External surface contaminations

Pitting corrosion may occur generaHy over an entire aHoy surface or be localized in a specific area. The latter is the more serious circumstance. Such attack occurs usuaHy at surfaces on which incomplete protective films exist or at external surface contaminants such as dirt. PotentiaHy serious types of corrosion that have clearly defined causes include stress—corrosion cracking, deaHoying, and corrosion fatigue (27—34). 

Among the lesser-used biological media studied as Pb-exposure markers are those with characteristics such as noninvasive accessibility that would appear to offer a simpler, inexpensive alternative. Mushak (1992) described the relative advantages and limitations of hair sampling as a Pb-exposure biomarker. Hair collection is noninvasive and offers an indefinitely stable medium. But hair is also a very problematic matrix for external surface contamination. Of most concern is the extreme difficulty of chemically debriding hair surfaces of any external Pb without simultaneously removing Pb from internal deposits in hair. Despite claims of effective contamination removal protocols, it remains to be established that the current state of the measurement art encourages hair Pb analyses (Barbosa et al., 2005 U.S. EPA, 2006). 

Subjects for direct measurements should be free of external surface contamination and in fresh clothing, often disposable paper garments. Accessories snch as... 

Monitoring of shipments of radioactive material. Any shipment of radioactive material that is received at or dispatched from the facility should be checked for both external surface contamination and radiation dose rates, which should conform to relevant national or international regulations (for further details see Ref. [21]). The measured results should be recorded, and... 

There has been considerable interest in the use of plants for bioremediation and this merits a rather extensive discussion. Plants can play an important role in bioremediation for several reasons (1) they can transport contaminants from the soil, (2) they can metabolize the contaminants after uptake, or (3) they can produce exudes that support microbial activity for degradation of the contaminants. In addition, bacteria can produce metabolites that counter the effect of toxins produced by fungi, and serve as biocontrol agents that diminish the need for the application of agrochemicals. Plant exudates play an important role in supporting the growth and activity of bacteria that carry out the degradation of contaminants in the rhizosphere and rhizoplane (the external surface of roots... 

A decontamination plan must be based on accurate knowledge of the kinds and extent of contamination present. Prior to the removal of systems, structures, and components (SSC) other than those needed for MPF operation, the external surfaces of equipment and components, as well as walls, floors, and ceilings of rooms and areas that have been contaminated with agent, will have to be decontaminated. Three methods will be used ... 

When a fluid sphere exhibits little internal circulation, either because of high K = Pp/p or because of surface contaminants, the external flow is indistinguishable from that around a solid sphere at the same Re. For example, for water drops in air, a plot of versus Re follows closely the curve for rigid spheres up to a Reynolds number of 200, corresponding to a particle diameter of approximately 0.85 mm (B5). In fact, many of the experimental points used in Section II to determine the standard drag curve refer to spherical drops in gas streams, where high values of k ensure negligible internal circulation. 

The use of surfactant-modified zeolite (SMZ) as a permeable barrier sorbent may offer several unique advantages when dealing with mixed contaminant plumes. Zeolites are hydrated aluminosilicate minerals characterized by cage-like structures, high internal and external surface areas, and high cation exchange capacities. Both natural and synthetic zeolites find use in industry as sorbents, soil amendments, ion exchangers,... 

The major minerals in coal are clays. Kaolinite is usually present in coal, but its identification by Moessbauer spectroscopy is very difficult due to the small amount of iron present and to surface contamination of the clay grains with iron oxides, mainly goethite. The other clay minerals present in coal are il-lite, chlorite and mixed clays. Their identification is not always easy. We have used a simple method, carrying out Moessbauer measurements at low temperatures and applying an external magnetic field to resolve the spectra and distinguish, for example, between illite and chlorite (11). 

It is generally admitted that these procedures are efficient and eliminate the majority of drugs fixed to the external surface of hair. Cone et al. and Welch et al. have shown that when the hair is very contaminated, washing procedures eliminate only a portion of the drugs retained (see Chapter 2 for further information on this problem). The washing procedure that we have retained is the following a tuft of hair (about 200 to 500 mg) is rapidly rinsed by percolation with 10 mL of MeOH, 10 mL HCl 0.1 M, 10 mL HjO, and, lastly, 10 mL of MeOH. The hair is then dried. 

Pour the solution of unknown composition (the titrand) into a beaker. Never place the pipette in the volumetric flask containing the solution as this can lead to contamination of the solution from the external surface of the pipette. 

When obtaining specimens, health care staff should use appropriate infection control precautions. After placing specimens in sealed plastic bags, they should transport them in a clearly labeled, durable, leak-proof container directly to the specimen-receiving area of the laboratory. Staff should carefully avoid contaminating the external surfaces of the specimen containers. 

Equipment glassware, the external surfaces of product containers and other such materials must be disinfected before transfer from a contained area using a validated method (see 47 above). Batch documentation can be a particular problem. Only the absolute minimum required to allow operations to GMP standards should enter and leave the area If obviously contaminated, such as by spills or aerosols, or if the organism involved is an exotic, the paperwork must be adequately disinfected through an equipment pass, or the information transferred out by such means as photocopy or fax. 

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