Atmospheric chemistry Secondary sources

On the other hand, the number of chemicals theoretically is endless. It is simple to assume that from all the chemical compounds ever produced by humans and by 

CHOCHO from biomass plumes 3 Stavrakou et al. (2009b) 

CH3OH from NMVOC, biomass burning 29-35 Holzinger et al. (2004) 

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A number of species have been designated hazardous air pollutants (HAPs) or toxic air contaminants (TACs). Most are directly emitted into the air, but some also have significant secondary sources, i.e., are formed by chemical reactions in air. Furthermore, the ultimate health impacts are determined not only by the emissions and formation of such compounds in air but also by their atmospheric fates. In short, some pollutants react in air to form less toxic species, whereas others form more toxic compounds. Thus, scientific risk assessments of these pollutants require an accurate and complete understanding of their atmospheric chemistry. Some specific examples are discussed in this chapter. 

Mylona, S. (1996) Sulphur dioxide emissions in Europe 1880-1991 and their effect on sulphur concentrations and depositions. Tellus 48B, 662-68 Myriokefalitakis, S., M. Vrekoussis, K. Tsigaridis, F. Wittrock, A. Richter, C. Bruhl, R. Volkamer, J. R Burrows and M. Kanakidou (2008) The influence of natural and anthropogenic secondary sources on the glyoxal global distribution. Atmospheric Chemistry and Physics 8, 4965-4981... 

Chemistry of environment. The presence of oxidant atmosphere (usually air) determines the start of oxidative degradation from the start of irradiation. An inert atmosphere like vacuum or nitrogen does not provide any source of secondary reactions with radicals that appear during radiolysis. The diffusion of oxygen into irradiation material influences the distribution of oxidation products that takes a parabolic shape with the maximum amoimt at the both external sides and minimum is placed on the symmetry axe [14]. The penetration of molecular oxygen allows the reactions of free radicals with it and the peroxyl radical are formed. They are the initiators of further oxidation, which advances as a chain process. 

FIGURE 20.7 Common active chemical agents and their less toxic simulant or structural analog. Source Steiner, W.E., et al. (2003) Secondary ionization of chemical warfare agent simulants atmospheric pressure ion mobility time-of-flight mass spectrometry. Analytical Chemistry, 75, 6068-6076. 

The definition of environmental chemistry shown in Figure 1.1 could very well be illustrated with nitrogen oxides, NO and NO2, emitted to the atmosphere. What would be the sources of these gaseous nitrogen oxides Which secondary air pollutant would they form interacting with volatile hydrocarbons in the sunlight Could acid rain result from these oxides and, if so, what would be the formula of the acid ... 

The nickel-catalyzed cross-coupling of boronic acids with secondary phosphine oxides is an attractive approach for the preparation of arylphosphine oxides (Scheme 4.208) [346], After some experimentation, the authors found that nickel(II) bromide was the most effective nickel source. A mineral base was needed and potassium carbonate was effective. The substrate scope of this reaction was exceptionally high, and a range of functionalized boronic acids as well as secondary phosphine oxides were successfully cross-coupled. One drawback to this system was the use of 1,2-dichloroethane as the solvent for this reaction. It was noteworthy that the chemistry could be carried out under an atmosphere of air for some examples with only a minor reduction in the yields of the arylphosphine oxides. Thus, this reaction is very attractive as no glovebox or vacuum manifold was needed. This chemistry has the potential to generate a large number of different arylphosphine oxides due to the vast array of boronic acids that are readily available. 

Aerosol Chemistry. The general relationship between gaseous and particulate pollutants in the urban atmosphere is depicted in Figure 1. Aerosols may be emitted directly from sources or be formed in the atmosphere as the result of condensation of secondary vapors formed in gas-phase reactions. 

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