286 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1956 



dividual sources or groups of sources. In our present example, we 

 have considered the concentration of pollutants referred to in figures 

 11 and 12. It may be necessary to examine the pollution levels for 

 other pollutants as well. A similar analysis would, of course, have 

 to be made for other locations in the urban area or in the surrounding 

 rural areas. A complete analysis will therefore require finding the 

 pollution patterns over Los Angeles County, similar to those illus- 

 trated in figure 8. If the air-zoning requirements take into account 

 the differences between the nature of possible damages in each of the 

 locations, then the allowable threshold concentrations may vary with 

 the location. 



This analysis refers to the mathematical model in which the mean 

 concentration patterns due to the over-all urban pollution sources are 

 considered. To approach more closely the real conditions, one must 

 take into account the possible departures from the mean concentra- 

 tions and the added effects of local sources of neighborhood pollution. 

 The mean concentration patterns were determined for the average 

 meteorological conditions for the month of September. In our mathe- 

 matical model, the description of the meteorological conditions was 

 based on hourly mean streamlines as measured in Los Angeles County 

 in September 1947. On each day of this month the streamlines depart 

 from this average. This departure results in a departure of the mean 

 concentration patterns, for a particular day, from the results obtained 

 from the analysis. However an important part of the present analy- 

 sis is to try to forecast the mean concentration patterns to determine 

 in advance whether any emergency measures are required. An analy- 

 sis based on general meteorological conditions corresponding to a 

 period of the year, such as the month of September, may be sufficient 

 for such a forecast. In the final result one would, however, take into 

 account the characteristics of the temperature inversion for the par- 

 ticular day for which the mean concentrations are determined since 

 they have a major influence on the levels of concentration. 



LOCAL SOURCES OF NEIGHBORHOOD POLLUTION 



Let us now consider a residential neighborhood with its own sources 

 of pollution that may include automobiles, indoor heating, home in- 

 cinerators, and so forth. Figure 13 illustrates a small neighborhood 

 with two houses and one incinerator. We should differentiate between 

 the contamination from the over-all sources of urban pollution and 

 the contamination from the local incinerator. The over-all sources 

 of urban pollution include, for instance, the numerous industrial 

 sources represented in our mathematical model. If our residential 

 neighborhood is located near the California Institute of Technology, 

 then the mean concentration originating from the over-all sources of 



