ATMOSPHERIC POLLUTION — FRENKIEL 



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prevail. If such extreme measures should be necessary, it would be 

 essential to reduce them to a minimum. It may indeed often be suf- 

 ficient to reduce only partially the operation of the sources of pollution 

 and to apply this measure only to some of the sources. It will also be 

 important to predict the unfavorable atmospheric conditions in ad- 

 vance to avoid the application of such measures after the damage has 

 started. What then is the most important information about the 

 atmospheric conditions required for such a prediction? It appears 

 to concern primarily the following factors : The velocity of the wind 

 that carries the pollutants, the characteristics of the turbulence that 

 disperses them, and the nature of the temperature inversions that 

 confine them to the lower levels of the atmosphere. With the ex- 

 ception of precipitation, these are the most important atmospheric 

 factors with which we should be directly concerned. 



One of the most common illustrations of turbulent diffusion, which 

 is directly related to atmospheric-pollution problems, is the dispersion 

 of smoke emitted from a stack. The dispersion of the smoke plume 

 is caused by two principal factors: (1) The general air motion that 



Figure 6. — Schematic illustration of various types of smoke plumes that can occur under 

 the same meteorological conditions. Mean concentration for an average smoke plume 

 in the framed figure can be compared with theoretical results. 



