This book presents the proceedings of a NATO Advanced Research Workshop
which was also financially supported by the National Research Council of
Italy. The Workshop was held from October 9 to 15, 1994, at the Centro
Ettore Maiorana in Erice, Italy. Over 40 researchers from a wide variety
of fields attended the Workshop, which brought to attention the ongoing
research on various phenomena related to urban air pollution. The
presence of high levels of atmospheric pollutants in the air of several
urban centres of developed and developing countries causes a great
concern among authorities and public opinion. Some 20% of the European
population live in cities of more than 500,000 inhabitants and about 40%
in cities of more than 50,000. Since exceedance of the Air Quality
Guidelines has been observed to occur worldwide, a great effort has been
addressed to the control of primary pollutants, but many problems
related to secondary pollutants such as nitrogen containing species
(nitrogen oxides, nitric and nitrous acid, ni trates) and photochemical
oxidants (ozone, PAN and others) are far from being solved. The
importance of atmospheric chemistry in understanding the processes
occurring in urban atmospheres has been well recognised, thus there is a
strong need to exchange experiences and results from urban centres in
different Countries. Indeed, atmospheric pollution is very much
dependent on the type of emissions which are very different according to
the economic development of the urban centre under consideration.