Particulate deposit

Particulates deposition possibly causing plugging of the bed or plates... 

Filtrate lost to the formation or particulates deposited in oil flow passages must not impair a well s flow potential when the well is returned to operation. 

The size of the fibrous particles that appear to induce disease in the animal models is compatible with the measured respiratory range in humans (Lipp-man, 1977). Most particulate deposition takes place not in the upper or conducting portion of the airways but in the alveolar region of the pulmonary tree (the respiratory unit). Some surface deposition may occur at bifurcations in the bronchial tree, but the actual amount at each location is influenced by anatomy, specific to the species—probably to an individual—as well as the variety of fiber. A large proportion of airborne particulates are rejected as part of the normal clearance mechanisms in animals, but in humans clearance mechanisms may be compromised by smoking, for example. We are unaware of any experiments on fiber toxicity using smoking rats ... 

Fig. 100. Schematic representation of the different semiconductor-coated BLMs. A single composition of particulate semiconductor deposited only on one side of the BLM constituted System A. Two different compositions of particulate semiconductors sequentially deposited on the same side of the BLM represent System B. Finally, two different compositions of particulates deposited on the opposite sides of the BLM made up System C [652]...

Between 10 and 180 L of air at a flow rate of 0.5 to 1 L/min is passed through a filter-bubbler assembly of a 0.8-pm cellulose ester membrane and 10 mL of 0.1 N KOH solution. While cyanide particulates retain over the filter membrane, HCN is trapped over the KOH solution in the bubbler. The membrane filter is then placed in 25 mL of 0.1 A KOH solution for 30 min to extract the cyanide particulates deposited on it. The KOH extract and the bubbler KOH solution are analyzed for cyanide by selective-ion electrode technique (see Chapter 1.9 for a detailed analytical procedure) using KCN standards. Calculate the concentration of particulate CN- in the air sampled as follows ... 

Recommended Method airborne particles collected on a sorbent cartridge containing polyurethane foam particulates deposited on the filter extracted with methylene chloride extract analyzed by GC-FID or GC/MS recommended air flow 5 L/min sample volume 1000 L. 

Pinder, J.E., Ciravolo, T.G. Bowling, J.W. (1987) The interrelationships among plant biomass, plant surface area and the interception of particulate deposition by corn. Health Physics, 55, 51-8. 

Respiratory effects typically associated with inhalation of particulates and lung overload have been observed in animals. The pulmonary toxicity of alchlor (a propylene glycol complex of aluminum chlorhydrate), a common component of antiperspirants, was examined in hamsters in a series of studies conducted by Drew et al. (1974). A 3-day exposure to 31 or 33 mg Al/m3 resulted in moderate-to-marked thickening of the alveolar walls due to neutrophil and macrophage infiltration and small granulomatous foci at the bronchioloalveolar junction (a likely site of particulate deposition). A decrease in the severity of the pulmonary effects was observed in animals killed 3, 6, 10, or 27 days after exposure termination. Similar pulmonary effects were observed in rabbits exposed to 43 mg Al/m3 for 5 days (Drew et al. 

Compared with on-column injection into 320-/ m-ID columns, the advantage of the retention gap approach is that large sample volumes can be injected. The effects of particulates deposited on the precolumn is not severe. The approach can be automated and the length of the flooded zone is more controllable. The length of the flooded zone in the column inlet and the evaluation of different retention gaps have been studied [27]. A comprehensive review of the retention gap technique has been published [28]. 

After the samples were collected the cyclone collection cups were carefully unloaded. Extreme care is required in this procedure to insure that all particulate deposits are recovered and placed in the proper sample container. 

It will be seen that the curves of deposit accumulation with time follow the general pattern of deposition discussed earlier. The effect of water pH is very marked with a maximum deposition occurring at a pH of around 6. The pH controls the magnitude and sign of the charge on the surface to which the particles attach, and the surface of the particles themselves. It might be possible to control particulate deposition by pH adjustment, but the additional problem of corrosion would have to be taken into account. 

Populations in areas with high levels of residual fuel oil consumption may also be exposed to above background levels of vanadium, both from increased particulate deposition upon food crops and soil in the vicinity of power plants and higher ambient air levels (Zoller et al. 1973). Cities in the northeastern United States frequently fall into this category, where ambient air levels often range from 150 to 1,400 ng/m (Zoller et al. 1973). 

Dry gaseous deposition is a complex process which depends on the physical-chemical properties of the PCBs, characteristics of the adsorbing surface, and environmental conditions (e.g., windspeed). In the ambient atmosphere, dry particulate deposition is predominantly in the form of fine aerosols (<1 pm), which deposit on surfaces by rapid, vibratory (Brownian) diffusion (Holsen and Noll 1992). However, in urban areas, PCBs are associated with course aerosols (>1 pm), and these particulates represent the majority of the dry deposition flux even though PCBs are largely in the vapor phase (Holsen et al. 1991). 

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