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Evolution of particle interactions between accidentally released aerosol particles generated from powdered engineered nanomaterials into a simulated workplace atmosphere
No full textInternational audienceThe evaluation of aerosol processes which alter the size distribution of accidentally released nanomaterial particles in an indoor environment can provide size resolved exposure estimations, and subsequently contribute to a more comprehensive risk analysis on engineered nanomaterials (ENMs). In this work processed suspensions of TiO2 and SiO2 nanopowders were introduced into the reservoir of a nebuliser, and injected continuously as nano-aerosols into a room-size dispersion facility for a fixed release time. Following injection, the concentration of the dispersed aerosols was allowed to naturally decay for a prolonged period. Airborne particle number concentration (PNC) and particle size distributions (PSD) were continuously measured at a point within the breathing zone near to the source, while deposited particles were collected for transmission electron microscopy (TEM) analysis. A log10-normal fitting program was used to determine the evolution of the modal groups present within the measured PSDs. A modeling approach that considered the experimentally determined particle decay rate as a sum of the pair to pair coagulation and deposition rates was employed to estimate the relative importance of size-resolved deposition compared to coagulation. Results indicated that the variation of PNC with time was accurately modelled, providing size-dependent insights into the contribution of the two particle removal mechanisms to the change of PNC over time. The deposition patterns obtained from the TEM images qualitatively supported the model results. Since a limited set of input parameters were used, we concluded that the proposed model could be an effective tool for a reasonable quantification of worker's exposure to aerosols originating from the accidental release of diffuse ENM in real workplaces
Environmental monitoring at a sediment source site to qualify for reuse
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Soil-Gas Concentrations and Flux Monitoring at the Lacq-Rousse CO2-Geological Storage Pilot Site (French Pyrenean Foreland): From Pre-Injection to Post-Injection
No full textInternational audienceSoil-gas concentrations and flux were measured during 20 separate measurement campaigns at the TOTAL Lacq-Rousse carbon capture and storage (CCS) pilot site, southern France, where 51,000 tons of CO2 were injected in a depleted natural gas field. Baseline data (September 2008 to December 2009) are compared to monitoring data from the injection (March 2010 to March 2013) and post-injection (February 2014 to December 2015) periods. CO2 soil-gas concentrations varied from atmospheric concentrations to more than 16% vol. with 1.4% as median value. Summer data showed high CO2 concentrations in the soil that remained quite high during winter. Median CO2 flux at the soil/atmosphere interface was close to 4.4 cm(3).min(-1.)m(-2). Carbon-isotope ratios measured on CO2 in soil gas had a mean value of -23.5 +/- 3.1 parts per thousand, some deviation being due to atmospheric CO2. Comparison between different gas species and the influence of temperature, pressure and soil-water content suggest that gases in near-surface environments are produced locally and naturally, and are unrelated to CO2 ascending from the storage reservoir. Monitoring of CO2 injection and the use of threshold levels is discussed as part of a practical approach considering specific regulations for the Lacq-Rousse CCS pilot experiment and constraints for the site operator
Polyols and glucose particulate species as tracers of primary biogenic organic aerosols at 28 French sites
No full textInternational audienceA growing number of studies are using specific primary sugar species, such as sugar alcohols or primary saccharides, as marker compounds to characterize and apportion primary biogenic organic aerosols (PBOAs) in the atmosphere. To better understand their annual cycles, as well as their spatiotemporal abundance in terms of concentrations and sources, we conducted a large study focusing on three major atmospheric primary sugar compounds (i.e., arabitol, mannitol, and glucose) measured in various environmental conditions for about 5300 filter samples collected at 28 sites in France. Our results show significant atmospheric concentrations of polyols (defined here as the sum of arabitol and mannitol) and glucose at each sampling location, highlighting their ubiquity. Results also confirm that polyols and glucose are mainly associated with the coarse rather than the fine aerosol mode. At nearly all sites, atmospheric concentrations of polyols and glucose display a well-marked seasonal pattern, with maximum concentrations from late spring to early autumn, followed by an abrupt decrease in late autumn, and a minimum concentration during wintertime. Such seasonal patterns support biogenic emissions associated with higher biological metabolic activities (sporulation, growth, etc.) during warmer periods. Results from a previous comprehensive study using positive matrix factorization (PMF) based on an extended aerosol chemical composition dataset of up to 130 species for 16 of the same sample series have also been used in the present work. The polyols-to-PMPBOA ratio is 0.024±0.010 on average for all sites, with no clear distinction between traffic, urban, or rural typology. Overall, even if the exact origin of the PBOA source is still under investigation, it appears to be an important source of particulate matter (PM), especially during summertime. Results also show that PBOAs are significant sources of total organic matter (OM) in PM10 (13±4 % on a yearly average, and up to 40 % in some environments in summer) at most of the investigated sites. The mean PBOA chemical profile is clearly dominated by contribution from OM (78±9 % of the mass of the PBOA PMF on average), and only a minor contribution from the dust class (3±4 %), suggesting that ambient polyols are most likely associated with biological particle emissions (e.g., active spore discharge) rather than soil dust resuspension
Comportement mécanique d'une mousse de polyuréthane sous sollicitations statiques et dynamiques
No full textNational audienceEven if previsions have been made to reduce risk, the hazard of an explosion with desastrous effects cannot be totally eliminated. The use of blast walls made with thermal insulating materials could be an economic and efficient way to mitigate the effects of the blast wave. In this paper, the mechanical response of a very low density polyurethane foam (30 kg/m 3) to compression is examined experimentally. Static compressive tests are conducted with a press and Split Hopkinson Pressure Bars (SHPB) are used to characterize the dynamic behavior. In addition to traditional strain gauges measurements, the Digital Image Correlation (DIC) technique is used to observe the inhomogeneous strain fields.Qu'elles soient d'origine accidentelle ou malveillante, les explosions sur un site industriel peuvent prendre des proportions dramatiques. Un moyen économique de répondre au besoin de protection pourrait être d'utiliser des matériaux développés pour l'isolation thermique afin d'atténuer les effets mécaniques de l'onde de souffle. Dans cet article, nous nous intéressons au comportement mécanique d'une mousse de polyuréthane de très faible densité (30 kg/m 3). Pour étudier la sensibilité à la vitesse des différentes caractéristiques mécaniques de la mousse que sont la contrainte seuil, la contrainte plateau moyenne et la déformation à la densification, des essais de compression quasi-statiques et dynamiques aux barres de Hopkinson sont réalisés. Une attention particulière est apportée au suivi des champs de déformation des échantillons dont la réponse, même pour les faibles vitesses de déformation, s'avère hétérogène
Sources of organic aerosols in Europe: a modeling study using CAMx with modified volatility basis set scheme
No full textInternational audienceSource apportionment of organic aerosols (OAs) is of great importance to better understand the health impact and climate effects of particulate matter air pollution. Air quality models are used as potential tools to identify OA components and sources at high spatial and temporal resolution ; however, they generally underestimate OA concentrations , and comparisons of their outputs with an extended set of measurements are still rare due to the lack of long-term experimental data. In this study, we addressed such challenges at the European level. Using the regional Comprehensive Air Quality Model with Extensions (CAMx) and a volatility basis set (VBS) scheme which was optimized based on recent chamber experiments with wood burning and diesel vehicle emissions, and which contains more source-specific sets compared to previous studies, we calculated the contribution of OA components and defined their sources over a whole-year period (2011). We modeled separately the primary and secondary OA contributions from old and new diesel and gasoline vehicles, biomass burning (mostly residential wood burning and agricultural waste burning excluding wildfires), other anthropogenic sources (mainly shipping, industry and energy production) and biogenic sources. An important feature of this study is that we evaluated the model results with measurements over a longer period than in previous studies , which strengthens our confidence in our modeled source apportionment results. Comparison against positive matrix factorization (PMF) analyses of aerosol mass spectrometric measurements at nine European sites suggested that the modified VBS scheme improved the model performance for total OA as well as the OA components, including hydrocarbon-like (HOA), biomass burning (BBOA) and oxygenated components (OOA). By using the modified VBS scheme, the mean bias of OOA was reduced from − 1.3 to −0.4 µg m −3 corresponding to a reduction of mean fractional bias from Published by Copernicus Publications on behalf of the European Geosciences Union. 15248 J. Jiang et al.: Sources of organic aerosols in Europe −45 % to −20 %. The winter OOA simulation, which was largely underestimated in previous studies, was improved by 29 % to 42 % among the evaluated sites compared to the default parameterization. Wood burning was the dominant OA source in winter (61 %), while biogenic emissions contributed ∼ 55 % to OA during summer in Europe on average. In both seasons, other anthropogenic sources comprised the second largest component (9 % in winter and 19 % in summer as domain average), while the average contributions of diesel and gasoline vehicles were rather small (∼ 5 %) except for the metropolitan areas where the highest contribution reached 31 %. The results indicate the need to improve the emission inventory to include currently missing and highly uncertain local emissions, as well as further improvement of VBS parameterization for winter biomass burning. Although this study focused on Europe, it can be applied in any other part of the globe. This study highlights the ability of long-term measurements and source apportionment mod-eling to validate and improve emission inventories, and identify sources not yet properly included in existing inventories
Investigating a transcriptomic approach on marine mussel hemocytes exposed to carbon nanofibers: An in vitro/in vivo comparison
No full textInternational audienceManufactured nanomaterials are an ideal test case of the precautionary principle due to their novelty and potential environmental release. In the context of regulation, it is difficult to implement for manufactured nanomaterials as current testing paradigms identify risk late into the production process, slowing down innovation and increasing costs. One proposed concept, namely safe(r)-by-design , is to incorporate risk and hazard assessment into the design process of novel manufactured nanomaterials by identifying risks early. When investigating the manufacturing process for nanomaterials, differences between products will be very similar along key physicochemical properties and biological endpoints at the individual level may not be sensitive enough to detect differences whereas lower levels of biological organization may be able to detect these variations. In this sense, the present study used a transcriptomic approach on Mytilus edulis hemocytes following an in vitro and in vivo exposure to three carbon nanofibers created using different production methods. Integrative modeling was used to identify if gene expression could be in linked to physicochemical features. The results suggested that gene expression was more strongly associated with the carbon structure of the nanofibers than chemical purity. With respect to the in vitro/in vivo relationship, results suggested an inverse relationship in how the physicochemical impact gene expression
Source apportionment of carbonaceous aerosols based on high-time resolution instrumentation
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Application of three approaches for quantitative AOP development to renal toxicity
No full textInternational audienceWhile hazard assessment of chemicals can make direct use of descriptive adverse outcome pathways (AOPs), risk assessment requires quantitative relationships from exposure to effect timing and magnitude. To seamlessly integrate the data generated by alternative methods or in vivo testing, quantitative AOPs (qAOPs) providing dose-time-response predictions are more valuable than qualitative AOPs. Here, we compare three approaches to qAOP building: empirical dose-response modeling, Bayesian network (BN) calibration, and systems biology (SB) modeling. These methods were applied to the quantification of a simplified oxidative stress induced chronic kidney disease AOP, on the basis of in vitro data obtained on RPTEC/TERT1 cells exposed to potassium bromate. Effectopedia was used to store the experimental data and the developed models in a unified representation so they can be compared and further analyzed. We argue that despite the fact that dose-response models give adequate fits to the data they should be accompanied by mechanistic SB modeling to gain a proper perspective on the quantification. BNs can be both more precise than dose-response models and simpler than SB models, but more experience with their usage is needed