Combustion-produced PAHs

We describe herein an investigation of the photochemical reactivity of five PAHs (anthracene, phenanthrene, pyrene, benzo[a]pyrene, and benz[a]anthracene) adsorbed on various coal ashes of widely diverse origin and composition. Each PAH was deposited on each coal ash from the vapor phase to attempt to simulate the adsorption of combustion-produced PAHs onto atmospheric particles (5) ... 

Combustion-produced PAHs transported by air are another likely source of these compounds in marine environments. Low-temperature combustion (such as 1100 K, as in a cigarette) will yield a soot with an abundance of the alkyl-substituted PAHs. Blumer and Youngblood (44) have concluded that PAHs found in several recent sediments are likely to have originated from forest fire particulates. Hites (6), however, refutes this conclusion and offers instead the belief that PAH mixtures are initially deposited by anthropogenic sources and then undergo an... 

Polycyclic aromatic hydrocarbons (PAHs, sometimes also called polynuclear aromatics, PNA) are a hazardous class of widespread pollutants. The parent structures of the common PAHs are shown in Fig. 4 and the alkylated homologs are generally minor in combustion emissions. PAHs are produced by all natural combustion processes (e.g., wild fires) and from anthropogenic activity such as fossil fuels combustion, biomass burning, chemical manufacturing, petroleum refining, metallurgical processes, coal utilization, tar production, etc. [6,9,15,18, 20,24,131-139]. 

The exact synthetic chemistry which produces PAH in a fuel-rich flame is not well known, even today. It is clear, however, that PAH can be produced from almost any fuel burned under oxygen deficient conditions. Since soot is also formed under these conditions, PAH are almost always found associated with soot. As an example of the PAH assemblage produced by combustion systems. Figure 1 shows gas chromatographic mass spectrometry (GCMS) data for PAH produced by the combustion of kerosene ( ). The structures of the major compounds are also given in Figure 1. We draw the reader s attention to a number of features of this PAH mix-... 

Polynuclear aromatic hydrocarbons (PAH), of widespread occurrence in the environment, result from incomplete combustion of carbon- and hydrogen-containing substances. Many PAHs are well-recognized carcinogens and mutagens. Several industrial processes, such as fossil fuel conversion and production of aluminium and ferroalloys, can produce PAHs and result in their occurence in the working environment. 

Fires. Combustion of any kind produces toxic particulate matter, smoke. The combustion can be natural such as a lightning-induced forest fire or unnatural such as the burning of fossil fuel for energy production, a petroleum refinery or plastics warehouse fire)22-23 In addition to particulates, fires produce PAHs, carbon monoxide, organic and inorganic cyanides, and free radicals that are toxicJ24-25 ... 

Pyrolysis of soot produces PAHs. Car and truck exhausts also contain volatile PAHs, such as naphthalene, antracene, phenathrene, etc., which are products of incomplete combustion. 

Comparison of PAH yields, including B[ ]P, produced by bulk pyrolysis of cigarette paper vs. pyrolysis of the paper in a cylindrical form approximating its configuration in the cigarette revealed that the cylindrical configuration combustion produced very little PAHs (or B[a]P) vs. bulk pyrolysis [Wright (4281)]. 

Polycyclic aromatic hydrocarbons (PAH) are widespread environmental contaminants and one of the most potent classes of carcinogenic chemicals. They are byproducts of combustion, and significant levels are produced in automobile exhaust, refuse burning, smoke stack effluents, and tobacco smoke. It is strongly suspected that PAH may play an important role in human cancer. 

The major route of formation of these nitro compounds is via the reaction of VOCs with the NO arising from hot flue gases, such as automobile exhaust gases and gas streams used for drying food stuffs, etc. In these combustion systems the aliphatics can react with nitro compounds or arenes to produce nitro-PAH and nitroarenes. Some of the NO produced are thus converted into C-nitroso compounds. The interactions and reaction chemistry of these compounds is complex and difficult to interpret. 

Polycyclic aromatic hydrocarbons (PAH) are produced by the combustion, under fuel rich conditions, of almost any fuel. Although a few PAH with vinylic bridges (such as acenaphthylene) are lost, most PAH are quite stable in the atmosphere and eventually accumulate in environmental sinks such as marine sediments. Spatial and historical measurements of PAH in sediments Indicate that these compounds are stable, conservative markers of man s energy producing activities. 

The PAH shown in Figure 1 are typical of those produced from the combustion of various fuels ( ). Without exception, the combustion of almost any fuel will produce the suite of compounds shown in Figure 1. The relative abundances, however, can be substantially different depending on the temperature of combustion. 

Polycyclic aromatic hydrocarbons (PAHs) are produced during the incomplete combustion of organic material. PAHs can also be produced through natural, non-combustion processes, and they may be present in uncombusted petroleum. Uncombusted petroleum can be a direct source to the waters of... 

The US Environmental Protection Agency has identified 16 priority PAHs due to their known or suspected carcinogenicity. The structures of these 16 PAHs are presented in Fig. 1, but there are almost limitless possibilities to the number of PAHs that can be produced. In addition to the structures presented in Fig. 1, PAH can also have alkyl chains or heteroatoms within their rings. These compounds are most often produce by the combustion of organic material. In this chapter we will discuss the sources, transport, sinks and toxicity of PAHs and how each of these areas relates to the Great Lakes. 

There are several natural non-combustion sources of PAHs. A study in 1980 by Wakeham [43] concluded that phenanthrene could be created by the dehydrogenation of steroids, retene could be produced by the diagenesis of abietic acid, and alkyl chrysenes could form from the degradation of the pentacyclic triterpenes alpha- and beta-amyrin, which are components of higher plant waxes. In this section we will look at the natural non-combustion sources of retene and perylene and how these sources might impact the Great Lakes. 

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