ATMOSPHERIC POLLUTION — FRENKIEL 291 



The concentration of pollutant for a section of an urban area repre- 

 sents the added contributions of its local sources and the over- all urban 

 sources. Atmospheric pollution control principles may be based on a 

 limitation of the proportions by which the local sources and the over- 

 all urban sources may contribute to the allowable concentrations of 

 pollutants. These limitations do not refer directly to the amount of 

 pollutants emitted into the atmosphere, but to the mean concentrations 

 of pollutant. To avoid contamination near the ground in an industrial 

 zone, tall stacks are often used. While such stacks do reduce the 

 atmospheric pollution of the local neighborhood, they change little, if 

 at all, their contribution to the over-all urban pollution, particularly 

 if there is a low-level temperature inversion. 



For pollutants formed by a photochemical reaction, such as ozone 

 and certain oxidants, it may be desirable to determine whether a night- 

 time dispersion will reduce the contamination sufficiently to justify 

 the expense of special equipment or the inconveniences of different 

 working hours. The possibility of collecting the pollutants during 

 unfavorable meteorological conditions and dispersing them into the 

 atmosphere at a later time might also be considered. In this connec- 

 tion, the use of natural underground caves and caverns can be con- 

 sidered whenever they can be found near industrial sources of 

 pollution. 



The problem of reducing the over-all pollution from such area 

 sources as motorcars, incinerators, house heating, and so forth, requires 

 very serious study. In the case of incinerators, consideration is often 

 given to replacing them by other methods of refuse disposal. The 

 possible reduction of pollutants should be evaluated by taking into 

 account the contamination for which an alternative method may be 

 directly or indirectly responsible. As far as motorcar pollution is 

 concerned, several abatement methods are considered. They include 

 the use of devices that would modify the exhaust gases into inoffen- 

 sive pollutants, the use of special fuel, and modification of engines. 

 Serious consideration should be given to a general analysis of traffic 

 patterns. An extensive use of expressways and roads without traffic 

 lights would greatly reduce the contribution of motorcars to over-all 

 urban pollution. In many urban areas the effect of an increase in 

 public transportation, including the building of subways, on the pollu- 

 tion pattern might be examined. An analysis of the driving habits of 

 the population and the conditions of the car engines could determine 

 whether proper improvements would reduce the fuel consumption. 

 In an urban area with hundreds of thousands of automobiles, a small 

 improvement for each car should not be neglected. The effects of 

 such undesirable habits as excessively long warm-up periods, rapid 

 decelerations, and parking with idling engines could be evaluated. 



