Multimedia fate and transport models: an overview

Several multimedia fate and transport models have been described. They basically fall into three classes: continuous (dynamic) site-specific models; generic (non-site-specific) screening models; and simple equilibrium partitioning screening models. The hydrologic components of site-specific models are all based on the Stanford Watershed Model. They all link existing single media models (e.g., air, land, water), but are not yet completely coupled. For each site-specific model, there are plans to eventually allow for feedback between media. The screening models take a variety of approaches, are much less data intensive than the site-specific models, and are mainly used to identify the media in which further efforts should be directed. As time goes on, many more multimedia methods will undoubtedly be developed and applied to problems of EPA concern. A major impediment to widespread use that needs to be overcome is a general lack of adequate data to test, calibrate, implement, and use the various models, particularly the more sophisticated ones. Many of the necessary monitoring data are lacking or inappropriate for modeling use, as are the needed chemical and environmental data. Therefore, modeling objectives will need to be considered in the planning of improved and expanded monitoring efforts. Better communication between users and modelers needs to be established (18). Bases of chemical and environmental data of known quality need to be developed, along with more structure-activity relationships for predicting chemical properties. In short, the widespread use of multimedia models will depend on the availability of data rather than on the availability of a model.