A Generalized Analytical Model for Crosswind Integrated Concentrations with Ground Level Deposition in the Atmospheric Boundary Layer

Abstract : A generalized mathematical model describing the crosswind-integrated concentrations is presented for dispersion of pollutants emitted from a continuous source in the atmospheric boundary layer with deposition to the ground surface. The model is based on a solution of the resulting two-dimensional steady state advection-diffusion equation with deposition to the ground surface. It considers the horizontal wind speed as a generalized function of vertical height above the ground surface and eddy diffusivity as a function of both downwind distance from the source and vertical height. Various special cases of the model are deduced. A sensitivity analysis of the model prediction of the ground-level crosswind-integrated concentrations with deposition velocity is performed. Various issues and limitations associated with this work are discussed. The model is evaluated with the observations of a depositing tracer obtained from Hanford dual diffusion experiment in stable conditions. The statistical measures show that the present model, by considering deposition, is performing well with the observations. The model is giving an over-predicting trend with the observations and predicts 100 % cases within a factor of two. On the other hand, the consideration of a non-depositing condition for a depositing tracer yields the severe over-prediction and thus, it introduces the significant errors in the model prediction. The selection of the lower boundary condition for a depositing tracer at the height of deposition surface gives better prediction than those at a height of surface roughness length.