Types of transport episodes in northern Europe

The long-distance transport of aerosols, particularly water-soluble particles and their sooty component, was studied in Sweden by means of particle sampling and analysis and a comparison of the results obtained with the directions of upper-level winds. It is found that coarse particles are essentially a mixture of sea salt and alkaline weathering products or ashes, that the weathering products or ashes had taken up HNO3 and SO2 from the air, resulting in the formation of nitrate and sulfite (later oxidized to sulfate), and that soot-containing fine particles are transported in episodes from central to northern Europe. The results indicate that H2SO4, which is initially formed by the photochemical oxidation of SO2, is probably introduced as droplets by means of turbulent diffusion into ground-level air layers, where the droplets meet a flow of NH3 from the ground and neutralization is usually incomplete