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Modelling black carbon absorption of solar radiation : combining external and internal mixing assumptions
No full textInternational audienceAn accurate simulation of the absorption properties is key for assessing the radiative effects of aerosol on meteorology and climate. The representation of how chemical species are mixed inside the particles (the mixing state) is one of the major uncertainty factors in the assessment of these effects. Here we compare aerosol optical properties simulations over Europe and North America, coordinated in the framework of the third phase of the Air Quality Model Evaluation International Initiative (AQMEII), to 1 year of AERONET sunphotometer retrievals, in an attempt to identify a mixing state representation that better reproduces the observed single scattering albedo and its spectral variation. We use a single post-processing tool (FlexAOD) to derive aerosol optical properties from simulated aerosol speciation profiles, and focus on the absorption enhancement of black carbon when it is internally mixed with more scattering material, discarding from the analysis scenes dominated by dust. We found that the single scattering albedo at 440nm (omega(0,440)) is on average overestimated (underestimated) by 3-5% when external (core-shell internal) mixing of particles is assumed, a bias comparable in magnitude with the typical variability of the quantity. The (unphysical) homogeneous internal mixing assumption underestimates omega(0,440) by 14%. The combination of external and core-shell configurations (partial internal mixing), parameterized using a simplified function of air mass aging, reduces the omega(0,440) bias to-1/-3%. The black carbon absorption enhancement (E-abs) in core-shell with respect to the externally mixed state is in the range 1.8-2.5, which is above the currently most accepted upper limit of 1.5. The partial internal mixing reduces E-abs to values more consistent with this limit. However, the spectral dependence of the absorption is not well reproduced, and the absorption Angstrom exponent AAE(675)(440) is overestimated by 70-120%. Further testing against more comprehensive campaign data, including a full characterization of the aerosol profile in terms of chemical speciation, mixing state, and related optical properties, would help in putting a better constraint on these calculations
Aseismic Mining Subsidence in an Abandoned Mine : Influence Factors and Consequences for Post-Mining Risk Management
No full textInternational audienceIn the Lorraine area of eastern France, decades of iron-ore mining from 1850 to 1997 have left vast underground cavities beneath or in the vicinity of urban areas. Several major collapses occurred in the southern part of this iron-ore basin in the 1990s, after the mine closure and the flooding of underground mine workings. Following these large-scale collapses, the French government initiated a strategy of post-mining risk management to prevent and control risks associated with these ground failures. The high-risk zones are secured either by reducing the vulnerability while the moderate risk zones are monitored for public safety purposes by using in situ monitoring. This monitoring relies mainly on real-time microseismic systems, to detect precursors to a rapid large-scale collapse. After the progressive closing and then flooding of the northern iron basin ending in 2008, subsidence was observed in a town of the Lorraine basin in autumn of 2009. However, this local subsidence, with a low velocity of few centimeters per month, was not clearly detected by the borehole microseismic monitoring station located nearby. Only some microseismic events were recorded, which could not be unambiguously related to the beginning of the subsidence event. To better understand this lack of microseismic precursor a geophysical investigation was launched. A calibration blast experiment was carried out from a remaining old underground access in order to answer to the following questions: (1) what is the seismic wave attenuation field?; (2) what is the minimum source power that can be detected by the sensors?; (3) what is the impact of the geology, the faults corridor and the integral pillar extraction zone on the wave propagation field? The results of this study show strong anelastic attenuation of the seismic waves though the monitored overburden most likely related to the extensive fault system intersecting the study site. Strong attenuation might explain the lack of detected microseismicity during the subsidence event. In order to clarify this issue, a mobile GPS monitoring system was designed and tested to address this type of situation in future
Cyberattaques : peut-on craindre des conséquences sur l’intégrité physique des personnes ?
No full textInternational audienceCertaines TPE/PME1 exploitent des installations mettant en oeuvre des matières dangereuses. Ces installations disposent pour la plupart de systèmes automatisés de contrôle qui peuvent être connectés à différents dispositifs de commande ou de supervision souvent reliés directement ou indirectement au réseau extérieur de l’entreprise. Une prise de contrôle à distance de ces installations par des cyber-attaquants pourrait leur permettre de provoquer des phénomènes physiques dangereux pour les personnels, les utilisateurs ou les riverains tels que des explosions, incendies ou rejets toxiques
Impact of geological heterogeneities on induced-seismicity in a deep sublevel stoping mine
No full textInternational audienceWith the aim of understanding the nature of mining-induced seismicity, microseismic activity in the deep metal mine of Garpenberg (Sweden) has been recorded during 2 years of excavations. The studied area of the mine is operated using sublevel stoping method with backfilling, between depths of around 1000 and 1300 meters. Spatiotemporal analysis of microseismic activity is presented and correlated with the occurrence of mining blasts. A clear dependence is observed between blasts and seismic sequences, even if the rock mass response to mining appears to be very variable across space and time. Two main clusters are observed: one located in the major production area (Central Cluster), while the second (Right Cluster) is located at some distance from the excavations, in a zone characterized by a heterogeneous distribution of weak materials and stiff rock masses. By analyzing seismic source parameters, we demonstrate that the two clusters are characterized by different dynamics. In addition, we show how Right Cluster events are mainly controlled by geological heterogeneities, which impose high stress concentrations in the stiff rock masses surrounding weak lenses. High apparent stresses and corner frequencies associated with the Right Cluster events agree with our proposed model. This suggests elevated stresses in the seismic source region and small source dimensions; indeed, fractures cannot propagate along great distances due to the presence of weak lenses interbedded with the breaking stiff rock mass
Comparaison et impact de différentes méthodes d’extraction d’eau sur l’analyse non ciblée par chromatographie liquide couplée à la spectrométrie de masse haute résolution
No full textNon-target screening (NTS) approaches based on high-resolution mass spectrometry coupled with chromatographic techniques allow the identification of a large number of chemical compounds of anthropic or natural origin present in water samples.However, these water samples generally require pre-treatment steps such as filtration, extraction, concentration and purification that may impact the quality of the information obtained. In this study, five different solid phase extraction methods (SPE) at different pH were applied to the same river water and compared based on the results obtained by suspected non-targeted analysis in liquid chromatography coupled with high resolution mass spectrometry. Surface water from the Gier River (Givors, Rhône) was filtered, spiked with deuterated surrogates and pH adjusted (pH 3 and 7). Then the water was extracted according to five distinct protocols in terms of SPE cartridges used (HLB or multilayer) and elution solvents (methanol, methanol/dichloromethane mixture, methanol/ethyl acetate mixture). The analyses were carried out using liquid chromatography coupled with high-resolution mass spectrometry in both ionization modes ESI (+) and ESI (-). The suspected research was based on a predefined list of 28 molecules to be investigated. The variability of the results in terms of substance detection does not allow selecting one single extraction method to be used that is the least specific possible to meet the objectives of the broadest non-targeted analysis. However, the results obtained with the three extraction methods at pH 7 make it possible to better detect suspected molecules (higher signal intensity), this pH should then be preferred for the extraction of water. Analysis in both ionization modes ESI (+) and ESI (-) is important because it provides additional information (some molecules are ionizable in only one of the two modes) and also further confirmation of the presence of ionizable molecules in both ionization modes.Les approches d’analyses non ciblées ou « non-target screening » (NTS) réalisées en spectrométrie de masse haute résolution couplée à des techniques chromatographiques permettent d’identifier un grand nombre de composés organiques anthropogéniques ou naturels présents dans les échantillons d’eau. Or, ces échantillons d’eau subissent généralement des étapes de préparation comme la filtration, l’extraction, la concentration et la purification qui peuvent impacter la qualité des informations obtenues. Dans cette étude cinq méthodes de préparation d’échantillons d’eau de rivière par extraction sur phase solide (SPE) et à différents pH ont été testées et comparées en fonction des résultats obtenus par analyse non ciblée de suspects (analyse suspectée par la suite du rapport) en chromatographie liquide couplée à la spectrométrie de masse haute résolution. L’eau du Gier (Givors, Rhône) après filtration, dopage en traceurs d’extraction deutérés et ajustement du pH (pH 3 et 7) a été extraite selon cinq protocoles distincts en terme de cartouches SPE utilisées (HLB ou multicouches) et de solvants d’élution (méthanol, mélange méthanol / dichlorométhane, mélange méthanol / acétate d’éthyle). Les analyses ont été réalisées en chromatographie liquide couplée à la spectrométrie de masse haute résolution dans les deux modes d’ionisation ESI (+) et ESI (-). La recherche suspectée s’est basée sur une liste prédéfinie de 28 molécules à rechercher qui avaient été précédemment retrouvées dans les eaux du Gier. La variabilité des résultats obtenus en terme de détection de substances ne permet pas de concluresur le choix d’une méthode d’extraction unique à utiliser qui soit la moins spécifique possible pour répondre aux objectifs d’une analyse suspectée la plus large possible. Toutefois les résultats obtenus avec les trois méthodes d’extraction à pH 7 permettent de mieux détecter les molécules suspectées (intensité des signaux plus importantes), ce pH d’extraction doit alors être privilégié. Les analyses dans les deux modes d’ionisation ESI (+) et ESI (-) sont nécessaires car elles apportent des informations complémentaires (certaines molécules ne sont ionisables que dans un des deuxmodes) mais aussi une confirmation supplémentaire de la présence des molécules ionisables dans les deux modes d’ionisation
Why do some people fear Digital Soil Maps? Good and bad reasons and ways to overcome this situation
No full textInternational audienc
Prédiction des temps de rétention chromatographique dans le cadre de l'analyse non-ciblée
No full text[Departement_IRSTEA]Eaux [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiplesLes analyses non-ciblées, effectuées par chromatographie couplée à un spectromètre de masse haute résolution, visent ladétection et l'identification de composés non recherchés initialement. L'identification d'une substance non-connue est généralement effectuée selon les informations qui peuvent être générées lors de l'analyse par spectrométrie de masse en comparaisonavec des bases de données spectrométriques. Un des éléments qui peut être pris en compte pour l'identification d'une substance est le temps de rétention chromatographique.En effet, c'est un paramètrerépétable et qui reflète les interactions et donc les propriétés physico-chimiques entre une substance d'intérêt et le système chromatographique. De nombreuses approches, des plus simples (prenant uniquement en compte le log D des composés), à de plus complexes (réseau de neurones, modèle LSER-Linear Solvatation Energy Relationships-,...) ont été explorées afin de pouvoir améliorer la précision des prédictions de la rétention chromatographique. Deux approches de prédiction de temps de rétention ont été évaluées lors de cette étude. Dans le cadre du réseau NORMAN, un modèle a été mis au point par l'Université d'Athènes pour la chromatographie liquide. Ce modèle peut être adapté à différentes conditions chromatographiques par l'injection d'un mélange qui sert à établir une courbe d'étalonnage spécifique au système utilisé. L'injection de composés modèles, dont le temps de rétention et la structure étaient connus, a permis de montrer que le modèle permettait d'obtenir en majorité des prédictions relativement correctes (±2 min) mais que dans 20% des cas, les prédictions n'étaient pas suffisamment précises. La relative imprécision obtenue pour certains composés dans ces essais doit être reliée aux conditions chromatographiques relativement différentes de celles ayant été utilisées pour développer le modèle et ce malgré l'utilisation de composés servant à l'étalonnage du modèle.Un modèle pour chromatographie liquide a été développé par Irstea sur la base d'une sélection des descripteurs les plus utilisés selon la littérature et facilement accessibles pour tout composé organique. Le modèle a été développé et validé en phase inverse et permet d'estimer la rétention d'un contaminant avec un intervalle de confiance de ±13,7% de phase mobile organique à l'élution quelle que soit la chaine analytique utilisée (soit ±1,9min en temps de rétention avec l'appareillage utilisé dans cette étude). L'applicabilité du modèle à différents lots de colonnes ainsi qu'à des échantillons en matrice réelle (injection directe d'eau de surface ou extrait SPE) a été démontrée
Synthèse des actions européennes et nationales sur les techniques de chimie non ciblée (non-target screening)
No full text[Departement_IRSTEA]Eaux [ADD1_IRSTEA]Systèmes aquatiques soumis à des pressions multiples [Type_IRSTEA]Rapport d'étudeL'objectif de cette action est d'informer les gestionnaires de la surveillance nationale sur les actions en cours au niveau européen et national; de renforcer le partage d'information et de pratiques entre les actions mises en oeuvre dans le cadre du réseau NORMAN, les actions AQUAREF et les actions nationales de recherche sur le sujet du NTS ; de faire remonter au niveau européen et national les travaux mis en oeuvre par AQUAREF afin d'enrichir les discussions sur la comparaison des méthodes, l'assurance qualité, la bancarisation des données... et de relayer une réflexion sur les aspects opérationnels de ces nouvelles techniques d'analyse NTS
Mass Balance of PAHs at the Scale of the Seine River Basin
No full textThe Seine River basin (France) is representative of the large urbanised catchments (78,650 km2) located in Northwestern Europe. As such, it is highly impacted by anthropogenic activities and their associated emissions of pollutants such as polycyclic aromatic hydrocarbons (PAHs). These compounds, originating from household heating and road traffic, are responsible for serious environmental issues across the basin. This study aims at establishing and using mass balance analyses of PAHs at the Seine River basin scale as an efficient tool for understanding PAH pathways in the environment. A dual-scale approach (urban vs. rural areas) was used successfully, and mass balances provided useful knowledge on the environmental fate of PAHs. In urban areas, runoff and domestic and industrial discharges contributed similarly to the PAH supply to the sewer system. During the wastewater treatment process, PAHs were mainly eliminated through sludge removal. At the basin scale, substantial amounts of PAHs were quantified in soils, and the limited annual inputs and outputs through atmospheric deposition and soil erosion, respectively, suggest that these compounds have long residence times within the basin. While wastewater and runoff discharges from urban areas account for a substantial part of PAH urban fluxes to the Seine River, soil erosion seems to be the predominant contributor at the basin scale. Overall, the PAH flux at the basin outlet was greater than supplies, suggesting that the Seine River system may currently be undergoing a decontamination phase
Assessment of heart rate variability under exposure to GSM 900-MHz signal from mobile phone in healthy young people
No full textInternational audiencePurpose: Recently a National Toxicology Program has issued their technical reports (NTP TR 595 [1] and NTP TR 596 [2]). They found that high exposure to radio frequency radiation (RFR) used by cell phones was associated with clear evidence of tumors in the hearts of male rats. In this context and given the large number of mobile phone users worldwide, the present study was focused on the effect of RFR of mobile phone on the heart rate variability (HRV). The aim of the present study was to analyze, in healthy subjects at rest, the influence of exposure to GSM 900MHz on HRV parameters. Participants and Methods: Twenty-six young healthy volunteers participated in the experiment. The volunteers were selected following a routine clinical examination. Inclusion criteria included regular sleep habits, no medication, no chronic disease or disability, no recent acute illness, no smoking, and no neurological or psychiatric illness. Participants having a history of cardiovascular disease were excluded. Volunteers participated into two ECG recording sessions. For each session, the participants were exposed for 26 min to sham or real GSM RF exposure. Exposure to RF EMF was performed by a commercial dual-band GSM mobile phone (Nokia 6650). The HRV was evaluated by both time domain and frequency domain analysis. Standard deviation of all R–R intervals (SDNN) and root-mean-square of successive differences (RMSSD) were measured in the time domain analysis of HRV. For frequency domain parameters, spectral analysis was performed by using fast-Fourier transform method. We analyzed the very low-frequency component (VLF), the low-frequency component (LF), and the high-frequency component (HF). The LF and HF powers were also converted into normalized units (LFnu, HFnu). Sympathovagal balance was expressed as the LF/HF ratio. Results: Analysis of time domain HRV parameters showed that SDNN was significantly higher during the exposure session when compared to the control session. Analysis of frequency domain HRV parameters demonstrated that absolute values of LF power and total power were significantly increased during exposure (p = 0.0463 and p = 0.0427 respectively). However, VLF, HF, LF n.u, HF n.u and LF/HF ration were not affected. In conclusion, it seems that most HRV parameters were not affected by GSM signal in our study. The weak effect observed on frequency domain HRV LF or total power is likely to represent a random occurrence rather than a real effect