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1.
Science ; 379(6627): 16-17, 2023 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-36603095
2.
Sensors (Basel) ; 22(23)2022 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-36501859

RESUMO

Precise and accurate measurements of ambient HNO3 are crucial for understanding various atmospheric processes, but its ultra-low trace amounts and the high polarity of HNO3 have strongly hindered routine, widespread, direct measurements of HNO3 and restricted field studies to mostly short-term, localized measurement campaigns. Here, we present a custom field-deployable direct absorption laser spectrometer and demonstrate its analytical capabilities for in situ atmospheric HNO3 measurements. Detailed laboratory characterizations with a particular focus on the instrument response under representative conditions for tropospheric measurements, i.e., the humidity, spectral interference, changing HNO3 amount fractions, and air-sampling-related artifacts, revealed the key aspects of our method: (i) a good linear response (R2 > 0.98) between 0 and 25 nmol·mol-1 in both dry and humid conditions with a limit of detection of 95 pmol·mol-1; (ii) a discrepancy of 20% between the spectroscopically derived amount fractions and indirect measurements using liquid trapping and ion chromatography; (iii) a systematic spectral bias due to water vapor. The spectrometer was deployed in a three-week field measurement campaign to continuously monitor the HNO3 amount fraction in ambient air. The measured values varied between 0.1 ppb and 0.8 ppb and correlated well with the daily total nitrates measured using a filter trapping method.


Assuntos
Poluentes Atmosféricos , Poluentes Atmosféricos/análise , Ar/análise , Nitratos , Lasers
3.
Zhonghua Yan Ke Za Zhi ; 58(11): 949-953, 2022 Nov 11.
Artigo em Chinês | MEDLINE | ID: mdl-36348539

RESUMO

With the expansion of human exploration and activities, increasing people work and live in special natural environments with relatively unique characteristics, which can not only lead to pathophysiological changes and metabolic disorders, but also have a great impact on eyes and intraocular pressure (IOP). This article reviews the effects of the high-altitude hypoxia environment, space microgravity environment, deep water environment, dark environment, cold environment and ambient air pollution on IOP, and discusses the mechanisms of related IOP changes.


Assuntos
Oftalmopatias , Pressão Intraocular , Humanos , Tonometria Ocular , Hipóxia , Ar
4.
Chest ; 162(5): 1145-1146, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36344116

Assuntos
Respiração , Água , Humanos , Ar
5.
J Phys Chem A ; 126(44): 8280-8294, 2022 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-36288121

RESUMO

Organic molecules, including α-hydroxyacids, are ubiquitous in the natural environment. Often found at water-air interfaces, organic molecules can alter the structure of the interface or participate in interfacial chemistry. Despite their prevalence in the environment, the structure and ordering of α-hydroxyacids have not been widely investigated at water-air interfaces, and the impact of the hydrophobic tail length on structure has not been explored. Here, for the first time, we use infrared reflection-absorption spectroscopy to assess the vibrational structure of α-hydroxyacids at a water surface as a function of surface partitioning and surface coverage. We study lactic acid, 2-hydroxyoctanoic acid, and 2-hydroxystearic acid, which have 1 carbon, 6 carbon, and 16 carbon tails, respectively. Vibrational features compared across the set of α-hydroxyacids studied here are used to determine the interaction of the polar headgroup with the water subphase and the ordering of the hydrophobic tail. We find that the carbonyl and α-hydroxyl groups participate in a complex hydrogen-bonding motif at the water-air interface that can be affected by the hydrophobic tail length and places the polar headgroup in or below the water-air interface. Furthermore, molecular ordering increases with the tail length or the surface coverage. The presence of the α-hydroxyl group causes the α-hydroxyacids to maintain a tilted orientation with respect to the surface normal even at high surface coverages. A combination of polar headgroup and hydrophobic tail effects dictates the overall orientation of α-hydroxyacids and can thus affect their ability to participate in chemistry and alter organic coatings on water surfaces.


Assuntos
Ar , Água , Água/química , Espectrofotometria Infravermelho/métodos , Ligação de Hidrogênio , Ácidos Carboxílicos , Carbono/química
6.
Sci Rep ; 12(1): 15887, 2022 09 23.
Artigo em Inglês | MEDLINE | ID: mdl-36151300

RESUMO

The interest around analysis of volatile organic compounds (VOCs) within breath has increased in the last two decades. Uncertainty remains around standardisation of sampling and whether VOCs within room air can influence breath VOC profiles. To assess the abundance of VOCs within room air in common breath sampling locations within a hospital setting and whether this influences the composition of breath. A secondary objective is to investigate diurnal variation in room air VOCs. Room air was collected using a sampling pump and thermal desorption (TD) tubes in the morning and afternoon from five locations. Breath samples were collected in the morning only. TD tubes were analysed using gas chromatography coupled with time-of-flight mass spectrometry (GC-TOF-MS). A total of 113 VOCs were identified from the collected samples. Multivariate analysis demonstrated clear separation between breath and room air. Room air composition changed throughout the day and different locations were characterized by specific VOCs, which were not influencing breath profiles. Breath did not demonstrate separation based on location, suggesting that sampling can be performed across different locations without affecting results.


Assuntos
Poluentes Atmosféricos , Líquidos Corporais , Compostos Orgânicos Voláteis , Ar/análise , Poluentes Atmosféricos/análise , Líquidos Corporais/química , Testes Respiratórios/métodos , Cromatografia Gasosa-Espectrometria de Massas/métodos , Compostos Orgânicos Voláteis/análise
7.
J Phys Chem A ; 126(39): 6908-6919, 2022 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-36129815

RESUMO

The spectroscopy of all-trans-retinoic acid (ATRA), an important molecule of biological origin that can be found in nature, is investigated at the air-water interface using UV-Vis and IR reflection spectroscopy. We employ a UV-Vis reflection absorption spectroscopy (RAS) experiment along with infrared reflection absorption spectroscopy (IR-RAS) to probe ATRA at the air-water interface. We elucidate the factors influencing the spectroscopy of ATRA at the air-water interface and compare its spectra at the water surface with results of bulk samples obtained with conventional spectroscopic methods and computational chemistry. Monolayers of pure ATRA as well as mixed ATRA with stearic-d35 acid were prepared, and the spectroscopy reveals that ATRA forms J-aggregates with itself, causing a significant redshift of its S0 to S1 electronic transition. Pure ATRA monolayers are found to be unstable at the air-water interface and are lost from the surface over time due to the formation of aggregates. The mixture of ATRA and stearic-d35 acid has been shown to stabilize the monolayers and inhibit the loss of surface ATRA. On the basis of our observations, we propose that ATRA could be a significant photosensitizer in natural aqueous environments.


Assuntos
Ar , Água , Fármacos Fotossensibilizantes , Espectrofotometria Infravermelho , Tretinoína , Água/química
8.
Environ Sci Process Impacts ; 24(10): 1821-1829, 2022 Oct 19.
Artigo em Inglês | MEDLINE | ID: mdl-36073596

RESUMO

Measurement of the composition of ambient air has become increasingly widespread over the last 50 years as the detrimental health effects of some air pollutants have become clearer and requirements for these measurements has been embedded in national and international legislation. The aim of this has been not only to assess exposure of the general population to air pollutants but also to assess the effectiveness of abatement strategies to reduce emissions of these pollutants at source. With a rich industrial heritage, the Swansea Valley (South Wales, UK) has long been associated with the refining and production of metal products, especially nickel. Despite a decline in output during the latter part of the twentieth century there is still sufficient activity to prompt a requirement for targeted air monitoring in the area. This is most important for nickel where there is a local history of measured concentrations exceeding legislative target values. This work demonstrates the effectiveness of nickel emissions abatement strategies over the last 50 years by tracking the falling air concentration of nickel over this period. It also demonstrates how the monitoring network in the Swansea Valley has expanded over this time and become significantly more sensitive to nickel emissions. The data presented represents a significant public health achievement - it is likely that the exposure to nickel in air of the population in the Swansea Valley has decreased more than 100-fold over the last 50 years - and reflects the progress in regulation, industrial efficiency, emissions abatement technology and air quality monitoring science achieved during this period.


Assuntos
Poluentes Atmosféricos , Poluição do Ar , Humanos , Níquel , Monitoramento Ambiental , Poluição do Ar/análise , Poluentes Atmosféricos/análise , Ar
9.
Water Res ; 224: 119027, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-36099759

RESUMO

Dissolved air flotation (DAF) is an efficient process to remove impurities from fresh or salt water. As the removal is based on the agglomeration of impurities on the generated microbubbles, the size distribution and concentration of air bubbles are key parameters in dissolved air flotation. However, the development of microbubbles in the whole flotation process remains unexplored. In this study, we show that state-of-the-art inline microscopy enables the image acquisition of bubbles in DAF. Based on image analysis, thousands of microbubbles (10-200 µm) were analyzed within 6-12 min experiments. Consequently, bubble size distributions and bubble concentrations can be determined with moderate effort. Bubble size distributions were measured in a lab-scale DAF comprising a saturation unit, a decompression valve in/after which the bubbles are formed, and the actual flotation tank. The state of the microbubbles is not only determined at different positions within the tank but also in the supply pipe from the decompression valve to the tank. All bubble size distributions were unimodal and can be described well with Burr XII distributions. For fresh water, bubble size increased while bubble concentration decreased along the supply pipe between the decompression valve and the inlet of the flotation tank, indicating bubble coalescence. Compared to freshwater, saltwater inhibited this bubble coalescence in the pipe. Within the flotation tank, the bubble size did not change drastically for neither salt- nor freshwater. However, the bubble concentration decreased for both waters, which could be explained by dilution effects. Our results demonstrate that the developed inline method is a promising tool to study the evolution of microbubbles in flotation systems. Further, it might also be applied to investigate microbubbles in other processes such as fermentation, decomposition of organic compounds, and fouling mitigation in membranes.


Assuntos
Microbolhas , Purificação da Água , Ar , Água Doce , Água , Purificação da Água/métodos
10.
J Chromatogr A ; 1682: 463507, 2022 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-36155078

RESUMO

Volatile halogenated compounds (VHCs) are important industrial chemicals and play a crucial role in potential stratospheric ozone-depletion and global warming. Profiling of VHCs is of great significance but replete with challenges due to the species' richness and diversity. In this study, we developed a novel method employing water removal mode combined with thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) for on-line measurement of VHCs at the ultratrace level. By removing water with Nafion dryer tandem cold trap device, VHCs could achieve better separation and identification, and detection precision of VHCs lower than 10%. The proposed method exhibited limits of detection for VHCs ranging from 0.1 to 6.2 pptv. Benefiting from the improved trapping efficiency due to water removal, we successfully quantified 34 VHCs at the Shangdianzi background station and achieved a comprehensive assessment of VHCs in ambient air.


Assuntos
Poluentes Atmosféricos , Compostos Orgânicos Voláteis , Ar/análise , Poluentes Atmosféricos/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Ozônio Estratosférico/análise , Compostos Orgânicos Voláteis/análise , Água/análise
11.
Opt Lett ; 47(17): 4339-4342, 2022 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-36048648

RESUMO

We study coherent anti-Stokes Raman spectroscopy in air-filled anti-resonance hollow-core photonic crystal fiber, otherwise known as "revolver" fiber. We compare the vibrational coherent anti-Stokes Raman signal of N2, at ∼2331 cm-1, generated in ambient air (no fiber present), with the one generated in a 2.96 cm of a revolver fiber. We show a ∼170 times enhancement for the signal produced in the fiber, due to an increased interaction path. Remarkably, the N2 signal obtained in the revolver fiber shows near-zero non-resonant background, due to near-zero overlap between the laser field and the fiber cladding. Through our study, we find that the revolver fiber properties make it an ideal candidate for the coherent Raman spectroscopy signal enhancement.


Assuntos
Lasers , Análise Espectral Raman , Ar , Luz , Fótons , Análise Espectral Raman/métodos
12.
J Therm Biol ; 108: 103276, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36031205

RESUMO

Vertical air temperature differences (VTDs) can have important influences on thermal comfort and the evaluation of air distributions. The air distributions might create either positive or negative VTDs. However, no research has clearly revealed the effect of different directions of VTDs on human comfort. To create environments with positive and negative VTDs in this study, the air temperature of half of the body was maintained at an air temperature of 25 °C, whereas the other half of the body (the upper or lower body part, respectively) was exposed to air temperatures of 22 °C, 25 °C, 28 °C, and 31 °C, respectively. That is two series of experiments with the same VTD value but different directions were compared, based on 16 subjects seated in a climatic box in a climate chamber. The thermal sensations, sick building syndrome (SBS) symptoms, and physiological responses of occupants were studied. The results showed that subjects were more sensitive to the VTD at the upper body part in warm environments with respect to thermal sensations, perceived air quality, and sweat intensity. The analysis indicated that there were more discomfort and heat stress for positive VTDs than negative VTDs. Thus, the criterion for acceptable negative VTDs should be different with the positive VTDs incorporated in current standards. Overall, the directions of the VTDs were suggested to be considered for evaluating the thermally stratified air distributions based on both of thermal comfort and energy efficiency in buildings.


Assuntos
Síndrome do Edifício Doente , Ar , Ar Condicionado , Humanos , Temperatura , Sensação Térmica
13.
Langmuir ; 38(32): 9751-9759, 2022 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-35921602

RESUMO

Interfacial properties of polymeric materials are significantly influenced by their architectural structures and spatial features, while such a study of topologically interesting macromolecules is rarely reported. In this work, we reported, for the first time, the interfacial behavior of catenated poly(l-lactide) (C-PLA) at the air-water interface and compared it with its linear analogue (L-PLA). The isotherms of surface pressure-area per repeating unit showed significant interfacial behavioral differences between the two polymers with different topologies. Isobaric creep experiments and compression-expansion cycles also showed that C-PLA demonstrated higher stability at the air-water interface. Interestingly, when the films at different surface pressures were transferred via the Langmuir-Blodgett method, successive atomic force microscopy imaging displayed distinct nanomorphologies, in which the surface of C-PLA exhibited nanofibrous structures, while that of the L-PLA revealed a smoother topology with less fiber-like structures.


Assuntos
Ar , Água , Microscopia de Força Atômica , Poliésteres/química , Polímeros/química , Propriedades de Superfície , Água/química
14.
J Phys Chem B ; 126(29): 5481-5489, 2022 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-35839485

RESUMO

This work investigates the interactions in cholesterol and sphingomyelin monolayers at the molecular level by high-resolution broadband sum frequency generation vibrational spectroscopy (HR-BB-SFG-VS). The SFG spectra of natural egg sphingomyelin (ESM) as a function of cholesterol concentration are obtained at an air/water interface under different polarization combinations. The analysis of the spectra shows that cholesterol can induce sphingomyelin conformational changes at an air/water interface. The mechanism is proposed. When cholesterol is inserted into the ESM monolayer, the inherent intramolecular hydrogen bonds between the phosphate moiety and 3OH in the sphingosine backbones are destroyed. During this process, the sphingosine backbones become more ordered, while the conformation of the N-linked long acid chain remains unaltered. The OH of the cholesterol head group can bind to the -PO-2 of the ESM molecule, and the orientation of the -PO-2 in the head groups changes to be more parallel to the interface.


Assuntos
Esfingomielinas , Água , Ar , Colesterol/química , Esfingomielinas/química , Esfingosina , Água/química
15.
Sensors (Basel) ; 22(13)2022 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-35808483

RESUMO

Pollen grains strongly affect human health by inducing allergies. Although the monitoring of airborne pollens particles is of major importance, the current measurement methods are manually conducted and are expensive, limiting the number of monitoring stations. Thus, there is a need for relatively low-cost instruments that can work automatically. The possible detection of pollen in urban ambient air (Paris, France) has been reported using the LOAC optical aerosol counter. These measurements indicate that the pollen grains and their nature could be determined using their scattering properties. For this purpose, the scattering functions (intensity and linear polarization) of 21 different airborne pollens were established in the laboratory using a PROGRA2 instrument. The linear polarization curves were close together, with a maximum polarization lower than 10% in the red domain and 5% in the green domain. The variability from one sample to another was partly due to the different sizes of the grains. An instrument with an absolute accuracy of about ±1% for polarization measurements should then be needed, coupled with a counting instrument to take into account the effects of size. On the other hand, the scattering curves for intensity presented with different shapes and strong differences up to a factor of 20 at some scattering angles, due to the size, shape, surface texture, and composition of the grains. Thus, we propose a proof of concept for new automated sensors that can be used in dense networks to count and identify pollen grains by analyzing the light they scatter at some specific angles.


Assuntos
Poluentes Atmosféricos , Monitoramento Ambiental , Aerossóis , Ar , Poluentes Atmosféricos/análise , Monitoramento Ambiental/métodos , Humanos , Pólen/química
16.
J Am Chem Soc ; 144(23): 10524-10529, 2022 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-35658415

RESUMO

Whether the air-water interface decreases or increases the acidity of simple organic and inorganic acids compared to the bulk is critically important in a broad range of environmental and biochemical processes. However, a consensus has not yet been achieved on this key question. Here we use machine learning-based reactive molecular dynamics simulations to study the dissociation of paradigmatic nitric and formic acids at the air-water interface. We show that the local acidity profile across the interface is determined by changes in acid and conjugate base solvation and that the acidity decreases abruptly over a transition region of a few molecular layers. At the interface, both acids are weaker than in the bulk due to desolvation. In contrast, acidities below the interface reach a plateau and are all the stronger compared to those in the bulk as the surface to volume ratio of the aqueous phase is large, due to the growing impact of the stabilization of the released proton at the surface of the water. These results imply that the measured degree of dissociation sensitively depends on the experimental probing length and system size and suggest a molecular explanation for the contrasting experimental results. The aerosol size dependence of acidity has important consequences for atmospheric chemistry.


Assuntos
Ar , Água , Formiatos , Simulação de Dinâmica Molecular , Água/química
17.
Phys Chem Chem Phys ; 24(22): 13510-13513, 2022 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-35640627

RESUMO

Understanding the acid/base behavior of environmentally relevant organic acids is of key relevance for accurate climate modelling. Here we investigate the effect of pH on the (de)protonation state of pyruvic acid at the air-water interface and in bulk by using the analytical techniques surface-specific vibrational sum frequency generation and attenuated total reflection spectroscopy. To provide a molecular interpretation of the observed behavior, simulations are carried out using a free energy perturbation approach in combination with electronic structure-based molecular dynamics. In both the experimental and theoretical results we observe that the protonated form of pyruvic acid is preferred at the air-water interface. The increased proton affinity is the result of the specific microsolvation at the interface.


Assuntos
Ar , Água , Ar/análise , Simulação de Dinâmica Molecular , Ácido Pirúvico , Análise Espectral , Água/química
18.
J Chem Phys ; 156(16): 164701, 2022 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-35490017

RESUMO

Sum-frequency generation (SFG) spectroscopy is frequently used to investigate the structure of monolayer films of long-chain fatty acids at the air-water interface. Although labeled a non-invasive technique, introducing intense SFG lasers onto liquid interfaces has the potential to perturb them. In the present work, narrowband picosecond SFG is used to study the structural changes that occur in palmitic acid and per-deuterated palmitic acid monolayers at the air-water interface in response to the high field strengths inherent to SFG spectroscopy. In order to determine structural changes and identify measurement artifacts, the changes in specific resonance intensities were measured in real-time and over a broad range of surface concentrations from films spread onto a stationary Langmuir trough. Using narrowband instead of broadband SFG minimizes the overlap of the incident infrared beam in the lipid C-H stretching region with resonances from the water sub-phase. Nevertheless, narrowband SFG still generates a thermal gradient at the surface, which produces a significant decrease in local concentration in the area of the laser spot caused by Bérnard-Marangoni convection originating in the sub-phase. The decrease in concentration results in an increase in the conformational disorder and a decrease in the tilt angle of lipid tails. Crucially, it is shown that, even at the highest monolayer concentrations, this gives rise to a measurement effect, which manifests itself as a dependence on the spectral acquisition time. This effect should be taken into account when interpreting the structure of monolayer films on liquid surfaces deduced from their SFG spectra.


Assuntos
Ar , Água , Ácido Palmítico , Análise Espectral , Propriedades de Superfície , Água/química
19.
Small ; 18(19): e2201039, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35419970

RESUMO

Silicon carbide (SiC) aerogels are promising thermal insulators that are lightweight and possess high thermal stability. However, their application is hindered by their brittleness. Herein, an air suction effect induction (ASEI) strategy is proposed to fabricate a super thermally insulating SiC aerogel (STISA). The ASEI strategy exploits the air suction effect to subtly regulate the directional flow of the SiO gas, which can induce directional growth and assembly of SiC nanowires to form a directional lamellar structure. The sintering time is significantly reduced by >90%. Significant improvements in the compression and elasticity performance of the STISA are achieved upon the formation of a directional lamellar structure through the ASEI strategy. Moreover, the lamellar structure endows the STISA with an ultralow thermal conductivity of 0.019 W m-1 K-1 . The ASEI strategy paves the way for structural design of advanced ceramic aerogels for super thermal insulation.


Assuntos
Ar , Compostos Inorgânicos de Carbono , Elasticidade , Compostos de Silício , Sucção , Condutividade Térmica
20.
J Am Soc Mass Spectrom ; 33(5): 865-874, 2022 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-35416666

RESUMO

Organophosphate esters are an emerging environmental concern since they spread persistently across all environmental compartments (air, soil, water, etc.). Measurements of semivolatile organic compounds are important but not without challenges due to their physicochemical properties. Selected ion flow tube-mass spectrometry (SIFT-MS) can be relevant for their analysis in air because it is a direct analytical method without separation that requires little preparation and no external calibration. SIFT-MS is based on the chemical reactivity of analytes with reactant ions. For volatile and semivolatile organic compound analysis in the gas phase, knowledge of ion-molecule reactions and kinetic parameters is essential for the utilization of this technology. In the present work, we focused on organophosphate esters, semivolatile compounds that are now ubiquitous in the environment. The ion-molecule reactions of eight precursor ions that are available in SIFT-MS (H3O+, NO+, O2•+, OH-, O•-, O2•-, NO2-, and NO3-) with six organophosphate esters were investigated. The modeling of ion-molecule reaction pathways by calculations supported and complemented the experimental work. Organophosphate esters reacted with six of the eight precursor ions with characteristic reaction mechanisms, such as protonation with hydronium precursor ions and association with NO+ ions, while nucleophilic substitution occurred with OH-, O•-, and O2•-. No reaction was observed with NO2- and NO3- ions. This work shows that the direct analysis of semivolatile organic compounds is feasible using SIFT-MS with both positive and negative ionization modes.


Assuntos
Ar , Dióxido de Nitrogênio , Ar/análise , Ésteres , Íons/química , Espectrometria de Massas/métodos , Dióxido de Nitrogênio/análise , Organofosfatos
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