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Exposure to Nanoparticles in Thermal Spraying — Vigilance Towards the Operator and the Outside Environment
No full textInternational audienceAbstract This paper presents the results of an emission study on plasma spraying equipment and processes. Various measurements and samples were taken outside the spraying booth, at the operator level, and in the suction ducts upstream and downstream of the filtration equipment, creating a detailed profile of the aerosol emitted by the injection of NiAl powder in the plasma jet. The results show the existence of two families of particles, one ranging in size from 0.5 to 20 µm, the other of nanometric proportions. Concentrations of the larger particles were in the range of 600 cm-3 in the booth. As for submicron particles, concentrations of up to 107 cm-3 were observed but decreased significantly at the outlet of the filter system. The aerosol samples examined were dominated by a nanometric background of aggregates made up of oxidized nickel particles. Aggregates up to 100 nm in size, consisting of finer particles in the 5-20 nm size range, were found in high concentrations upstream of the filtration system. G
Meteorology-driven variability of air pollution (PM1) revealed with explainable machine learning
No full textInternational audienceAir pollution, in particular high concentrations of particulate matter smaller than 1 µm in diameter (PM1), continues to be a major health problem, and meteorology is known to substantially influence atmospheric PM concentrations. However, the scientific understanding of the ways in which complex interactions of meteorological factors lead to high-pollution episodes is inconclusive. In this study, a novel, data-driven approach based on empirical relationships is used to characterize and better understand the meteorology-driven component of PM1 variability. A tree-based machine learning model is set up to reproduce concentrations of speciated PM1 at a suburban site southwest of Paris, France, using meteorological variables as input features. The model is able to capture the majority of occurring variance of mean afternoon total PM1 concentrations (coefficient of determination (R2) of 0.58), with model performance depending on the individual PM1 species predicted. Based on the models, an isolation and quantification of individual, season-specific meteorological influences for process understanding at the measurement site is achieved using SHapley Additive exPlanation (SHAP) regression values. Model results suggest that winter pollution episodes are often driven by a combination of shallow mixed layer heights (MLHs), low temperatures, low wind speeds, or inflow from northeastern wind directions. Contributions of MLHs to the winter pollution episodes are quantified to be on average ∼5 µg/m3 for MLHs below <500 m a.g.l. Temperatures below freezing initiate formation processes and increase local emissions related to residential heating, amounting to a contribution to predicted PM1 concentrations of as much as ∼9 µg/m3. Northeasterly winds are found to contribute ∼5 µg/m3 to predicted PM1 concentrations (combined effects of u- and v-wind components), by advecting particles from source regions, e.g. central Europe or the Paris region. Meteorological drivers of unusually high PM1 concentrations in summer are temperatures above ∼25 ∘C (contributions of up to ∼2.5 µg/m3), dry spells of several days (maximum contributions of ∼1.5 µg/m3), and wind speeds below ∼2 m/s (maximum contributions of ∼3 µg/m3), which cause a lack of dispersion. High-resolution case studies are conducted showing a large variability of processes that can lead to high-pollution episodes. The identification of these meteorological conditions that increase air pollution could help policy makers to adapt policy measures, issue warnings to the public, or assess the effectiveness of air pollution measures
French Guide to Conformity Assessment and Certification of Hydrogen Systems
No full textInternational audienceHydrogen as energy carrier is referenced in French and European political strategies to realize the transition to low-carbon energy. In 2020 in France the government was launching a major investment plan amounting to 7.2 billion euros until 2030, to support the deployment of large-scale hydrogen technologies [1]. The implementation of this strategy should lead to the arrival of several new hydrogen systems that will need to be evaluated and certified regarding their compliance with safety requirements before being commercialized. Conformity assessment and certification play an important role to achieve a good safety level on the EU market for the protection of workers and consumers. It is a way for the manufacturer to prove that hazards have been identified and risks are managed and to demonstrate his commitment to safety that are key to access to the EU market. To assist manufacturers in identifying the applicable regulations, standards and procedures for putting their product on the market, Ineris elaborated a guidebook [2], with financial and technical support by ADEME, the French Agency for Ecological Transition and France Hydrogen, the French Association for Hydrogen and Fuel Cells. The preparation of this document also led to identifying gaps in the Regulations, Codes and Standards (RCS) framework and necessary resources for the implementation of the conformity assessment procedures. This paper first describes the main regulatory procedures applicable for various types of hydrogen systems. Then describes the role of the actors involved in this process, with a special focus on the French context. And finally focuses on some of the gaps that were identified and formulates suggestions to address them
Modulation of magnetoencephalography alpha band activity by radiofrequency electromagnetic field depicted in sensor and source space
No full textInternational audienceSeveral studies reported changes in spontaneous electroencephalogram alpha band activity related to radiofrequency electromagnetic fields, but findings showed both an increase and a decrease of its spectral power or no effect. Here, we studied the alpha band modulation after 900 MHz mobile phone radiofrequency exposure and localized cortical regions involved in these changes, via a magnetoencephalography (MEG) protocol with healthy volunteers in a double-blind, randomized, counterbalanced crossover design. MEG was recorded during eyes open and eyes closed resting-state before and after radiofrequency exposure. Potential confounding factors, known to affect alpha band activity, were assessed as control parameters to limit bias. Entire alpha band, lower and upper alpha sub-bands MEG power spectral densities were estimated in sensor and source space. Biochemistry assays for salivary biomarkers of stress (cortisol, chromogranin-A, alpha amylase), heart rate variability analysis and high-performance liquid chromatography for salivary caffeine concentration were realized. Results in sensor and source space showed a significant modulation of MEG alpha band activity after the radiofrequency exposure, with different involved cortical regions in relation to the eyes condition, probably because of different attention level with open or closed eyes. None of the control parameters reported a statistically significant difference between experimental sessions
Comparison of five methodologies to apportion organic aerosol sources during a PM pollution event
No full textInternational audienceThis study presents a comparison of five methodologies to apportion primary (POA) and secondary organic aerosol (SOA) sources from measurements performed in the Paris region (France) during a highly processed PM pollution event. POA fractions, estimated from EC-tracer method and positive matrix factorization (PMF) analyses, conducted on measurements from PM10 filters, aerosol chemical speciation monitor (ACSM) and offline aerosol mass spectrometry (AMS), were all comparable (2.2–3.7 μg m−3 as primary organic carbon (POC)). Associated relative uncertainties (measurement + model) on POC estimations ranged from 8 to 50%. The best apportionment of primary traffic OA was achieved using key markers (EC and 1-nitropyrene) in the chemical speciation-based PMF showing more pronounced rush-hour peaks and greater correlation with NOx than other traffic related POC factors. All biomass burning-related factors were in good agreement, with a typical diel profile and a night-time increase linked to residential heating. If PMF applied to ACSM data showed good agreement with other PMF outputs corrected from dust-related factors (coarse PM), discrepancies were observed between individual POA factors (traffic, biomass burning) and directly comparable SOA factors and highly oxidized OA. Similar secondary organic carbon (SOC) concentrations (3.3 ± 0.1 μg m−3) were obtained from all approaches, except the SOA-tracer method (1.8 μg m−3). Associated uncertainties ranged from 14 to 52% with larger uncertainties obtained for PMF-chemical data, EC- and SOA-tracer methods. This latter significantly underestimated total SOA loadings, even including biomass burning SOA, due to missing SOA classes and precursors. None of the approaches was able to identify the formation mechanisms and/or precursors responsible for the highly oxidized SOA fraction associated with nitrate- and/or sulfate-rich aerosols (35% of OA). We recommend the use of a combination of different methodologies to apportion the POC/SOC concentrations/contributions to get the highest level of confidence in the estimates obtained
How Raw and Gypsum Modified Bauxite Residues Affect Seed Germination, Enzyme Activities, and Root Development of Sinapis alba
No full textInternational audienceThis study aimed to better understand the impact of different bauxite residues (BR) on the germination and the development of Sinapis alba (white mustard). Unamended BR from Provence, France (PRO), and Guinea (GUI) bauxite were selected, and modified bauxite residues from PRO and GUI (MBRPRO and MBR-GUI) were obtained by gypsum application and repeated leaching, in order to reduce their pH, electrical conductivity (EC), and exchangeable sodium percentage (ESP). Germination rates were monitored in soil-BR mixtures with increasing concentrations of BR. A rhizotron experiment was done, where Sinapis alba was allowed to develop in a layer of soil on the top of a layer of bauxite residue. To assess the impact of the residue on root development, the WhinRhizo (R) software was used to measure the architectural traits of roots. Peroxidase and fluorescein hydrolase activities were also assessed on the roots grown either in the soil or in the residue layers. Results showed that (i) bauxite residue origin, (ii) bauxite residue modification by gypsum, and (iii) bauxite residue concentration had significant effects on the germination, the root development and architecture, and the enzymatic activities of the roots of Sinapis alba. The PRO residue had a far stronger phytotoxic effect compared to the GUI residue on every measured variable. The toxic effect was strongly modulated by the origin of bauxite residue. The gypsum application efficiently reduced the phytotoxic effect of the residues, but significant negative effects on the different variables were still recorded
Comparison Between Twelve Nanomaterial's Accumulation and Elimination Behavior on Microcrustaceans (Daphnia magna)
No full textInternational audienceNanomaterials (NMs) production and usage have been raising concerns for the last decades. Since such substances are particulate contaminants, their first contact with organisms is a physical encounter ruled by physicochemical processes that can determinate the potential NMs accumulation, toxicity, and trophic transfer. There is still a lack of understanding on the main NMs properties that drive the accumulation and epuration processes. This work aims at studying and comparing the accumulation and epuration profiles of a set of twelve well characterized NMs with the microcrustacean Daphnia magna in equal conditions and to investigate the NMs properties that influence this phenomenon. The NMs set is constituted by 6 TiO2, 3 SiO2, 2 CeO2 and 1 ZnO NMs. The accumulation phase of the study was carried out during 24h of waterborne exposure to 1mg/L NMs suspension. Then, the organisms passed to the elimination phase of 120h in clean media. Samples were taken during the whole accumulation and elimination phases and were analyzed by ICP-OES. Using the biodynamic metal bioaccumulation model, the influx and loss rate constants have been found and compared. Differences have been determined on the accumulation and epuration kinetics of the NMs. These differences appeared to be linked to the NMs physicochemical properties as zeta potential measures can be correlated to the elimination rate constants. Similar observations were made concerning the same NMs and another type of organisms as microalgae, which highlights the importance of the physicochemical properties’ role on the nano-bio interaction. These findings open the possibility of grouping the NMs based on their relationship with organisms for risk assessment purposes
Bioanalytical characterization and source identification of a high glucocorticoid contamination in a river under urban and industrial pressures
No full textInternational audienceSynthetic glucocorticoids (GCs) are a group of steroids that are massively used as anti-inflammatory drugs to treat a broad spectrum of deseases such as asthma or arthritis. They may enter surface waters via urban, hospital and/or pharmaceutical industry effluents and were already detected in surface waters at concentrations ranging from < 1 to tens of ng/L. In organisms, GCs are designed to act through the glucocorticoid receptor (GR) and some studies have reported adverse effects on aquatic vertebrates, such as fish. Overall, there is still a need for knowledge on the sources and driver compounds for GR activity in different contexts. In the frame of a French national survey of EDCs in surface waters using in vitro bioassays, we previously identified a hotspot river site with high GR activity. To further identify the source(s) and the nature of this contamination, an investigative monitoring based on bioassay (MDA-Kb2) and chemical analyses was implemented in the current study. A contamination mapping was established on the basis of bioassay data, along a 40 km streatch upstream and downstream of the contaminated site allowing identification of the discharge of the contamination in the river and of its highly probable industrial origin in the sewerage network, although the contribution of waste waters from a hospital could not be excluded. By using a suspect screening approach based on HR-MS, fluticasone propionate as well as few other GCs were identified in the samples. Mass balance analysis based on quantitave chemical analysis confirmed fluticasone propionate main role in the measured GR activity. The high mobility and persistence of this contamination points out possible high environmental concern in terms of its fate and hazard for aquatic organisms
Large-Scale Model for the Dissolution of Heterogeneous Porous Formations: Theory and Numerical Validation
No full textInternational audienceIn this paper, we study the dissolution of a porous formation made of soluble and insoluble materials with various types of Darcy-scale heterogeneities. Based on the assumption of scale separations, i.e., the convective and diffusive Damkohler numbers are smaller than certain limits which are documented in the paper, we apply large-scale upscaling to the Darcy-scale model to develop large-scale equations, which are used to describe the dissolution of porous formations with Darcy-scale heterogeneities. History-dependent closure problems are provided to get the effective parameters in the large-scale model. The large-scale model validity is tested by comparing numerical results for a 1D flow problem in a stratified system and a 2D flow problem in a nodular system to the Darcy-scale ones. The good agreement between results at Darcy and large scales shows the robustness of the large-scale model in representing the Darcy-scale results for the stratified system, even when the dissolution front is very sharp. Large-scale results for the nodular system represent satisfactorily the averaged Darcy-scale behaviors when the dissolution front is relatively thick, i.e., when model assumptions are satisfied, while there may be as expected some discrepancy generated between direct numerical simulations and large-scale results in the case of thin dissolution front. Overall, this study demonstrates the possibility of building a fully homogenized large-scale model incorporating dissolution history effects, and that the resulting large-scale model is capable to catch the main features of the Darcy-scale results within its applicability domain
Modeling of salt and gypsum dissolution: applications, evaluation of geomechanical hazards
No full textInternational audienceThis article addresses the problem of modeling the dissolution of cavities in gypsum and halite (salt), followed by the assessment of potential collapse or subsidence of the geological formation, which may induce damaging consequences for population and infrastructures. Hazard prediction relies mostly on numerical modeling. This article discusses several issues associated to the development of dissolution numerical models involving the coupling between transport, dissolution and geomechanical modeling: type of model, parameters and numerical strategies. Hazard prediction relies mostly on numerical modeling. This article discusses several issues associated to the development of dissolution numerical models involving the coupling between transport, dissolution and geomechanical modeling: type of model, parameters and numerical strategies. The methodology is illustrated on several boundary value problems typical of actual situations in mining or civil engineering