Les auteurs rapportent les résultats obtenus dans l'étude de la contribution des particules au phénomène d'intoxication par inhalation d'aérosols obtenus par thermolyse de divers m...
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Les auteurs rapportent les résultats obtenus dans l'étude de la contribution des particules au phénomène d'intoxication par inhalation d'aérosols obtenus par thermolyse de divers matériaux. L'analyse réalisée par actographie montre un retard significatif dans les délais de perte d'activité, mettant en évidence l'influence des particules dans le processus d'intoxication. Une meilleure connaissance de la nature chimique des particules ainsi que de leur granulométrie permettra, vraisemblablement, de mieux prévoir la toxicité des effluents de thermolyse des matériaux et d'adapter les mesures de protection les plus appropriées. The authors report results of a study of the contribution of particles to the phenomenon of intoxication by inhalation of aerosols resulting from thermolysis of various materials. An actography analysis showed significant delay in loss of activity latencies, showing the influence of particles in the intoxication process. Better knowledge of the chemical nature of particles and their granulometry will probably make prediction of thermolysis effluents easier and promote the implementation of the most appropriate means of protection.
Seawater-soluble nutrient fractions of aerosols better represent the contribution of aerosol dry deposition to the nutrient load from this source to the ocean than any estimates based on aerosol nutrients leached in p...
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Seawater-soluble nutrient fractions of aerosols better represent the contribution of aerosol dry deposition to the nutrient load from this source to the ocean than any estimates based on aerosol nutrients leached in pure water or acidic solutions. To understand the solubility difference between seawater and pure water, 31 pairs of aerosol samples collected from the Gulf of Aqaba were extracted in Sargasso seawater and pure water under consistent experimental conditions and procedures. Major inorganic N species (NO(3)(-) and NH(4)(+)) in the aerosols show similar solubilities in Sargasso seawater (average 44 and 23 nmol m(-3)) and pure water (average 41 and 23 nmol m(-3)). Seawater-soluble PO(4)(3-) concentrations (average 0.4 nmol m(-3)) are slightly lower than the purewater concentrations (average 0.5 nmol m(-3)). Total soluble N and P, which include dissolved organic compounds, extracted from the aerosols into the seawater (average 65 and 0.4 nMol m(-3)) are significantly lower than those extracted by pure water (average 75 and 0.7 nmol m(-3)). It was found that the dissolution of crustal-dominated trace metals (e.g. Fe and Al) strongly decrease in the seawater compared to that in pure water, while similar amounts of aerosol Zn are leached in both seawater and pure water. The percentage solubilities of non-crustal trace metals (Cu, Ni and Zn) are about one or two orders of magnitude higher than those of Fe and Al in the seawater. Our comparison experiments suggest that some previous reports may have overestimated the dry deposition inputs of aerosol P, Fe, Al, Cu, and Ni to the ocean as a result of the use of solubility estimates obtained from pure water extractions. The estimated dry deposition fluxes of soluble nutrients showed that the atmospheric nutrient input could increase the possibility of P limitation in the Gulf of Aqaba and also contribute a significant fraction of dissolved nutrients to the euphotic zone during stratification period (April to October)
The real and imaginary refractive indexes of organic-based nonvolatile aerosols produced by burning vegetation are reported for the infrared spectral region. The data were obtained by an iterative Kramers-Kronig analy...
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The real and imaginary refractive indexes of organic-based nonvolatile aerosols produced by burning vegetation are reported for the infrared spectral region. The data were obtained by an iterative Kramers-Kronig analysis of the transmission spectra (2-25-mu-m) obtained from thin-film samples deposited on a KBr substrate immersed directly in the smoke plumes of small-scale test fires. The results include samples from fires fueled by lawn grass, alfalfa, mesquite, tumbleweed, pine needles, and mixed twigs, leaves, and weeds. The most significant characteristics of all spectra are as follows: (a) strong absorptions in the 3-5-mu-m region owing to condensed water and CH3/CH2 groups of aliphatic hydrocarbons;(b) characteristic peaks in the 6-, 8-, and 10-mu-m regions owing to skeletal modes of aromatic and terpenic groups;and (c) relatively little absorption in the 10-12-mu-m region. The imaginary refractive index of all samples is comparable (approximately 0.10-0.30) in the 3-5- and 8-10-mu-m regions and is 3-10 times lower in the 10-12-mu-m region. In the 3-5-mu-m region, most of the absorption takes place in the interval between 3 and 4-mu-m as opposed to the 4-5-mu-m interval which shows significantly less absorption. It is also noteworthy that there is insignificant absorption in the 2.0-2.5-mu-m window region. Results are significantly different from values for elemental carbon which are known to be relatively wavelength independent in these spectral regions and of magnitude between approximately 0.50 and 1.0 for the imaginary index. Theoretical calculations, assuming particle sizes in the Rayleigh scattering regime, yields a mass extinction coefficient (m2/g) for the organic smokes on the order of approximately 0.20 for the 8-10-mu-m region and as high as 0.40 at 3-mu-m to near zero at 5-mu-m in the 3-5-mu-m window.
Thermodynamics dictate the direction of all chemical and physical processes. In the case of aerosols, maximization of entropy leads to a broadening of the size distribution as the system proceeds toward equilibrium. T...
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Thermodynamics dictate the direction of all chemical and physical processes. In the case of aerosols, maximization of entropy leads to a broadening of the size distribution as the system proceeds toward equilibrium. The expectation is that as an aerosol ages, the size distribution will broaden. Contrary to this expectation, in this work we demonstrate that the unique nonequilibrium environment in a low temperature plasma can modify particulate materials to make the size distribution narrower. Submicrometer aerosols composed of bismuth particles with a polydispersed size distribution were prepared and passed through a low temperature argon plasma. For lower powers at which the plasma operated near room temperature, the incoming polydispersed aerosol was converted into a monodispersed aerosol of geometric standard deviation approximately 1.1 with 65% mass yield. The mechanism by which the process took place involved the particles vaporizing in the plasma operating at near room temperature, which resulted in very large supersaturation of metal vapor. Particle heating and sputtering by ion bombardment are discussed as possible mechanisms leading to vaporization that causes the change in the size distribution to make it narrower.
A screen type diffusion battery was used as a model screen filter for studying the filtration of chain aggregate aerosols. The aerosols, with well-defined diameter and length, were generated with a system that include...
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A screen type diffusion battery was used as a model screen filter for studying the filtration of chain aggregate aerosols. The aerosols, with well-defined diameter and length, were generated with a system that included a flame aerosol generator and a differential mobility analyzer. Particle sizes were characterized using transmission electron microscopy and a digital image processing technique. The penetration efficiency of the aerosols through even stages of the diffusion battery at certain flow velocities were measured using a condensation nucleus counter (CNC). Quantitative data were obtained by operating the CNC in count mode simultaneously with a laser aerosol spectrometer. Results indicated that penetration efficiency decreased exponentially with the number of screens and increased with flow velocity. In addition, theoretical analysis of filtration mechanisms based on the fan model theory has been made and compared with the measurements of penetration efficiency. Results showed that the collection of chain aggregates on model screen niters was in the regime dominated by an interception mechanism. Average orientation angles of the aerosols with respect to the flow field were also estimated.
Aerosol samples (TSP) were collected during a cruise in the North (3 degrees 05'N-34 degrees 02'N) and South (6 degrees 59'S-25 degrees 46'S) Pacific to investigate the spatio-temporal distributions of...
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Aerosol samples (TSP) were collected during a cruise in the North (3 degrees 05'N-34 degrees 02'N) and South (6 degrees 59'S-25 degrees 46'S) Pacific to investigate the spatio-temporal distributions of water-soluble dicarboxylic acids and related compounds. The molecular distributions of diacids were characterized by the predominance of oxalic (C-2) acid followed by malonic (C-3) and then succinic (C-4) acid. However, we found a predominance of C-4 over C-3 in the aerosol sample that was collected in the western North Pacific Rim with a heavy influence from continental air masses. Atmospheric abundances of short chain diacids (C-2-C-4) are 2-3 times higher in the North Pacific than in the South Pacific. During the cruise, abundances of C-2 in the western North Pacific are 5 times higher than those in the rest of the samples collected. Moreover, the aerosol samples collected in the western North Pacific demonstrated that glyoxylic (omega C-2) acid and methylglyoxal (MeGly) were dominant together with C-2. We found a strong correlation between C-2 and omega C-2 (r = 0.87) and C-2 and MeGly (r = 0.97) in the western North Pacific aerosols but the correlations are significantly weak in the samples from the central North Pacific and Southern Ocean. Diacids were found to account for 1.6 to 14% of organic carbon with higher values in the western North Pacific. These results, together with 7-day backward air mass trajectories, indicate that omega C-2 and MeGly are both originated from the photochemical oxidation of continent-derived organic precursors including isoprene, which can serve as precursors for the production of C-2 during long-range atmospheric transport. (C) 2016 Elsevier B.V. All rights reserved.
The size analysis of ultrafine aerosol particles using a differential mobility analyzer combined with a CNC is discussed from two standpoints: (1) particle loss caused by Brownian diffusion in the analyzer, and (2) da...
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The size analysis of ultrafine aerosol particles using a differential mobility analyzer combined with a CNC is discussed from two standpoints: (1) particle loss caused by Brownian diffusion in the analyzer, and (2) data reduction procedure where Fuchs' charging theory is applied. As a result, it has been found that (1) particle loss becomes significant when particle size is smaller than about 15 nm, and (2) a simple and practical data reduction procedure may be used, where the stationary bipolar charge distribution given by Boltzmann's law is modified by using Fuchs' charge distribution in the smaller size range.
The comprehensive effects of anthropogenic aerosols (sulfate, black carbon, and organic carbon) on terrestrial aridity were simulated using an aerosol-climate coupled model system. The results showed that the increase...
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The comprehensive effects of anthropogenic aerosols (sulfate, black carbon, and organic carbon) on terrestrial aridity were simulated using an aerosol-climate coupled model system. The results showed that the increase in total anthropogenic aerosols in the atmosphere from 1850 to 2010 had caused global land annual mean precipitation to decrease by about 0.19 (0.18, 0.21) mm day(-1), where the uncertainty range of the change (minimum, maximum) is given in parentheses following the mean change, and reference evapotranspiration ET0 (representing evapotranspiration ability) to decrease by about 0.33 (0.31, 0.35) mm day(-1). The increase in anthropogenic aerosols in the atmosphere from 1850 to 2010 had caused land annualmean terrestrial aridity to decrease by about 3.0% (2.7%, 3.6%). The areal extent of global total arid and semiarid areas had reduced due to the increase in total anthropogenic aerosols in the atmosphere from preindustrial times. However, it was found that the increase in anthropogenic aerosols in the atmosphere had enhanced the terrestrial aridity and thus resulted in an expansion of arid and semiarid areas over East and South Asia. The projected decrease in anthropogenic aerosols in the atmosphere from 2010 to 2100 will increase global land annual mean precipitation by about 0.15 (0.13, 0.16) mm day(-1) and ET0 by about 0.26 (0.25, 0.28) mm day(-1), thereby producing a net increase in terrestrial aridity of about 2.8% (2.1%, 3.6%) and an expansion of global total arid and semiarid areas.
Santiago de Chile frequently suffers from atmospheric pollution that contributes to the decrease of solar irradiance on the surface, leading to losses in the energy output of photovoltaic systems. In this study, a sim...
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Santiago de Chile frequently suffers from atmospheric pollution that contributes to the decrease of solar irradiance on the surface, leading to losses in the energy output of photovoltaic systems. In this study, a simple model is used to estimate the effect of aerosols on the solar irradiance over the city throughout the year, using as input AERONET sunphotometer data and other in-situ measurements. The results show reductions of 3.5% and 14.1% for global horizontal and direct normal irradiance respectively and an increase of 35.4% for diffuse horizontal irradiance between the actual condition in Santiago and a hypothetical atmosphere free of aerosols. These effects translate approximately to an annual difference in the energy output of -7.2% and -8.7% for monocrystalline and amorphous silicon PV technologies respectively, and an annual difference of -16.4% for a CPV technology, showing that aerosols can have a significant effect on the photovoltaic energy production. (C) 2019 Elsevier Ltd. All rights reserved.
Photometric radiation measurements in a desert area during two campaigns in April and May of 1986 and 1987 allow the determination of desert aerosol characteristics. The data correspond to 15 non-consecutive days from...
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Photometric radiation measurements in a desert area during two campaigns in April and May of 1986 and 1987 allow the determination of desert aerosol characteristics. The data correspond to 15 non-consecutive days from each of the two campaigns which show very variable atmospheric conditions. The method of inversion of King and a nonlinear least-squares minimization technique between experimental and theoretical data is then applied to retrieve and compare the particle-size distribution function of desert aerosols. The method assumes Junge and log-normal functions to represent the columnar size distribution function.
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