Stream-subsurface interactions have been demonstrated to control the downstream transport of various contaminants, such as metals, radionuclides and arsenic, as well as the release of these substances from contaminated sediments. The purpose of the proposed research is to develop fundamental physical and chemical understanding of the basic processes controlling the exchange of contaminants and other substances between flowing streams and their underlying sediments and to integrate this understanding into a unified set of models that will describe net exchange in natural streams based on easily-measurable physical and chemical parameters. Flume experiments will be used to study exchange processes under carefully controlled conditions. Field experiments will be used to study large-scale exchange processes and to observe the effect of multiple exchange processes operating simultaneously. Fundamental descriptions of individual exchange processes will be developed and these process descriptions will be integrated into a unified set of models for net exchange. The exchange of both conservative solutes and select non-conservative substances will be considered. The educational plan will prepare future researchers and practicing engineers to work on interdisciplinary environmental problems. It consists of components targeting graduate education, undergraduate education and underprivileged high school students. A fourth component will be the development of an engineering-oriented M.S. program in International Development.
