It has long been recognized that the pattern of particle deposition in the respiratory tree affects how far aerosols penetrate into the deeper zones of the arterial tree, and hence contribute to either their pathogeni...
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It has long been recognized that the pattern of particle deposition in the respiratory tree affects how far aerosols penetrate into the deeper zones of the arterial tree, and hence contribute to either their pathogenic potential or therapeutic benefit. In this paper, we introduce an anatomically-inspired model of the human respiratory tree featuring the generations 0-7 in the Weibel model of respiratory tree (i.e., the conducting zone). This model is used to study experimentally the dynamics of inhaled aerosol particles (0.5-20 mu m aerodynamic diameter), in terms of the penetration fraction of particles (i.e., the fraction of inflowing particles that leave the flow system) during typical breathing patterns. Our study underline important modifications in the penetration patterns for coarse particles compared to fine particles. Our experiments suggest a significant decrease of particle penetration for large-sized particles and higher respiratory frequencies. Dimensionless numbers are also introduced to further understand the particle penetration into the respiratory tree. A decline is seen in the penetration fraction with decreasing Reynolds number and increasing Stokes number. A simple conceptual framework is presented to provide additional insights into the findings obtained. (C) 2017 IPEM. Published by Elsevier Ltd. All rights reserved.
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.
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.
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.
This work is focused on the effect of marine aerosols on soda-lime, potash-lime and lead silicate glass samples. Two kinds of tests were carried out, the first one under laboratory controlled condition during 36 days ...
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This work is focused on the effect of marine aerosols on soda-lime, potash-lime and lead silicate glass samples. Two kinds of tests were carried out, the first one under laboratory controlled condition during 36 days to evaluate the alteration of glass surface by NaCl aerosols, and the second one in a marine atmosphere in Cabo Vilano (Galicia, Spain) for up to three months. Both tests showed similar results. NaCl aerosols acted as condensation nuclei in high humidity environments favoring the lixiviation of the alkaline and alkaline-earth ions from the glass surface and the solubilization of atmospheric gases (CO2, SO2). Marine aerosols could also accelerate the corrosion attack inducing the loss of the surface hydrogen bonds and the opening of the network accelerating the corrosion mechanism. Results also confirmed that high humidity favored the alteration of the glass surface and the formation of new crystalline phases. Soda-lime silicate and lead silicate glasses were the most durable ones, whereas potash-lime silicate glass presented a fissured alteration layer due to the hydrolytic attack of the surface. New crystalline phases including chlorides, carbonates and sulfates were detected on the glass surfaces which can be related to marine aerosols, environmental particles and the reaction of the cations lixiviated from the glass with the atmospheric gases.
Refractory black carbon (rBC) aerosol is an important climate forcer, and its impacts are greatly influenced by the species associated with rBC cores. However, relevant knowledge is particularly lacking at the Tibetan...
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Refractory black carbon (rBC) aerosol is an important climate forcer, and its impacts are greatly influenced by the species associated with rBC cores. However, relevant knowledge is particularly lacking at the Tibetan Plateau (TP). Here we report, for the first time, highly time-resolved measurement results of rBC and its coating species in central TP (4730 m a.s.l), using an Aerodyne soot particle aerosol mass spectrometer (SP-AMS), which selectively measured rBC-containing particles. We found that the rBC was overall thickly coated with an average mass ratio of coating to rBC (R-BC) of similar to 7.7, and the coating species were predominantly secondarily formed by photochemical reactions. Interestingly, the thickly coated rBC was less oxygenated than the thinly coated rBC, mainly due to influence of the transported biomass burning organic aerosol (BBOA). This BBOA was relatively fresh but formed very thick coating on rBC. We further estimated the "lensing effect" of coating semiquantitatively by comparing the measurement data from a multiangle absorption photometer and SP-AMS, and found it could lead to up to 40% light absorption enhancement at R-BC > 10. Our findings highlight that BBOA can significantly affect the "lensing effect", in addition to its relatively well-known role as light-absorbing "brown carbon."
During March 20-22, 2012 Delhi experienced a massive dust-storm which originated in Middle-East. Size segregated sampling of these dust aerosols was performed using a nine staged Andersen sampler (5 sets of samples we...
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During March 20-22, 2012 Delhi experienced a massive dust-storm which originated in Middle-East. Size segregated sampling of these dust aerosols was performed using a nine staged Andersen sampler (5 sets of samples were collected including before dust-storm (BDS)), dust-storm day 1 to 3 (DS1 to DS3) and after dust storm (ADS). Sugars (mono and disaccharides, sugar-alcohols and anhydro-sugars) were determined using GC-MS technique. It was observed that on the onset of dust-storm, total suspended particulate matter (TSPM, sum of all stages) concentration in DS1 sample increased by >2.5 folds compared to that of BDS samples. Interestingly, fine particulate matter (sum of stages with cutoff size <2.1 mu m) loading in DS1 also increased by >2.5 folds as compared to that of BDS samples. Sugars analyzed in DS1 coarse mode (sum of stages with cutoff size >2.1 mu m) samples showed a considerable increase (similar to 1.7-2.8 folds) compared to that of other samples. It was further observed that mono-saccharides, disaccharides and sugar-alcohols concentrations were enhanced in giant (>9.0 mu m) particles in DS1 samples as compared to other samples. On the other hand, anhydro-sugars comprised similar to 13-27% of sugars in coarse mode particles and were mostly found in fine mode constituting similar to 66-85% of sugars in all the sample types. Trehalose showed an enhanced (similar to 2-4 folds) concentration in DS1 aerosol samples in both coarse (62.80 ng/m(3)) and fine (8.57 ng/m(3)) mode. This increase in Trehalose content in both coarse and fine mode suggests their origin to the transported desert dust and supports their candidature as an organic tracer for desert dust entrainments. Further, levoglucosan to mannosan (L/M) ratios which have been used to predict the type of biomass burning influences on aerosols are found to be size dependent in these samples. These ratios are higher for fine mode particles, hence should be used with caution while interpreting the sources usin
The soluble fraction of aerosol Fe, mainly Fe(II), represents a large source of nutrient iron to the open ocean. Fe(II) may also play an important role in the adverse health effects of ambient aerosols. Our current un...
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The soluble fraction of aerosol Fe, mainly Fe(II), represents a large source of nutrient iron to the open ocean. Fe(II) may also play an important role in the adverse health effects of ambient aerosols. Our current understanding of the reduction of Fe(III) to Fe(II) in aerosols suggests that the major pathway is the photoreduction of Fe(III)-oxalate complexes, but this pathway cannot explain the observed nighttime Fe(II) in ambient aerosols and is also limited by the supply of oxalate. Here we propose a new pathway initiated by gaseous HO2 uptake, followed by Cu-Fe redox coupling, which can sustain nighttime Fe(II) and also dominate Fe(III) reduction in the absence of Fe(III)-oxalate complexes. Consequently, aqueous OH production is substantially enhanced via the Fenton reaction and sustained by the influx of HO2 from the gas phase. This mechanism is potentially the major mechanism for sustaining soluble Fe(II) in ambient aerosols and can be tested by a combination of modeling and aerosol Fe speciation measurements. We hypothesize that this mechanism may also be relevant to mineral Fe dissolution in dust aerosols.
Generation of aerosols by electrostatic spraying of liquids from the tip of a needle placed into a capillary has been studied at a voltage lower than that corresponding to the corona ignition in the regime of the form...
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Generation of aerosols by electrostatic spraying of liquids from the tip of a needle placed into a capillary has been studied at a voltage lower than that corresponding to the corona ignition in the regime of the formation of single monodisperse droplets. The peculiarities of the jet-type motion of low-volatile liquid droplets with submicron sizes have been considered.
The nonuniformity of aerosol distribution over filter surface was studied. It was found that the distribution depends on the properties of the studied object and on the sampler type: particle concentration is often hi...
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The nonuniformity of aerosol distribution over filter surface was studied. It was found that the distribution depends on the properties of the studied object and on the sampler type: particle concentration is often higher in the center of the filter, but in some cases, they shift to the edges;the uniform distribution of particles is observed rarely. It was shown that, if the emitter in X-ray fluorescence analysis (XRF) is a disk 3 cm in diameter cut from the center of a filter 5 cm in diameter, the systematic error of the results of analysis may be higher than 0.30. Recommendations on the choice of the conditions of sampling aerosols and emitter preparation are formulated. If these conditions are met, the results of XRF analysis of nonuniform filters are characterized by s(r) = 0.05, which satisfies the admissible error.
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