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IDENTIFICATION AND COMPILATION OF UNSATURATED/VADOSE ZONE MODELS
Citation:
van der Heijde, P. K. IDENTIFICATION AND COMPILATION OF UNSATURATED/VADOSE ZONE MODELS. U.S. Environmental Protection Agency, Washington, DC, EPA/600/SR-94/028, 1994.
Impact/Purpose:
publish information
Description:
Many ground-water contamination problems are derived from sources at or near the soil surface. Consequently, the physical and (bio-)chemical behavior of contaminants in the shallow subsurface is of critical importance to the development of protection and remediation strategies. Mathematical models, representing our understanding of such behavior, provide tools useful in assessing the extent of pollution problems and evaluating means to prevent and remediate them. In classifying models generally applied to soil- and ground-water pollution problems, a distinction can be made between the transport of the contaminants from the point of their introduction into the subsurface (i.e., contaminant source) to the location of concern (i.e., point of exposure), and the (bio-)chemical transformations that may occur in the subsurface. Models specifically simulating fluid flow are referred to as flow models. Models describing the movement of dissolved chemicals and their interaction with the soil or rock matrix in terms of concentrations and mass fluxes are often referred to as contaminant transport models or solute transport models. Furthermore, somevadose modelsfocus on the resulting fate of contaminants, in particular, simulating the (bic-)chemical changes and transformations that occur in the subsurface. Increasingly, combinations of these three model types are employed to adequately simulate site-specific pollution problems and their remediation. To identify existing models for simulation of flow and contaminant transport in the unsaturated subsurface, a database search and literature review were conducted. From the review a catalogue was developed consisting of approximately 100 flow and transport models that may be used for the simulation of flow and transport processes in the unsaturated zone to determine the effectiveness of soil remediation schemes among other uses. The models considered range from simple mass balance calculations to sophisticated, multi-dimensional numerical simulators. There are six categories of models listed, including models for single-fluid flow, coupled and uncoupled flow and solute and/or heat transport, and solute transport for given pressure head distribution. Finally, models are listed that provide soil parameters from column experiments on soil samples. In the full report each model is described in an uniform way by a set of annotations describing its purpose, majorhydrological, mathematicalandoperational characteristics, input requirements, simulative capabilities, level of documentation, availability, and applicability. In some cases, the model description includes comments made by the model author and the investigator concerning development, testing, quality assurance and use, as well as references of studies using the model and references that are part of the documentation or considered pertinent to the model.