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

©2001 CRC Press LLC
Preface
This book is about the behavior of organic chemicals in our multimedia environment
or biosphere of air, water, soil, and sediments, and the diversity of biota
that reside in these media. It is a response to the concern that we have unwisely
contaminated our environment with a large number of chemicals in the mistaken
belief that the environment’s enormous capacity to dilute and degrade will reduce
concentrations to negligible levels. We now know that the environment has only a
finite capacity to dilute and degrade. Certain chemicals have persisted and accumulated
to levels that have caused adverse effects on wildlife and even humans. Some
chemicals have the potential to migrate from medium to medium, reaching unexpected
destinations in unexpectedly high concentrations. We need to understand
these processes, not only qualitatively in the form of assertions that DDT evaporates
and bioaccumulates, but quantitatively as statements that DDT in a particular region
evaporates at a rate of 100 kg per year and bioaccumulates from water at a concentration
of 1 ng/L to fish at levels of 1 mg/g.
We have learned that chemical behavior in the complex assembly of environmental
media is not a random process like leaves blowing in the wind. The chemicals
behave in accordance with the laws of nature, which dictate chemical partitioning
and rates of transport and transformation. Most fundamentally, the chemicals are
subject to the law of conservation of mass, i.e., a mass balance exists for the chemical
that is a powerful constraint on quantities, concentrations, and fluxes. By coupling
the mass balance principle with expressions based on our understanding of the laws
of nature, we can formulate a quantitative accounting of chemical inputs and outputs.
This book is concerned with developing and applying these expressions in the form
of mathematical statements or “models” of chemical fate. These accounts or models
are invaluable summaries of chemical behavior. They can form the basis of remedial
and proactive strategies.
Such models can confirm (or deny) that we really understand chemical fate in
the environment. Since many environmental calculations are complex and repetitive,
they are particularly suitable for implementation on computers. Accordingly, for
many of the calculations described in this book, computer programs are described
and made available on the Internet with which a variety of chemicals can be readily
assessed in a multitude of environmental situations.
The models are formulated using the concept of fugacity, which was introduced
by G.N. Lewis in 1901 as a criterion of equilibrium and has proved to be a very
convenient and elegant method of calculating multimedia equilibrium partitioning.
It has been widely and successfully used in chemical processing calculations. In this
book, we exploit it as a convenient and elegant method of explaining and deducing
the environmental fate of chemicals. Since publication of the first edition of this
book ten years ago, there has been increased acceptance of the benefits of using
fugacity to formulate models and interpret environmental fate. Multimedia fugacity
models are now routinely used for evaluating chemicals before and after production.
Much of the experience gained in these ten years is incorporated in this second
edition. Mathematical simulations of chemical fate are now more accurate, compre-