ABSTRACT
Risk-based environmental decision making is crucial to responding effectively and efficiently to environmental problems. The identification of an environmental problem and the definition of an appropriate response in such a framework rely on having quantitative tools that relate the sources of the environmental problem to the human or ecological receptors that are negatively impacted. The fate and transport models define the exposure of receptors to environmental contaminants, which when combined with information on the adverse ecological effects of contaminants fully define their risks. All contaminants, however, are subject to molecular diffusion, the mixing process associated with the random motion of molecules. In the laboratory, it is generally possible to design experiments to explore specific transport processes and diffusion-controlled experiments are often used to define effective diffusion, sorption, or reaction rates. The geometry of environmental fate and transport problems varies greatly.
