ABSTRACT
This chapter discusses the movement and alterations of pollutants from the power plant stack to ground levels in surrounding locations. Meteorological factors such as the wind direction, wind speed, cloud cover, sunshine, and temperature gradients are all taken into account with a Gaussian plume dispersion model. The atmospheric dispersion model assumes that airborne substances distribute themselves normally around a centerline which is determined by the direction of the wind. The most complicated aspect of generating the twenty-four weather conditions is determining stability classes. The fraction of material removed by wet deposition is assumed to be proportional to the amount of time the particle remains in the atmosphere and the average rate of precipitation. Chemical reactions which occur while the emittant is in transit significantly alter the mix of pollutants over even intermediate distances. Population exposures are particularly sensitive to the rate of chemical change of sulfur dioxide to sulfate.
