ATMOSPHERIC POLLUTION — FRENKIEL 



293 



required to eliminate either nitrogen dioxide or hydrocarbons, then 

 we will be able to compare each of these control methods with their 

 effects. Most probably a practical solution will be unable to eliminate 

 entirely either nitrogen dioxide or hydrocarbons. We should, there- 

 fore, also try to examine the effects of partial reductions for each of 

 these pollutants (an example is represented by one of the curves on 

 fig. 16). 



The contribution of motor-vehicle exhausts to the production of 

 ozone appears to be very large and deserves an extensive study. We 

 will give here only some results obtained by an analysis similar to the 

 one made for the industrial sources. It is known that the exhausts 

 contain relatively large quantities of hydrocarbons during idling and 

 deceleration periods. Some thought is given to either reducing those 

 periods or using methods to intercept hydrocarbons. Figure 17 rep- 



0.00016 



0.00012 - 



0.00008 - 



0.00004 



10 12 14 

 HOUR OF DAY 



22 24 



Figure 17. — Effects of general improvements of motor-vehicle^operation or construction on 



the ozone pollution. 



resents some results obtained for our model, using available data on 

 the nature of the exhaust gases during various periods of motor ve- 

 hicle operation [12] . It appears that a complete elimination of idling 

 and deceleration periods would reduce the ozone concentration to 

 about half of its value obtained with all the combined pollution 

 sources. This result assumes that the methods used for such a reduc- 

 tion do not themselves add ozone-producing pollutants. One must, 

 for instance, consider whether burning hydrocarbons in the exhaust 

 gases does not produce too large quantities of nitrogen dioxide. Fig- 

 ure 17 shows that a complete elimination of nitrogen dioxide from the 

 exhaust gases would have a smaller effect than the elimination of 



