Composition of Particles

Important periods for the quantitative export of particles in the Eastern Gotland Basin are the spring bloom, the summer maximum characterized by aggregates of cyanobacteria, and a more or less intensive phytoplankton bloom during autumn, dominated by diatoms (Wasmund, et al., 2000). 

For the biogenic metals Cd, Zn, and Ni, a comparable annual distribution pattern was observed, while for Cu a less distinctive seasonal signal was registered in the trap material, which has been attributed to the presence of copper complexing dissolved organic ligands in the water column as described by Muller (1996). 

Between December 1999 and March 2000, the composition of the trap material was dominated by Al and Fe, tracers for the lithogenic fraction and typically during low biogenic export periods. Estimations of the clay fraction base on Al concentrations constituted 33% of the total mass flux. The distribution pattern of Pb and As was linked to this lithogenic fraction. 

The very low content of the particulate Mn fraction in the trap material between June and July 2000 was suggested to be as a result of the partial suboxic or anoxic conditions in the trap horizon at 120 m depth, which caused reductive dissolution of Mn oxides from settling particles. From August 2000 until March 2001, the Mn content in the trap material was increasing, with maximum values during wintertime. 

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Composites are combinations of two or more materials with the properties shown by individual components. They are made to perform as a single material. Nature made the first composite in living things. Wood is a composite of cellulose fibers held together with a matrix of lignin. Most sedimentary rocks are composites of particles bonded together by... 

Besides, without addictive AICI3 as a crystal conversion agent, phase composition of most neogenic Ti02 particles was anatase in our experiment. Conversions active energy finm anatase to rutile was 460 kJ/mol [5], with temperature arose, crystal conversion rate as well as mass fraction of rutile would increase [6,7]. Hence, after a lot of heat accumulated, phase composition of particle-sintered layer was rutile. 

This schematic diagram shows that the true composition of particles can be obtained only when the probe hole covers the particle entirely. When the probe hole covers both the particle and the matrix, the measured concentration is lower than the real one. Again, when an interface is not perpendicular to the cylinder of analysis, the apparent concentration change at the interface appears diffuse, even if the real concentration change is discrete. The standard deviation for concentration, a, is given by... 

The chemical composition of particles can be just as varied as their shape. Commercial particles can consist of polymers or copolymers, inorganic constructs, metals and semiconductors, superparamagnetic composites, biodegradable constructs, and synthetic dendrimers and dendrons. Often, both the composition of a particle and its shape govern its suitability for a particular purpose. For instance, composite particles containing superparamagnetic iron oxide typically are used for small-scale affinity separations, especially for cell separations followed by flow cytometry analysis or fluorescence-activated cell sorting (FACS). Core-shell semiconductor particles, by... 

While modeling the structure and properties of porous materials one usually is interested in structural properties of a desirable hierarchical level. For example, for chemical properties the molecular structure is major, and the specific adsorption and catalytic properties are guided by the structure and composition of particle surface. Diffusion permeability is determined by the supramolecular... 

Greenberg, R. R, Gordon, G. E. Zoller, W. H. Composition of Particles from the Nicosia Municipal Incinerator,... 

A critical requirement for the success of receptor models for atmospheric particles Is that the compositions of particles from all major sources in an area be accurately known. Chemical element balances (CEBs) of 130 samples taken In Washington, D.C. and analyzed for 40 elements yielded nearly the same source strengths when 28 elements are used In the least-squares fit as when only nine carefully chosen elements are used. Certain elements are important to the stability of CEB fits (Na, Ca, V, Mn, As and Pb) and should be measured carefully In particles from sources. For three of the nine elements (Al, Fe and Zn), other elements can serve as surrogates (many lithophlles for Al and Fe, Sb and Cd for Zn). Measurements on many more sources of each Important type should be done In order that trends can be observed that will allow one to predict compositions of particles from unmeasured sources. Instack measurements should Include collections of at least two size fractions of particles plus vapor-phase species. Measurements of at least 20 elements plus some classes of carbonaceous material should be made. 

Because of the uncertainties In the use of source-emissions Inventories to estimate contributions from various sources to ambient levels of suspended particles, many workers have been developing and testing aerosol receptor models (1 ). The basic Idea of receptor models Is that chemical compositions of particles from various types of sources are sufficiently different that one can determine contributions from the sources by making detailed measurements of the compositions of ambient aerosols and of particles from the sources. Several computational methods have been used... 

In view of our knowledge of the composition of particles from most sources In the Washington area. It Is appropriate to use the CEB method rather than methods that extract source compositions from data on ambient particles. According to the CEB method, the concentration of an element 1 In a receptor sample Is given by... 

Coal-Fired Power Plants. Detailed studies of compositions of particles collected from stacks of about ten coal-fired power plants have been performed (, 27-36). In a few cases, the composition has been determined for particles In several size groups. Some measurements on suspended particles have been aug-... 

As noted above, we had hoped that one could perform measurements on several sources of a particular class and observe trends that would allow one reliably to predict compositions of particles from other members of that class to avoid the need to study each Individual major source In an area before performing receptor-model Interpretations of ambient aerosols of that area. 

When sources are studied, several things should be done to provide data needed for receptor-model applications. First, particles should be collected In at least two different size fractions corresponding to the division at about 2.5-ym dlam now used In many studies of ambient aerosols. In some cases. It may be desirable to have more size cuts. As noted above, compositions of particles from coal combustion change dramatically below about 0.5-pm dlam (44, 46). Above we Identified a minimum of about twenty elements that should be measured. Also, In order to develop adequate markers for sources that emit carbonaceous particles, measurements of organic compounds and other properties related to carbonaceous particles should be made. 

In this paper, we have focussed on the weaknesses of our present knowledge about the compositions of particles from sources that are needed as Input for receptor models. However, despite these weaknesses, we feel that the receptor model is probably already capable of more accurate determinations of TSP contributions from various types of sources than the classical methods of source emissions inventories coupled with dispersion models. If the measurements suggested are made, then the receptor models should provide very accurate estimates of those contributions. 

In general, we feel that there are far too few studies of the composition of particles in the submicrometer region. More studies are needed to adequately characterize the human health and environmental hazards associated with utility coal combustion, and to more accurately determine their contribution to urban pollutant inventories. 

There are a number of estimates of the actinic flux at various wavelengths and solar zenith angles in the literature (e.g., see references in Madronich, 1987, 1993). Clearly, these all involve certain assumptions about the amounts and distribution of 03 and the concentration and nature (e.g., size distribution and composition) of particles which determine their light scattering and absorption properties. Historically, one of the most widely used data sets for actinic fluxes at the earth s surface is that of Peterson (1976), who recalculated these solar fluxes from 290 to 700 nm using a radiative transfer model developed by Dave (1972). Demerjian et al. (1980) then applied them to the photolysis of some important atmospheric species. In this model, molecular scattering, absorption due to 03, H20, 02, and C02, and scattering and absorption by particles are taken into account. 

However, it is not only in marine areas that nitrate is found associated with larger particles. Table 9.14 for example, shows the composition of particles from the Amazon Basin where there was no significant sea salt contribution (Artaxo et al., 1988). Concentrations of... 

Because certain sources emit particles with characteristic elemental signatures, in principle one ought to be able to measure the composition of particles in the atmosphere and then work backward to calculate how much each source contributed to obtain the final, observed particle composition. This approach involves the use of receptor models, defined as models that assess contributions from various sources based on observations at sampling sites (the receptors) (Gordon, 1988). 

The discussion thus far has focused on the elemental composition of particles, which can be determined using such techniques as neutron activation or X-ray fluorescence analysis (see Chapter 11). One of the questions of increasing interest is the chemical form in... 

Most studies of the chemical composition of particles in the troposphere to date have used analysis of bulk samples, which are usually collected in the boundary layer close to the earth s surface. As discussed in Chapter 6. J.3, there is a great deal of interest in the chemistry of the upper troposphere. Much less is known about the chemical composition in this region, particularly of particles. However, it appears that organics are also important constituents of particles in this region as well. For example, Novakov et al. (1997) in studies of particles both onshore and offshore of the eastern United States found that the mass fraction of the particles due to carbon compounds increased as a function of altitude. In the boundary layer, the fraction was typically 10-40%, increasing to 50-90%atan altitude of 2-3 km. 

FIGURE 9.54 Composition of particles in Los Angeles, at west end of air basin, and in Rubidoux, at east end (adapted from Rogge et al., 1993d). 

Kinne, S O. B. Toon, G. C. Toon, C. B. Farmer, E. V. Browell, and M. P. McCormick, Measurements of Size and Composition of Particles in Polar Stratospheric Clouds from Infrared Solar Absorption Spectra, J. Geophys. Res., 94, 16481-16491 (1989). 

The chemical composition of particles collected in the museums was also compared to that outdoors using a mass balance model. The results indicated that there were significant indoor sources of fine particle organics and that this source(s) was a significant fraction of the total indoor fine particle organic concentration (Ligocki et al., 1993). A similar conclusion was reached by Naik et al. (1991) in measurements made in a telephone... 

Environmental impact. Contamination by fallout from downwind transport of emitted particulate matter from the oil-shale power stations has been demonstrated throughout northeastern Estonia, as far as c. 140 km northwards to Finland and as far as 100 km to the southwest within Estonia (Jalkanen et aL 2000). Indeed, Teinemaa et al. (2002) and Jalkanen et aL (2000) examined the morphology of particles in power station fly ash (see Fig. 9) and found similarities in structure, size and chemical composition of particles collected from moss surfaces in northeastern Estonia and southeastern Finland. Although the emissions of SO2 and NOx from the BPP and EPP are generally similar to, or lower than, those from conventional... 

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... 

Deposition of POPs may take place by (1) snow and rain scavenging of gases and aerosols (wet deposition), (2) dry particle deposition and (3) gas exchange with surfaces [61], The distributions of POPs between the gas and particle phases depend on their physical-chemical properties (Fig. 8) as well as the environmental conditions in the atmosphere, such as temperature, amounts and composition of particles [26, 35]. 

Typically, the LRT smoke episodes are first detected by the increase in the PM concentration at the measurement site. If adequate real-time instruments are available, also the changes in the physical properties (e.g., particle size) and chemical composition of particles can be observed. Every PM pollution episode observed in Northern Europe is not associated with LRT smokes. Therefore, the origin of the polluted air masses must be identified, e.g., by using the backward air mass trajectory models (e.g., HYSPLIT provided by the National Oceanic and Atmospheric Administration or FLEXTRA [34]), that shows the path of air masses before arriving the measurement site. Additionally, Web Fire Mapper (http //maps. geog.umd.edu) shows the location and intensity of fires areas obtained from MODerate-resolution Imaging spectroradiometer (MODIS [10]) onboard the satellites. 

Particle physical properties typically change under the impact of smoke plume but these changes may not be specific for the wildfire smoke. In addition to biomass burning, particle mass or number concentration can increase due to the biogenic or other anthropogenic sources, e.g., traffic or industrial emissions. Chemical composition of particles is more unique to particle source, however, particles with similar chemistry can have different origin. Physical and chemical properties of the LRT biomass burning particles observed in Northern Europe are discussed below. Physical properties and the chemical components measured from the smoke particles are summarized in Table 2. The measurements of PM mass concentrations are excluded from Table 2 as nearly all the studies had some measurements of particle mass. 

The results of two surveys are reported on Fig. 6, S.S.A. appears to be lower in the river part, especially for the Gironde estuary. It usually increases as soon as the tidal influence is observed with a clear maximum located around the salt intrusion. Many processes can affect particulate matter in this part of estuaries. The increase could be due to the destruction of some floes formed upstream as observed by Eisma (personal communication) or to a chemical evolution of the superficial composition of particles as discussed below. 

Finally, the size composition of particles in the last section of the mill is described via Eq. (3). The first term on the right hand side expresses the amount of those particles that moved forwards from the previous column. The second term represents particles that have not changed at all, while the third term gives the amount of particles that remained in the last column and have broken from some size larger than x, to the interval in question. 

Mannino, A., and Harvey, H. R. (2000). Biochemical composition of particles and dissolved organic matter along an estuarine gradient Sources and implications for DOM reactivity. Limnol. Oceanogr. 45, 775-788. 

Variability of Compositions of Particles Released by Coal-Fired Power Plants... 

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