Long-Range Transport: GIS 164 Research Articles © ecomed publishers, D-86899 Landsberg, Germany and Ft. Worth/TX, USA • Tokyo, Japan • Mumbai, India • Seoul, Korea ESPR – Environ Sci & Pollut Res 8 (3) 164 – 172 (2001) Research Articles Development of Continental Scale Multimedia Contaminant Fate Models: Integrating GIS David G. Woodfine 1 , Matthew MacLeod 1 , Donald Mackay 1 and Jennifer R. Brimacombe 1 1 Canadian Environmental Modelling Centre Trent University Peterborough, ON, K9J 7B8 Corresponding author: Donald Mackay; e-mail: dmackay@trentu.ca of interest is divided into a large number of connected boxes or sets of boxes representing connected ecosystems. Examples are the global model of Scheringer (1996), Scheringer et al. (2000), and Wania and Mackay (1996), which includes atmo- spheric and oceanic transport and the riverine models of Gobas et al. (1998) and Connolly et al. (2000). Here we outline the use of Geographic Information Systems (GIS) and geographically referenced (georeferenced) data in the development of the Berkeley-Trent North America con- taminant fate model (BETR North America). For more in- formation on the detailed structure of the model see MacLeod et al. (this volume). The BETR North America model requires a description of the North American continent in terms of 24 distinct re- gions, each composed of seven compartments; lower and up- per air, fresh water, soil, sediment, vegetation and coastal water (Fig. 1). Each of the resulting 168 (24 x 7) compart- ments is treated as being homogeneous or well mixed with respect to the chemical of interest (see MacLeod et al., this issue). DOI: http://dx.doi.or g/10.1065/espr2001.06.073 Abstract. The incentives and approaches for modelling chemi- cal 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 environmental compartments represents a reasonable compromise between the issues of the need for detailed resolution, avoidance of excessive data demands and inherent complexity and transparency. Strat- egies adopted in compiling the Berkeley-Trent (BETR) model for North America are discussed and used to illustrate the issues of selecting appropriate number and nature of segments, treatment of air and water flows and the acquisition of environmental data. It is suggested that GIS software can play a valuable role in gathering and processing environmental data and in the display and interpretation of the results of the model assessment. The BETR model should prove to be a useful tool for describing the fate and long-range transport potential of chemicals of concern in the North American environment. Keywords: BETR; fugacity; long-range transport; multimedia; North America; regional; segmentation; transport Introduction It is now apparent that for certain persistent organic chemi- cals there is need for continental scale mass balance models that address transport over distances of 1000 to 5000 km. As Beyer et al. (2000) have shown, some chemicals are ex- pected to travel distances of >1000 km before being either degraded or permanently isolated in soil or sediment. If lo- cal exposure is to be adequately understood and quantified, then distant sources must be accounted for in the models. One approach for atmospheric transport is to employ re- peated Lagrangian calculations in which the fate of parcels of contaminated air is followed for days and weeks, gener- ating a picture of probability of reaching a given distant destination. These calculations essentially apply meteoro- logical models in retrospect, for example HYSPLIT (NOAA 1997) as used by Commoner (2000) to track dioxins from the Southern US to the Arctic. Transport in water requires different treatment because it depends on the local hydro- logical or circulation conditions. The more common approach is to use a multimedia or mul- tiple compartment or Eulerian approach in which the region (1) Upper Air (2) Lower Air (3) Vegetation (6) Soil (4) Fresh Water (7) Sediment (5) Coastal Water Fig. 1: Box diagram of the seven compartments of the BETR North America regional fate model. Arrows indicate the advective flows between regions for air, freshwater and coastal water compartments Each region of the BETR North America model is parameterized with individual hydrological, meteorological, geographical and physical attributes. This requires the specification of more than 70 individual input parameters for each region. [ 119 ]