Airborne particles sources

D. Wienke and P. K. Hopke, Ami. Chim. Acta, 291,1 (1994). Projection of Prim s Minimal Spanning Tree into a Kohonen Neural Network for Identification of Airborne Particle Sources by Their Multielement Trace Patterns. 

Receptor Models. Receptor models, by their formulation, are effective in determining the contributions of various sources to particulate matter concentrations. In classic studies, sources contributing to airborne particle loadings have been identified in Washington, D.C. (78), St. Louis (9,24), Los Angeles (7,12), Portiand, Oregon (78), and Boston (79—81), as well as other areas including the desert (82). 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

A dust cloud comprising a distribution of particle sizes soon fractionates, e.g. visible matter settles to the ground in a few minutes. Hence the size distribution of airborne particles may differ significantly from that of the source material. (This is particularly relevant to occupational hygiene measurements involving toxic dust emissions.)... 

The accident at the Chernobyl, Ukraine, nuclear reactor on April 26, 1986, contaminated much of the northern hemisphere, especially Europe, by releasing large amounts of radiocesium-137 and other radionuclides into the environment. In the immediate vicinity of Chernobyl at least 30 people died, more than 115,000 others were evacuated, and the consumption of locally produced milk and other foods was banned because of radiocontamination. The most sensitive local ecosystems were the soil fauna and pine forest communities. Elsewhere, fallout from Chernobyl measurably contaminated freshwater, marine, and terrestrial ecosystems, including flesh and milk of domestic livestock. Reindeer (Rangifer tarandus) calves in Norway showed an increasing frequency of chromosomal aberrations that seemed to correlate with cesium-137 tissue concentrations tissue concentrations, in turn, were related to cesium-137 in lichens, an efficient absorber of airborne particles containing radiocesium and the main food source of reindeer during winter. A pattern similar to that of reindeer was documented in moose (Alces) in Scandinavia. 

Airborne particles collected with filters distributed across Vitoria, Brazil were analyzed by MB spectroscopy, whereby certain Fe-bearing minerals indicated different pollution sources. For example, hematite comes mostly from iron ore pellet plants, pyrite from handling and storing coal in the industrial area, and magnetite is related to steelwork plants (de Souza et al. 2001). 

The basic assumption of these receptor models is that the ambient airborne particle concentrations measured at a receptor can be apportioned between several sources. In other words, each chemical element concentration at the receptor is considered as a linear combination of the mass fraction of the source contributions. 

Conventional studies generally involve the collection of an assemblage of airborne particles followed by determinations of the average or bulk concentrations of pollutant species present (12). However, the results often lack the analytical specificity required to identify particle sources, to determine particle speciation and reactivity, or to assess particle toxicity. 

Excerpt 4E is taken from an article in Chemical Research in Toxicology and involves the toxicity of fine particulate matter, airborne particles with effective diameters <2.5 pm (also known as PM2 5). The fine particulate was collected using a PM2 5 monitor. Ambient air is pulled through the monitor, diverting the larger particles (>2.5 pm) and capturing only the smaller ones onto a filter. Such fine particles arise from a number of sources including industrial emissions, vehicle exhaust, and forest fires and may lead to asthma, bronchitis, and possibly cancer. 

In both component and factor analysis, the properties of the system being observed are assumed to be linearly additive functions of the contribution from each of the m causalities that actually govern the system. For example, for airborne particles, the amount of particulate lead in the air could be considered to be a sum of contributions from several sources including automobiles, incinerators and coal-fired power plants, etc. 

Alpert, D. J.j Hopke, P. K. A Determination of the Sources of Airborne Particles Collected During the Regional Air Pollution Study, Atmospheric Environ., in press, I98I. 

Identifying and Estimating the Relative Importance of Sources of Airborne Particles," Environ. Sci. Technol., 1980, 62. 

Kleeman, M. J., G. R. Cass, and A. Eldering, Modeling the Airborne Particle Complex as a Source-Oriented External Mixture, J. Geophys. Res., 102, 21355-21372 (1997). 

Humidifiers can be a significant source of airborne particles if tap water is used because as the water evaporates from the aerosol, the solids that were in water are left as particles. For example, Highsmith et al. (1988, 1992) showed that the airborne particle concentration increased linearly with the total dissolved... 

Source Identification of Airborne Particles, In recent years, ingenious methods of identifying the point source of airborne particles have been developed. If not specific point sources of pollution, rather small regional areas can often be identified. Source of particles can be important for numerous reasons, including the enforcement of regulation and also in sorting out. for example, the various distant sources that contribute to acid rain pollution. 

AQEG (1999) Source apportionment of airborne particulate matter in the United Kingdom. Report of the Airborne Particles Expert Group, p 158. http //www.environment.detr.gov.uk/ airq/... 

Atmospheric diffuse dust emissions constitute a pollution source, which is difficult to be quantified. In fact, a diffuse emission is defined as a polluting atmospheric flux which is spread out over a large area or which is not concentrated [1]. In the case of steelwork sites, diffuse dust emissions can represent many as 20% of airborne particle pollution, they result from conveyances and handling of materials and from wind erosion of exposed aggregate storage piles. This latter category of emission source is widely predominant. 

The research on persistent pesticides in the atmosphere has focused on the gas phase, particulate phase, rainfall, and pine needles. In China, there are only a limited number of studies on POP pesticides in the atmosphere, and these focus mainly on airborne particles. The spatial difference in concentration of persistent pesticides in air is small due to diffusion and transport. Since the agricultural ban on use in 1983, the concentration of POP pesticides in the atmosphere has decreased dramatically in China. In some regions, however, the concentrations of pesticide POPs in the atmosphere are unusually high, particularly for DDTs, which indicates that there might be new sources of POPs in these regions, such as Dicofol. In China, no environmental quality standards about pesticide POPs in the atmosphere have been established. 

Airborne particles may be delivered to surfaces by wet and dry deposition. Several transport mechanisms, such as turbulent diffusion, precipitation, sedimentation, Brownian diffusion, interception, and inertial migration, influence the dry deposition process of airborne particles. Large particles (dNIOAm) are transported mainly by sedimentation hence, large particulate PAHs tend to be deposited nearer the sources of emission Small particles (dblAm), which behave like gases, are often transported and deposited far from where they originated (Baek et al., 1991 Wu et al., 2005). 

Exposure to toxicants from terrestrial sources is very common because of the intimate association between animals and plants that live on the land with soil. Modem agricultural practices call for the application of large quantities of herbicides and other pesticides to plants and soil residues of these substances may readily enter living organisms. Soil is the repository of a variety of air pollutants, especially airborne particles that settle onto soil. Improper disposal of industrial wastes and toxic substances washed from or blown off of hazardous waste sites has contributed to exposure of soil. 

Trace element compositions of airborne particles are important for determining sources and behavior of regional aerosol, as emissions from major sources are characterized by their elemental composition patterns. We have investigated airborne trace elements in a complex regional environment through application of receptor models. A subset (200) of fine fraction samples collected by Shaw and Paur (1,2) in the Ohio River Valley (ORV) and analyzed by x-ray fluorescence (XRF) were re-analyzed by instrumental neutron activation analysis (INAA). The combined data set, XRF plus INAA, was subjected to receptor-model interpretations, including chemical mass balances (CMBs) and factor analysis (FA). Back trajectories of air masses were calculated for each sampling period and used with XRF data to select samples to be analyzed by INAA. 

Respirators protect the user in two basic ways. The first is by the removal of contaminants from the air. Respirators of this type include particulate respirators that filter out airborne particles and gas masks that filter out chemicals and gases. Other respirators protect by supplying clean respirable air from another source. Respirators that fall into this category include airline respirators that use compressed air from a remote source and self-contained breathing apparatus (SCBA) that include their own air supply. 

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