Sources, Particle Size Distribution and Transport of Aerosols

Abstract

Various modes of aerosols with respect to their size are described. Natural and anthropogenic sources of aerosols are presented and their fluxes are evaluated. Gas-to-particle conversion processes, including transformations of gaseous hydrocarbons from vegetation, seem to generate the largest amounts of natural aerosols followed by sea spray and desert dust. The annual anthropogenic flux of aerosols contributes about 60% of the total aerosol burden in the atmosphere. Major anthropogenic sources of aerosols include direct emissions from stationary and mobile sources, and formation of secondary aerosols from their gaseous precursors released from power stations, industrial plants, and mobile sources. Atmospheric transport of aerosols on global and regional scale is then discussed together with their removal processes from the atmosphere. Major focus is placed on particle size as this parameter governs the atmospheric transport and dry and wet deposition of aerosols. Major dispersion models applied in Europe and North America to study the aerosol transport are presented. Results of several receptor models used to assess the origin of aerosols at various remote locations are also discussed. Information from a number of measurement programs is used, together with the results of dispersion and receptor models, to discuss global distribution of aerosols and their trends. While fluxes of aerosols from natural sources are quite unchanged over the years, anthropogenic aerosols, after dramatic increase during the 1970s and 1980s, seem to show a slight decrease in the last few years. General description of research needs is presented in the final part.