Atmospheric dispersal, plume elevation

This equation represents a Gaussian distribution, where C (Bq.m 3) represents the radionuclide concentration, Q (Bq.s1) the source strength, and H (m) the corrected source released height. Dispersion parameters, ay (m) and az (m), are the standard deviations of the plume concentration in the horizontal and vertical directions respectively. The atmospheric transport is done at wind-speed (height-independent), u (m.s1), to a sampling position located at surface elevation, z (m), and transverse horizontal distance, y (m), from the plume centre. 

Dispersion of the pollutant depends on the mean wind speed and atmospheric turbulence, described in more detail in the next section. Dispersion of a plume from a continuous elevated source increases with increasing sitrface roughness and with increasing upward convective air cm-rents. Thus a clear srnmner day produces the best meteorological conditions for dispersion, and a cold winter morning with a strong inversion results in the worst conditions for dispersion. 

Transport involves the mean wind speed and direction. Dispersion is produced primarily by atmospheric turbulence and is discussed in more detail below. Transformations of the pollutants are due to chemical reactions, deposition, and interactions with liquid water. These constitute separate problems treated elsewhere. Most air pollution arises from continuous emitting sources, such as stacks or highways. They may be groimd or elevated sources. An important parameter in the determination of concentration is the effective source height, which is the sum of physical source height and plume rise. 

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