Aerosol primary

Secondary Aerosols aerosol formed by the interaction of two or more gas molecules and/or primary aerosols. 

Most of the non-gaseous impurities in ice were once atmospheric aerosols. Atmospheric aerosols raining onto an ice sheet are of two types primary aerosols, which are incorporated directly into the atmosphere as aerosols (these include continental dust and sea spray), and secondary aerosols which form in the atmosphere from gases. In addition to aerosol-derived impurities, some soluble gases in the atmosphere (HNO3 HCl, H2O2, and NH3) adsorb directly onto ice, and so are measured in a core... 

The concentration of primary aerosols (Fig. 18-19) was substantially higher in the atmosphere... 

Fig. 18-19 Enhancement, relative to modem values, of marine and continental primary aerosols in Greenland through the last ice age (derived from Mayewski et al, 1997).

Examples of inferred enhancements of atmospheric primary aerosol concentration in the glacial atmosphere relative to the modem are factors of 4 to 7 for insoluble particles from continents, and 3 for seasalts (Alley et al, 1995), over Greenland. 

Particulate carbon in the atmosphere exists predominantly in three forms elemental carbon (soot) with attached hydrocarbons organic compounds and carbonates. Carbonaceous urban fine particles are composed mainly of elemental and organic carbon. These particles can be emitted into the air directly in the particulate state or condense rapidly after Introduction into the atmosphere from an emission source (primary aerosol). Alternatively, they can be formed in the atmosphere by chemical reactions involving gaseous pollutant precursors (secondary aerosol). The rates of formation of secondary carbonaceous aerosol and the details of the formation mechanisms are not well understood. However, an even more fundamental controversy exists regarding... 

Hildemann, L. M., W. F. Rogge, G. R. Cass, M. A. Mazurek, and B. R. T. Simoneit, Contribution of Primary Aerosol Emissions from Vegetation-Derived Sources to Fine Particle Concentrations in Los Angeles, J. Geophys. Res., 101, 19541-19549 (1996). 

A chromel-alumel thermocouple is used to monitor the temperature of the ceramic boat and also acts as a sensor for the furnace temperature controller. A constant flow of clean, dry N2 gas is maintained through the quartz tube. The metal vapor is carried out of the furnace with N2 and condensed to form a polydisperse aerosol. The primary aerosol is diluted by mixing with a filtered dry air stream. The diluted aerosol is then routed to the chamber as required and the excess aerosol is vented out through a glass fiber filter. 

Particles in the atmosphere arise from natural sources, such as windbome dust, sea spray and volcanoes, and from anthropogenic activities, such as combustion of fuels. Emitted directly as particles (primary aerosol) or formed in the atmosphere by gas-to-particle conversion processes (secondary aerosol), atmospheric aerosols are generally considered to be the particles that range in from a few nanometres to tens of micrometres in diameter [1]. 

Fundamental Processes That Control Aerosol Generation and Transport. The size of the aerosol drops in the initial (primary) aerosol depends on the design of the nebulizer, the nebulizer gas flow rate, and, to a lesser extent, the sample... 

The primary aerosol droplets become smaller as the nebulizer gas flow rate is increased (Fig. 3.7). Often, the average aerosol size is described by the Sauter... 

Figure 7 Effect of nebulizer gas flow rate and sample uptake rate on primary and tertiary aerosol drop size distributions. A Meinhard TR-30 nebulizer was used with a double-pass spray chamber, (a) Primary aerosol produced by nebulizer as a function of nebulizer gas flow rate for a 1-mL/min sample uptake rate, (b) Tertiary aerosol exiting spray chamber as a function of nebulizer gas flow rate, (c) Primary aerosol as a function of sample uptake rate at a nebulizer gas flow rate of 0.8 L/min. (d) Tertiary aerosol exiting spray chamber as a function of sample uptake rate. (From Ref. 18.)...

The primary aerosol droplets also become slightly smaller as the sample uptake rate is decreased. However, the Sauter mean diameter is not as sensitive to changes in sample uptake rate as it is to the nebulizer gas flow rate. For example, when the uptake rate was decreased from 1.0 to 0.6 mL/min, the Z>3 2 value decreased by only 4% (10.9 to 10.5 at a nebulizer gas flow rate of 0.8 L/min) [5]. 

Figure 9 Ratio of tertiary to primary aerosol volume as a function of drop size for different sample uptake rates. A Cetac microconcentric nebulizer (MCN) was used in a double-pass spray chamber. Other concentric nebulizers behave similarly. (From Ref. 422.)...

Streets D et al (2003) An inventory of gaseous and primary aerosol in Asia in the year 2000. 

Processes needed aerosol thermodynamics/d3mamics, aqueous-phase chemistry, gaseous precursor emissions, primary aerosol emissions, and water uptake... 

The coarse mode is largely composed of primary particles generated by mechanical pro-ce.sses such as soil dust raised by llie wind and/or vehicular traffic and construction activities. Coarse particles arc also emitted in gu.ses from industrial sources such as coal combustion and smelting. The coarse mode often peaks at about lO/tin. The chemical composition of the coarse mode is for the most part the sum of the chemical components of the primary aerosol emissions. However, there may be some contributions from gas-to-particle conversion, such as ammonium nitrate, as discussed below. 

Figure 13.15 shows Ogi for various aerosol chemical components. Elements present in the primary emissions include the metals, silicon, and black carbon (BC). Among the primary aerosol emission sources are automotive emissions and tire wear, residual fuel oil combustion, crustal materials, and the marine aerosol. Despite the variety of primary emission sources, values of a,- fell within a narrow band, 1.8.5 0.14. Similar results were obtained for data. sets at other Los Angeles sites. Thus variations in the ambient... 

Noncontagious threat agents have many of the characteristics of contagious ones, except that noncontagious organisms infect individuals only by direct exposure and cannot be transmitted from one person to another. Thus, individuals exposed to noncontagious threat agents are limited to those who come in direct contact with the initially released material or with material that remains viable in the environment after the primary aerosol cloud has dissipated. 

Duce (1978) found an acceptable residence time (2 days) for larger organic particles when he took into account only primary sources. These primary aerosol particle sources are partly natural (e.g. materials from ocean waters, wind erosion of soil3, biospheric matter, forest wildfires) and partly anthropogenic (mostly from... 

The major processes for creating atmospheric fine particles (diameter < 2.5 pm) are combustion and gas-to-particle conversion (GPC). Whereas combustion particles are emitted directly to the atmosphere (primary aerosol), gas-to-particle conversion refers to the chemistry that leads to particulate matter by converting volatile gases into condensable substances under atmospheric conditions. Gas-to-particle conversion leads to an increase in the mass of preexisting particles and under some circumstances may lead to the creation of new particles. Particulate material produced by GPC is referred to as secondary aerosol. 

Sea spray, volcanic eruptions, soil dust, as well as some industries (cement manufacturing) produce the so called primary aerosols, i.e. the material is emitted directly in particulate state (Klockow, 1982), and they are both line and coarse. Secondary aerosols are produced in the atmosphere usually by eondensation after emission from high temperature sources, and they are fine as a rule. Considering the difference in the chemical composition it is recognized that the major components of the fine aerosols are toxie substances of anthropogenic origin such as As, Cd, Pb, Se, Zn etc. while the course aerosols are enriched in elements like Ca, Fe, Si coming from erosion, sea aerosols and other natural sources. 

The underlying hypothesis is that because EC and primary OC often have the same sources, there is a representative ratio of OC/EC for the primary aerosol. If the measured ambient OC/EC ratio exceeds this expected value, then the additional OC can be considered to be secondary in origin. A weakness of that approach is that OC/EC emission rates vary by source and therefore the primary ratio will be influenced by meteorology, diurnal and seasonal fluctuations in emissions, and local sources. 

As aerosols in the atmosphere originate from multiple sources, the composition of nutrients changes considerably over the four seasons. Nitrate, NOJ, and NHJ are defined as secondary aerosol-associated species and are not associated with primary aerosols. The combustion of fossil fuels is a significant source of NO, whereas NHj may originate from anthropogenic emissions such as animal waste and the application of chemical fertilizers. 

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