An Overview of Atmospheric Reactive Pollutant Models

Air quality models have been developed for the purpose of relating ambient concentrations of reactive pollutants to the emissions of primary pollutants under specified meteorological conditions. Some of the substances of interest from a health and welfare point of view include gas phase oxidants (such as ozone, nitrogen dioxide, organic nitrates, and oxygenated hydrocarbons), as well as condensed phase materials (such as sulfates or nitrates). The atmospheric concentrations of these materials are influenced both by transport and transformation. Computer simulations have been developed to describe the pollutant phenomenology in terms of advection, turbulent diffusion and a variety of chemical reaction steps both homgeneous and heterogeneous. Inputs include wind velocities, stability data, emissions data, and initial concentrations in the ambient atmosphere. The most interesting output quantities are the surface concentrations of pollutants for times and locations of interest. The time and space resolution of the models set many of the requirements placed on input data. This paper will provide a description of available models, a discussion of related measurement requirements, and directions for future developments. Models are assessed in terms of detail, computer resource requirements, and ease in data handling. The spatial and temporal requirements on input data vary widely according to the methodology employed to solve the governing equations. Future work should be directed toward the satisfaction of new requirements of additional species and phenomenology, but, at the same time, toward preserving or enhancing the efficiency of the computation.