can react with the energy-related pollutants and secondary ozone to form a variety of
compounds found in smog aerosols (see Hydrocarbons in the Atmosphere).
Carbonaceous soots can also be emitted directly from automobiles and diesel engines.
These soots contain oily organic coatings and associated polycyclic aromatic
hydrocarbons (PAHs) and have received some attention as air toxics. Road dusts from
tire erosion, road work, and traffic are also a major source of aerosols in many urban
areas. Sea-salt aerosols from surf and wind spray can also add to the aerosol burden near
ocean shores. Wind blown dusts especially in arid (desert) regions can be important and
have been found to travel very large distances including transport across the Atlantic
and Pacific Oceans. These windblown dusts are adding to the background in many cities
like Beijing, China and contribute to the brown clouds in Asia. All of the aerosol
species (organic and inorganic) can play important roles in the radiative balance of the
atmosphere on urban, regional, and global scales (see Greenhouse Gases and Global
Warming; Atmospheric Chemistry).