UV observations with Cassini ISS Narrow Angle Camera of Titan's detached haze is an excellent tool to probe its aerosols content without being affected by the gas or the multiple scattering. Unfortunately, its low...
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UV observations with Cassini ISS Narrow Angle Camera of Titan's detached haze is an excellent tool to probe its aerosols content without being affected by the gas or the multiple scattering. Unfortunately, its low extent in altitude requires a high resolution calibration and limits the number of images available in the Cassini dataset. However, we show that it is possible to extract on each profile the local maximum of intensity of this layer and confirm its stability at 500 +/- 8 km during the 2005-2007 period for all latitudes lower than 45 degrees N. Using the fractal aggregate scattering model of Tomasko et al. (2008) and a single scattering radiative transfer model, it is possible to derive the optical properties required to explain the observations made at different phase angles. Our results indicates that the aerosols have at least ten monomers of 60 nm radius, while the typical tangential column number density is about 2 . 10(10) agg m(-2). Moreover, we demonstrate that these properties are constant within the error bars in the southern hemisphere of Titan over the observed time period. In the northern hemisphere, the size of the aerosols tends to decrease relatively to the southern hemisphere and is associated with a higher tangential opacity. However, the lower number of observations available in this region due to the orbital constraints is a limiting factor in the accuracy of these results. Assuming a fixed homogeneous content we notice that the tangential opacity can fluctuate up to a factor 3 among the observations at the equator. These variations could be linked with short scale temporal and/or longitudinal events changing the local density of the layer. (C) 2017 Elsevier Inc. All rights reserved.
aerosols are defined as any mixture of solid or liquid particles/droplets that are stable as a suspension in air. aerosols influence the lives of a large majority of the population. A proportion of particulates exacer...
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aerosols are defined as any mixture of solid or liquid particles/droplets that are stable as a suspension in air. aerosols influence the lives of a large majority of the population. A proportion of particulates exacerbate or induce lung disease. Other aerosols are used in the prevention or control of lung disease or in the investigation of disease. This review covers the mechanisms of deposition of aerosols, the production and sizing of aerosols, factors affecting the variability in output from nebulisers and the use of radionuclides in defining drug deposition from therapeutic nebulisers.
1) The particle size distribution of the droplets of atomized liquids and three particulate dusts have been measured. 2) The particle size distribution of a commercially available atomizer, especially designed to prod...
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1) The particle size distribution of the droplets of atomized liquids and three particulate dusts have been measured. 2) The particle size distribution of a commercially available atomizer, especially designed to produce small particles reveals that approximately 6 per cent by weight of the droplets produced by this nebulizer may reach the aveolar ducts. 3) Three samples of commercially available penicillin dusts designed for inhalation therapy show important differences in the particle size distribution. One of these dusts has particles so large that it is practically useless for therapy of the lungs. Two others have particle size distributions by which approximately 40 to 80 per cent of the particle weight may reach the aveolar ducts. 4) The difficulties of using dusts in connection with tropical storage and maintenance of suitable particle size distribution is pointed out. It is emphasized that if penicillin dust therapy is to be suitable at all, the particle size distribution to begin with must be so designed that penetration into the nose, oropharynx and larynx of a reasonable fraction should be possible.
The publication contains abstracts of 53 papers presented at the meeting. The paper abstracts are grouped under the following general topics: natural aerosols, aerosols of human origin, theory of aerosols, condensatio...
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The publication contains abstracts of 53 papers presented at the meeting. The paper abstracts are grouped under the following general topics: natural aerosols, aerosols of human origin, theory of aerosols, condensation nuclei; biological effects, and laboratory experiments.
By combining observations and numerical simulations, we investigated the responses of the surface energy budget and the convective boundary layer (CBL) dynamics to the presence of aerosols. A detailed data set contain...
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By combining observations and numerical simulations, we investigated the responses of the surface energy budget and the convective boundary layer (CBL) dynamics to the presence of aerosols. A detailed data set containing (thermo) dynamic observations at CESAR (Cabauw Experimental Site for Atmospheric Research) and aerosol information from the European Integrated Project on Aerosol, Cloud, Climate, and Air Quality Interactions was employed to design numerical experiments reproducing two typical clear-sky days, each characterized by contrasting thermodynamic initial profiles: (i) residual layer above a strong surface inversion and (ii) well-mixed CBL connected to the free troposphere by a capping inversion, without the residual layer in between. A large-eddy simulation (LES) model and a mixed-layer (MXL) model, coupled to a broadband radiative transfer code and a land surface model, were used to study the impacts of aerosols on shortwave radiation. Both the LES model and the MXL model results reproduced satisfactorily the observations for both days. A sensitivity analysis on a wide range of aerosol properties was conducted. Our results showed that higher loads of aerosols decreased irradiance imposing an energy restriction at the surface, delaying the morning onset of the CBL and advancing its afternoon collapse. Moderately to strongly absorbing aerosols increased the heating rate contributing positively to increase the afternoon CBL height and potential temperature and to decrease Bowen ratio. In contrast, scattering aerosols were associated with smaller heating rates and cooler and shallower CBLs. Our findings advocate the need for accounting for the aerosol influence in analyzing surface and CBL dynamics.
Interactions between water and solid substrates are of fundamental importance to various processes in nature and *** control is widely used to modify interfacial water,where the influence of surface charges is *** we ...
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Interactions between water and solid substrates are of fundamental importance to various processes in nature and *** control is widely used to modify interfacial water,where the influence of surface charges is *** we obtain positively and negatively charged surfaces using Li Ta O_(3) crystals and observe that a large net surface charge up to 0.1 C/m;can nominally change the contact angles of pure water droplets comparing to the same uncharged ***,even a small amount of surface charge can efficiently increase the water contact angle in the presence of *** results indicate that such surface charges can hardly affect the structure of interfacial water molecular layers and the morphology of the macroscopic droplet,while adsorption of a small amount of organic contaminants from aerosols with the help of Coulomb attraction can notably decrease the wettability of solid *** results not only provide a fundamental understanding of the interactions between charged surfaces and water,but also help to develop new techniques on electric control of wettability and microfluidics in real aerosol environments.
aerosols were measured with two aircraft-mounted spectrometer probes from 0.1 to 23.5 .mu.m particle radius, between 1000 and 600 mb pressure altitude (100-4300 m MSL), and up to 200 km distance off the shores of Virg...
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aerosols were measured with two aircraft-mounted spectrometer probes from 0.1 to 23.5 .mu.m particle radius, between 1000 and 600 mb pressure altitude (100-4300 m MSL), and up to 200 km distance off the shores of Virginia and Bermuda. The particle size distributions, typically bimodal with models around 0.1 .mu.m and several .mu.m particle radius, were integrated analytically to yield mass and number concentrations. The relatively long-lived accumulation mode, of greater importance to long-range transport of S pollutants than the shorter-lived, coarse-mode aerosol fraction, showed both horizontal and vertical variabilities. Horizontally, the atmosphere was patchy in its aerosol content from tens to hundreds of km. Vertically, the accumulation-mode mass formed three atmospheric layers: A boundary layer below 900 mb that contained 10-20 .mu.g m-3 aerosol mass, a band between 700 and 900 mb with 2-5 .mu.g m-3, and a layer above 700 mb that had less than 2 .mu.g m-3 of particles. No statistically significant differences in aerosol masses between the U.S. east coast and Bermuda could be detected within the lowest and highest atmospheric layers that were investigated. Between 700 and 900 mb pressure altitudes, however, the accumulation-mode mass concentration off the Virginia coast was twice than what was measured at Bermuda. In terms of fluxes, computed from the spectrometer probe-derived masses and Loran-C-measured wind velocities, it was found that 65% of the particulate burden leaving the U.S. east coast reached Bermuda. At Bermuda, the particulate burden reaching the islands from the west was 1.6 times the fluxes of background aerosols from the south and/or the east.
aerosols have been shown to affect the quantity and quality of solar radiation on the Earth's surface. Savanna regions are subject to frequent burning and release of aerosols that may impact on radiation component...
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aerosols have been shown to affect the quantity and quality of solar radiation on the Earth's surface. Savanna regions are subject to frequent burning and release of aerosols that may impact on radiation components and possibly vegetation productivity in this region. Therefore, in this study, we have analyzed the optical properties of aerosols (aerosol optical depth (AOD) and Angstrom coefficient) from the Atmospheric Radiation Measurement site in Darwin for the periods from April 2002 to June 2005 as measured by a multifilter rotating shadowband radiometer. The influence of aerosols and their effect on surface shortwave incoming solar radiation and savanna productivity were examined for the dry season using sky radiation collection of radiometers and eddy covariance measurements from the Howard Springs flux site. Results indicated that aerosol concentrations in the region were relatively low compared to other savanna regions with the maximum monthly average AOD over the period being the greatest in October (0.29 +/- 0.003 standard error at 500 nm). The highest monthly average Angstrom exponent was also found in October (1.38 +/- 0.008). The relatively low aerosol concentration in this region can be attributed to the mixture of smoke aerosols with humidity haze and local circulations. Over a range of AODs from 0.1 to 0.4, we found a modest increase in the fraction of diffuse radiation to total radiation from 11% to 21%. This small increase in diffuse fraction did not affect the carbon flux significantly. However, because the current range of AOD in the region is relatively low, the region could be sensitive to increases in aerosols and diffuse fraction in the future.
The number of publications on atmospheric aerosols has dramatically increased in recent years. This review, predominantly from a European perspective, summarizes the current state of knowledge of the role played by ae...
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The number of publications on atmospheric aerosols has dramatically increased in recent years. This review, predominantly from a European perspective, summarizes the current state of knowledge of the role played by aerosols in environmental pollution and, in addition, highlights gaps in our current knowledge. Aerosol particles are ubiquitous in the Earth's atmosphere and are central to many environmental issues;ranging from the Earth's radiative budget to human health. Aerosol size distribution and chemical composition are crucial parameters that determine their dynamics in the atmosphere. Sources of aerosols are both anthropogenic and natural ranging from vehicular emissions to dust resuspension. Ambient concentrations of aerosols are elevated in urban areas with lower values at rural sites. A comprehensive understanding of aerosol ambient characteristics requires a combination of measurements and modeling tools. Legislation for ambient aerosols has been introduced at national and international levels aiming to protect human health and the environment.
Secondary organic aerosols(SOAs) are an important component of particulates, but whether biogenic SOAs(BSOAs) or anthropogenic SOAs(ASOAs) are the dominant contributors to haze pollution remains poorly characterized. ...
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Secondary organic aerosols(SOAs) are an important component of particulates, but whether biogenic SOAs(BSOAs) or anthropogenic SOAs(ASOAs) are the dominant contributors to haze pollution remains poorly characterized. In this study, particulate samples were collected from September 2014 to August 2015 at an urban site in Jinan, which is the capital of Shandong Province and a typical city in the North China Plain. The PM2.5 samples were analyzed for BSOA(isoprene(SOAI) and monoterpenes(SOAM)) and ASOA(aromatic(SOAA)) tracers. The concentrations of the SOAAtracer(1.1 ± 1.0 ng/m3) were lowest, and those of SOAItracers(41.8 ± 86.2 ng/m3) were highest, with the concentrations of SOAMtracers(19.4 ± 9.9 ng/m3) being intermediate. The SOAItracers were more abundant in the summer and less abundant in the winter. Both SOAIand SOAMincreased with increasing ozone level but decreased with increasing NOx level. Correlation analysis revealed a good correlation between 2,3-dihydroxy-4-oxopentanoic acid and levoglucosan levels in three seasons. These results suggested that biomass burning activities occurring in the NCP can enhance the emissions of aromatics and should be controlled, especially in the autumn and winter. SOA tracers were classified according to pollution degree, and the results showed that as pollution increases, the contributions of SOAAincrease. These results indicate that reducing anthropogenic emissions is necessary to prevent SOA pollution, especially during heavy pollution episodes.
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