Environmental Fluid Mechanics 1:
Mass Transfer and Diffusion

Course Script > Ch 5

Chapter 5:  Boundary mixing:  Air-water and sediment-water interfaces

In the previous chapter we introduced transformation and described both homogeneous and heterogeneous reactions.  Now, we would like to look in more detail at heterogeneous reactions and discuss the chemical and physical processes at interfaces that lead to boundary fluxes of chemical species. The two major boundary types in environmental fluid mechanics are the air-water and sediment-water interfaces.  Because the processes at both boundaries are very similar, we treat them together in this chapter under the heading of boundary exchange.

This chapter is divided into three main sections.  First, the boundary layer in the vicinity of the interface is described, and two common models for treating the boundary dynamics are introduced without specifying what type of boundary is involved.  Second, the air-water interface is introduced, and methods are described for treating gas exchange across the interface.  As an example, the Streeter-Phelps equation for predicting oxygen concentrations downstream of an organic waste stream is introduced.  Third, the sediment-water interface is described, including the complex physical and transformation processes that bring sediment and water into contact, and a short description of the chemistry that occurs at the sediment-water interface is provided.

See Lecture 9 and Lecture 10.




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