Atmospheric degradation

Atmospheric haze has been observed in both the western and eastern portions of the United States. Typical visual ranges in the East are <15 miles and in the Southwest >50 miles. The desire to protect visual air quality in the United States is focused on the national parks in the West. The ability to see vistas over 50-100 km in these locations makes them particularly vulnerable to atmospheric haze. This phenomenon is generally associated with diffuse or widespread atmospheric degradation as opposed to individual plumes. 

The formation of peroxyacetyl nitrate from isoprene (Grosjean et al. 1993a) and of peroxy-propionyl nitrate (Grosjean et al. 1993b) from ctT-3-hexen-l-ol that is derived from higher plants, illustrate important contributions to atmospheric degradation (Seefeld and Kerr 1997). 

Franklin J (1994) The atmospheric degradation and impact of perchloroethylene. Toxicol Environ Chem 46 169-182. 

Kirchner F, LP Thuner, I Barnes, KH Becker, B Donner, F Zabel (1997) Thermal lifetimes of peroxynitrates occurring in the atmospheric degradation of oxygenated fuel additives. Environ Sci Technol 31 1801-1804. 

Tuazon EC, SM Aschmann, R Atkinson (2000) Atmospheric degradation of volatile methyl-silicon compounds. Environ Sci Technol 34 1970-1976. 

Figure 6.4. General reaction scheme for the atmospheric degradation of an alkane VOC.

R. Atkinson and J. Arey Atmospheric degradation of volatile organic compounds, Chem. Rev. 2003,103, 4605. 

Muller, M., Klein, W. (1991) Estimating atmosphere degradation processes by SARs. Sci. Total Environ. 109/110, 261-273. 

Photochemical transformation of benzole (e)pyrene (BeP), a polycyclic aromatic hydrocarbon, adsorbed on silica gel and alumina surfaces, is reported by Fioressi and Arce (2005). This study was designed to define the atmospheric degradation of the PAH adsorbed on particulates that originated from wind erosion of the land surface. It can be assumed that similar behavior occurs at the land surface-atmosphere interface. 

No studies on the transformation or degradation of fuel oils in the atmosphere were located. However, volatile components of fuel oils such as benzene, toluene, xylenes, and PAHs may be expected to enter the atmosphere where they are subjected to degradation processes. Further information on the atmospheric degradation of selected volatile hydrocarbons are presented in the ATSDR toxicological profiles for these chemicals (ATSDR 1989, 1990a, 1991a, 1991b). 

The chemistry of the troposphere (the layer of the atmosphere closest to earth s surface) overlaps with low-temperature combustion, as one would expect for an oxidative environment. Consequently, the concerns of atmospheric chemistry overlap with those of combustion chemistry. Monks recently published a tutorial review of radical chemistry in the troposphere. Atkinson and Arey have compiled a thorough database of atmospheric degradation reactions of volatile organic compounds (VOCs), while Atkinson et al. have generated a database of reactions for several reactive species with atmospheric implications. Also, Sandler et al. have contributed to the Jet Propulsion Laboratory s extensive database of chemical kinetic and photochemical data. These reviews address reactions with atmospheric implications in far greater detail than is possible for the scope of this review. For our purposes, we can extend the low-temperature combustion reactions [Equations (4) and (5)], whereby peroxy radicals would have the capacity to react with prevalent atmospheric radicals, such as HO2, NO, NO2, and NO3 (the latter three of which are collectively known as NOy) ... 

Ball, J. C and T. J. Wallington, Formation of Trifluoroacetic Acid from the Atmospheric Degradation of Flydrofluorocarbon 134a A Human Health Concern Air Waste, 43, 1260-1262 (1993). Barone, S. B A. A. Turnipseed, and A. R. Ravishankara, Kinetics of the Reactions of the CFsO Radical with Alkanes, J. Phys. Chem., 98, 4602-4608 (1994). 

Bednarek, G M. Breil, A. Hoffmann, J. P. Kohlmann, V. Moers, and R. Zellner, Rate and Mechanism of the Atmospheric Degradation of 1,1,1,2-Tetrafluoroethane (HFC-134a), Ber. Bunsenges. Phys. Chem. Chem. Phys., 100, 528-539 (1996). 

Thiopentone sodium (Figure 4.3) is available as a yellow powder, stored in nitrogen to prevent atmospheric degradation, and mixed with 5% anhydrous sodium carbonate. The sodium carbonate prevents precipitation of the insoluble free acid and results in a solution with a pH of 10.5-11.0. The oil/water partition coefficient is 4.7 and the pKa 7.6. Although thiobarbiturate solutions are stable, if refrigerated, for up to two weeks, they should not be stored for longer than 24 hours as the solutions do not contain any antibacterial preservative. 

Predicting Atmospheric Degradation by Oxidation and Photolysis 469 Table 16.3 HYDROWIN training set statistics and linear free energy relationship (LFER) equations. 

Designing for Abiotic Degradation Case Studies for Hydrolysis and Atmospheric Degradation 477... 

Saturated copolymer types are much more stable to atmospheric degradation than those with unsaturations, both in the backbone and in the side chains. 

With current estimates of the rates of alkoxy radical reactions [27], isomerization is likely to be the more important of these latter two processes. Clearly, a better understanding of these reactions is required before their role in the atmospheric degradation of aromatic hydrocarbons can be assessed. 

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