Complex pollution problems Mixtures

Monitoring the concentrations of various pollutants in industrial wastewater, as well as surface and ground water, with precision and accuracy is a difficult task. Wastewater is a complex matrix that normally contains organic pollutants of non-polar to polar nature in addition to bulk inorganic contaminants. Additionally, interferences are likely when handling complex mixtures of compounds. Under these circumstances, chromatography has played an important role and has provided solutions to complex analytical problems. It is extremely important to have an excellent analytical technique that can accurately... 

Actual water treatment challenges are multicomponent. For example, contamination of groundwater by creosote [8021-39-4], a wood (qv) preservative, is a recurring problem in the vicinity of wood-preserving faciUties. Creosote is a complex mixture of 85 wt % polycycHc aromatic hydrocarbons (PAHs) 10 wt % phenohc compounds, including methylated phenols and the remaining 5 wt % N—, S—, and O— heterocycHcs (38). Aqueous solutions of creosote are therefore, in many ways, typical of the multicomponent samples found in polluted aquifers. 

Difficult to measure accurately and deal with effectively, organic pollutants continue to be a major hazard in the environment. Significantly expanded, the second edition of Organic Pollutants An Ecotoxicological Perspective describes the mechanistic basis of ecotoxicology, using major groups of pollutants as illustrative examples. It also explores the problem of complex mixtures of chemicals. 

Another problem in analyzing the effects of contamination in the field is the complex, fluctuating mixture of pollutants that typically exist in impacted environments. 

Using predictive models for measuring environmental chemodynamics of organic pollutants in complex mixtures requires literature data on partition coefficient values. In some cases the values cited are not strictly experimental, being derived from linear free energy relations, while in others wide variations are reported in experimental values. The main problem is how one should evaluate which values are correct. Thus, Table 2 provides some basis to discriminate between reported values of partition coefficients, as well as predictive equations for partition coefficient calculations [21,62,65-85]. 

In real atmospheres a wide array of pollutant combinations may occur. Plant responses described here represent only experimental combinations of major pollutants shown to inhibit CO2 absorption rates. Effects of other important phytotoxic atmospheric pollutants such as ethylene should also be examined along with more complex mixtures. Information regarding the responses of a wider range of plants subjected to varied environmental conditions would further aid in clarifying the problem. 

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). 

Environmental exposures are present through the human lifetime. However, they may vary considerably over time at the same location, for example, because of the local or global changes in emission and environmental pollution levels. Environmental exposures of humans consist of exposures outdoors and indoors as well as at workplaces these environments may significantly differ. The exposure media include air, water, and soil and dust. Historically, research on human exposures to chemicals and associated health effects has been conducted mostly on single chemicals. In addition, several studies have dealt with complex mixtures, such as diesel fuel and gasoline, by-products from coal combustion, and tobacco smoke. A common problem of complex mixtures is that the composition may vary from one exposure to another and, as a result, the associated toxicity may vary. For a better understanding... 

Mass spectrometry (MS) is now a well-accepted tool for the identification as well as quantitation of unknown compounds. The combination of MS with powerful separation methods such as gas chromatography (GC) or high-performance liquid chromatography (LC) provides a technique which is widely accepted for the identification of unknown components in complex mixtures from a wide variety of problems such as environmental pollutants, biological fluids, insect pheromones, chemotaxonomy, and synthetic fuels. The importance of such analyses has grown exponentially in the last few years there are now well over a thousand GC/MS instruments in use around the world, most with dedicated computer systems which make possible the collection from each of hundreds of unknown mass spectra per day (1). 

Numerous pollutants are discharged directly into the atmosphere by human industry, where winds may transport them to Earth s most remote corners. It is important, however, to note that industry is not the sole source of contaminants individuals also contribute to this problem through the use of household pesticides and fertilizers, improper disposal of hazardous materials (e.g., used motor oil, paints, cleaning products), and even by driving the family car. Consequently, sites with one predominant contaminant are a rarity complex mixtures and subsequent exposures define the real world. 

Environmental criteria have been established for many of these, but the utility and applicability of such criteria for indoor environments is controversial for at least four reasons. Eor example, the goals of the threshold limit values often do not include preventing irritation, a primary concern in indoor environments with requirements for close eye work at video display terminals. For most of the pollutant categories, the problem of interactions, commonly termed the multiple contaminants problem , remains inadequately defined. Even for agents that are thought to affect the same receptor, such as aldehydes, alcohols, and ketones, no prediction models are well established. Finally, the definition of representative compounds for measurement is unclear. That is, pollutants must be measurable, but complex mixtures vary in their composition. It is unclear whether the chronic residual odor annoyance from environmental tobacco smoke correlates better with nicotine, particulates, carbon monoxide, or other pollutants. The measure total volatile organic compounds is meanwhile... 

Environmental pollution requirements have been responsible for the interest in analysis of polyaromatic hydrocarbons (PAH). John and Soutar have reviewed the problems of using luminescence techniques for examination of oil spill. Various methods have been devised to deal with the analysis of complex mixtures involved. Synchronous fluorescence is a useful method using comparatively simple equipment. Rank annihilation methods applied to data acquired as an... 

For complex mixtures, which often occur in biochemical and environmental problems, the mass spectrometer can serve as a highly specific detector for a gas chromatograph. For example, the organic extract of polluted waters may contain hundreds of organic compounds which cannot be perfectly separated by one pass through a GC. Thus, what appears to be a single peak by GC may actually be a... 

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