Particles contaminant

Laser Doppler Velocimeters. Laser Doppler flow meters have been developed to measure Hquid or gas velocities in both open and closed conduits. Velocity is measured by detecting the frequency shift in the light scattered by natural or added contaminant particles in the flow. Operation is conceptually analogous to the Doppler ultrasonic meters. Laser Doppler meters can be appHed to very low flows and have the advantage of sensing at a distance, without mechanical contact or interaction. The technique has greatest appHcation in open-flow studies such as the deterrnination of engine exhaust velocities and ship wake characteristics. 

Contaminant Particle size Specific gravity Unit operation... 

By-Product Calcium Sulfate. There are many iadustrial chemical processes that produce by-product calcium sulfate in one of its forms. Whereas the most common is the neutralization of spent sulfuric acid, many of those processes do not produce a commercially useful by-product because of contaminants, particle size, or volume produced. There are, however, six chemical processes that do produce sufficient volume to have potential commercial value. Each is named after its chemical process. 

The basic principle of wet collectors is to wet the contaminant particles m order to remove them from the gas stream. There is a wide range in scrubber design, cost, and performance." " " Because of this wide variability, scrubbers must be carefully matched to specific applications. 

While the lung is the major organ exposed to airborne dusts, such agents may also be swallowed following mucociliary transport and removal from the lung. Contaminating particles contained in food and drink also gain direct access into the gut. 

Harrison JD, Hodgson A, Haines JW, et al. 1993. The biokinetics of plutonium-239 and americium-241 in the rat after subcutaneous deposition of contaminated particles from the former nuclear weapons site at Maralinga Implications for human exposure. Hum Exp Toxicol 12 313-321. 

Hydrocyclones. Particle separation in hydrocyclones uses the centrifugal force as the means of separation. The slurry, consisting of clean soil and contaminated particles, is separated... 

Flotation. In many cases, contaminants adsorbed on the surface of clay particles, or contaminants occurring in soil as discriminate particles, have different surface properties to clean soil particles. By adding special chemical substances, the formation of a hydrophobic surface on the contaminated particles is possible. Pulp aeration results in the attachment of hydrophobic contaminated particles to the surface of the small bubbles that are formed. In this way, selective flotation of these particles is achieved. Contrary to the gravimetric separation methods, flotation offers the possibility to separate contaminated and noncontaminated particles of the same grain size and density but with different surface properties. 

If there is a potential that vectors may be involved, care must be taken to kill any vectors (e.g., lice, fleas) remaining either on the cadaver or residing in fomites. Remove all potentially infested clothing depositing it in a container that will trap and eliminate vectors. Dispose contaminated particles at an appropriate medical waste disposal facility. 

It is quite clear that many if not most contaminants can be present in the environment as colloids or particulates. These may consist of pure aggregated molecules, or they may exist in various associations with other molecules. Whatever the form, they may be taken up by the relatively poorly studied process of endocytosis, which has recently been comprehensively reviewed [120], and they may contribute to deleterious effects, either directly in the exposed organism or indirectly through the food chain. Perhaps for obvious reasons, the pathological conditions in humans have related mainly to the inhalation of contaminant particles where the role of endocytosis is clearly established. For other organisms living in terrestrial and aquatic environments, it is well established that contaminants tend to be concentrated on to soil particles and into sediments, where their long-term fate is poorly understood. 

Compare the bioremediation time for a small, highly contaminated particle to that of a larger, less contaminated particle having an equal initial mass of contaminant. 

Ninety percent of the mussels collected in 1985 at various points along the St. Lawrence River contained mirex at levels up to 1.6 pg/kg (ppb). The only source of mirex was contaminated particles entering the river from Lake Ontario mussels collected from the Ottawa River, which does not receive its water from Lake Ontario, did not contain any mirex. The mirex concentrations in the mussels decreased with distance from the lake (Metcalf and Charlton 1990). 

Vinten et al. (1983) demonstrated that the vertical retention of contaminated suspended particles in soils is controlled by the soil porosity and the pore size distribution. Figure 5.8 illustrates the fate of a colloidal suspension in contaminated water during transport through soil. Three distinct steps in which contaminant mass transfer may occur can be defined (1) contaminant adsorption on the porous matrix as the contaminant suspension passes through subsurface zones, (2) contaminant desorption from suspended solid phases, and (3) deposition of contaminated particles as the suspension passes through the soil. 

To show the effect of having zeolite present in the contaminated particles, a REY commercial cracking catalyst with a matrix surface area of ca. 85 m /g was also contaminated with nickel and vanadium, and steamed (1450 F, 4 hrs, 90% steam, 10% air) to age the metals. Its select vities were compared to the non-zeolitic additive having the same surface area and chemical composition blended with sufficient metals-free active cracking component to give the same conversion. 

Hydrocarbon adsorption experiments show significant differences between the nickel contaminated zeolitic and non-zeolitic particles at metals levels comparable to those of the catalytic experiments. Neither hexane nor 1-hexene showed any interaction with nickel on the low surface area, non-zeolitic particles (the unpromoted material of Table I) at temperatures up to 425 C. Additionally, no interaction between hexene and the nickel on the zeolitic particles was observed over the temperature range studied. However, the nickel on the zeolitic component did cause significant retention of hexane at temperatures as low as 200 C with generation of what appeared to be higher molecular weight products. No cracking products were observed. With the uncontaminated zeolitic particles, hexane retention only occurred at temperatures above 300°C. Thus, the lower temperature retention for the contaminated particles appears to be due to the presence of nickel. 

Many processes are operative in the environment that contribute to the regional elimination of a contaminant by altering its distribution. Contaminants with sufficiently high vapor pressure can evaporate from contaminated terrestrial or aquatic compartments and be transferred through the atmosphere to new locations. Such processes of global distillation are considered largely responsible for the worldwide distribution of relatively volatile organochlorine pesticides such as lindane and hexachlorobenzene. Entrainment by wind and upper atmospheric currents of contaminant particles or dust onto which the contaminants are sorbed also contribute to contaminant redistribution. Sorption of contaminant to suspended solids in an aquatic environment with commensurate sedimentation can result with the removal of contaminants from the water... 

Absorption of a mycotoxin will occur when it crosses body membranes and enters the blood stream. The primary sites of mycotoxin absorption are the gastrointestinal tract (ingestion of contaminated food), lungs (inhalation of contaminated particles or toxin-containing fungal spores) and the skin (direct contact with contaminated materials or pure mycotoxins). When the mycotoxin enters the blood it is then available for distribution. Livers and kidneys have a high capacity to bind many mycotoxins while other mycotoxins are highly lipophilic and can concentrate in body fat. In the final outcome a toxic response by a mycotoxin will be critically influenced by the rate of absorption, distribution, biotransformation and excretion (Smith et al., 1994). 

Occupational exposure to CDDs most likely occurs mainly through inhalation of CDD-contaminated particles or dust and through dermal contact with solutions containing CDDs. However, data indicate that oral exposure to low levels of CDDs from contaminated food (including milk) represents the major route of environmental exposure for the general population and for people living in areas with known dioxin contamination (Connett and Webster 1987 Schecter et al. 1994a Travis and Hattemer-Frey 1987). 

Figure 5. EDA spectra comparison of safe insulation. The upper comparison is between contaminant particles on the clothing and the control specimen. The bottom comparison is between contaminants on a tool and the control specimen. The dotted spectrum in both cases is the control and the solid spectrum is the evidence. Major peaks are S and Ca.

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