3.0 INITIAL SOURCE DISPERSION

        All releases have initial dilution related to the characteristics of the release. For an area source, the initial dilution is related to the distribution of the release over an area. For a point source, the volume of flow associated with the release controls the initial dilution. Because a sector average model's horizonal dispersion parameter is fixed as a sector width, initial dilution can only be accounted for by increasing the initial vertical dispersion parameter (vertical standard deviation of the distribution of material, ó_z).