Deposition is normally considered to be one of two types: dry deposition is the process by which aerosols and gases in the air are deposited on the surface of the earth (soil, water, rock, plants, etc.); this is termed 'dry' deposition even when the @RT06841@ surface is moist. Wet deposition is that process which involves the transport of chemicals to the surface of the earth by water droplets or snow crystals which scavenge pollutants as they form and fall through the atmosphere.