is prohibited and strictly enforced and all incineration is performed in multiplechamber incinerators. 5. Restrictions on the evaporation of gasoline from storage tanks and those on certain industrial processes will not add greatly to the overall area reduction in hydrocarbons, but may be necessary to minimize the hydrocarbon emissions in localized areas. 6. A reduction in hydrocarbon emissions in the St. Louis area is expected as a result of limiting emissions from automobiles and the implementation of regulations relating to refuse disposal. An overall decrease of approximately 23 percent by 1970 and 37 percent by 1980 can be expected. 7. The emissions of hydrocarbons are greatest in areas of high traffic densities, principally in the central business district. The actual concentration of hydrocarbons in this area has not been determined; however, available information indicates the advisability of starting to limit hydrocarbon emission in this area now. An important reduction would occur as a result of decreased traffic density if a rapid transit system that will be used by large segments of the population is developed. 8. Since not all of the hydrocarbons enter into photochemical reactions to produce smog, a precise estimate of the impact of these reductions on concentrations of total oxidant in the area is not possible at present. 9. The formulation of relationships between traffic densities, hydrocarbon and nitrogen oxide emissions, and observed concentrations of total oxidant is necessary to provide a useful guide for future transportation studies. To undertake the development of such relationships, information relating to existing and projected traffic volumes, traffic speeds, and diurnal variation in traffic are needed. Carbon monoxide is emitted primarily from motor vehicles. Consequently, the emission patterns and ambient air concentrations are closely related to the traffic patterns with respect to both time and location. If major reductions in ambient air concentrations of carbon monoxide are to be achieved, automotive emissions must be reduced. The air quality can be improved by limiting the emissions from automobiles through the installation of central equipment and by reducing the number of vehicles on the road by the development of a rapid transit system. Both of these approaches are needed to lessen the emissions of pollutants in the Study area. Air-Quality Goals A maximum 8-hour average concentration of 30 ppm and a 1-hour average concentration of 120 ppm have been proposed as the air-quality goals for the Study area. Although these goals are based on effects, there is some question whether the selected goal of 30 ppm is sufficiently low to meet the needs of certain population groups living in the central urban area. The effects of carbon monoxide are discussed in detail in Volume VI of this report. Existing Concentrations Continuous monitoring of carbon monoxide concentrations has been performed at the CAMP station in St. Louis since March 1964. During the period from March 1964 to September 1965, the average monthly concentrations varied from 5 to 10 ppm, with an overall average of approximately 6 ppm. The maximum 24-hour, 1-hour, and 5-minute average concentrations observed during this period were 17 ppm, 27 ppm, and 53 ppm, respectively, which, allowing for time-concentration relationships, are within the air-quality goals. Since these measurements represent the concentrations at only one location, this comparison of existing concentrations and air quality goals cannot be extended to include the entire city or even the entire central business district. For example, the concentrations of carbon monoxide observed at the CAMP site represent the conditions some 30 or 40 feet away from the street. Recent investigations have shown that the concentrations in vehicles are about two times the CAMP values and those in traffic are as much as four times as high as those recorded at the CAMP site. It is probable that the concentrations of carbon monoxide in the more heavily traveled parts of the central business district are higher than those observed at the CAMP station. Furthermore, one can expect much lower concentrations in areas outside of the central business district and away from major traffic arteries. Existing and Projected Emissions During 1963, an estimated 1,115,000 tons of carbon monoxide was emitted to the air of the St. Louis Metropolitan Area. Gasoline-powered motor vehicles accounted for approximately 98 percent of this amount. Projections indicate that by 1980 the rate of gasoline consumption in the area will be double that of 1963. If automobile exhausts continue uncontrolled, the emissions of carbon monoxide would increase in proportion to more than 2 million tons annually in the year 1980. 4 The uncontrolled emissions of carbon monoxide in the exhaust gases are approximately 3.1 percent by volume under average urban operating conditions. Depending on the average route speed, the rate of emission varies from approximately 6 percent by volume at 5 miles per hour to 2 percent at 60 miles per hour. The 3.1 percent by volume corresponds to an average route speed of 25 miles per hour. On the basis of the average speed in urban areas and the average daily mileage traveled, an average of 4.2 pounds of carbon monoxide is emitted daily per automobile. Emission Reduction Plan Federal Law S-306 authorizes the Secretary of Health, Education, and Welfare to set limitations on air pollutant emissions from automobiles. The limitations on carbon monoxide emissions have been specified as 1.5 percent by volume for all vehicles with an engine displacement in excess of 140 cubic inches. (For smaller engines a slightly higher emission rate is allowed.) These limitations will go in effect starting with the 1968 models. The overall reduction in emissions achieved by these controls, although decreasing the emissions per equipped vehicle by 50 percent, is almost negated by the expected increase in automobile travel. The net effect, as shown in Figure 20, is the maintenance of the existing emissions quantities for the next 20 years. Assuming that emissions of carbon monoxide from motor vehicles will be controlled to 1 percent by volume, starting with the 1971 models, a reduction as shown in Figure 20 can be expected. (The State of California requires that carbon monoxide be controlled to 1 percent by volume starting with the 1970 models.) The implementation of this emission limitation would reduce overall emissions in 1980 to 20 percent below the 1963 amounts. The curves in Figure 20 as well as the above discussion are based on the existing and projected emissions of carbon monoxide for the entire Study area. It is, however, the central business district where the traffic density and hence pollutant emissions are high and of primary concern. Before the impact of these Figure 20. Projected carbon monoxide emissions from gasoline-powered motor vehicles with and without control devices. reductions on that area can be evaluated, more detailed information on the expected increase in traffic density is needed. An air-use plan for nitrogen oxides, as such, is not included in this report. The primary reason for this omission has been the lack of air-quality measurement data and criteria, which in turn make the setting of air-quality goals for this class of pollutants impractical. Whenever the air-quality goals are prescribed, the emissions of nitrogen oxides and the resulting ambient concentrations of these pollutants will need to be evaluated in terms of these goals and, if necessary, reductions in these emissions will have to be prescribed and measures will have to be taken to achieve the reductions. As a first step in the design of an air-use plan, this report chapter relates nitrogen oxides emissions to the various types of sources, and gives estimates of future emissions. By far the most important source of nitrogen oxides is the combustion of fuels. The ever-increasing population and the continuous urbanization of the Study area will undoubtedly result in higher energy requirements. These requirements, at least in part, will be fulfilled by increased consumption of fossil fuels, which will, unless controlled, increase the emissions of nitrogen oxides. The magnitude of increase is dependent not only on the future energy requirements, but more importantly on the types of fuels used to meet the requirements. Existing Concentrations Nitric oxide and nitrogen dioxide have been monitored at the St. Louis CAMP site since March 1964. The monthly mean concentrations of nitrogen dioxide during the period from March 1964 to September 1965 varied from 0.02 to 0.05 ppm. The maximum 24-hour average concentration observed during this time was 0.12 ppm, whereas the highest 1-hour average concentration during the same time period was 0.22 ppm. The frequency distribution of measurement data observed from March 1964 to February 1965 showed a geometric mean value of 0.028 ppm and a 99 percentile value of 0.091 ppm. Comparison of the observed concentrations with the State of California airquality standard, which is 0.25 ppm for a maximum 1-hour average concentration, shows that this air-quality goal was not exceeded at the CAMP site. The CAMP measurements cannot be used, however, as the maximum value for the St. Louis area. Existing Emissions During 1963, an estimated 138,300 tons of nitrogen oxides was released to the air of the Study area. In terms of their contribution to the total area emissions, the various source categories accounted for the following percentages: electric power generation, 38 percent; transportation sources, 35 percent; industrial fuel use, 16 percent; residential-commercial fuel use, 6 percent; industrial processes, 3 percent; and other sources, 2 percent. The burning of refuse material accounts for less than 1 percent of the community total. Stationary Combustion Sources - During 1963, an estimated 85,500 tons of nitrogen oxides was emitted from the combustion of fuels in stationary sources. The combustion of coal accounted for 83 percent, natural gas for 12 percent, and fuel oil for 5 percent. During the same time period, coal supplied 57.7 percent; gas, 31.1 percent; and fuel oil, 4.2 percent of the energy requirements. These figures are based on a total heat input of 312 X 1012 Btu. Emission rates of nitrogen oxides according to Btu output from coal, fuel oil and gas are given in Table 21. Fuel Table 21. EMISSION RATES OF NITROGEN OXIDES IN Industrial boilers Domestic-commercial units 0.4 0.9 0.2 Fuel Consumption - Fuel consumption for the Study area has been projected by Ridker5 for the years 1970 to 1980 and is listed by user category in Table 22. The projections for 1980 indicate an increase above the 1963 consumption levels of Table 22. PROJECTIONS OF FUEL CONSUMPTION IN |