An Atmospheric Diffusion Model for Metropolitan Areas

An urban diffusion model, which does not require the use of an electronic computer, is presented. The main simplifying assumptions are that continuous pollutant sources are uniformly distributed over the urban area and vertical diffusion occurs until the effluent from each line source reaches the top of the mixing layer, after which the effluent is uniformly distributed through the mixing layer. After the appropriate vertical diffusion coefficient is specified, the calculated concentration is a function of source strength, linear dimension of the metropolis, mixing depth, and wind speed. The calculated concentration is interpreted either as a representative maximum concentration or, through integration, as the average concentration over the metropolitan area. When a representative pollutant concentration is known, the model may be used to determine the apparent “uniform” source strength.     

A Multivariable Model for Atmospheric Dispersion Predictions

In conjunction with a 15-month air quality survey of Jacksonville, Fia., a mathematical model has been developed to describe the dispersion of atmospheric pollutants. The source inventory used with the model was compiled, in part, from the data obtained from the sampling of all major sources within the area. The major sources were considered separately from the one-mile square area sources which accounted for the remainder of the emissions. Meteorological data was recorded continuously in the city including vertical temperature observations to 750 ft. The model was compiled in FORTRAN and can be used for both gaseous and particulate pollutants, by utilizing proper decay rates. The variant nature of meteorological parameters and emission rates are considered. The ground level concentrations of several pollutants which were determined for 24 hr periods at 11 sites and continuously at two other sites were used to check the model. A limited tracer study was carried out in conjunction with the project.     

The Detection and Estimation of Part Per Billion Concentrations of Hydrocarbons

The addition of a freeze-out step in liquid nitrogen prior to analysis by gas chromatography with flame ionization detection permits the accurate determination of C₂ and higher hydrocarbons in the part per billion (ppb) range. Concentrations of C₂ and higher hydrocarbons have been measured in commercial cylinders of nitrogen, helium and hydrogen. Using a 150 ml sample of gas, recovery of ppb concentrations is 95 to 100 percent.     

Control of Contaminant Emissions From Fossil Fuel-Fired Boilers

The importance of fuels combustion was brought into sharp focus recently in a report on air pollution to the United States Senate in which it was stated, “These processes replace usable air with potentially harmful pollutants, and the capability of the atmosphere to disperse and dilute these pollutants—especially in urban areas where people, vehicles, and industries congregate in even greater numbers—is strictly limited.”¹ The overwhelming burden of emissions of sulfur compounds, as well as nitrogen compounds and particulate matter in the U. S. today, originates from the burning of coal and fuel oil in stationary combustion sources. Thus, combustion has a large influence on the quality of the atmosphere in most urban areas. The air pollution effects of these contaminants are many and varied and all are objectionable and undesirable. Without a doubt, the most serious air pollution problem in the nation today is that created by the combustion of fossil fuels.     

Comparison of Wind at 500 Feet Over Minneapolis and Louisville With Geostrophic Wind

Measurements of wind speed at 500 ft on a television tower in the Minneapolis-St. Paul area are compared with geostrophic wind speeds and lapse rates. The roughness length for the builtr-up area surrounding the tower is estimated using geostrophic boundary-layer models. Similar data for Louisville are also considered. The results are relevant to-the application of existing boundary-layer models to the estimation of wind speed and turbulent mixing over a city.     

Sulfur Dioxide Removal and Recovery from Pulp Mill Power Plants

The use of soda ash liquor to scrub SO₂ rich power plant flue gases was studied using an Airetron pilot scrubber with a maximum capacity of 3000 cfm. The relative effects of the major operating variables— temperature, soda ash concentration, and the gas/liquid flow ratio—on the absorption phenomenon were determined. Orthogonal factorial experiments were used to derive a response function relating mass transfer values to operating variables. The economics of a full scale NSSC installation are discussed.     

National Emission Standards Introduction

A feature of the 63rd annual meeting of the Air Pollution Control Association, held June 14–18, 1970 in St. Louis, was a plenary session on national emission standards. Presided over by John S. Lagarias, APCA past president, the session explored the theme for both motor vehicles and stationary sources through the presentations of Delbert S. Barth and Arthur C. Stern and the discussions of John A. Maga and Robert L. Harris, Jr. The essence of their remarks appears on the following pages.