ABSTRACT
Trace gases are atmospheric constituents that occur in relatively small and sometimes highly variable concentrations. Most of them are of natural or anthropogenic origin, but some like chlorofluorocarbons are only generated by human activities. Some trace gas concentrations have changed rapidly during the last three centuries and human activities account for most of these changes. As some of these gases may play a crucial role in the earth’s radiative balance and atmospheric chemistry and be important pollutants, they are the subject of intensive scientific study. Once emitted into the atmosphere they can be transformed by a chain of complex chemical reactions. Air quality models are used as a unique method for the simulation of trace gas concentrations in time and space, thus yielding a powerful tool for the achievement of optimal pollution abatement strategies.
