Industrial contaminants, determination

Industrial atmospheres usually accelerate the corrosion of zinc. When heavy mists and dews occur in these areas, they are contaminated with considerable amounts of acid substances such as sulphur dioxide, and the film of moisture covering the metal can be quite acid and can have a pH as low as 3. Under these conditions the zinc is dissolved but, as the corrosion proceeds, the pH rises, and when it has reached a sufficiently high level basic salts are once more formed and provide further protection for the metal. These are usually the basic carbonate but may sometimes be a basic sulphate. As soon as the pH of the moisture film falls again, owing to the solution of acid gases, the protective film dissolves and renewed attack on the metal occurs. Hudson and Stanners conducted tests at various locations in order to determine the effect of atmospheric pollution on the rate of corrosion of steel and zinc. Their figures for zinc are given in Table 4.34 and clearly show the effect which industrial contamination has on the corrosion rate. 

Today, the scientific community can identify tiny trace amounts of chemicals in the environment. A quarter-century after Wallace Carothers introduced science-based industrial research to the United States, Clair Patterson adapted techniques developed for determining the age of the Earth to identify microtraces of global pollutants. Today scientists can analyze industrial contaminants in the parts per billion in 1991 when a university scientist discovered in the atmosphere a harmful, low-level contaminant produced by the manufacture of nylon, industry volunteered within weeks to change production methods. 

Chloride-containing impurities are determined by various test methods (ASTM D5194, D5808, D6069) that have sensitivity to 1 mg/kg, reflecting the needs of industry to determine very low levels of these contaminants. 

In addition to the THM methods, EMSL-Cincinnati has developed purge and trap methods for selected halogenated (29) and aromatic (30) compounds that are considered to be chemical indicators of industrial contamination. The methods are applicable to 47 halogenated compounds (Method 502) and 33 compounds that have ionization potentials less than 10.2 eV and that are aromatic or contain a doubly bonded carbon (Method 503). Seven of these compounds are halogenated and are also included in the method for halogenated compounds. Another method, Method 524 (31), provides for GC-MS determination of 28 purgeable volatiles. Single laboratory precision and accuracy data for these compounds are provided in the EMSL methods. 

The Determination of Halogenated Chemical Indicators of Industrial Contamination in Water by the Purge and Trap Method Environmental Monitoring and Support Laboratory. U.S. Environmental Protection Agency Cincinnati, OH, 1979 Method 502. 

Often, many simultaneously occurring pollutants or contaminants determine an environmental problem. In industry, agriculture, and households, products are often mixtures of many compounds. The process of production and consumption is accompanied by emissions and consequently by contamination. One example is the use of toxaphene in the past, a very complex mixture of polychlorinated camphenes, as a pesticide. Technical toxaphene consists of more than 175 individual compounds. A second example is industrial and domestic emissions resulting from the combustion of fossil fuels. The emissions contain both a mixture of gases (SO2, NOx, CO2, etc.) and airborne particulate matter which itself contains a broad range of heavy metals and also polycyclic aromatic hydrocarbons (PAH). 

To better understand the step-wise approach for method development and validation, it is necessary to give examples. They are taken from organic and inorganic trace analysis of environmental matrices. Figure 2.2 illustrates the steps for the validation of the analytical procedure for the determination of polychlorobiphenyls (PCB) in industrially contaminated soil. Figure 2.3 shows the steps necessary to validate the determination of trace elements and particularly arsenic in a fish tissue. Each step of the procedure will provide the necessary information so that the next step can be done with confidence. In practice, the analyst will develop a procedure to quantify all primary and secondary method characteristics as defined in section 2.1.4. 

With the batch reactors used in the fine-chemical industry, the rate of the catalytic reaction is generally not decisively important. The number of catalyst particles per unit volume of the liquid to be treated is one of the experimental factors determining the apparent activity of the catalyst. Because the size of the catalyst particles usually affects the apparent activity of the catalyst only, the size is not critical, provided the particles are no smaller than ca 3 pm. When the size of the particles is below this, separation of the catalyst from the reaction product(s) is difficult, and with still smaller sizes even impossible. The requirement to avoid particles smaller than ca 3 pm imposes fairly severe requirements on the mechanical strength of catalyst particles employed in slurry-phase reactors. When the catalyst particles are liable to attrition, which leads to particles smaller than 3 pm, it is difficult to purify the reaction product(s) completely from the catalyst. Especially with fine-chemicals to be used in the food or pharmaceutical industry, contamination of the reaction product with the catalyst is usually not acceptable. Either mechanically strong catalyst particles must therefore be employed with slurry-phase catalysts or the reactor must be adapted to minimize attrition. With a bubble-column reactor the attrition of suspended catalyst particles is much smaller than with a reactor equipped with a stirrer that vigorously agitates the suspension. 

Contamination. Contamination of samples by external sources can be a serious source of error and may be extremely variable. An excellent example of how serious this can be has been documented in the analysis of samples for polychlorinated biphenyls (PCBs). PCBs are synthetic mixtures of organochlorine compounds that were first manufactured in 1929 and have become of concern as significant environmental pollutants. It has been demonstrated that samples archived since 1914, before PCBs were manufactured, picked up measurable amounts of PCBs in a few hours just sitting in a modem laboratory (Erickson). Aluminum levels in the dust in a normal laboratory are so high that dust prohibits the determination of low ppb levels of aluminum in samples. A special dust-free clean lab or clean bench with a filter to remove small dust particles may be required, similar to the clean rooms needed in the semiconductor industry, for determination of traces of aluminum, silicon, and other common elements such as iron. When trace (inorganic analysis is required, the laboratory environment can be a significant source of contamination. 

Previous sections have illustrated the complexity of most of the compound-specific analyses developed in the environmental field. It is easy then to figure out that the accurate determination of a possible enantiomeric enrichment of chiral pollutants is even more difficult owing to the many co-elution problems and low concentration levels of the analytes. This difficulty could explain the somehow limited research conducted on this topic. However, its interest is clear. Industrial contaminants, such as PCBs or toxafene, are released into the environment as racemates. Therefore, a nonracemic composition of these pollutants might be evidence of selective biotransformation and/or bioaccumulation. Some studies have also pointed to different biological and toxic behaviour for each of the enantiomers [56], something that can be especially relevant for pesticides exhibiting chiral properties. 

At an air temperature of 283 K (10 °C), an air pressure of 1,013 hPa and 60% relative humidity the water content is around 5.7 g/m. At 303 K (30 °C) and relative humidity of 100%, the water content rises to 31.4 g/m. The water film that condenses when the temperature drops or on relatively cold surfaces is always saturated with oxygen. Whereas corrosive action in a non-marine atmosphere is mainly determined by moisture content and potential industrial contaminations, the marine atmosphere is characterised by a raised content of salt particles carried on the wind from the sea spray. Since the salt particles deposited on the metal surface, or aerosols containing salt, also contain hygroscopic components, e.g. calcium and magnesium chlorides, liquid films form on the surface with very high salt content levels, even if the air is still above the dewpoint. 

The other two methods used by industry to examine the purity of maleic anhydride are the crystallization point (168) and color deterrnination of the sample (169). These tests determine the temperature at the point of solidification of the molten sample and the initial color properties of the melt. Furthermore, the color test also determines the color of the sample after a two-hour heat treatment at 140°C. The purpose of these tests is to determine the deviation in properties of the sample from those of pure maleic anhydride. This deviation is taken as an indication of the amount of contaminants in the maleic anhydride sample. 

Skin. The skin may become contaminated accidentally or, in some cases, materials may be deHberately appHed. Skin is a principal route of exposure in the industrial environment. Local effects that are produced include acute or chronic inflammation, allergic reactions, and neoplasia. The skin may also act as a significant route for the absorption of systemicaHy toxic materials. Eactors influencing the amount of material absorbed include the site of contamination, integrity of the skin, temperature, formulation of the material, and physicochemical characteristics, including charge, molecular weight, and hydrophilic and lipophilic characteristics. Determinants of percutaneous absorption and toxicity have been reviewed (32—35,42,43,46—49). 

The developed assay was successfully applied for the arsenite and arsenate determination in contaminated waters of the gold recovery plant and in snow covers of the industrial anthropogenic sources vicinities as well. The data produced are in a good agreement with the results of independent methods atomic absorptioin and atomic emission spectrometry and capillary electrophoresis. 

Demand-controlled ventilation (DCV) is one approach to reduce energy consumption due to ventilation, that is gaining popularity in both industrial and nonindustrial applications. It is used in cases where ventilation requirements vary with time, regularly or irregularly. The control is based on a specified level of indoor air quality by means of continuous measurement of the parameters, that are expected to primarily determine the lAQ, such as the concentration of the main contaminant liberated from the production process. The principle is thus similar to the one in some better-known nonindustrial applications, e.g., CO2 levels in rooms with dense human occupancy (theaters, classrooms, etc.) or nicotine concentration in smoking rooms. See also Section 9.6. 

The purity ot the scrap mainly determines the fraction of energy needed to produce metal from it, and the value of recycling. Clean copper scrap need only be remelted and cast to form recycled copper if the copper is contaminated with organic materials and other metals, more complex separation processes are needed that are similar to production from ores. It is easier to remelt the steel of a car driven in Arizona compared to one rusted by the road salt in snowy areas. Scrap that is produced as a by-product of metal processing can be easily recycled, and it can be collected from relatively few locations. There has been a strong effort to educate both householders and industrial users to separate scrap and return it to waste collectors, leading to a supply of reasonably separated scrap. 

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