Dry Deposition of Sub-micron Aerosols Over Water Surfaces According to Air-Water Streams

In nuclear accident scenario context with atmospheric releases, initial state of continental hydro-systems contaminations is mainly associated with radioactive sub-micron aerosol particle deposits in the course of their transport. Since the 70s, numerous studies address dry deposition of aerosol over water surfaces through measurments both in experimental flume devices and over large water surface areas such as lakes or oceans. They conducted to the usual well known V-shape relation between deposition velocity versus particle sizes and empirical models adjusted through friction velocity, aerosol size (Slinn and Slinn, 1982) and water surface conditions (Williams, 1984). In this context, we present experimental results for dry deposition of sub-micron particles generated from uranine solutions in a wind tunnel providing co- and counter-current air/water flow conditions. The objective is to characterize the mechanisms of dry deposition onto water surfaces according to air/water streams. The results highlight significant variations of the deposit velocities with the orientation of the water stream. They are induced by the water surface conditions which are modified by this orientation. The more the water stream is counter the wind, the more coarse is its surface with roughnesses which produce an increase of deposition velocities