Development of continental scale multimedia contaminant fate models: Integrating GIS

The incentives and approaches for modelling chemical fate at a continental scale are discussed and reviewed. It is suggested that a multi-media model consisting of some 20-30 regions, each of which contains typically seven en vironmental compartments represents a reasonable compromise between the iss ues of the need for detailed resolution, avoidance of excessive data demand s and inherent complexity and transparency. Strategies adopted in compiling the Berkley-Trent (BETR) model for North America are discussed and used to illustrate the issues of selecting appropriate number and nature of segmen ts, treatment of air and water flows and the acquisition of environmental d ata. It is suggested that GIS software can play a valuable role in gatherin g and processing such data and in the display and interpretation of the res ults of the model assessment. The BETR model will be a useful tool for desc ribing the nature of persistence and long-range transport of chemicals of c oncern in the North American environment.