Date of Award

1988

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

First Advisor

Danny D. Reible

Abstract

Contaminant transport from riverine sediments was investigated via physical and mathematical models. Due to its remote nature, there exists a lack of understanding of transport mechanisms and rates at the sediment-water interface of rivers. This dissertation is focused on evaluation of potential abiotic transport processes which affect the movement of contaminants across this sediment-water interface. Only non-dispersive transport of passive contaminants was considered allowing the research to focus on the movement of the sediment pore water which carries the contaminants. The abiotic processes studied include the advection by flow of sediment pore water and the movement and turnover of sediment through erosion by the overlying river flow. Pore water flow driven by a mean hydraulic gradient between the river and its associated ground-water aquifier and driven by the local pressure variations associated with the uneven surface of the river sediment was considered. Mathematical models of the transport mechanisms considered are presented and used to compare the importance of each. The preliminary results indicate the potential importance of a heretofore largely unexamined mechanism, advective transport by the local pressure variations over the uneven bed sediment. The mathematical models developed for the flow and transport processes in the bottom sediments can be applied to a variety of realistic river conditions. A very general model of ground-water flow based on the boundary element method and capable of describing flow in heterogeneous media with arbitrary boundary conditions and with point sources and sinks was developed in both two and three dimensions. Techniques were also developed to employ the structure of the boundary element method to trace individual streamlines or equipotential surfaces and to solve special classes of hyperbolic and parabolic problems. A mathematical model of river sediment movement as bed load was also developed that was capable of describing the dynamics and spatial variations of contaminants within a moving sediment bed.

Pages

387

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