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Modelling molecular composition of SOA from toluene photo-oxidation at urban and street scales
No full textInternational audienceNear-explicit chemical mechanisms representing toluene SOA formation are reduced using the GENOA algorithm and used in 3D simulations of air quality over Greater Paris and in the streets of a district near Paris. The SOA concentrations formed by the toluene photo-oxidation are found to mostly originate from molecular rearrangement with ring opening of a bicyclic peroxy radical (BPR) with an O–O bridge (45%), followed by OH-addition on the aromatic ring (22%), Highly Oxygenated organic Molecules (HOM) formation without ring opening (13%), condensation of methylnitrocatechol (8%), irreversible formation of SOA from methylglyoxal (6%), and ring-opening pathway (3%). The concentrations simulated using the most comprehensive reduced chemical scheme (rdc. Mech. 3) are also compared to those simulated with a SOA scheme based on chamber measurements, and one reduced from the Master Chemical Mechanism. Using rdc. Mech 3 leads to between 50% and 75% more toluene SOA concentrations than the other schemes, mostly because of molecular rearrangement. The SOA compounds from rdc. Mech. 3 are more oxidized and less volatile, with molecules of different functional groups. Concentrations of methylbenzoquinones, which may be of particular health interest, represent about 0.5% of the toluene SOA concentrations. Those are slightly higher in streets than in the urban background (by 2%)
Toward Regulatory Monitoring with Passive sampling: French experience
No full textInternational audienceFor over 20 years, the European Water Framework Directive (2000/60/EC) has strengthened the monitoring of water bodies, including surface waters. Ambitious monitoring programmes have been set up to monitor 45 priority substances or families of substances. Among the difficulties regularly identified in these programmes are those of ensuring that sampling is representative for substances showing significant temporal variability, such as pesticides, or of achieving, using conventional laboratory techniques, the quantification limits required for a reliable comparison with the Environmental Qualiy Standards (EQS). The current revision of this directive could further increase the latter difficulty by adding new priority substances for which the EQS are particularly low (e.g. pyrethrinoid compounds).Passive sampling tools are likely to provide solutions to these difficulties. The Directive 2013/39/EU recommends further development of passive sampling techniques as a promising tool for future application in compliance checking and trend monitoring of priority substances.In France, a very recent regulatory text ("monitoring" decree of 26/4/22) officially authorised the use of passive sampling as part of monitoring programs for surface water bodies. In the framework of the French Prospective Monitoring Network (‘RSP’), this authorization follows a major demonstration campaign coordinated by Aquaref (French national reference laboratory for aquatic environment monitoring), which demonstrated the usefulness of these tools for large-scale application in a regulatory context. It follows also the results of MONITOOL project – New tools for water quality monitoring - European Atlantic Area project (2017-2023), regarding EQS marine water adaptation to DGT (Diffusive Gradient in thin Films) for priority substances (Pb, Cd, Ni).As part of its support for the Ministry, Aquaref produced a note in 2024 defining a first set of substances for which the use of passive samplers (DGT, POCIS , silicone rubber) was possible in the context of monitoring (fresh and marine water) .In order to ensure the successful use of passive samplers in this context (in particular the comparability of data at a national scale), and in cooperation with the Ministry of the Environment and the French Biodiversity Agency, Aquaref has developed various guidance documents or “tools” to help river basin authorities in charge of the implementation of the WFD monitoring programmes and laboratories operating this monitoring.The aim of this presentation is to present the various actions that have been necessary in order to achieve the implementation of passive sampling tools in a regulatory context, from scientific developments to policy support. In particular, we will describe the national technical guides relating to sampling and analysis for passive sampling, the organisation and responsibility defined for passive sampling operation separating laboratory operations from field and calculation operations when necessary, the rules for data banking and, finally, the requirements in terms of quality assurance and analytical performance. We finally highlight some of the questions that are still pending
Simulation moléculaire appliquée au génie des procédés: Un travail pionnier autour du vecteur hydrogène
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Hydromechanical modelling of salt caverns subjected to cyclic hydrogen injection and withdrawal
No full textInternational audienceThe present work is devoted to the study of underground hydrogen storage in salt caverns. Based on the hydromechanical characteristics of rock salts obtained from some laboratory experiments, we propose a novel model that includes short- and long-term mechanical behaviour. Specifically, the short-term part incorporates the elastoplastic and instantaneous damage mechanisms. Concerning the long-term behaviour, in addition to the primary and secondary creep phases, the tertiary phase takes into account a delayed damage mechanism.As application, we performed hydromechanical modelling of two vertical salt caverns with different depths based on existing hydrogen gas caverns, which are subjected to cyclic hydrogen injection and withdrawal (seasonal and daily scenarios). Gas transport is also modelled taking into account diffusion and advection mechanisms. Mechanical results indicate that the stability problem of a very deep cavern is more worrying in comparison with a shallow cavern, as expected. However, the gas extension is the same for both caverns because the gas flow is mainly by diffusion transport, while the permeability does not significantly increase. Since field data at very depths are limited, a sensibility analysis of material properties was carried out to provide insight into key mechanisms that may occur. Typically, a decrease in mechanical properties increases the extent of the damage around deep cavern but did not lead to significant increase in the extent of gas leakage. Under the assumptions made, these findings suggest that the use of salt caverns for green hydrogen storage, even with aggressive operating conditions to regulate variations between renewable energy production and peak power demands, should not significantly affect the stability of salt cavern nor promote an increase in hydrogen loss
Strategies to Assess Occupational Exposure to Airborne Nanoparticles: Systematic Review and Recommendations.
No full textInternational audienceIn many industrial sectors, workers are exposed to manufactured or unintentionally emitted airborne nanoparticles (NPs). To develop prevention and enhance knowledge surrounding exposure, it has become crucial to achieve a consensus on how to assess exposure to airborne NPs by inhalation in the workplace. Here, we review the literature presenting recommendations on assessing occupational exposure to NPs. The 23 distinct strategies retained were analyzed in terms of the following points: target NPs, objectives, steps, "measurement strategy" (instruments, physicochemical analysis, and data processing), "contextual information" presented, and "work activity" analysis. The robustness (consistency of information) and practical aspects (detailed methodology) of each strategy were estimated. The objectives and methodological steps varied, as did the measurement techniques. Strategies were essentially based on NPs measurement, but improvements could be made to better account for "contextual information" and "work activity". Based on this review, recommendations for an operational strategy were formulated, integrating the work activity with the measurement to provide a more complete assessment of situations leading to airborne NP exposure. These recommendations can be used with the objective of producing homogeneous exposure data for epidemiological purposes and to help improve prevention strategies
Développement et test d’un indicateur de la pression de pollution chimique sur le bassin de la Seine
No full textUnderstanding the “blues of safety professionals”
No full textInternational audienceSomething is not right in the safety profession. Many books written by professionals in the 2010s express a strong discontent. These professionals are highly critical of their situation, practice, role and identity. In these books, they express what this article describes as the “blues of safety professionals”. Although varying in writing style, tone, theoretical inspiration, emphasis, and experience, they address similar issues which relate to practices corresponding, in their eyes, to outmoded, inadequate, or even perverse ideas. The aim of this article is to introduce, summarise, explain, and problematise the significance of this literature. Following a methodological section, the ‘safety professional blues’ is introduced. It is argued in another section that the ‘blues’ pinpoints what these authors consider to be flawed assumptions about many of the core ingredients of the safety profession. The roots of this discontent are the topic of another section, while a final section problematises the ‘blues’
Origin of seismic repeaters in a deep mine: what do we learn from in-situ investigation coupling geology, geomechanics and geophysics?
No full textInternational audienceSeismic repeaters (i.e. seismic events with highly similar waveforms) have beenobserved in the deep mine of Garpenberg, Sweden. In natural seismology, repeaters are commonlyassociated with the presence of aseismic slip (i.e. creep) on fault planes, loading seismogenicasperities. This raises questions regarding what these asperities and creeping zone consist of and howthey behave from a mechanical point of view. A local monitoring network has been installed in situ,close to the source area of one family of repeaters at 1km depth, with the objective of identifying theorigin of these repeaters. The network comprises boreholes, geophones and strain cells. We showthat the presence of a fault plane with creeping portions and an asperity is compatible with field data.We also discuss the difficulty of clearly identifying the origin of the repeaters, as we couldn’t reachthe seismic asperity itself, even with such a local network
Meteorological export and deposition fluxes of black carbon on glaciers of the central Chilean Andes
No full textInternational audienceAir pollution in the central zone of Chile is not only a public health concern but also threatens water resources and climate, in connection with the transport and deposition of black carbon (BC) from urban centers onto the glaciers of the Andes. Chemistry-transport simulations reveal a seasonal dichotomy in the flux and latitudinal pattern of BC deposition on glaciers of the central Chilean Andes. The average deposition flux of BC on glaciers between 30 and 37° S is 4 times larger in winter, affecting mostly low-elevation glaciers, whereas the smaller summertime flux affects glaciers evenly, irrespective of their elevation. The contribution of emissions from the city of Santiago is dominant in summertime with more than 50 % along the Andes but minor in wintertime with less than 20 % even close to the capital city. Transport at larger scales and more local sources likely account for the remaining flux. The superimposition of synoptic-scale circulation and local mountain-valley circulation along the Andes drives the differences between summertime and wintertime deposition fluxes and generates a greater meteorological export potential during summer months. Future emissions and climate projections suggest that under the RCP8.5 scenario the gap between summertime and wintertime BC export and deposition flux could decrease, thereby pointing to summertime emission control gaining relevance. The chemistry-transport modeling approach for BC deposition on the Andes sheds light on the importance of the often disregarded summertime emissions on the radiative balance of its glaciers, particularly in the vicinity of Santiago
Investigation of four-year chemical composition and organic aerosol sources of submicron particles at the ATOLL site in northern France
No full textInternational audienceThis study presents the first long-term online measurements of submicron (PM1) particles at the ATOLL (ATmospheric Observations in liLLe) platform, in northern France. The ongoing measurements using an Aerosol Chemical Speciation Monitor (ACSM) started at the end of 2016 and the analysis presented here spans through December 2020. At this site, the mean PM1 concentration is 10.6 μg m−3, dominated by organic aerosols (OA, 42.3%) and followed by nitrate (28.9%), ammonium (12.3%), sulfate (8.6%), and black carbon (BC, 8.0%). Large seasonal variations of PM1 concentrations are observed, with high concentrations during cold seasons, associated with pollution episodes (e.g. over 100 μg m−3 in January 2017). To study OA origins over this multiannual dataset we performed source apportionment analysis using rolling positive matrix factorization (PMF), yielding two primary OA factors, a traffic-related hydrocarbon-like OA (HOA) and biomass-burning OA (BBOA), and two oxygenated OA (OOA) factors. HOA showed a homogeneous contribution to OA throughout the seasons (11.8%), while BBOA varied from 8.1% (summer) to 18.5% (winter), the latter associated with residential wood combustion. The OOA factors were distinguished between their less and more oxidized fractions (LO-OOA and MO-OOA, on average contributing 32% and 42%, respectively). During winter, LO-OOA is identified as aged biomass burning, so at least half of OA is associated with wood combustion during this season. Furthermore, ammonium nitrate is also a predominant aerosol component during cold-weather pollution episodes – associated with fertilizer usage and traffic emissions. This study provides a comprehensive analysis of submicron aerosol sources at the recently established ATOLL site in northern France from multiannual observations, depicting a complex interaction between anthropogenic and natural sources, leading to different mechanisms of air quality degradation in the region across different seasons