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Numerical analysis of the mechanical stability of salt caverns for Underground Hydrogen Storage under cyclic solicitations
No full textInternational audienc
Comportement des CAP-O dans les sols
No full textInternational audienceSur les sites pollués par des HAP (Hydrocarbures Aromatiques Polycycliques), d’autres familles de composés aromatiques polycycliques pourraient contribuer à l’impact et donc au risque pour l’Homme et l’Environnement, comme les CAP-O (Composés Aromatiques Polycycliques Oxygénés). Cependant, ils ne sont pas pris en compte actuellement car leur comportement dans les sols n’est pas suffisamment documenté. Dans le cadre de ces travaux, l’évaluation de la sorption dans le sol, au laboratoire, de HAP et de CAP-O a montré que, d’une manière générale, les mécanismes sous-jacents et les sites de sorption sont différents pour les deux familles de molécules. Ainsi, le taux de matière organique du sol n’est pas le paramètre principal contrôlant la sorption des CAP-O, contrairement aux HAP. La sorption des CAP-O serait contrôlée par des mécanismes ayant lieu à la surface des particules de sol, de type échange d’ions.. Par ailleurs, il a été montré que, d’une part, les CAP-O présentent une affinité plus faible pour la matrice solide que les HAP, et que, d’autre part, les CAP-O sont relargués préférentiellement dans l’eau par rapport aux HAP,, ce qui implique une mobilité plus importante des CAP-O dans les sols, comparativement aux HAP
Pressure-Liquefied Ammonia Jet Dispersion: Multi-Model Intercomparison Using Desert Tortoise and FLADIS Field Data
No full textInternational audienceThis paper presents the findings of an international model inter-comparison exercise that was undertaken in the period 2021-2024 to assess the performance of atmospheric dispersion models for simulating releases of pressure-liquefied ammonia. The exercise used data from ammonia field trialsdating from the 1980s and 1990s: the Desert Tortoise and the FLADIS trials. Concentration data from two arcs of sensors in the Desert Tortoise trials and three arcs of sensors in the FLADIS trials were used. Twenty-one independent modelling teams from North America and Europe participated in the exercise and provided in total twenty-seven sets of results from a range of different models, including empirically-based nomograms, integral, Gaussian puff, Lagrangian particle, and Computational Fluid Dynamics (CFD) models. The work is novel in presenting the results from such a large cohort of models,examining specifically the dispersion behaviour of ammonia. This is particularly relevant at the current time, given the growing international interest in using ammonia as a clean energy vector and shipping fuel.The study found that the agreement between model predictions and measurements (as determined by performance measures such as geometric mean bias and geometric variance) varied between different models. At any downwind distance, the range in predicted plume arc-max concentrations spanned arange of up to one or two orders of magnitude about the measurements. Several modelling teams used the same models and, in most cases, their predictions differed. Given appropriate inputs, most models generally predicted concentrations that agreed with the data within commonly-used model acceptance criteria. There was no single class of model that provided superior predictions to others; predictions from several empirically-based nomograms, integral, Gaussian puff, Lagrangian particle, and CFD models were all in close agreement with the data (as defined by the model acceptance criteria).The findings of the exercise are being used to help plan a programme of future ammonia experiments in the USA, called the Jack Rabbit III trials. The results are also useful for assessing the performance of models that may be applied to assess risks at ammonia facilities, and for emergency planning and response
Combining sensitivity analysis and scaling analysis for nuclear thermal-hydraulic studies
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Source apportionment of organic gaseous and particulate compounds using a combined positive matrix factorization approach in summer (2020) in the Paris region (France)
No full textInternational audienceGaseous and particulate organic compounds are key components of atmospheric chemistry and better understanding their composition, sources and processes is essential to limit their impacts. Source apportionment using positive matrix factorization (PMF) is customarily performed for such studies. Combining organic aerosol data with their gaseous precursors was shown to be a promising approach, however very rarely attempted so far, to refine their origins using PMF. In this study, co-located continuous proton-transfer-reaction mass spectrometer (PTR-MS) and aerosol chemical speciation monitor (ACSM) measurements were performed at the suburban SIRTA station located in the Paris region. A combined dataset using both instruments during summer (June–August 2020) was then used in an exploratory PMF analysis to investigate the sources and processes of organic compounds, particularly the influences of biogenic emissions and important photochemical reactions on the formation of secondary organic aerosol (SOA) in this period of the year. Specific parameters and evaluation procedures were needed to ensure an equivalent representation of both instruments in the PMF model. A weighing factor was applied to the PTR-MS uncertainties which was controlled and optimized based on the analysis of the modelled scaled residuals. Seven main factors were obtained, describing anthropogenic sources (hydrocarbon-like organics, cooking-like organics), primary biogenic volatile organics, nighttime VOC, oxidized organics, aged organics and a specific isoprene oxidation factor which contributed 11 % to VOC and 4 % to OA. Compared to single-instrument PMFs, more factors were obtained, notably including the cooking-like factor which is not usually resolved using only ACSM data. This method also showed a better mathematical performance for the PTR-MS variables (mean absolute scaled residuals lower for the combined PMF (11.2) than for the PTR-MS-only PMF (38.2)) and a better separation of the factors for the ACSM variables in the combined PMF
Simulating synergism or antagonism in binary mixtures with different modeling approaches – A case study focused on the effect of disinfection by-products on algal growth
No full textInternational audienceThis paper aims to test several modeling approaches for predicting toxicity of binary mixtures with potential synergy and antagonism. The approach based on the construction of isoboles was first tested and criticized. In contrast to conventional approaches, and in order to be mathematically consistent with the additivity assumptions, non-linear isoboles have been constructed. This approach was compared with that proposed by Minto et al. (2000), which measures deviations from additivity by considering standardized variables and which considers the entire Hill concentration-response curves. The selected models were tested on a case study related to chlorine-based disinfectant by-products (DBPs), using experimental data describing the effect of five DBPs (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid and 1,1-dichloropropan-2-one) on a unicellular green algae Raphidocelis subcapitata. The approach based on the construction of isoboles has shown its limitations. Indeed, in cases where the individual substances involved have different slopes in terms of their Hill concentration-effect relationships, the so-called zone of indetermination can be large. Furthermore, conclusions drawn from isoboles based on EC50s or EC20s may not be consistent. Minto's approach makes it possible to construct interaction indicators that consider the entire Hill concentration-response curve. Response surfaces can be constructed to visualize the areas of concentration of the two substances involved that maximize the interaction effects
Reduction in Brake Wear Emissions with Cr2O3 and WC-CoCr Coatings for Cast Iron Discs
No full textInternational audienceThe present contribution showcases the potential brake emission reduction with Cr2O3 (chromium oxide) and WC-CoCr (tungsten carbide–chromium–cobalt) rotor coatings, as realized in our joint public–private research consortium. Particulate matter (PM) emissions from automotive braking systems have been characterized using a pin-on-disc tribometer equipped with particle measurement devices: a CPC (Condensation Particle Counter), an APS (Aerodynamic Particle Sizer), an SMPS (Scanning Mobility Particle Sizer), and a PM2.5 sampling unit. Brake pad samples made from the same low-steel friction material were tested against a grey flake cast iron disc and two types of custom coated discs: a Cr2O3-coated disc and a WC-CoCr-coated disc. The friction pairs were investigated at a constant contact pressure of 1.2 MPa while the sliding velocity varied during the test, starting with 25 sequences at 3.6 m/s, followed by 19 sequences at 6.1 m/s, and finishing with 6 sequences at 11.2 m/s. The test results show encouraging 64% to 84% reductions in particle number (PN) emissions between 4 nm and 3 µm and 84% to 95% reductions in mass emissions (PM2.5) thanks to the respective coated discs. SEM-EDXS (Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy) analyses show that the hardness and roughness of the discs, the chemical reactivity (oxidation), and the abrasiveness of the three friction pairs are parameters that might explain this reduction in emission
Workshop report: scoping for the development of a proposal for an OECD guidance document on fish vitellogenin assessment
No full textInternational audienceThis report summarizes discussions of an international workshop in May 2024, aiming to scope the development needs of a proposal for an Organisation for Economic Cooperation and Development (OECD) Guidance Document on vitellogenin (VTG) analysis and assessment. Vitellogenin, an egg-yolk precursor protein in oviparous species, is an informative marker of possible chemical-induced endocrine activity (particularly estrogenicity). Vitellogenin measurement is included in several standardized test guidelines published by the OECD and USEPA for the assessment of endocrine activity of chemicals in fish (and one in amphibians). However, in vivo VTG data across and within fish species can be highly variable and influenced by both technical and biological factors, affecting the reliability and interpretation of results. This poses a challenge for regulatory decision-making and can trigger potentially unnecessary vertebrate studies or prevent necessary further investigations. The workshop brought together 42 experts from different sectors and geographies to discuss three key aspects regarding VTG assessment: (1) technical/laboratory factors and VTG quantification, (2) data handling and statistics, and (3) interpreting the biological relevance of VTG responses. The workshop participants discussed the development and needs of a guidance document to provide harmonized recommendations, best practices, quality assurance criteria, and minimum reporting standards for VTG assessment in regulatory studies across the different test guidelines. Several areas were identified where further work and discussion are needed to inform on the development of the guidance document, such as the use of historical control data, the identification of potential outliers, the presentation of data, and analysis of case study examples. Provision of such a guidance document will further support the use of VTG as a relevant marker for a key aspect of endocrine activity assessment for regulatory decision-making. A formal project was subsequently accepted into the OECD Test Guideline workplan in April 2025
Endocrine effects of Imazalil on aromatase expression, vitellogenesis and ovarian histology using cyp19a1a-eGFP-casper transgenic zebrafish
No full textInternational audienceConsidering the hazards and risks posed by endocrine disrupting chemicals (EDC) to organisms, there is a need to study their effects. To that end, transgenic fish are powerful models that can provide mechanistic information regarding the endocrine activity of test chemicals. In this study, we used a newly developed transgenic zebrafish line (cyp19a1a-eGFP-casper) in the OECD 21-day fish assay (OECD TG 230) to provide additional mechanistic insight on Imazalil (IMZ; 1.9; 9.9 and 140.7 μg/L). After 21 days of exposure to IMZ, the circulating concentrations of 17-β-estradiol (E2) and vitellogenin decreased in females, reflecting the aromatase activities inhibition. Exposure to 140.7 μg/L of IMZ for 21 days also resulted in a change in the proportion of the different oocyte stages in the ovaries, with an accumulation of large oocytes in exposed females. In addition to the classical endpoints, in vivo GFP fluorescence was quantified in the ovaries during the time course of the exposure to follow gonadal aromatase expression. After seven days of exposure, ovarian aromatase expression increased in females exposed to medium and high concentrations of IMZ, persisting over the 21-day of exposure in fish from the highest concentration group and reflecting a compensatory response to the aromatase enzymatic activities inhibition. Results from the present study provided valuable information on the mode of action and the effects of IMZ in zebrafish. Transgenic zebrafish exposure to IMZ caused a cascade of responses consistent with effects reported for wild-type fish exposed to azole fungicides, both qualitatively and quantitatively. The cyp19a1a-eGFP (-casper) transgenic zebrafish lines, allowed in vivo monitoring of gonadal aromatase expression in a time- and concentration-dependent manner thereby demonstrating their relevance to provide complementary mechanistic information on aromatase in regulatory assays such as OECD TG 230
Morbidity and its economic impacts attributable to long-term exposure to fine particles in France
No full textInternational audienceTo the best of our knowledge, this study provides the first broad-scale, nation-wide analysis of a set of long-term morbidity effects of air pollution and assessment of their economic impacts in France.We used the Health Risk Assessment method and the latest concentration-response functions, both from the World Health Organization (WHO). The economic analysis - a comprehensive cost of illness approach - includes direct health and non-health care costs, indirect and intangible costs.Beyond its impact on mortality, the study shows that lowering PM2.5 levels over time in France would produce substantial health and well-being benefits by reducing the onset of several diseases.Documented here as attributable to long-term exposure to anthropogenic PM2.5 on average in a given year are 20 % of new cases of respiratory diseases in children and 7–11 % of new cases of respiratory, cardiovascular or metabolic diseases in adults. We also show that reducing PM2.5 concentrations to WHO’s air-quality guideline (AQG) levels would reduce morbidity attributable to this anthropogenic pollution by up to 75 %. Finally, if average PM2.5 levels were reduced to their anthropogenic thresholds, annual benefits to health and well-being for the diseases studied would total €201812.88 billion. Given these findings, complying with WHO AQG would reduce mortality and morbidity attributable to air pollution in France and help achieve the objective of WHO’s Global Action Plan for the Prevention and Control of Noncommunicable Diseases, namely a one-third reduction in the risk of dying from a chronic disease by 2030