with measured data on particle properties in such plumes and accompanied by an adequate treatment of background pollutants.
Analysis of new single sources close to the source:
The most advanced reactive plume models available, hybridized with measured data on particle properties in the plumes of similar sources and accompanied by an adequate treatment of background pollutants.
Analysis of single sources at the regional scale:
Insertion of the single source in question into an appropriately chosen multiple-source description of the regional haze problem.
The hybrid models mentioned above are available to the extent that the necessary pieces of the modeling systems exist. Any novel combination of existing models should be carefully evaluated.
For the reasons explained in the introduction to this chapter, most source apportionment studies would benefit from the use of several candidate models, and hence groups of models rather than single models are noted above. We emphasize that the skill and knowledge of the personnel executing a modeling study are often more important in determining the quality of the study than is the choice of the modeling method.
We recommended research to achieve several goals. First, fully developed mechanistic models for the chemical composition, size distribution, and optical properties of atmospheric particles and gases should be created and tested. Two types of mechanistic models are needed: an advanced reactive plume aerosol process model for analysis of single-source problems close to the source and a grid-based multiple-source regional model for analysis of regional haze. In pursuit of those objectives, a program of careful field experiments and data analysis must be designed and conducted to support the use of aerosol process models (for example, to collect data on the degree of uptake of water by airborne particles) and to better characterize emission sources (to measure the chemical composition and size distribution of primary particles at their source in addition to the gaseous precursor emissions). Finally, experimental programs must be designed and conducted to test the performance of completed models of all kinds against field observations on emissions and air quality.