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Comparing Sentinel-5P TROPOMI NO 2 column observations with the CAMS regional air quality ensemble
No full textInternational audienceThe Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) instrument, launched in October 2017, provides unique observations of atmospheric trace gases at a high resolution of about 5 km, with near-daily global coverage, resolving individual sources like thermal powerplants, industrial complexes, fires, medium-scale towns, roads, and shipping routes. Even though Sentinel-5P (S5P) is a global mission, these datasets are especially well suited to test high-resolution regional-scale air quality (AQ) models and provide valuable input for emission inversion systems.In Europe, the Copernicus Atmosphere Monitoring Service (CAMS) has implemented an operational regional AQ forecasting capability based on an ensemble of several European models, available at a resolution of 0.1∘ × 0.1∘. In this paper, we present comparisons between TROPOMI observations of nitrogen dioxide (NO2) and the CAMS AQ forecasts and analyses of NO2. We discuss the different ways of making these comparisons and present quantitative results in the form of maps for individual days, summer and winter months, and a time series for European subregions and cities between May 2018 and March 2021.The CAMS regional products generally capture the fine-scale daily and averaged features observed by TROPOMI in much detail. In summer, the comparison shows a close agreement between TROPOMI and the CAMS ensemble NO2 tropospheric columns with a relative difference of up to 15 % for most European cities. In winter, however, we find a significant discrepancy in the column amounts over much of Europe, with relative differences up to 50 %. The possible causes for these differences are discussed, focusing on the possible impact of retrieval and modeling errors. Apart from comparisons with the CAMS ensemble, we also present results for comparisons with the individual CAMS models for selected months.Furthermore, we demonstrate the importance of the free tropospheric contribution to the estimation of the tropospheric column and thus include profile information from the CAMS configuration of the ECMWF's (European Centre for Medium-Range Weather Forecasts) global integrated model above 3 km altitude in the comparisons. We also show that replacing the global 1∘ × 1∘ a priori information in the retrieval by the regional 0.1∘ × 0.1∘ resolution profiles of CAMS leads to significant changes in the TROPOMI-retrieved tropospheric column, with typical increases at the emission hotspots up to 30 % and smaller increases or decreases elsewhere. As a spinoff, we present a new TROPOMI NO2 level 2 (L2) data product for Europe, based on the replacement of the original TM5-MP generated global a priori profile by the regional CAMS ensemble profile. This European NO2 product is compared with ground-based remote sensing measurements of six Pandora instruments of the Pandonia Global Network and nine Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instruments. As compared to the standard S5P tropospheric NO2 column data, the overall bias of the new product for all except two stations is 5 % to 12 % smaller, owing to a reduction in the multiplicative bias. Compared to the CAMS tropospheric NO2 columns, dispersion and correlation parameters with respect to the standard data are, however, superior
Operational management of cavity risks in France: background, principles, tools and perspectives
No full textInternational audienceFor nearly three decades, central government and local authorities, developers, experts and landowners involved in managing underground cavities have formulated and implemented scientific and administrative tools and methods designed to incorporate these cavities into their development and land-use management plans. The modus operandi of this operational documentation centres on a detailed, precise characterisation and understanding of cavities and their degradation mechanisms. This documentation is summarised in this article in the form of feedback that will be of interest to any individual or body keen to appropriate or adapt it to their field of activities. Several barriers or restrictions still need to be eliminated today in France: factoring the element of time into the mechanisms of cavity degradation; high-performance cavity detection methods and standardising and objectifying assessment methods. The State has organised itself in this regard by launching PAPRICAs (cavity prevention action plans) and a Cavity Roadmap. On the one hand, these aim to support local government authorities and developers as they manage cavity risks on a day-to-day basis; and, on the other hand, to coordinate research and development actions on a national scale to upgrade the tools for preventing and handling this very specific risk
Constitutive Model for Thermal Compaction of Clayey Geomaterials and Application to COx Claystone
No full textInternational audienceClay formations present very favourable conditions for the long-term containment of radioactive waste due to their low hydraulic conductivity, high radionuclide retention capacity and limited fracturing in their natural state. But it is also due to the very low permeabilities of clays and claystone that drained conditions occur only at very slow temperature increases. The response is then partially drained or undrained with the consequence of thermal pressurisation induced by the thermal gradient. Furthermore, thermo-hydro-mechanical characterisations under drained and undrained conditions carried out on samples of the Callovo-Oxfordian (COx) clay formation and in situ experiments performed by Andra at the Meuse/Haute-Marne underground research laboratory (LS M/HM) have also highlighted the strongly coupled and complex thermo-hydro-mechanical processes of this material. In particular, the volume changes of the COx claystone, subjected to a temperature rise under a constant isotropic stress close to the in situ conditions of the LS M/HM laboratory in saturated and drained conditions, were highlighted. A behaviour comparable to that of over-consolidated clays depending on temperature is then experimentally observed, i.e. thermoelastic expansion followed by thermoplastic contraction: the transition temperature between these two volumetric deformation mechanisms would correspond to the maximum temperature value undergone by the COx claystone during its geological history. Based on the extensive literature on the thermomechanical behaviour of clays and clayey soils, recent thermo-hydro-mechanical tests conducted on COx samples, as well as the database on the instantaneous behaviour of COx claystone, a constitutive model for the thermomechanical behaviour of COx claystone is proposed, then implemented in a commercial computation code. The transverse isotropic elastic and then elastoplastic instantaneous behaviour (beyond the elastic limit) up to the peak strength of the COx claystone, thermoplastic and hydrostatic compactions are taken into account. The model is first validated on triaxial and hydrostatic paths. The simulation of one of the drained hydrostatic stress heating tests performed by Braun et al. verified that the proposed model was able to reproduce the thermal compaction phenomenon highlighted by the authors and to show its operational character
A Regularised Anisotropic Elastoplastic Damage and Viscoplastic Model and Its Hydromechanical Application to a Meuse/Haute-Marne URL Drift
No full textInternational audienceClay formations are one of the options currently being considered for the storage of radioactive wastes worldwide. In France, the National Radioactive Waste Management Agency (Andra) operates the Meuse/Haute-Marne Underground Research Laboratory in the Callovo-Oxfordian (COx) clay formation to assess the feasibility and safety of an industrial radioactive waste repository. A good level of understanding of the thermo-hydromechanical behaviour of the host rock is paramount for the safety assessment. A new anisotropic elastoplastic damage and viscoplastic model is proposed to describe the hydromechanical behaviour of the COx claystone based on a large dataset of experimental evidence. The model is based on the Hoek and Brown criterion and considers recent findings of the COx hydromechanical behaviour. The key mechanisms considered are: plastic strain hardening prior to reaching the peak strength, a post-peak behaviour characterised by strain softening in the frame of continuum damage mechanics and a residual stage represented by a perfectly plastic behaviour. Time-dependent deformations are also included based on a creep model, which in this work is coupled with damage. The proposed model was implemented with a regularisation scheme based on the non-local implicit gradient in Comsol Multiphysics® with the purpose of performing THM modelling (1D, 2D and 3D) in the framework of the Cigéo project. The numerical implementation is first validated based on several simulations of creep tests at different deviatoric stress and triaxial compression tests at different confining pressures and angles between the loading direction and the bedding, α. Then, the GCS drift hydromechanical behaviour is simulated considering transverse isotropic conditions. It is shown that the model is capable of reproducing the measured peak of pore pressure in sensors near the GCS wall as well as the drift convergence. Importantly, the predicted extent of damaged zones around the drift is consistent with the in situ observations. The impact of damage on the time-dependent behaviour and the permeability was investigated numerically. It was found that the magnitude and anisotropy of drift convergence and the pore pressure drop are sensitive to this coupling and the best agreement was obtained when this effect was taken into account. Finally, the performance of the regularisation scheme is demonstrated with a set of simulations of the drift with different mesh refinements. It is concluded that the proposed model captures the key features of the hydromechanical behaviour of the COx claystone
On 2D approximations for dissolution problems in Hele-Shaw cells
No full textInternational audienceIn this paper, we study the dissolution problems occurring in laterally large 3D systems with very small dimensions along the third coordinate, such as fractures or Hele-Shaw cells. On the basis of the scale separation assumption, we apply upscaling to the 3D pore-scale model using the volume averaging method to develop 2D averaged equations. The influence of the choice of momentum equations on the accuracy of the 2D Hele-Shaw model is discussed, and we show that the results obtained using Darcy-Brinkman equations are better than those obtained using Darcy’s law, because of the consideration of the viscous boundary layer. The validity and accuracy of the resulting 2D model are assessed based on comparisons with full 3D solutions for problems corresponding to the existence of geometrical 3D features to which a simple averaging procedure along a line (i.e., the height of the gap) perpendicular to the 2D plane cannot be applied, such as the dissolution of pillars. The results show that when Péclet and Reynolds numbers exceed certain limits, 3D effects must be considered. Moreover, natural convection effects are important when the Rayleigh number is large
The upcoming European Soil Monitoring Law: An effective instrument for the protection of terrestrial ecosystems?
No full textInternational audienceSoils are a precious resource consistently placed under several threats and urgently in need of protection within a regulatory framework at the European level. Soils are central to the provision of environmental services as well as human existence on earth. The need to protect soil has been identified by several recent European strategies and fortunately, a specific European regulation for soil protection is on the way—the European Soil Monitoring Law (formerly: Soil Health Law). However, efforts need to ensure that the upcoming Soil Monitoring Law closes gaps between existing regulations for chemicals and acknowledges current European strategies for environmental protection and sustainability. This brief communication started from a fruitful discussion among SETAC Global Soils Interest Group members on a recent public consultation on the newly proposed Soil Monitoring Law of the European Commission and highlights critical points focusing on the chemical pollution of soils. We emphasize urgent needs such as the essential definition of a “healthy state” of soils; the implementation of a suitable set of indicators and quality standards for the description of physical, chemical, and biological states of soils; the enforcement of the “polluter-pays” principle; and the establishment of a Europe-wide monitoring program. Results from monitoring need to be fed back into regulatory frameworks, including the regulation of chemicals. Guidance documents for the risk assessment of chemicals are outdated and need to be updated. Finally, actions need to be taken to foster healthy soils, stop biodiversity decline, and ensure the functioning of ecosystem services for future generations. Integr Environ Assess Manag 2023;00:1–6. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC)
A roadmap to strengthen standardisation efforts in risk governance of nanotechnology
No full textInternational audienceA roadmap was developed to strengthen standardisation activities for risk governance of nanotechnology. Its baseline is the available standardised and harmonised methods for nanotechnology developed by the International Organization for Standardization (ISO), the European Committee for Standardization (CEN), and the Organisation for Economic Co-operation and Development (OECD). In order to identify improvements and needs for new themes in standardisation work, an analysis of the state-of-the-art concepts and interpretations of risk governance of nanotechnology was performed. Eleven overall areas of action were identified, each including a subset of specific topics. Themes addressed include physical chemical characterisation, assessment of hazard, exposure, risk and socio-economic factors, as well as education & training and social dialogue. This has been visualised in a standardisation roadmap spanning a timeframe of ten years and including key outcomes and highlights of the analysis. Furthermore, the roadmap indicates potential areas of action for harmonisation and standardisation (H&S) for nanomaterials and nanotechnology. It also includes an evaluation of the current level (limited, moderate, intense) of ongoing H&S activities and indicates the time horizon for the different areas of action. As the identified areas differ in their state of development, the number and type of actions varied widely amongst the different actions towards achieving standardisation. Thus, priority areas were also identified. The overall objective of these actions is to strengthen risk governance towards a safe use of nanomaterials and nano-related products. Though not explicitly addressed, risk-based legislation and policies are supported via the proposed H&S actions
Modélisation mécaniste de la dynamique de biomarqueurs chez les poissons téléostéens : lien entre exposition et effetsprécoces
No full textBiomarkers are useful tools for the diagnosis of environmental risk in aquatic ecosystems. Nevertheless, the measurement of these sub-individual markers still presents some limitations for the assessment of ecosystem health, including the characterisation of the complex dynamics of responses of these non-lethal effects as a function of time or dose, or the extrapolation of responses from one scale of biological organisation to another. One of the solutions that seems promising for characterising the dynamics of these responses from a change of scale perspective would be to integrate the biomarkers into mechanistic models that make it possible to predict these dynamics and explain the mechanisms underlying the effects. This thesis proposes to build mechanistic models of physiologically based toxicokinetics and toxicodynamics (PBTK-TD) to better characterise and understand the response dynamics of biomarkers. In this context, the problem of biomarker dynamics was divided in two. First, the "toxico-kinetic" or TK makes it possible to link the external dose, present in the environment, to the internal dose, present in the organism. Second, the "toxico-dynamic" or TD, makes the link between the internal dose and the effect. Accordingly, the first step in this thesis was to collect a set of TK and TD data in our model species, the three-spined stickleback, on a family of compounds, the bisphenols, and more specifically, BPA, BPS and BPF. These data, collected from short-term exposures (seven days of contamination and seven days of depuration) and long-term exposure (21 days), were used to compare the modulating effects of bisphenols on biomarkers. In particular, markers of innate immunity were strongly impacted by these substances. Differences in kinetics between BPA and BPS were also highlighted. Subsequently, the data collected during the exposures were used to build a physiologically based TK model (PBTK) for BPA, then a PBTK model coupled with TD sub-models (PBTK-TD) describing the dynamics of certain immunomarkers in the stickleback. Finally, a last PBTK-TD model was built to demonstrate the feasibility of this modelling approach for integrating exposure conditions more representative of those in the natural environment, i.e. for a mixture of substances. Taken as a whole, this thesis demonstrates the attractiveness of coupling the experimental approach consisting in measuring biomarkers and modelling.Les biomarqueurs sont des outils d'un grand intérêt mis en oeuvre pour établir un diagnostic de risque environnemental pour les écosystèmes aquatiques. Néanmoins, la mesure de ces marqueurs sub-individuels présentent encore certaines limitations pour l'évaluation de la qualité des écosystèmes, parmi lesquelles la caractérisation des dynamiques parfois complexes de réponses de ces effets non-léthaux en fonction du temps ou de la dose ou encore l'extrapolation des réponses d'une échelle d'organisation biologique à une autre. Une des solutions semblant prometteuses pour caractériser la dynamique de ces réponses dans une optique de changement d’échelle serait d’intégrer les biomarqueurs à des modèles mécanistiques permettant de prédire cette dynamique et d’expliquer les mécanismes sous-jacents à l’apparition des effets. Ainsi, ce travail de thèse propose de construire des modèles mécanistiques de toxicocinétique et toxicodynamie à base physiologique (PBTK-TD) pour mieux caractériser et mieux comprendre les dynamiques de réponse des biomarqueurs. Dans ce cadre, pour aborder cette problématique, une stratégie décomposée en deux sous-parties a été utilisée. Tout d’abord une étude de la partie « toxico-cinétique » ou TK a permis de relier la dose externe, présente dans l’environnement, à la dose interne, présente dans l’organisme. Puis, la partie « toxico-dynamique » ou TD a été développé pour faire le lien entre la dose interne et l’effet. Dans un premier temps, ce travail de thèse a consisté à collecter un ensemble de données TK et TD chez notre espèce-modèle, l’épinoche à trois épines, sur une famille de molécules, les bisphénols, et plus particulièrement, le BPA, le BPS et le BPF. Ces données récoltées à partir d’expositions de courte durée (sept jours de contamination et sept jours de dépuration) et d’une exposition de longue durée (21 jours) ont tout d’abord permis de comparer les effets de modulation des bisphénols sur les biomarqueurs. Les marqueurs de l’immunité innée ont notamment été fortement impactés par ces substances. Des différences de cinétique entre le BPA et le BPS ont par ailleurs été mise en avant. Par la suite, les données collectées au cours des expositions ont été utilisée pour construire un modèle TK à base physiologique (PBTK) pour le BPA, puis un modèle PBTK couplé à des sous-modèles TD (PBTK-TD) décrivant la dynamique de certains immunomarqueurs. Enfin, un dernier modèle PBTK-TD a été construit pour démontrer la faisabilité de cette démarche de modélisation pour intégrer des conditions d’exposition plus représentatives de celles du milieu naturel, i.e. pour un mélange de substances. Considéré dans son ensemble, ce travail de thèse démontre l’attractivité du couplage entre l’approche expérimentale par la mesure de biomarqueurs et la modélisation
Harmonisation in Atmospheric Dispersion Modelling Approaches to Assess Toxic Consequences in the Neighbourhood of Industrial Facilities
No full textInternational audienceIn the land use planning framework in the neighbourhood of industrial facilities, the current approach to predicting the consequences of massive toxic gas releases is generally based on Gaussian or integral models. For many years, CFD models have been more and more used in this context, in accordance with the development of high-performance computing (HPC). The present paper focuses on harmonising input data for atmospheric transport and dispersion (AT&D) modelling between the widely used approaches. First, a synthesis of the practice’s harmonisation for atmospheric dispersion modelling within the framework of risk assessment is presented. Then, these practices are applied to a large-scale INERIS ammonia experimental release. For illustration purposes, the impact of the proposed harmonisation will be evaluated using different approaches: the SLAB model, the FDS model, and the Code_Saturne model. The two main focuses of this paper are the adaptation of the source term dealing with a massive release and the wind flow modelling performance using an experimental signal for CFD model inflow. Finally, comparisons between the modelling and experimental results enable checking the consistency of these approaches and reinforce the importance of the input data harmonisation for each AT&D modelling approach
Insights into secondary organic aerosol formation from the day- and nighttime oxidation of polycyclic aromatic hydrocarbons and furans in an oxidation flow reactor
No full textInternational audienceSecondary organic aerosols (SOAs) formed by oxidation of typical precursors largely emitted by biomass burning, such as polycyclic aromatic hydrocarbons (PAHs) and furans, are still poorly characterized. We evaluated and compared the formation yields, effective density (ρ eff), absorption Ångström exponent (α), and mass absorption coefficient (MAC) of laboratory-generated SOAs from three furan compounds and four PAHs. SOAs were generated in an oxidation flow reactor under day-(OH radicals) or nighttime (NO 3 radicals) conditions. The ρ eff , formation yields, α, and MAC of the generated SOAs varied depending on the precursor and oxidant considered. The ρ eff of SOAs formed with OH and NO 3 tended to increase with particle size before reaching a "plateau", highlighting potential differences in SOA chemical composition and/or morphology, according to the particle size. Three times lower SOA formation yields were obtained with NO 3 compared with OH. The yields of PAH SOAs (18 %-76 %) were five to six times higher than those obtained for furans (3 %-12 %). While furan SOAs showed low or negligible light absorption properties, PAH SOAs had a significant impact in the UV-visible region, implying a significant contribution to atmospheric brown carbon. No increase in the MAC values was observed from OH to NO 3 oxidation processes, probably due to a low formation of nitrogen-containing chromophores with NO 3 only (without NO x). The results obtained demonstrated that PAHs are significant SOA precursors emitted by biomass burning, through both, day-and nighttime processes, and have a substantial impact on the aerosol light absorption properties