural radionuclides already present in environment such as 7Be. Results will be discussed during the conference

Development of new low-level iodine 129 analysis method applied to the understanding of iodine’s transfer mechanisms in the environment

International audience129I is chronically and regulatory released by fuel reprocessing plants e.g. Sellafield (UK) and ORANO La Hague (France) and also released in the atmosphere by nuclear power plants during normal operation process or in case of an accident. Iodine 129 is released by reprocessing plants not only in the atmosphere but also into the marine environment. The objective of this study is to develop a new 129I quantification method in order to evaluate for the first time the re-emission of iodine from the marine environment to the coast by gas or aerosol emission against direct atmospheric releases. To achieve this objective, two High Volume Sampler (HVS) are installed 2 km north of ORANO La Hague and are surrounded by the ocean except the east side. These HVS are connected to a proportional counter (LB134, Berthold). When 85Kr is detected, the first HVS is automatically started and the collected iodine is attributed to the reprocessing plant. When 85Kr is not detected anymore, the other HVS is started and the collected iodine is mainly attributed to reemission from marine environment. HVS contains filters to trap aerosols and coal cartridges to trap gaseous iodine. Filters and coal were selected after a study to be compatible with the analytical procedure. In fact, a new analytical method has been developed to analyse 129I and 129I/127I in these complex samples. ICP-MS measurement following a chemical treatment is an excellent alternative to AMS for the determination of 129I and 129I/127I isotopic ratio. ICP-MS technique allows reaching LOD of ~ 0,3 mBq/L for 129I and 10-8 for 129I/127I (Honda et al., 2018). Difficulties during purification and measurement are related to the extreme volatility of iodine and to its multiple oxidation degrees. Spectral interferences are mainly due to the isobaric 129Xe+ , present as impurity in the Argon gas and to polyatomic interferences generated by 127IH2 + , 127ID+ , 97MoO2 + 113CdO+ , 113InO+ , 115In14N + and 89Y 40Ar+ (Ežerinskis et al., 2014). Non-spectral interferences are related to the matrix and memory effects. In the presented work, the ICP-MS measurements were performed using an ICP-MS/MS (8900 Agilent® ). The medium was meticulously studied to minimize spectral and non-spectral interferences. The octopole collision/reaction cell and the two quadrupole mass filters allowed minimizing polyatomic interferences. The isobaric interference due to 129Xe was eliminated after studying different reaction gas (O2, N2O and CO2) with on-mass and mass-shift detection modes. Solid phase extraction was developed and adapted to ICP-MS measurement medium. The new method, therefore, allows the measurement of iodine 129 either directly or after chemical treatment. The chemical treatment time has been reduced to 40 min. This step increased the test sample up to 1 L. A gain in sensitivity up to a factor 200 was observed and allowed reducing the detection limit up to 0,06 mBq/L after chemical treatment, which is 100 times lower than some current method

Development of new low-level iodine 129 analysis method applied to the understanding of iodine’s transfer mechanisms in the environment

International audience129I is chronically and regulatory released by fuel reprocessing plants e.g. Sellafield (UK) and ORANO La Hague (France) and also released in the atmosphere by nuclear power plants during normal operation process or in case of an accident. Iodine 129 is released by reprocessing plants not only in the atmosphere but also into the marine environment. The objective of this study is to develop a new 129I quantification method in order to evaluate for the first time the re-emission of iodine from the marine environment to the coast by gas or aerosol emission against direct atmospheric releases. To achieve this objective, two High Volume Sampler (HVS) are installed 2 km north of ORANO La Hague and are surrounded by the ocean except the east side. These HVS are connected to a proportional counter (LB134, Berthold). When 85Kr is detected, the first HVS is automatically started and the collected iodine is attributed to the reprocessing plant. When 85Kr is not detected anymore, the other HVS is started and the collected iodine is mainly attributed to reemission from marine environment. HVS contains filters to trap aerosols and coal cartridges to trap gaseous iodine. Filters and coal were selected after a study to be compatible with the analytical procedure. In fact, a new analytical method has been developed to analyse 129I and 129I/127I in these complex samples. ICP-MS measurement following a chemical treatment is an excellent alternative to AMS for the determination of 129I and 129I/127I isotopic ratio. ICP-MS technique allows reaching LOD of ~ 0,3 mBq/L for 129I and 10-8 for 129I/127I (Honda et al., 2018). Difficulties during purification and measurement are related to the extreme volatility of iodine and to its multiple oxidation degrees. Spectral interferences are mainly due to the isobaric 129Xe+ , present as impurity in the Argon gas and to polyatomic interferences generated by 127IH2 + , 127ID+ , 97MoO2 + 113CdO+ , 113InO+ , 115In14N + and 89Y 40Ar+ (Ežerinskis et al., 2014). Non-spectral interferences are related to the matrix and memory effects. In the presented work, the ICP-MS measurements were performed using an ICP-MS/MS (8900 Agilent® ). The medium was meticulously studied to minimize spectral and non-spectral interferences. The octopole collision/reaction cell and the two quadrupole mass filters allowed minimizing polyatomic interferences. The isobaric interference due to 129Xe was eliminated after studying different reaction gas (O2, N2O and CO2) with on-mass and mass-shift detection modes. Solid phase extraction was developed and adapted to ICP-MS measurement medium. The new method, therefore, allows the measurement of iodine 129 either directly or after chemical treatment. The chemical treatment time has been reduced to 40 min. This step increased the test sample up to 1 L. A gain in sensitivity up to a factor 200 was observed and allowed reducing the detection limit up to 0,06 mBq/L after chemical treatment, which is 100 times lower than some current method

Quantification de l'iode 129 et du rapport isotopique 129I/127I par ICP-MS triple quadripolaire

International audienceL’iode est un halogène volatil1 possédant 37 isotopes, dont l’iode 129, le radio-isotope ayant la période la plus longue (16,1 millions d’années). Ce radionucléide est rejeté de façon chronique et réglementée par les usines de retraitement du combustible nucléaire usé, comme Orano La Hague, dans l’atmosphère et dans environnement marin. L’iode 129 est souvent analysé par spectrométrie gamma mais les limites de détections obtenues avec cette technique peuvent être supérieures aux activités potentiellement mesurables dans l’environnement. La spectrométrie de masse permettrait d’atteindre les niveaux environnementaux et de mesurer le rapport isotopique 129I/127I, contrairement à la spectrométrie gamma. La spectrométrie de masse par accélérateur (AMS) présente une excellente sensibilité et sélectivité3 mais cette technique n’est pas accessible à tous les laboratoires. L’ICP-MS4 est une excellente alternative à cette technique. Celle-ci présente de nombreux avantages notamment sa rapidité, son principe de fonctionnement indépendant de l’énergie d’émission et la possibilité de quantifier le rapport isotopique 129I/127I.Cependant, des difficultés peuvent être rencontrées lors de la mesure en raison des interférences spectrales et non spectrales. La première contrainte est liée aux effets mémoires 5, accentués par l’extrême volatilité de l’iode et ses nombreuses formes. Pour y remédier, différents milieux de mesure et de rinçage du système d’introduction ont été comparés et un milieu optimal a été retenu. La seconde contrainte est liée à la présence d’interférents. Ces interférents peuvent être polyatomiques (127IH2+, 127ID+, 97MoO2+, 113CdO+, 113InO+,115In14N+ et 89Y40Ar+) ou isobariques, essentiellement 129Xe+ qui est présent comme impureté dans l’argon. Afin de s’en affranchir, des gaz avec des potentiels d’oxydation différents (CO2, N2O et O2) ont été insérés dans la cellule de collision/réaction d’un ICP-MS/MS. La configuration permettant d’obtenir les meilleures performances a été sélectionnée après une optimisation des paramètres de mesure, aux modes on-mass et mass-shift. Pour améliorer davantage la limite de détection, un traitement chimique préalable à la mesure a été développé et adapté à la mesure par ICP-MS.La nouvelle méthode mise en place permet donc la mesure de l’iode 129 en direct ou après un traitement chimique. La durée de l’ensemble des étapes est d’une journée et une large prise d’essai peut être traitée. Un gain en sensibilité jusqu’à un facteur 200 a été observé et a permis d’estimer la limite de détection de 129I à 1,26 ng.L-1 (8 mBq.L-1) et à 0,02 ng.L-1 (0,15 mBq.L-1) après traitement chimique, ce qui est 100 fois inférieur à certaines méthodes actuelles basées sur le comptage nucléaire