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The dissolution kinetics of natural gypsum: a case study of Eocene facies in the north-eastern suburbs of Paris
No full textInternational audienceThe dissolution kinetics of different varieties of natural gypsum samples with different porosity and content of insoluble impurities are experimentally investigated under unsaturated conditions. The main goal of this work is to verify whether and how the petrophysical and petrographic nature of gypsum influence its dissolution rate. Gypsum samples were taken from Priabonian (Ludian) and Lutetian formations located in the north-eastern suburbs of Paris, where the development of sinkholes due to gypsum dissolution is a common phenomenon. Experiments using the rotating disk technique allow us to determine the kinetic rate model parameters of each sample in pure water following the empirical rate expression derived from mixed kinetic theory. The kinetic order n shows a dispersion around a mean value n=1.2 and k, the pure dissolution rate coefficient varies according to the facies and the experimental conditions (k ≈1×10−6 to 8×10−6 mmol/cm2/s). These results are adjusted according to the specific roughness and texture of each sample, for the results to be more representative of in situ conditions. Batch experiments are also performed to evaluate the extremely low dissolution rates when the solution is close to equilibrium. The results reveal a double kinetics: far from equilibrium, the dissolution rates show that the linear behavior and the kinetic parameters are relatively close with the values found using the rotating disk method. For concentrations greater than 0.94 ± 0.02 of the equilibrium concentration Cref, the dissolution rates show a linear behavior but with greater slope depending on the texture of the mineral. No changes of the dissolution rates were observed on pure gypsum crystals when non soluble solid impurities are added. However, a small degree of uncertainty around the value of Cref show a significant effect on the parameters of the second kinetics
Overview of the French Operational Network for In Situ Observation of PM Chemical Composition and Sources in Urban Environments (CARA Program)
No full textInternational audienceThe CARA program has been running since 2008 by the French reference laboratory for air quality monitoring (LCSQA) and the regional monitoring networks, to gain better knowledge—at a national level—on particulate matter (PM) chemistry and its diverse origins in urban environments. It results in strong collaborations with international-level academic partners for state-of-the-art, straightforward, and robust results and methodologies within operational air quality stakeholders (and subsequently, decision makers). Here, we illustrate some of the main outputs obtained over the last decade, thanks to this program, regarding methodological aspects (both in terms of measurement techniques and data treatment procedures) as well as acquired knowledge on the predominant PM sources. Offline and online methods are used following well-suited quality assurance and quality control procedures, notably including inter-laboratory comparison exercises. Source apportionment studies are conducted using various receptor modeling approaches. Overall, the results presented herewith underline the major influences of residential wood burning (during the cold period) and road transport emissions (exhaust and non-exhaust ones, all throughout the year), as well as substantial contributions of mineral dust and primary biogenic particles (mostly during the warm period). Long-range transport phenomena, e.g., advection of secondary inorganic aerosols from the European continental sector and of Saharan dust into the French West Indies, are also discussed in this paper. Finally, we briefly address the use of stable isotope measurements (δ15N) and of various organic molecular markers for a better understanding of the origins of ammonium and of the different organic aerosol fractions, respectively
The CHIMERE v2020r1 online chemistry-transport model
No full textInternational audienceThe CHIMERE chemistry-transport model v2020r1 replaces the v2017r5 version and provides numerous novelties. The most important of these is the online coupling with the Weather Research and Forecasting (WRF) meteorological model via the OASIS3 – Model Coupling Toolkit (MCT) external coupler. The model can still be used in offline mode; the online mode enables us to take into account the direct and indirect effects of aerosols on meteorology. This coupling also enables using the meteorological parameters with sub-hourly time steps. Some new parameterizations are implemented to increase the model performance and the user's choices: dimethyl sulfide (DMS) emissions, additional schemes for secondary organic aerosol (SOA) formation with volatility basis set (VBS) and H2O, improved schemes for mineral dust, biomass burning, and sea-salt emissions. The NOx emissions from lightning are added. The model also includes the possibility to use the operator-splitting integration technique. The subgrid-scale variability calculation of concentrations due to emission activity sectors is now possible. Finally, a new vertical advection scheme has been implemented, which is able to simulate more correctly long-range transport of thin pollutant plumes
CNC/AgNP hybrids as safer-by-design biocides in paints
No full textInternational audienceIn this work, biocidal paints are designed by a safer-by-design approach where an efficient antibacterial activity is provided by nanohybrids consisting of silver nanoparticles (AgNPs) nucleated on a bio-based substrate (cellulose nanocrystals, CNCs), to be included in an amount as low as possible and dispersed in an aqueous suspension. Three CNC/AgNP hybrids varying in CNC surface modifications are characterized in depth by transmission electron microscopy, atomic absorption spectroscopy and X-ray diffraction, and used in realistic paint formulations. The analysis of dry-film degradation followed by artificial weathering and mechanical solicitation (i.e., abrasion) reveals a reduced airborne emission of particles that could have harmful impact on human health and the environment. However life cycle assessment shows a weak beneficial impact due to the low amount compared to the paint manufacturing impact. Finally, the biocidal activity was clearly detected on dry paints using Bacillus Subtilis bacteria. It demonstrates that the resulting dry-state paints containing the AgNPs best dispersed and with the smallest size (i.e., 11 nm) show the strongest biocidal effect. This approach allows considerable reduction of the Ag amount to reach an antibacterial effect comparable to AgCl. Moreover, no specific toxicity is revealed and only biodegradable CNCs will persist in the environment at the end of the antimicrobial activity provided by AgNPs. The development of such CNC/AgNP hybrids, considering the overall life cycle of the material like paint, opens the road to the development of highly efficient and more eco-friendly materials
Blueprint for a self-sustained European Centre for service provision in safe and sustainable innovation for nanotechnology
No full textInternational audienceThe coming years are expected to bring rapid changes in the nanotechnology regulatory landscape, with the establishment of a new framework for nano-risk governance, in silico approaches for characterisation and risk assessment of nanomaterials, and novel procedures for the early identification and management of nanomaterial risks. In this context, Safe(r)-by-Design (SbD) emerges as a powerful preventive approach to support the development of safe and sustainable (SSbD) nanotechnology-based products and processes throughout the life cycle. This paper summarises the work undertaken to develop a blueprint for the deployment and operation of a permanent European Centre of collaborating laboratories and research organisations supporting safe innovation in nanotechnologies. The proposed entity, referred to as “the Centre”, will establish a ‘one-stop shop’ for nanosafety-related services and a central contact point for addressing stakeholder questions about nanosafety. Its operation will rely on significant business, legal and market knowledge, as well as other tools developed and acquired through the EU-funded EC4SafeNano project and subsequent ongoing activities. The proposed blueprint adopts a demand-driven service update scheme to allow the necessary vigilance and flexibility to identify opportunities and adjust its activities and services in the rapidly evolving regulatory and nano risk governance landscape. The proposed Centre will play a major role as a conduit to transfer scientific knowledge between the research and commercial laboratories or consultants able to provide high quality nanosafety services, and the end-users of such services (e.g., industry, SMEs, consultancy firms, and regulatory authorities). The Centre will harmonise service provision, and bring novel risk assessment and management approaches, e.g. in silico methodologies, closer to practice, notably through SbD/SSbD, and decisively support safe and sustainable innovation of industrial production in the nanotechnology industry according to the European Chemicals Strategy for Sustainability
Disparities in particulate matter (PM10) origins and oxidative potential at a city scale (Grenoble, France) – Part 2: Sources of PM10 oxidative potential using multiple linear regression analysis and the predictive applicability of multilayer perceptron neural network analysis
No full textInternational audienceThe oxidative potential (OP) of particulate matter (PM) measures PM capability to potentially cause anti-oxidant imbalance. Due to the wide range and complex mixture of species in particulates, little is known about the pollution sources most strongly contributing to OP. A 1-year sampling of PM10 (particles with an aerodynamic diameter below 10) was performed over different sites in a medium-sized city (Grenoble, France). An enhanced fine-scale apportionment of PM10 sources, based on the chemical composition, was performed using the positive matrix factorization (PMF) method and reported in a companion paper (Borlaza et al., 2020). OP was assessed as the ability of PM10 to generate reactive oxygen species (ROS) using three different acellular assays: dithiothreitol (DTT), ascorbic acid (AA), and 2,7-dichlorofluorescein (DCFH) assays. Using multiple linear regression (MLR), the OP contributions of the sources identified by PMF were estimated. Conversely, since atmospheric processes are usually non-linear in nature, artificial neural network (ANN) techniques, which employ non-linear models, could further improve estimates. Hence, the multilayer perceptron analysis (MLP), an ANN-based model, was additionally used to model OP based on PMF-resolved sources as well. This study presents the spatiotemporal variabilities of OP activity with influences by season-specific sources, site typology and specific local features, and assay sensitivity. Overall, both MLR and MLP effectively captured the evolution of OP. The primary traffic and biomass burning sources were the strongest drivers of OP in the Grenoble basin. There is also a clear redistribution of source-specific impacts when using OP instead of mass concentration, underlining the importance of PM redox activity for the identification of potential sources of PM toxicity. Finally, the MLP generally offered improvements in OP prediction, especially for sites where synergistic and/or antagonistic effects between sources are prominent, supporting the value of using ANN-based models to account for the non-linear dynamics behind the atmospheric processes affecting OP of PM10
Maternal Ambient Exposure to Atmospheric Pollutants during Pregnancy and Offspring Term Birth Weight in the Nationwide ELFE Cohort
No full textInternational audienceBackground: Studies have reported associations between maternal exposure to atmospheric pollution and lower birth weight. However, the evidence is not consistent and uncertainties remain. We used advanced statistical approaches to robustly estimate the association of atmospheric pollutant exposure during specific pregnancy time windows with term birth weight (TBW) in a nationwide study. Methods: Among 13,334 women from the French Longitudinal Study of Children (ELFE) cohort, exposures to PM2.5, PM10 (particles < 2.5 mu m and <10 mu m) and NO2 (nitrogen dioxide) were estimated using a fine spatio-temporal exposure model. We used inverse probability scores and doubly robust methods in generalized additive models accounting for spatial autocorrelation to study the association of such exposures with TBW. Results: First trimester exposures were associated with an increased TBW. Second trimester exposures were associated with a decreased TBW by 17.1 g (95% CI, -26.8, -7.3) and by 18.0 g (-26.6, -9.4) for each 5 mu g/m(3) increase in PM2.5 and PM10, respectively, and by 15.9 g (-27.6, -4.2) for each 10 mu g/m(3) increase in NO2. Third trimester exposures (truncated at 37 gestational weeks) were associated with a decreased TBW by 48.1 g (-58.1, -38.0) for PM2.5, 38.1 g (-46.7, -29.6) for PM10 and 14.7 g (-25.3, -4.0) for NO2. Effects of pollutants on TBW were larger in rural areas. Conclusions: Our results support an adverse effect of air pollutant exposure on TBW. We highlighted a larger effect of air pollutants on TBW among women living in rural areas compared to women living in urban areas
Exposure of the population of southern France to air pollutants in future climate case studies
No full textInternational audiencePopulation exposure to air pollutants varies dramatically with time and location on the globe. Taking into account the changing climate, the engaged emission reduction policies and the expected increase in population, the health risks associated with this phenomenon may also change significantly in the near future. In regions such as the Mediterranean, exposed to multiple forms of air pollution and highly sensitive to climate change, it is obviously critical to define trends in human exposure to air pollutants. The objective of this article is to explore the features of population exposure to air pollution in the French Mediterranean coast, under different climatic situations, using distinct emission configurations, and for divergent scenarios of population growth. The use of contrasting situations for these 3 parameters makes it possible to better address the variability of exposure in the different areas of the territory, as a global risk for populations. For this purpose, five 12 month-duration simulations have been carried out as case studies in the Provence Alpes Côtes d’Azur (PACA) region, located in the south-east of France: a 2005 simulation is used as the reference situation, and two more years of simulation are used as samples of time horizons 2030 and 2050, each of which was simulated twice sampling representative future climate years according to representative concentration pathway scenarios RCP4.5 and RCP8.5. Estimates of population change were prepared for the study area, using shared socioeconomic pathways (SSPs) scenarios. The results show that albeit the growing population, the exposure to most atmospheric components decreases because of emission reduction policies. This, however, is not true for all species. The population exposure to dust species increases for spring, when most dust episodes occur. In addition, exposure to ozone – while decreasing on the average - shows an increase in urban areas. Finally, while the concentrations of BSOA (secondary organic aerosol of biogenic origin) increase in the future scenarios, this tendency is not marked enough to offset the population decrease in rural areas in most SSP scenarios. On the reverse, exposure to BSOA does show an increase in urban areas where population is expected to grow. A county per county analysis is conducted, showing that the three coastal counties of the PACA region will experience higher ozone, PM10 and PM2.5, dust and BSOA exposure. The purpose of our work is to produce a case study in which we compare pollutant concentration changes and population weighed exposure changes on a meteorological situation that goes out of the current distribution. For this case study, we propose to distinguish the part of exposure changes due pollutant concentration and population changes. The choice of the study case (weather and horizon) is discussed in the text. This approach differs from the scenario approach, which focuses on the analysis of a trend representative of future years
