The long range transport of airborne material and its removal by deposition and washout - I. General considerations.

摘要: Abstract The lifetime and decay distance of airborne pollution downwind from a large area source are examined assuming that the transport takes place between ground, or sea level, an inversion only removal mechanisms deposition washout by rain. Rainout chemical reactions not included in this preliminary account Part I concentrations taken to be uniform with height. detailed effects turbulent diffusion upon concentration profiles considered II. In absence rain decays exponentially, “decay” “travel” equal height multiplied ratio mean wind speed velocity. For sulphur dioxide passing over dry land is typically several hundred, so heights about 1 km give rise lifetimes day distances hundred kilometres. It shown as conditions vary there maximum rate at each which independent velocity decreases inversely source. When conversion sulphate aerosol place, again under assumption rainfall absent, corresponding life times increased order magnitude. extension analysis based on assumptions variable velocities indicated. moderate (1 mm h−1) present reduces On annual average basis remains comparable process, rates kilometres industrial areas being most small fraction g S m−2, per annum. effective process.