Comparison of methods of accounting for deposition in a long-term atmospheric dispersion model

A long-term, climatological-type dispersion model is modified to account for dry deposition with the tilted-plume, source depletion, and surface depletion models of the deposition process. Computer software is developed to reflect these modifications and adapted to the Climatological Dispersion Model (CDM) computer code.

The deposition models are used to predict air concentrations at ten receptor elevations at downwind distances between 100 meters and 100 kilometers for three sets of meteorological conditions and two deposition velocities. The concentrations predicted by the deposition models are normalized to the concentrations predicted by the nondepositing atmospheric dispersion model.

The performance of each model under varying meteorological conditions and deposition strengths is assessed, and the performance of each of the deposition models is compared. Conclusions and recommendations are made.