McKay, Donald. "Front matter" Multimedia Environmental Models ...

©2001 CRC Press LLC
CHAPTER 8
Applications of Fugacity Models
8.1 INTRODUCTION, SCOPE, AND STRATEGIES
The ability to define Z values for a variety of media, and D values for processes
such as advection, reaction, and intermedia transport, enables us to set up mass
balance equations and then deduce fugacities, concentrations, fluxes, and amounts.
We thus have the capability of addressing a series of environmental modeling
problems in addition to the Level I, II, and III calculations described earlier.
The aim of this chapter is to provide the reader with a description of the
calculation of chemical fate in a variety of environmental situations in the expectation
that the parameter values describing the environment and the chemical can be
modified to simulate specific situations. It may be desirable to add or delete processes
or change the model structure to suit individual requirements. Many of the models
apply to steady-state conditions and can be reformulated to describe time-varying
conditions by writing differential rather than algebraic equations. These differential
equations can be solved algebraically or integrated numerically, depending on their
complexity.
Some of the most satisfying moments in environmental science come when a
model is successfully fitted to experimental or observed data and it becomes apparent
that the important chemical transport and transformation processes are being represented
with fidelity. Even more satisfying is the subsequent use of the model to
predict chemical fate in as yet uninvestigated situations leading to gratifying and
successful “validation.” Failure of the model may be disappointing, but it is a positive
demonstration that our fundamental understanding of environmental processes is
flawed and further investigation is needed. For a review of the history of environmental
mass balance models, the reader is referred to Wania and Mackay (1999).
8.1.1 Scope
In this chapter, several models are described. We start with a recapitulation of
the Level I, II, and III models, including descriptions of various software and