Primary aerosol particles

EgjersdorferML, Kadau D, Herrmann HJ, Pratsinis SE Aggregate morphology evolution by sintering number and diameter of primary particles,/Aerosol Sci 46 7—19, 2012. 

Although this disease mainly affects horses, untreated systemic glanders in humans is almost 100% fatal. The primary way that terrorists would weaponize glanders would be to make it an aerosol. The incubation period for the disease ranges from 3 to 14 days, and is dependent upon the sizes of the particles aerosolized and the dose. 

The relative contribution of primary and secondary carbon to urban aerosol is discussed in this paper. Some data from the ACKEX study in Los Angeles have been reexamined using new values for the carbon and lead emissions. Data on total carbon, elemental carbon and lead in fine particle samples collected in St. Louis are presented. Lead and elemental carbon have been shown to be useful tracers of primary carbonaceous aerosol. It is concluded that secondary carbon is most likely to be a significant portion of the urban carbonaceous aerosol in the summer and in the middle of the day. Secondary carbon can best be measured with short time resolution sampling (At 6h). 

Finally, the use of aerosol lead and elemental carbon have been shown to be useful tracers for primary carbonaceous aerosol. If these data were combined with information on the detailed speciation of the organic carbon particles, a rather complete understanding of the carbonaceous aerosol would be possible. 

All these methods generally give (< 1 /xm) polydisperse aerosols of the solid particles and, unless rapid air dilution is provided, coagulation leads to large agglomerates of the small primary particles. 

The Mediterranean Basin is highly influenced by shipping emissions due to its extremely busy shipping routes. These emissions may account for 2 1% of the mean annual ambient air PM10 levels (25% primary particles and 75% secondary particles) and for 14% of the mean annual PM2.5 in Mediterranean urban areas [51]. It has been estimated that 54% of the total sulphate aerosol column burden over the Mediterranean in summer originates from ship emissions [52],... 

Table 4 Comparison of primary particle diameters of TEM and Lll obtained with the CAST aerosol generator (Schraml et al., 2004)...

Figure 1 shows a schematic of a typical atmospheric aerosol particle (if such an entity can be assumed to exist). The particle consists of sulfates, nitrates, water, ammonium, elemental and organic carbon, metals, and dust. After a primary particle is emitted, gas-phase reactions occur, converting oxides of nitrogen to nitric acid, sulfur dioxide to sulfuric acid, and hydrocarbons to oxidized, low-vapor-pressure condensable organics. 

Atmospheric aerosols are important nuclei for the condensation of water droplets (cloud, rain, fog). The dissolution of the water-soluble aerosol components contributes to the composition of the aqueous phase [e.g., NH4NO3, (NH4)2S04]. Aerosols may contain, in addition to the absorbed gases, a substantial fraction of atmospheric components that return ultimately to the earth surface by dry or wet deposition. The particle diameter ranges from 0.01 nm up to a few hundred micrometers. Primary atmospheric aerosols consist of dust and smoke particles while secondary aerosols are made up of constituents of the gas phase. 

The technique of nebulization of solutions to produce aerosols can also be used for suspensions. Insoluble or inert particles can be resuspended by nebulizing a suspension and by heating the aerosol to drive off the volatile liquid. A monodisperse aerosol of polystyrene particles can be generated with this method. To avoid having doublets or triplets of the primary particles, the suspension concentration should be less than that necessary to have less than one... 

In addition, because the respirable fraction of the aerosol cloud that is emitted from a suspension MDI is highly dependent on the geometric size of the bulk drug particles (i.e., the aerodynamic size cannot be smaller than the initial geometric size of the primary particles), there are limitations to the respirable fraction that can be achieved. As such, solution formulations offer opportunities to circumvent some of these problems, particularly with drugs that have a significant solubility in the volatile propellants, where greater respirable fractions can be obtained [36]. 

The experiments with MgO and ZnO agglomerates (Fig. 8.7a) lend qualitative support to this analysis. A transmission electron photomicrograph of the MgO aerosol showed large agglomerates composed of small primary particles about 5 nm in diameter. The appearance of the ZnO aerosol was quite different. The ZnO agglomerates were much smaller than the MgO particles but were composed of larger primary particles about 10 nm in diameter. Similar effects have been observed for the agglomerates produced by industrial aerosol reactors (Ulrich, 1984). 

Aerosol product properties of interest include primary particle size (and/orsize distribution) and substructure (grain boundary, pore size, and defect concentrations and crystalline... 

PRIMARY PARTICLE SIZE EFFECTS OF AEROSOL MATERIAL PROPERTIES... 

Particle fonnation is thought to have proceeded as follows Metal oxide molecules formed as the aerosol vapor precursor reacted near the jet orifice. The oxide molecules collided to form particles that grow by the colli.sion-coalescence mechanism until the temperature fell to the point where coalescence was quenched. Particle coalescence was probably driven by solid-state diffusion and. perhap.s. surface diffusion. Metal oxides with higher diffusion coelTicients would be expected to fomt larger primary particles because they continue to coalesce at lower temperatures during the cooling period. 

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