Oxygenates urban atmosphere

Exchange of volatile compounds across the air-water interface, e.g., oxygen (reaeration that affects aerobic or anaerobic conditions) and release of odorous substances Release of odorous substances to the urban atmosphere and change of reaeration due to a lower atmospheric oxygen concentration Extent of the processes... 

In polluted urban atmospheres, singlet molecular oxygen may play an essential part in the oxidation of nitric oxide to nitrogen dioxide.5,6 The... 

Singlet molecular oxygen is of interest in connection with atmospheric chemistry with respect both to its mode of excitation and to the consequences of its presence in the upper or lower atmosphere. The first part of this section deals with processes of importance in normal, unpolluted atmospheres, while the second part examines the possibility, only recently appreciated, that singlet molecular oxygen may play a part in the chemistry of polluted urban atmospheres. 

The XAD-8 resin separation of hydrophobic and hydrophilic components of WSOM was also employed by Sannigrahi et al. (2006). The 13C-NMR results indicated that WSOM in urban atmospheric particles is mostly aliphatic in nature (-95% C mass) with major contributions from alkyl and oxygenated alkyls (-80%), carboxylic acid (-10%), and aromatic functional groups (-4%). The authors also found that urban aerosol WSOC are only qualitatively similar to aqueous humic material in terms of functional group distribution. 

Singlet oxygen 102( dg) has been identified in urban atmospheres in thep.p.m. range [156,356]. The rapid ageing of polymers in contaminated atmospheres in towns should also be examined from the view point of oxidation involving singlet oxygen. 

Fe-containing particles. Actually, it was found that many Fe-containing particles contain carbon, however, these particles were classihed as Fe-containing. Here, the particles classihed as carbonaceous are mostly composed of carbon, nitrogen, and oxygen without iron. These carbonaceous particles might be from outdoor sources, since it is well known that anthropogenic carbonaceous particles are one of the major chemical species in urban atmosphere. 

Pitts, I N. Jr. (1970) Singlet molecular oxygen and the photochemistry of urban atmospheres. 

Stress corrosion cracking of brass commonly occurs when brass is subjected to an applied or residual tensional stress or while in contact with a trace of ammonia or amine in the presence of moisture and oxygen. The risk of stress corrosion cracking in brasses is greatest in industrial and urban atmospheres, characterized by high contents of sulfur dioxide and ammonia. The stress corrosion susceptibility is markedly lower in marine atmospheres. The relative resistance to stress corrosion cracking of the brasses is as follows ... 

In this paragraph, dependence of O3 production on NO and VOC concentrations under the conditions of polluted urban atmosphere is summarized referring to the photochemical smog chamber experiments (see Column 2 p. 317). The almost sole reaction of direct O3 formation in the troposphere is the reaction of O2 with the ground state oxygen atom 0( P) from the photolysis of NO2,... 

Aldehydes are the most important class of oxygenates in facilitating the generation of ozone. They react rapidly with OH radicals, and they photolyze readily. As seen in table I-D-1, the urban concentrations of formaldehyde and acetaldehyde are often quite high, especially in areas with limited or no pollution controls. Obviously, the rates of generation of aldehydes must be large to sustain the observed concentrations in the face of rapid removal reactions. Even the larger aldehydes are detectable in many urban atmospheres. 

Atmospheric corrosion results from a metal s ambient-temperature reaction, with the earth s atmosphere as the corrosive environment. Atmospheric corrosion is electrochemical in nature, but differs from corrosion in aqueous solutions in that the electrochemical reactions occur under very thin layers of electrolyte on the metal surface. This influences the amount of oxygen present on the metal surface, since diffusion of oxygen from the atmosphere/electrolyte solution interface to the solution/metal interface is rapid. Atmospheric corrosion rates of metals are strongly influenced by moisture, temperature and presence of contaminants (e.g., NaCl, SO2,. ..). Hence, significantly different resistances to atmospheric corrosion are observed depending on the geographical location, whether mral, urban or marine. 

In addition to being removed from the atmosphere by physical processes, atmospheric chemicals can be removed by chemical transformations. Chemical transformations also can be sources of atmospheric pollutants a notorious example is the production of urban smog by reactions involving hydrocarbons, nitrogen oxides, and oxygen. 

Mountains. The same naturally occurring reactive compounds have been found to also contribute to urban photochemical smogs [1]. Estimates of the global atmospheric contribution by plants of terpenes and oxygenated terp-enes range from 2 x 10 to 10 tonne/year. 

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