PAHs , in atmospheric

Major sources of PAHs in atmospheric and aquatic environments... 

Table 25.2 Major Sources of PAHs in Atmospheric and Aquatic Environments...

The NH2O formed in the series of chain reactions is anticipated to be a short-lived intermediate which could interact with polyaromatic hydrocarbons (PAH) in atmosphere to give nitroarenes or nitro-PAH. 

Omar, N.Y., Abas, M.R., Ketuly, K.A., Tahir, N.M., 2002. Concentrations of PAHs in atmospheric particulate (PM-10) and roadside soil particles collected in Kuala Lumpur, Malaysia. Atmos. Environ. 36, 247-254. 

Figure 10. Total content of PAH in atmospheric air of industrial towns in Uzbekistan.

Moreira Vaz, J., Screening direct analysis of PAHS in atmospheric particulate matter with SPME, Talanta, 60, 687-693, 2003. 

Polycyclic aromatic hydrocarbons (PAH) in atmospheric particles have received a great deal of attention because of the known carcinogenic effects of some of these compounds. The most prominent of these compounds is benzo(a)pyrene and other examples are benz(a)anthracene, chrysene, benzo(e)pyrene, benz(e)acephenanthrylene, benzo(j)fluoranthene, and indenol. Some representative structures of PAH compounds are given as follows ... 

HPLC methods with fluorescence detection have also been developed for the determination of nitro-policyclic aromatic hydrocarbons (PAHs) (among which 9-nitroanthracene and 1-nitronaph-thalene) [238] in atmosphere. Samples have been collected in a standard high-volume sampler with a Teflon-coated glass fiber filter, and the Soxhlet extraction was performed with dichloromethane as the solvent. RP HPLC/UV techniques are used for the determination of aldehydes, ketones, and carbonylic compounds after derivatization with DNPH [239],... 

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. 

A particularly interesting group of compounds in combustion effluents are those with a vinylic bridge such as acenaphthylene (peak 4) and cyclopenteno[cd]pyrene (peak 32). Peak 23, although not labeled, has been positively identified as acephenanthrylene, a compound which also has a vinylic bridge. We emphasize this structural feature because of its chemical reactivity (compared to the fully aromatic portions of the PAH). We shall see later that this reactivity is important when considering the fate of PAH in the atmosphere. 

Of particular interest in terms of atmospheric chemistry are reactions of certain PAHs in VOC-NOx-air atmospheres to form biologically active polycyclic aromatic compounds, PACs. Thus, not only is the fundamental chemistry of the formation and fates of these secondary air pollutants of interest, but it can also have major toxicological implications. For example, in some airsheds certain PACs that are reaction products (e.g., nitro-PAH and nitro-PAH lactones) contribute signifi-... 

However, reactions of PAHs in ambient air to form more polar species (e.g., nitro-PAHs, ketones, quinones, lactones, and dicarboxylic acids) greatly enhance their solubilities in aqueous systems. This has major implications when one considers the distribution of PAHs, and their atmospherically formed PAC derivatives, through the air, water, and soil environments. These increases in solubility upon reaction are important not only from an environmental chemistry perspective but also in terms of possible impacts on public health and ecosystems, e.g., in both the exposure and the health effect... 

Values recommended by Mackay et al. (1992) and Mackay and Callcott (1998) for the vapor pressures of a number of PAHs of atmospheric interest and several properties used in theoretical calculations of their gas-particle partitioning in ambient air are given in Table 10.6 for examples of their use, see discussion of gas-particle partitioning theory in Chapter 9.D and references cited above. 

II This H is for Henry s law expressed as H = P/[PAH], where P is the gas-phase concentration in pascals and [PAH] is the liquid-phase concentration in moles per cubic meter. Traditionally in atmospheric chemistry, Henry s law is expressed as H = [X]/Px. 

Clearly, a sound evaluation of the total mutagenic/carcinogenic potencies of a complex mixture of POM emissions (e.g., diesel exhaust) should include not only the PEFs of the primary particle- and vapor-phase PAHs and PACs but also those of the mutagens formed in atmospheric reactions of precursor PAHs (see, for example, Arey et al. (1992), Lewtas (1993b), Atkinson and Arey (1994), Nielsen et al. (1996), Arey (1998a), and Section F). For examples of such formal scientific health risk assessments prepared by the State of California Air Resources Board and Office of Environmental Health Hazard Assessment, see Benzo[ ]pyrene as a Toxic Air Contaminant (CARB, 1994) and Identification of Diesel Exhaust as a Toxic Air Contaminant (CARB, 1998). 

Interestingly, these nitro-PAH lactones are not found in primary emissions of particulate POM they are formed in atmospheric reactions (Atkinson and Arey, 1994 Arey, 1998a, and references therein see Section F.2). 

To better understand the effects of atmospheric processes (reactions, gas-particle partitioning, etc.) on the size distributions of PAHs in ambient aerosols, Venkataraman and Friedlander (1994b) carried out measurements of gases and particles during winter and... 

See Table 10.24 for concentrations of these PAHs in various urban atmospheres. 

As we have seen, a great deal is known about emission sources and strengths, ambient levels, and mutagenic/carcinogenic properties of the particle-phase PAHs in airborne POM. However, because of the tremendous physical and chemical complexity of the aerosol surfaces on which photolysis, photooxidations, and gas-particle interactions take place in real polluted ambient air, much less is known about the structures, yields, and absolute rates and mechanisms of formation of PAH and PAC reaction products, especially for the more polar PACs. This is one area in which there exists a major gap in our knowledge of their atmospheric chemistry and toxicology. 

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