Contamination measurement

Such defects result from abnormal manufacturing operations such as insufficient lubrication between the metal and the mandrel during the tube-forming process. The lubricant may have been contaminated. Measurement indicated that some of these defects penetrated 8% of the tube wall thickness. Defects of this type can act as corrosion-initiation sites in a sufficiently aggressive environment. 

Sometimes local supply air is combined with exterior hoods to protect the worker from escaping contaminants. Measuring the breathing zone concentra-... 

The starting point for design of a dilution ventilation scheme is normally a hygiene survey in which levels of pollutants and the ventilation rate are measured under worst conditions. The required ventilation rate is then calculated by ratio of level of contamination measured and required, where... 

The present paper tests the assumed original and enhancement mechanisms with rates and conversions for a broad range of contaminants measured under a fixed mass concentration (50 mg/m ) feed condition. The plots compared are reaction rates vs. (1) dark adsorption, Ot. (2) second order rate constant for (OH ) (TCE absent) or (Cl ) (TCE present), and (3) the product of these gas phase second order rate constant times the reactant dark coverage. Where a second order gas phase rate constant was not available, we estimated its value from correlations of kci vs. koH for tke same class of compounds. 

Health advisories have been issued near Lawrence, Kansas, based on chlordane levels in edible fish tissues. In fish from the Kansas River, Kansas, in 1986, chlordanes were detected more frequently and at higher levels than other contaminants measured (Arruda et al. 1987). More than 80% of the sites sampled in Kansas had detectable chlordanes in fish at more than 50% of these sites, levels exceeded 0.1 mg/kg fresh weight — a guideline for the protection of predatory fish. At three urban sites in Kansas, concentrations of chlordanes in fish have approached or exceeded... 

Analysis for total petroleum hydrocarbons (EPA Method 418.1) provides a one-number value of the petroleum hydrocarbons in a given environmental medium. It does not, however, provide information on the composition (i.e., individual constituents) of the hydrocarbon mixture. The amount of hydrocarbon contaminants measured by this method depends on the ability of the solvent used to extract the hydrocarbon from the environmental media and the absorption of infrared light (infrared spectroscopy) by the hydrocarbons in the solvent extract. The method is not specific to hydrocarbons and does not always indicate petroleum contamination, since humic acid, a nonpetroleum material and a constituents of many soils, can be detected by this method. 

Apparatus can be expensive (but much cheaper than many non-electrochemical alternatives). Measurements sensitive to contaminants Measurements sensitive to dissolved oxygen (although this is not true for square-wave voltammetry)... 

Currie et al. (1990) evaluated the concentrations of diazinon in indoor air and on working surfaces for a period of 10 days after application in commercial offices. The highest concentrations of diazinon (163 and 158 pg/m3) were measured 4 hours postapplication in two empty offices, while the concentration in the furnished office was 27 pg/m3. One day postapplication, levels were 125 and 70 pg/m3 in the two empty offices and 27 pg/m3 in the furnished office. Air concentrations of diazinon continued to decline and on day 6 postapplication were approximately 35 pg/m3 in the empty offices and 8 pg/m3 in the furnished office. Airborne levels of diazinon were distinctly lower in the furnished office, and this was attributed to obstruction of the applicator s spraying path by office furniture so that a lower amount of diazinon was applied. Diazinon deposition on aluminum plates was measured as an indicator of surface contamination, measurements ranged from 0.4-15 ng/cm2. No overall decrease in surface contamination occurred over time. Plates suspended 1.5-2.1 m above the floor generally exhibited higher diazinon levels 24 hours... 

National Environment Protection Council (1999) Schedule B(l) Guideline on the Investigation Levels for Soil and Groundwater, National Environment Protection (Assessment of Site Contamination) Measure, Adelaide. 

Trace analysis requires a high degree of accuracy and precision, since contaminants measured at ppb or even ppt levels, and sometimes lower, may pose human and/or ecological health hazards [WENNING and ERICKSON, 1994],... 

These instruments find a ready market in measuring low-level contamination in pharmaceutical suspensions such as intravenous liquids, and for contamination measurements in industrial liquids, and are being increasingly used for on-line process monitoring. 

Hiac PC4000 portable liquid particle counter is a contamination measurement tool, designed to run on-line analyses of hydraulic systems and fluids. The fully self-contained counter operates in the light-blocking mode using a laser diode and reports contamination levels at 4, 6, 10, 14, 21,38 and 70 pm at a flow rate of 60 ml min. ... 

There are two different methods used to assess contamination (1) experimental measurements of contamination and (2) prediction of the possible contamination. We considered above some of the detailed predictive methods. For contamination measurements there are chemical methods and bioassays. In the first case a more detailed assessment of the composition of the contaminants is done. The clear identification of the components related to the pollution phenomenon is useful in identifying the remediation or mitigation initiatives to be adopted. However, there are limitations to the chemical approach ... 

The properties of the spent sulfuric acid vary widely. It might be acid, which is diluted but otherwise uncontaminated, to acid, which is less concentrated and contaminated with metals or other impurities, to acid which is both diluted and contaminated. Measures for recovery and recycle therefore vary in complexity from simple reconcentration, to water removal accompanied by chemical purification steps. Occasionally, thermal destruction of impurities accompanied by dissociation of the acid and recycle of the sulfur content for acid remanufacture may be required. For these reasons the appropriate acid recycle method depends on the use of the original acid, and the condition of the spent acid obtained. Specific examples follow. 

For the future, while recycling can be by-passed in discovery research, it nevertheless has to be better understood in order to facilitate catalytic reactions, with, perhaps, in such cases the help of stronger supports like grafted silica. For the future also, outside of the reaction yields and of the contamination measurements, the transformations should be explored within the solid matrix using appropriate techniques (e.g. microscopy, solid-state MAS NMR) in order to identify and to prevent any possible problems. 

Notes. 1. To avoid interference by possible copper contamination, measure the absorbance of the extract at 620 nm (A-max for dithizone), shake the extract with KI solution buffered at pH 4, and re-measure the absorbance of the extract at 620 nm. The difference in the absorbance values corresponds to the mercury content. 

There are already several methods to measure the availability of contaminants. Measured values of various indicators of the chemical availability results in a close correlation with effects. In this chapter, we do not want to give an overview of all these methods. In a more general way Alexander etal. (2003) distinguished between the following chemical measures of bioavailability ... 

With respect to the different shifts of S13C-values in the recovery procedure it has to be noted, that a satisfactory determination of carbon isotope ratios depends not only on the analytical methods applied but also on the individual substances analysed. Therefore, in order to evaluate the quality of compound specific isotope analyses of riverine contaminants measurements of field samples have to be accompanied by recovery experiments of individual substances. 

Direct toxicity assessment (DTA) can also be used to account for the combined effects of contaminants. Measurements taken from biological and ecotoxicological tests are more directly related to ecological risk, because they measure the biological effects from a mixture of contaminants and, in doing so, provide an implicit indication of the bioavailability of the contaminants. Some tests can be simple and cost-effective in comparison to screening for multiple chemical... 

Sinks and drains in clean areas shall be installed at suitable site to minimize the risks of contamination. Measures shall be taken to avoid contamination from the opening of drains. They shall be excluded from class 100 areas. 

Today, real-time, parts per billion trace gas and particulate contamination measurements are provided to customers manufacturing information systems. This allows customers to understand the purity of their process gases cubic meter by cubic meter. Such information is essential to process quality control and has contributed to the effectiveness of semiconductor manufacturing. 

As constant interfacial tension is no guarantee of absence of contamination, measurement of the upward velocity of a bubble in solution seems a much more sensitive criterion. Thus, the verification of the Hadamard-Rybczynski equation could be considered as a criterion, indicating that the solution has reached a purity beyond which there is no longer any contamination [22]. 

Users should develop specific contamination measurement techniques relevant to their particular circumstances. Such techniques include the use of smears and appropriate survey instruments. The instruments and detectors selected should take into account the likely radionuclides to be measured. Particular care should be taken in selecting instruments of appropriate energy dependence when low energy beta or alpha emitters are present. It should be recognized that the size of the smear and the size of the sensitive area of the detector are important factors in determining overall efficiency. 

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