A parametric study of gaseous plume depletion by ground surface adsorption

Total plume depletion by ground surface adsorption was calculated via the one dimensional parabolic diffusion equation. Solutions of this differential equation were obtained by digital computer for sets of eddy diffusivity (K) and wind velocity (u) profiles representative of stable, neutral and unstable conditions. Calculations were made for perfect sink and typical partial sink boundary conditions at ground level to a distance of 105m from the source for various source heights. This method of estimating plume depletion was found to be extremely sensitive to K values in the lower levels and source height. The resultant vertical concentration profiles from a depleting plume show markedly non-gaussian distributions with the height of the maximum concentration increasing with travel distance. This departure from the gaussian distribution is most pronounced in stable conditions. It appears that this parabolic diffusion equation provides realistic vertical concentration profiles and, consequently, reasonable plume depletion estimates. (author)