Composition of the dust

The major silicate minerals in most of the fine-grained, anhydrous IDPs and in the Wild 2 particles are olivine and pyroxene. 

Other amorphous silicates are also found in IDPs. The compositions range from ferromagnesian silica, with variable Mg/Fe ratios, containing Ca and Al (Bradley 1988) to Fe-Mg-bearing aluminosilica(Klock Stadermann 1994). Bradley (1988) reported pyroxene glass in one IDP. 

From infrared spectroscopy it is very difficult to obtain the composition of the amorphous silicates. This is because the spectral signature observed is a combination of grain composition, shape, size, and structure, making it difficult to isolate the pure amorphous silicate signal. This, in combination with the relatively small spectral changes caused by the composition of the silicates, makes it hard to get a definitive answer in most cases. In the case of interstellar dust we have a unique opportunity the grains are very small and (almost) all silicates are amorphous. 

Both the anhydrous, porous IDPs and Tempel 1 appear to have a higher crystalline to amorphous silicate ratio than is inferred from infrared spectroscopy of interstellar or most circumstellar grains. This could simply be a result of grain alteration in interstellar space, with radiation processing converting crystalline silicates to amorphous silicates. 

Carbon grains have a very smooth continuum opacity in the infrared making their detection difficult, so proper removal of stellar photosphere and scattered light contributions is critical to determining their abundance properly. Also, it is 

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Temperature Dry wire-pipe ESPs can operate at very high temperatures, up to 700°C (1300°F). Operating gas temperature and chemical composition of the dust are key factors influencing dust resistivity and must be carefully considered in the design of an ESP. 

While several factors determine ESP collection efficiency, ESP size is most important. Size determines treatment time, the longer a particle spends in the ESP, the greater its chance of being collected. Maximizing electric field strength will maximize ESP collection efficiency. Collection efficiency is also affected to some extent by dust resistivity, gas temperature, chemical composition (of the dust and the gas), and particle size distribution. 

This paper reports on the aspects of dust formation in livestock buildings, the material composition of the dust, the emission of dust-bome odourants like volatile fatty acids (VFA) and simple phenols and indoles from piggeries, the importance of particle-borne... 

Dust from animal houses consists mainly of organic matter (23). The preferred technique for investigating both the material composition of the dust and feed stuff is the WEENDER Analysis Technique (24). Table II shows the composition of dust from pig and hen houses compared to the feed fed. The differences in the protein content between dust and feed support the opinion that an important part of the dust originates from feathers, hairs, and skin cells of the animals. 

In short, the combination of absorption and scattering of light by mineral dusts, combined with an increase in these due to anthropogenic activities, has the potential to contribute to climate change. However, many uncertainties need to be removed before these effects can be confidently quantified. For example, the infrared absorption depends on the composition of the dust and as seen in Fig. 14.35, this can be quite variable from location to location and even as a function of time from one source. This one effect alone can lead to a large variability in the predicted effects on radiative forcing (Sokolik et al., 1998). 

All of the bodies in the solar system formed from the same mixture of gas and dust inherited from the Sun s parent molecular cloud. The composition of the dust is best approximated by Cl chondrites. The current compositions of the bodies in our solar system came about because various chemical and physical processes fractionated the elements and isotopes in that initial composition. Understanding how and why elements and isotopes fractionate is a central theme of cosmochemistry. It is easy to visualize fractionations using certain kinds of diagrams that compare elements and isotopes with different chemical characteristics. 

The bulk chemical composition of the dust, obtained by averaging the compositions of particles in numerous tracks (Fig. 12.11a) and impact crater residues (Fig. 12.11b), is chondritic for iron, silicon, titanium, chromium, manganese, nickel, germanium, and selenium, within the 2o confidence level (Flynn el al., 2006). Copper, zinc, and gallium are... 

The explosibility of a carbonaceous dust is governed by its fineness and its volatile content. A hazardous dust would, in general, have a fineness greater than 200 mesh and a volatility greater than 13%. A governing factor for a metal or alloy would be its fine ness and for a plastic, molecular configuration plays a part. Other factors that play important roles in the initiation and development of an explosion are composition of the dust, concentration of the dust cloud, composition of the atmosphere and the ignition source. 

During the process of transmission through the atmosphere a change in the chemical composition of the dust takes place, basically as a result of meteorologically induced chemical and physical processes. 

At one sampling point near the Technical University of Kosice (Slovakia) (see Fig. 7-13) sedimented airborne particulate matter was sampled by the above described BER-GERHOFF method (see also Section 7.2.1.1) over a period of two and a half years. Tab. 7-5 shows the analytical methods applied for the determination of the elemental composition of the dust samples. 

Tab. 7-5. Analytical methods applied for the determination of the elemental composition of the dust samples...

Table VI shows the chemical composition of the dust from the direct combustion system.

The total separation efficiency cannot express differences between separations of particular dust fractions. This value varies depending on the granulometric composition of the dust entering the separator, since the efficiency is dependent on grain size. 

Figure 7. Same as Fig. 6 but for cosmic organics [74], Similar plots have been obtained for the particles that have the composition of the dust of comet IP/FIalley. 

Sampling and analytical methods for the collection and measurement of different size classes of PM as well as of particle-bound metals, organic compounds, and other substances are a major issue of the present book. Routine air monitoring networks based on physico-chemical measurements provide continuously data on ambient PMio and PM2.5 concentrations, but in most cases do not inform about the chemical composition of the dust load. If trace compounds of PM are monitored at aU, such measurements are restricted to few components. Hence, knowledge about the chemical composition of PM, the local and regional distribution of airborne particle-bound substances and their toxic, genotoxic and ecotoxic potential is still very limited. Moreover, data on atmospheric pollutant concentrations do not permit to draw conclusions on possible adverse effects on human beings and ecosystems as their sensitivity to air pollution is influenced by many abiotic and biotic factors. 

As for the chemical composition of the particulate matter, there is no published data regarding the melting of steel, but there is reason to believe that it is close to that of the composition of the dust emitted during the melting of cast iron as shown in Table 3.13. The presence of Zn, Pb or Cd will lead to metallic fumes during the meltdown of the charge. 

The selection of an extinguisher depends on factors such as the composition of the dust, its situation, and the presence of other hazardous materials. The most commonly used extinguisher, water, cannot be used for fire involving electric equipment or reactive metals (e.g., aluminum or magnesium). Gases or vapors such... 

Hand grinding of a mixture of ammoni-um sulfate, ammonium bisulfate, sodium chloride, potassium bicarbonate, and talc in dry nitrogen produces a dust that can readily be dispersed onto test substrates. The resulting particles are typically 1-5 pm in diameter. A typical composition is shown in Table 9-5. The composition of the dust can be adjusted to match the electrical leakage properties on circuit boards of fine-particle dust found in field locations. Two methods of dispersion were found to be effective ... 

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