On the correlation between hygroscopic properties and chemical composition of cloud condensation nuclei obtained from the chemical aging of soot particles with O3 and SO2

Soot particles released in the atmosphere have long been investigated for their ability to affect the radiative forcing. Although freshly emitted soot particles are generally considered to yield only positive contributions to the radiative forcing, atmospheric aging can activate them into efficient cloud condensation or ice nuclei, which can trigger the formation of persistent clouds and ultimately provide a negative contribution to the radiative forcing. Depending on their residence time in the atmosphere, soot particles can undergo several physical and chemical aging processes that affect their chemical composition, particle size distribution and morphology, and ultimately their optical and hygroscopic properties. The impact of the physical-chemical aging on the properties of soot particles is still difficult to quantify, as well as their effect on the radiative forcing of the atmosphere. This work investigates the hygroscopic properties of chemically aged soot particles obtained from the combustion of aviation fuel, and in particular the interplay between aging mechanisms initiated by two widespread atmospheric oxidizers (O3 and SO2). Activation is measured in water supersaturation conditions using a cloud condensation nuclei counter. Once particle morphology and size distribution are taken into account, the hygroscopicity parameter κ is derived using κ-Köhler theory and correlated to the change of the chemical composition of the particles aged in a simulation chamber. While fresh soot particles are poor cloud condensation nuclei (κ < 10-4) and are not significantly affected by either O3 or SO2 at the timescale of the experiments, rapid activation is observed when they are simultaneously exposed to both oxidizers. Activated particles become efficient cloud condensation nuclei, comparable to the highly hygroscopic particulate matter typically found in the atmosphere (κ = 0.2-0.6 at RH = 20 %). Statistical analysis reveals a correlation between the activation and sulfur-containing ions detected on the chemically aged particles that are absent from the fresh particles.

Complex urban atmosphere alters alveolar stem cells niche properties and drives lung fibrosis

There is growing evidence suggesting that urban pollution has adverse effects on lung health. However, how urban pollution affects alveolar mesenchymal and epithelial stem cell niches remains unknown. This study aimed to determine how complex representative urban atmospheres alter alveolar stem cell niche properties. Mice were placed in an innovative chamber realistically simulating the atmosphere of a megalopolis, or "clean air," for 7 days. Lungs were collected, and fibroblasts and epithelial cells (EpCAM+) were isolated. Proliferative capacities of fibroblasts were tested by population doubling levels (PDL), and microarray analyses were performed. Fibroblasts and EpCAM+ cells from exposed, nonexposed, or naive mice were cocultured in organoid assays to assess the stem cell properties. Collagen deposition (Sirius red), lipofibroblasts (ADRP, COL1A1), myofibroblasts (αSMA), alveolar type 2 cells (AT2, SFTPC+), and alveolar differentiation intermediate cell [ADI, keratin-8-positive (KRT8+)/claudin-4-positive (CLDN4+)] markers were quantified in the lungs. Fibroblasts obtained from mice exposed to urban atmosphere had lower PDL and survival and produced fewer and smaller organoids. Microarray analysis showed a decrease of adipogenesis and an increase of genes associated with fibrosis, suggesting a lipofibroblast to myofibroblast transition. Collagen deposition and myofibroblast number increased in the lungs of urban atmosphere-exposed mice. AT2 number was reduced and associated with an increase in ADI cells KRT8+/CLDN4+. Furthermore, EpCAM+ cells from exposed mice also produced fewer and smaller organoids. In conclusion, urban atmosphere alters alveolar mesenchymal stem cell niche properties by inducing a lipofibroblast to myofibroblast shift. It also results in alveolar epithelial dysfunction and a fibrotic-like phenotype.NEW & NOTEWORTHY Urban pollution is known to have major adverse effects on lung health. To assess the effect of pollution on alveolar regeneration, we exposed adult mice to a simulated high-pollution urban atmosphere, using an innovative CESAM simulation chamber (Multiphase Atmospheric Experimental Simulation Chamber, https://cesam.cnrs.fr/). We demonstrated that urban atmosphere alters alveolar mesenchymal stem cell niche properties by inducing a lipofibroblast to myofibroblast shift and induces alveolar epithelial dysfunction.

Infrared optical signature reveals the source-dependency and along-transport evolution of dust mineralogy as shown by laboratory study

Advancing knowledge of the mineralogical composition of dust is key for understanding and predicting its climate and environmental impacts. The variability of dust mineralogy from one source to another and its evolution during atmospheric transport is not measured at large scale. In this study we use laboratory measurements to demonstrate that the extinction signature of suspended dust aerosols in the 740 - 1250 cm-1 atmospheric window can be used to derive dust mineralogy in terms of the main infrared - active minerals, namely quartz, clays, feldspars and calcite. Various spectral signatures in dust extinction enable to distinguish between multiple global sources with changing composition, whereas modifications of the dust extinction spectra with time inform on size - dependent particles mineralogy changes during transport. The present study confirms that spectral and hyperspectral infrared remote sensing observations offer great potential for elucidating the size - segregated mineralogy of airborne dust at regional and global scales.

Correction to Brown Carbon from Photo-Oxidation of Glyoxal and SO2 in Aqueous Aerosol

[This corrects the article DOI: 10.1021/acsearthspacechem.3c00035.].

Brown Carbon from Photo-Oxidation of Glyoxal and SO2 in Aqueous Aerosol

Aqueous-phase dark reactions during the co-oxidation of glyoxal and S(IV) were recently identified as a potential source of brown carbon (BrC). Here, we explore the effects of sunlight and oxidants on aqueous solutions of glyoxal and S(IV), and on aqueous aerosol exposed to glyoxal and SO₂. We find that BrC is able to form in sunlit, bulk-phase, sulfite-containing solutions, albeit more slowly than in the dark. In more atmospherically relevant chamber experiments where suspended aqueous aerosol particles are exposed to gas-phase glyoxal and SO₂, the formation of detectable amounts of BrC requires an OH radical source and occurs most rapidly after a cloud event. From these observations we infer that this photobrowning is caused by radical-initiated reactions as evaporation concentrates aqueous-phase reactants and aerosol viscosity increases. Positive-mode electrospray ionization mass spectrometric analysis of aerosol-phase products reveals a large number of C_xH_yO_z oligomers that are reduced rather than oxidized (relative to glyoxal), with the degree of reduction increasing in the presence of OH radicals. This again suggests a radical-initiated redox mechanism where photolytically produced aqueous radical species trigger S(IV)-O₂ auto-oxidation chain reactions, and glyoxal-S(IV) redox reactions especially if aerosol-phase O₂ is depleted. This process may contribute to daytime BrC production and aqueous-phase sulfur oxidation in the atmosphere. The BrC produced, however, is about an order of magnitude less light-absorbing than wood smoke BrC at 365 nm.

Kinetics, Products, and Brown Carbon Formation by Aqueous-Phase Reactions of Glycolaldehyde with Atmospheric Amines and Ammonium Sulfate

Glycolaldehyde (GAld) is a C₂ water-soluble aldehyde produced during the atmospheric oxidation of isoprene and many other species and is commonly found in cloudwater. Previous work has established that glycolaldehyde evaporates more readily from drying aerosol droplets containing ammonium sulfate (AS) than does glyoxal, methylglyoxal, or hydroxyacetone, which implies that it does not oligomerize as quickly as these other species. Here, we report NMR measurements of glycolaldehyde’s aqueous-phase reactions with AS, methylamine, and glycine. Reaction rate constants are smaller than those of respective glyoxal and methylglyoxal reactions in the pH range of 3–6. In follow-up cloud chamber experiments, deliquesced glycine and AS seed particles were found to take up glycolaldehyde and methylamine and form brown carbon. At very high relative humidity, these changes were more than 2 orders of magnitude faster than predicted by our bulk liquid NMR kinetics measurements, suggesting that reactions involving surface-active species at crowded air–water interfaces may play an important role. The high-resolution liquid chromatography–electrospray ionization–mass spectrometric analysis of filter extracts of unprocessed AS + GAld seed particles identified sugar-like C₆ and C₁₂ GAld oligomers, including proposed product 3-deoxyglucosone, with and without modification by reactions with ammonia to diimine and imidazole forms. Chamber exposure to methylamine gas, cloud processing, and simulated sunlight increased the incorporation of both ammonia and methylamine into oligomers. Many C₄–C₁₆ imidazole derivatives were detected in an extract of chamber-exposed aerosol along with a predominance of N-derivatized C₆ and C₁₂ glycolaldehyde oligomers, suggesting that GAld is capable of forming brown carbon SOA.

Kinetic Study of the Temperature Dependence of OH-Initiated Oxidation of n-Dodecane

Reaction rate constants for the reaction of n-dodecane with hydroxyl radicals were measured as a function of temperature between 283 and 303 K, using the relative rate method in the CESAM chamber (French acronym for "experimental multiphasic atmospheric simulation chamber"). The rate constants obtained at 283, 293, and 303 K are (1.27 ± 0.31) × 10^-11, (1.33 ± 0.34) × 10^-11, and (1.27 ± 0.40) × 10^-11 cm³ molecule^-1 s^-1, respectively. Rate constants measured were in excellent agreement with the few available data in the literature over the studied temperature range (283-340 K). Rate constants estimated by the structure-activity relationship and transition state theory methods agreed with our experimental data within 14%. From these data combined with previous literature measurement, the following Arrhenius expression, k_DDC+OH = (9.77 ± 6.19) × 10^-11 × exp[(-595 ± 5580)/T] cm³ molecule^-1 s^-1, was found to be valid over a temperature range (283-340 K) of the tropospheric interest.

Water content of limestones submitted to realistic wet deposition: a CIME2 chamber simulation

An experimental chamber (CIME2) has been specially designed to simulate wet atmospheric deposition on limestones used in Paris cultural heritage. This instrument is a complementary tool to CIME, a previously developed chamber dedicated to the simulation of dry atmospheric deposition on monuments and artifacts. The aim of this paper is to describe CIME2 and characterize the wet deposits produced inside it. Mist (fog), drizzle, and rainfall are differentiated in order to document their ability to saturate the limestones most currently used in Paris monuments: The Saint-Maximin's limestone, the Liais of Saint-Maximin, and the Chauvigny's limestone are tested. The comparison between normalized and environmental petrophysical data shows that in the wet deposition simulations, limestones are not systematically water-saturated. Moreover, the realistic experimental conditions chosen favor a more rapid evaporation of the stone water. The quantification of the non-saturation state is a first step that has to be taken into account to improve the geochemical models used to predict the alteration.

Nitrogen-Containing, Light-Absorbing Oligomers Produced in Aerosol Particles Exposed to Methylglyoxal, Photolysis, and Cloud Cycling

Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon aerosol particles collected from cloud cycling/photolysis chamber experiments, where gaseous methylglyoxal and methylamine interacted with glycine, ammonium, or methylammonium sulfate seed particles. Eighteen N-containing oligomers were identified in the particulate phase by liquid chromatography/diode array detection/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry. Chemical formulas were determined and, for 6 major oligomer products, MS² fragmentation spectra were used to propose tentative structures and mechanisms. Electronic absorption spectra were calculated for six tentative product structures by an ab initio second order algebraic-diagrammatic-construction/density functional theory approach. For five structures, matching calculated and measured absorption spectra suggest that they are dominant light-absorbing species at their chromatographic retention times. Detected oligomers incorporated methylglyoxal and amines, as expected, but also pyruvic acid, hydroxyacetone, and significant quantities of acetaldehyde. The finding that ∼80% (by mass) of detected oligomers contained acetaldehyde, a methylglyoxal photolysis product, suggests that daytime methylglyoxal oligomer formation is dominated by radical addition mechanisms involving CH₃CO*. These mechanisms are evidently responsible for enhanced browning observed during photolytic cloud events.

Cloud Processing of Secondary Organic Aerosol from Isoprene and Methacrolein Photooxidation

Aerosol-cloud interaction contributes to the largest uncertainties in the estimation and interpretation of the Earth's changing energy budget. The present study explores experimentally the impacts of water condensation-evaporation events, mimicking processes occurring in atmospheric clouds, on the molecular composition of secondary organic aerosol (SOA) from the photooxidation of methacrolein. A range of on- and off-line mass spectrometry techniques were used to obtain a detailed chemical characterization of SOA formed in control experiments in dry conditions, in triphasic experiments simulating gas-particle-cloud droplet interactions (starting from dry conditions and from 60% relative humidity (RH)), and in bulk aqueous-phase experiments. We observed that cloud events trigger fast SOA formation accompanied by evaporative losses. These evaporative losses decreased SOA concentration in the simulation chamber by 25-32% upon RH increase, while aqueous SOA was found to be metastable and slowly evaporated after cloud dissipation. In the simulation chamber, SOA composition measured with a high-resolution time-of-flight aerosol mass spectrometer, did not change during cloud events compared with high RH conditions (RH > 80%). In all experiments, off-line mass spectrometry techniques emphasize the critical role of 2-methylglyceric acid as a major product of isoprene chemistry, as an important contributor to the total SOA mass (15-20%) and as a key building block of oligomers found in the particulate phase. Interestingly, the comparison between the series of oligomers obtained from experiments performed under different conditions show a markedly different reactivity. In particular, long reaction times at high RH seem to create the conditions for aqueous-phase processing to occur in a more efficient manner than during two relatively short cloud events.

Brown Carbon Production in Ammonium- or Amine-Containing Aerosol Particles by Reactive Uptake of Methylglyoxal and Photolytic Cloud Cycling

The effects of methylglyoxal uptake on the physical and optical properties of aerosol containing amines or ammonium sulfate were determined before and after cloud processing in a temperature- and RH-controlled chamber. The formation of brown carbon was observed upon methylglyoxal addition, detected as an increase in water-soluble organic carbon mass absorption coefficients below 370 nm and as a drop in single-scattering albedo at 450 nm. The imaginary refractive index component k₄₅₀ reached a maximum value of 0.03 ± 0.009 with aqueous glycine aerosol particles. Browning of solid particles occurred at rates limited by chamber mixing (<1 min), and in liquid particles occurred more gradually, but in all cases occurred much more rapidly than in bulk aqueous studies. Further browning in AS and methylammonium sulfate seeds was triggered by cloud events with chamber lights on, suggesting photosensitized brown carbon formation. Despite these changes in optical aerosol characteristics, increases in dried aerosol mass were rarely observed (<1 μg/m³ in all cases), consistent with previous experiments on methylglyoxal. Under dry, particle-free conditions, methylglyoxal reacted (presumably on chamber walls) with methylamine with a rate constant k = (9 ± 2) × 10^-17 cm³ molecule^-1 s^-1 at 294 K and activation energy E_a = 64 ± 37 kJ/mol.

High-NOx Photooxidation of n-Dodecane: Temperature Dependence of SOA Formation

The temperature and concentration dependence of secondary organic aerosol (SOA) yields has been investigated for the first time for the photooxidation of n-dodecane (C₁₂H₂₆) in the presence of NO_x in the CESAM chamber (French acronym for "Chamber for Atmospheric Multiphase Experimental Simulation"). Experiments were performed with and without seed aerosol between 283 and 304.5 K. In order to quantify the SOA yields, a new parametrization is proposed to account for organic vapor loss to the chamber walls. Deposition processes were found to impact the aerosol yields by a factor from 1.3 to 1.8 between the lowest and the highest value. As with other photooxidation systems, experiments performed without seed and at low concentration of oxidant showed a lower SOA yield than other seeded experiments. Temperature did not significantly influence SOA formation in this study. This unforeseen behavior indicates that the SOA is dominated by sufficiently low volatility products for which a change in their partitioning due to temperature would not significantly affect the condensed quantities.

Characterisation of CIME, an experimental chamber for simulating interactions between materials of the cultural heritage and the environment

An approach consisting in combining in situ and laboratory experiments is often favoured for investigating the mechanisms involved in the weathering of the materials of the cultural heritage. However, the realistic simulation in the laboratory of the environmental conditions ruling the interactions of atmospheric compounds with materials is a very complex task. The aim of this work is to characterise CIME, a new chamber specially built to simulate the interactions between materials of the cultural heritage and the environment. The originality of this instrument is that beside the usual climatic parameters (temperature, relative humidity, solar radiation) and gaseous pollutants, it also allows the controlled injection of different types of particulate matter such as terrigenous, marine and anthropogenic. Therefore, varied realistic atmospheric environments (marine or urban) can be easily simulated within CIME. In addition to the technical description of CIME, this paper shows the first results obtained by the impact of gaseous pollutants on non-durable glass, bronze and limestone. The first experiments for the deposition of different particles (calcite, clays, soot and halite) are also presented.

Variable-length cell for studies of gas spectra with extremely short optical paths

We present a cell for studies of light transmission through very strongly absorbing gases. It uses a fixed window and a mirror, parallel to the latter and attached to a micrometric linear motion feedthrough monitoring mirror-window distances from 0 to a couple of centimeters. This device is tested by recording CO2 gas spectra near 4.3 μm using a Fourier transform spectrometer. Their analysis shows that optical-path lengths between 20 and 2000 μm have been obtained. This now enables spectroscopic measurements of self-broadening coefficients of O16C12O16 lines in the ν3 band, for instance, and opens perspectives for optical soundings of thin films of porous materials.

Atmospheric fate of a series of carbonyl nitrates: photolysis frequencies and OH-oxidation rate constants

Multifunctional organic nitrates are potential NO(x) reservoirs whose atmospheric chemistry is somewhat little known. They could play an important role in the spatial distribution of reactive nitrogen species and consequently in ozone formation and distribution in remote areas. In this work, the rate constants for the reaction with OH radical and the photolysis frequencies of α-nitrooxyacetone, 3-nitrooxy-2-butanone, and 3-methyl-3-nitrooxy-2-butanone have been determined at room temperature at 1000 mbar total pressure of synthetic air. The rate constants for the OH oxidation were measured using the relative rate technique, with methanol as reference compound. The following rate constants were obtained for the reaction with OH: k(OH) = (6.7 ± 2.5) × 10(-13) cm(3) molecule(-1) s(-1) for α-nitrooxyacetone, (10.6 ± 4.1) × 10(-13) cm(3) molecule(-1) s(-1) for 3-nitrooxy-2-butanone, and (2.6 ± 0.9) × 10(-13) cm(3) molecule(-1) s(-1) for 3-methyl-3-nitrooxy-2-butanone. The corresponding photolysis frequencies extrapolated to typical atmospheric conditions for July first at noon at 40° latitude North were (4.8 ± 0.3) × 10(-5) s(-1), (5.7 ± 0.3) × 10(-5) s(-1), and (7.4 ± 0.2) × 10(-5) s(-1), respectively. The data show that photolysis is a major atmospheric sink for these organic nitrates.

[Uterine leiomyosarcoma. Nine case reports, review of the literature]

OBJECT OF THE STUDY

To evaluate management and outcome of the treatment of uterine leiomyosarcoma.

PATIENTS AND METHODS

Retrospective study of a series of 9 patients treated for uterine leiomyosarcoma in this hospital from 1982 to 1994.

RESULTS

The condition is rarely suspected preoperatively, diagnosis is usually made on histological examination of the operative specimen. The outcome is related to the mitotic activity of the tumour and to the infiltration of nearly structures. Surgery is the only effective treatment, chemotherapy is ineffective, adjuvant radiotherapy improves local control of the tumour but has no incidence on survival.

CONCLUSION

In the absence of an effective adjuvant treatment uterine leiomyosarcoma bears a poor prognosis with the only exception of small non infiltrating tumours with a low mitotic activity.

[Hydranencephaly. Report of a new case]

Hydranencephaly is the total or virtually total absence of the cerebral hemispheres, which are reduced to a membranous sac of glial tissue, with no ependymal coating, in an intact skull. This is rare disorder (0.5 per thousand births). It is classified as a circulatory encephalopathy. Two opposing theories are generally advanced: the encephaloclastic or destructive theory and the theory of dysontogensis or malformation, due to early disruption of organogenesis. It has many causes (vascular, viral, parasitic, genetic, toxic, estrogenic...). It appears to be readily diagnosed by ultrasound, the neurological findings may be normal at birth, but transillumination of the skull remains a simple and reliable diagnostic test. Transfontanellar ultrasound, CT scanning and anatomical confirmation alone can establish the diagnosis. The prognosis is hopeless and there is no treatment.

[Fatal maternal streptococcus A infection after cesarean section]

A case is reported of an infection with Streptococcus pyogenes, occurring 24 hours after an elective Caesarean section in a 30 year old woman. She worsened during the first 48 h, with shock (Pasys less than 70 mmHg, pH 7.28) as well as abdominal tenderness and guarding. Laparotomy revealed peritonitis, and subtotal hysterectomy was carried out. Gram positive cocci were found in the peritoneal exudate, with bacterial cultures yielding Streptococcus pyogenes. Histopathological examination of the specimen revealed necrosing endomyometritis with septic thrombophlebitis. During the immediate post-operative period, there were several prolonged episodes of circulatory arrest treated with dobutamine, adrenaline, and noradrenaline. Multiple organ failure occurred during the next five days, despite antibiotic therapy (vancomycin, tienamycin, amikacin) and intensive care. It included jaundice, thrombocytopaenia (10 G.l(-1] adult respiratory distress syndrome (ARDS). A further laparotomy was carried out because of abdominal and thigh cellulitis, with completion of the hysterectomy and bilateral salpingo-oophorectomy. Streptococcus pyogenes was still present in the peritoneal cavity. There followed an improvement, with a return to normal of the platelet count, haemodynamic stability such that vasoactive drugs were no longer needed, and a decrease in the degree of jaundice. However, the ARDS worsened, and the patient died 15 days after the Caesarean section. There have been recent reports of similar cases, suggesting an increase in the virulence of group A streptococci linked to a re-emergence of exotoxin A.

[Lobular carcinoma in situ of the breast. Apropos of 3 cases]

The authors explain the particular nature of these multifocal tumors: absence of node involvement, difficulties of diagnosis, relatively favorable prognosis and a therapeutic dilemma: limited procedure with strict surveillance, subcutaneous bilateral mastectomy.