Abstract for presentation at 14th IUAPPA World Congress

Dry fluxes are typically calculated independently for each species as the product of an overall deposition velocity and concentration. An effective deposition velocity, vd, is determined from ratio of the vertical flux and the concentration at a reference height, where vd, is a net mass-transfer coefficient including the aerodynamic turbulent mass transfer, boundary-layer diffusional transfer and canopy surface chemical resistances to dry deposition. This approach ignores the influence of atmospheric reactions as pollutants deposit and considers the ground level surfaces to be only sinks. In the current research, concentration and flux profiles from Eulerian models with chemical kinetics and first-order or second-order flux closure are used to calculate vd for species with reactions that couple with the mass transport. Damkohler numbers are calculated to distinguish the relative importance of chemical and mass transport processes in turbulent flow as a function of elevation. Comparisons are made between the vertical flux at the reference height and the flux to the canopy surface, to contrast apparent fluxes with depositional impacts. The influence of ground level source terms on the apparent deposition of photochemically reactive species is also estimated by numerical simulation.