ATMOSPHERIC POLLUTION — FBENKIEL 281 



values referring to each of the curves indicate the relative magnitudes 

 of the mean concentration In this analysis we have not taken into 

 account the topographic situation of Los Angeles and have assumed 

 that there is no temperature inversion. 



RELATIVE RESPONSIBILITIES OF POLLUTION SOURCES 



A more complete study has been made to determine the theoretical 

 mean concentration at one location in Los Angeles County — California 

 Institute of Technology in Pasadena. We have assumed a thermal 

 inversion at 1,500 feet above sea level and have found the probable 

 mean concentrations using the average meteorological conditions in 

 Los Angeles County as measured in September 1947. We have further 

 taken into account the topographic situation of the Los Angeles Basin 

 by including in our model the San Gabriel Mountains, which are 

 north of Pasadena. 



Sources of pollution distributed over a large area such as motor 

 vehicles, gasoline service stations, home incinerators, and house chim- 

 neys can be represented as area sources. An area source can be 

 considered as a large number of point sources spread over the area 

 or represented by an appropriate mathematical equation correspond- 

 ing sufficiently closely to the real area source. In order to illustrate 

 the analysis for an area source, we shall consider the motor-vehicle 

 traffic distribution in the Los Angeles Basin. The geographic traffic 

 distribution is based on some of the available data [6], and the 

 density of traffic in squares of size 4 by 4 miles has been determined. 

 In figure 9, the area of each black circle placed at the center of the 

 square is proportional to the corresponding traffic density. A model 

 of the geographic traffic distribution has been described by a mathe- 

 matical equation. Figure 10 represents the hourly variation of the 

 traffic volume measured at a particular location in Los Angeles County. 

 Obviously, the hourly traffic distribution does not change in each of 

 the squares in the same way; however, we shall assume that it does 

 for our model, because more complete data on the traffic variations 

 were not obtainable. 



Using similar methods, it is possible to include in our mathe- 

 matical model of Los Angeles County several other sources of 

 pollution and to consider their relative contributions to the mean 

 concentration at each locality in the area. We have considered four 

 classes of pollution sources, namely: (1) Motorcars, (2) oil and gas 

 heating, (3) refuse incinerators, and (4) industry. In what follows, 

 I shall try to illustrate what kind of data can be found on these rela- 

 tive contributions of various sources of pollution. We shall first 

 add to our mathematical model an area source representing the pollu- 

 tion from refuse incinerators. Not having available information on 



