Measurement in a wind tunnel of dry deposition velocities of submicron aerosol with associated turbulence onto rough and smooth urban surfaces

Dry deposition of a submicron aerosol is studied in a wind tunnel to measure dry deposition velocities onto horizontal and vertical urban surfaces of glass, cement facing and grass for several wind speeds and to measure the turbulence parameters associated with these deposition velocities. These deposition velocities are then compared to data of the literature and to the results of two models for dry deposition. The dry deposition velocity of the fluorescein aerosol increases with the intensity of the turbulence. This highlights the importance of the turbulent processes of impaction and interception in deposition. However, the ratio of dry deposition velocity to friction velocity depends on the surface type. It depends on the turbulence conditions in the boundary layer. These turbulent dry deposition processes thus vary in importance depending on the studied surface. Finally, settling represents a significant part of the deposition for low wind speeds and for smooth surfaces. This wind tunnel study permits the study of the deposition as a function of turbulent processes. It should be supplemented by in situ experiments to take into account all the physical processes involved under real conditions.

► Submicron aerosol deposition velocities on urban surfaces are quantified. ► Deposition velocities vary by about two orders of magnitude, depending on friction velocity. ► Sedimentation dominates for horizontal smooth surfaces at low wind speeds. ► Useful data to validate predictions from deposition models.