Uncertainties in the effects of organic aerosol coatings on polycyclic aromatic hydrocarbon concentrations and their estimated health effects

International audienceAbstract. We used the CAM5 model to examine how different particle-bound polycyclic aromatic hydrocarbon (PAH) degradation approaches affect the spatial distribution of benzo(a)pyrene (BaP). Three approaches were evaluated: NOA (no effect of OA coatings state on BaP), shielded (viscous OA coatings shield BaP from oxidation under cool and dry conditions) and ROI-T (viscous OA coatings slow BaP oxidation in response to temperature and humidity). Results show that BaP concentrations vary seasonally, influenced by emissions, deposition, transport and degradation approach, all of which are influenced by meteorological conditions. All simulations predict higher population-weighted global average (PWGA) fresh BaP concentrations during December–January–February (DJF) compared to June–July–August (JJA), due to increased emissions from household activities and reduced removal processes during colder months. The shielded and ROI-T approaches, which account for OA coatings, result in 2–6 times higher BaP concentrations in DJF compared to NOA. The shielded simulation predicts the highest PWGA fresh BaP concentration (1.3 ng m−3), with 90 % of BaP protected from oxidation. In contrast, the ROI-T approach forecasts lower concentrations in middle to low latitudes, as it assumes less effective OA coatings under warmer, more humid conditions. Evaluations against observed BaP concentrations show the shielded approach performs best, with a normalized mean bias (NMB) within ± 20 %. The combined incremental lifetime cancer risk (ILCR) for both fresh and oxidized PAHs is similar across simulations, emphasizing the importance of considering both forms in health risk assessments. This study highlights the critical role of accurate degradation approaches in PAH modeling

User guide for ACSM data processing and PMF application using SoFi Pro

This document is intended for everyone who wants to investigate source apportionment using the PMF method on SoFi Pro software. This version is specifically designed for the analysis of ACSM data. It details all the steps for the preparation of data in Igor within the ACSM data acquisition software (ACSM Local, Aerodyne Research Inc.) and then the steps to perform PMF using SoFi (Source Finder Datalystica Ltd., Villigen, Switzerland)

Simulating synergism or antagonism in binary mixtures with different modeling approaches – A case study focused on the effect of disinfection by-products on algal growth

International audienceThis paper aims to test several modeling approaches for predicting toxicity of binary mixtures with potential synergy and antagonism. The approach based on the construction of isoboles was first tested and criticized. In contrast to conventional approaches, and in order to be mathematically consistent with the additivity assumptions, non-linear isoboles have been constructed. This approach was compared with that proposed by Minto et al. (2000), which measures deviations from additivity by considering standardized variables and which considers the entire Hill concentration-response curves. The selected models were tested on a case study related to chlorine-based disinfectant by-products (DBPs), using experimental data describing the effect of five DBPs (monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid and 1,1-dichloropropan-2-one) on a unicellular green algae Raphidocelis subcapitata. The approach based on the construction of isoboles has shown its limitations. Indeed, in cases where the individual substances involved have different slopes in terms of their Hill concentration-effect relationships, the so-called zone of indetermination can be large. Furthermore, conclusions drawn from isoboles based on EC50s or EC20s may not be consistent. Minto's approach makes it possible to construct interaction indicators that consider the entire Hill concentration-response curve. Response surfaces can be constructed to visualize the areas of concentration of the two substances involved that maximize the interaction effects

Mechanical stability of salt caverns under intensive gas storage conditions using LOCAS and DISROC

International audienceIn gas storage operations, injection and withdrawal rates can reach high levels to meet increasing demand. Salt caverns intensive exploitation methods introduce significant mechanical challenges, particularly wall spalling. Spalling involves the detachment of plates or blocks from the cavern walls or roof, occurring with minimal volume loss, unlike progressive closure through creep. This study focuses on the detachment of overhanging blocks within specific salt caverns. Wall spalling is of particular concern because it can compromise the structural stability of the caverns, damaging well tubing posing risks to both the safety and the efficiency of storage operations. This article explores the mechanical stability of salt caverns using two finite element software. LOCAS software identifies potential failure zones in continuous media. It helps to examine damage initiation due to salt dilation and the onset of effective tensile stresses at the cavern wall. Dilatancy refers to the volume increase accompanying material deformation under stress, leading to microcracks formation. DISROC software simulates crack initiation and propagation for detailed failure analysis. It employs joint element model to visualize failure mechanisms in the selected cavern blocks. Simulating crack formation and propagation at the joints between blocks, offers a detailed perspective on how failure develop and extend within the cavern structure. These two methods are compared to assess the onset of damage and associated mechanisms in salt caverns under intensive gas storage conditions

Technical note: Reconstructing missing surface aerosol elemental carbon data in long-term series with ensemble learning

International audienceGround-based measurements of elemental carbon (EC) – classified under thermal–optical methods and considered a surrogate for black carbon – are essential for assessing air quality and evaluating climate impacts. However, data gaps caused by technical challenges impede comprehensive analyses of long-term trends. This study proposed an ensemble learning modeling method to address these challenges. The model used readily accessible ground observation air pollutant data as proxies for EC-related tracers, along with meteorological parameters, to enhance prediction accuracy. It integrated outputs from Gradient Boosting Regression Trees, eXtreme Gradient Boosting, and random forest models, combining them through ridge regression to produce robust predictions. We applied this approach to reconstruct hourly EC concentrations from 2013–2023 for four cities in eastern China, filling 45 %–79 % of missing data and improving prediction performance by 8 %–17 % compared to individual models. Over the 11-year period, EC exhibited an overall decline (−0.20 to -0.14µgm-3a-1), with a more significant decrease from 2013–2020 (−0.24 to -0.15µgm-3a-1). During this time, the average EC concentration in the four cities dropped from 3.26 to 1.59 µg m−3, followed by a noticeable slowdown in the rate of decline from 2020–2023 (−0.12 to -0.04µgm-3a-1). Additionally, a fixed emission approximation method based on ensemble learning was proposed to quantitatively analyze the drivers of long-term EC trends. The analysis revealed that anthropogenic emission controls were the predominant contributors, accounting for approximately 92 % of the changes in EC trends from 2013–2020. However, their influence weakened post-2020, contributing approximately 80 %. These findings highlighted that while China's Clean Air Actions implemented since 2013 have substantially reduced black carbon concentrations, sustained and enhanced strategies are still necessary to further mitigate black carbon pollution

Identification of new PFAS for severe interference with thyroid hormone transport: A combined in vitro/silico approach

International audienceA tiered in vitro/in silico approach was developed to screen 12,654 per- and polyfluoroalkyl substances (PFAS) for their potential to disrupt the thyroid hormone transport. Initially, a set of 45 PFAS was tested using TTR-TRβ-CALUX bioassay, which was subsequently employed to develop a classification model, distinguishing active and inactive PFAS. The model fulfills all good practices for QSAR model validation and can predict whether a given PFAS can disrupt plasma transport of the thyroid hormone (T4). Subsequently, active compounds were used to develop two regression approaches: (i) multiple linear regression MLR, and (ii) second approach aimed at identifying multiple valid QSAR models based on different data-splitting strategies. Finally, a comprehensive virtual screening of a large PFAS dataset was conducted to assess their potency in disrupting thyroid hormone transport. The predictions indicated that more than 7500 compounds were active with over 100 PFAS potentially causing even greater adverse effects than PFOA. These findings highlight the critical role of integrating New Approach Methodologies (NAM)-based in vitro toxicity testing with multifaceted molecular modeling in assessing the risks associated with PFAS contamination in environmental matrices

La fabrique de la prévention des risques industriels majeurs en chimie de spécialité : bilan et perspectives

International audienceCe chapitre se nourrit du long travail effectué depuis 2004 conjointement, ou séparément par les deux auteur.e.s pour comprendre la fabrique de laprévention des risques industriels majeurs au sein d’entreprises de la chimie, et en particulier de la chimie de spécialité1, mais aussi d’autres systèmes à risques, tels que des installations nucléaires de base, des stockages de déchets nucléaires, des usines pyrotechniques, de la métallurgie ou le transport de gaz… La recherche commune porte sur cinq grands cas de chimie de spécialité que nous avons observés, décrits et analysés en étant attentifs au travail de la grande pluralité d’acteurs contribuant dans ces entreprises à produire la sécurité industrielle3 par interactions avec des acteurs externes

Évaluation des sols contaminés en cours de renaturation à l’aide d’indicateurs de la fonctionnalité et de l’écotoxicité des sols pollués aux métaux

International audienceL’écosystème constitué par le continuum sol-plante-eau peut être exposé à des situations de pollution, notamment aux métaux. De nouvelles utilisations des sols pollués peuvent être envisagées afin de les protéger et de restaurer voire d’améliorer leurs fonctions tout en réduisant l’exposition aux polluants. Dans ce contexte, des approches de réhabilitation écologique qui prennent en compte le degré de dégradation de l’écosystème, les utilisations futures des terres, le caractère abordable des solutions et l’impact du changement climatique peuvent être pertinentes. Ainsi, à travers 2 projets en cours (REVE, REECOL), plusieurs couvertures végétales sur plusieurs sites contaminés par des métaux seront suivies. De plus, divers indicateurs physico-chimiques, biologiques et écotoxicologiques seront mesurés pour caractériser la qualité du sol en relation avec ces couverts végétaux ainsi que la qualité et la santé de ces derniers. Les meilleures stratégies pour réduire l’exposition aux métaux tout en offrant d’autres avantages sur les fonctions du sol, l’amélioration de la biodiversité et les services écosystémiques seront étudiées. Les résultats présentés ici se concentrent exclusivement sur le projet REVE

Biodegradability of commercially available cellulose-PLA based compostable food trays – Influence of usage and UV aging

International audienceThis study aimed to assess the biodegradability and behavior of cellulose trays coated with PLA-based liners, marketed as compostable alternatives to non-biodegradable polyolefin trays. Three commercial trays were analyzed by NMR, FTIR and SEC, revealing that their liners contained two to four polymers. Furthermore, the time and temperature conditions to which the material is exposed prior to consumption may influence certain properties of these innovative cellulose-based trays, ultimately affecting their biodegradability. A usage protocol simulating real-life conditions was developed. Post-usage analysis revealed structural failures in the trays, while the relative polymer composition of the liners remained almost unchanged. In addition, the question of whether solar irradiation during time spent in the sun on the surface of various ecosystems, in the case of unintentional release, could also affect biodegradability was examined. Simulated environmental exposure by UV irradiation led to changes in the composition of some liners. Both aging processes appear to have a non significant effect on biodegradation. Interestingly, biodegradation studies indicated varying degradation level among the trays, despite their similar cellulose content. Trays biodegradation percentages ranged from 70 to just 40 % after 60 days. The biodegradation of the liners themselves was lower, ranging from 30 % to 0 %. 1H NMR analysis revealed that the biodegradation level can be correlated with the presence of specific polymers. These findings highlight concerns about the environmental impact of combined materials when one fraction, here the liner, that fails to biodegrade, even if the trays themselves pass biodegradation tests. The study underlines the importance of assessing the biodegradation of the final packaging as a whole, rather than evaluating only the raw materials

Influence of vent distribution on the violence of a gas explosion

International audienceThe development of new energies has led to their implementation in ISO maritime containers, raising the risk of flammable gas accumulation and explosion. Vent panels are commonly used to release excess gas produced by combustion and limit explosion overpressure. However, explosion discharge orifices are generally concentrated in one area. Little research has been done on the impact of vent distribution across the enclosure's surface. This article presents the results of an experimental study in which 1.2 m2 of vent area was distributed over the surface of a 37 m3 blast chamber. Four vent surface distribution configurations are studied. Two flammable mixtures, 15.5% and 17.4% hydrogen-air, respectively, were used, with two ignition source locations (backwall, central). An experimental study found that vent distribution reduces internal overpressure in the case of backwall ignition but has little influence when the ignition source is central. However, vent distribution plays a significant role in reducing external pressure effects