The Atmosphere as a Global Catalytic and Photocatalytic Reactor

The principal components of the atmosphere are nitrogen 78.09%, oxygen 20.95%, argon 0.932%, and carbon dioxide 0.03% (vol%, dry atmospheric air). The water content varies from 0.1 to 2.8vol%. However, there are some other components which in spite of their low concentrations exert strong influence on atmospheric chemistry [4]. Table 1 shows the natural content (i.e. average stationary concentrations) of the principal trace components, their average lifespans and rates of supply and removal from the atmosphere. Two latter values are equal to each other and are calculated as the ratio of the stationary concentration of an atmospheric component to its residence time in the atmosphere. 

Note that the period of vertical stirring of the atmosphere is ss80 days [4]. Thus, those trace gases whose residence time is less than 80 days are distributed non-uniformly in the atmosphere. Examples of such gases are CO, NO., NH3, SO2, etc. In the vicinity of their sources their concentrations and the removal (supply) rates may be higher than the values shown in Table 1. 

Atmospheric aerosols may be both in the liquid (droplets of water or water solution) and solid states. Solid aerosols, i.e. ensembles of ultrasmall particles that sometimes are embedded into liquid droplets can be roughly divided into two categories  

The average composition of aerosol particles (primary and secondary) in normal (background) atmospheric conditions at various altitude is considered to be  

Local variations in the composition of aerosols can also occur. Of importance to heterogeneous chemistry is the observation of high ( 100-fold) enrichment of solid aerosols with transition metals such as Zn, Cd, Pb, etc. over their average (Clark) content in the Earth s crust [6]. 

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