Multimedia Environmental Models

The Fugacity Approach

J. Mark Parnis, Donald Mackay

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000095135
• Edition: 3
• Topic: Naturwissenschaften
• Subtopic: Chemie

Multimedia Environmental Models: The Fugacity Approach, Third Edition, takes a broad approach of viewing chemical behavior in the total biosphere of connected biotic and abiotic compartments. Chemicals are subject to the laws of "mass balance, " a constraint that provides the opportunity to establish quantitative expressions for chemical fate that are central to chemical management and regulatory legislation.

This book employs both the conventional concentration-based procedures and those based on application of the more elegant and powerful concept of fugacity to characterize equilibrium, steady-state distribution, and time-dependent transport between environmental phases such as air, water, and soil. Organic chemicals are emphasized because they are more easily generalized when assessing environmental behavior.

Features

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• Illustrates professional approaches to calculating the fate of chemicals in the environment

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• Explicitly details all worked examples in an annotated step-by-step fashion

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• Presents real-life freely downloadable models of use to government, industry, and private consulting professionals and students alike

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• Clarifies symbols and notation

1 Basic Concepts

The Essentials

Closed Systems at Equilibrium

$\text{Moles}\text{of}\text{chemical}\text{in}\text{phase}“\text{i}”=\text{phase}“\text{i}”\text{concentration}\left(\text{mol}{\text{m}}^{-3}\right)\times \text{phase}“\text{i}”\text{volume}\left({\text{m}}^3\right)$

$m_i=C_i{V}_i$

$\text{Total}\text{moles}\text{of}\text{chemical}\text{in}\text{system = sum}\text{of}\text{moles}\text{of}\text{chemical}\text{in}\text{n}\text{phases}$

$m_{\text{Sys}}={\displaystyle \sum _{i=1}^n{m}_i}={\displaystyle \sum _{i=1}^n{C}_i{V}_i}$

Steady-State “Open” Systems

$\text{Total}\text{chemical}\text{input}\text{rate}=\text{total}\text{chemical}\text{output}\text{rate}\left(\text{mol}{\text{h}}^{-1}\right)$

$r_{\text{Tot}}^{\text{In}}={\displaystyle \sum _{i=1}^{\text{All}\text{inputs}}{r}_i}={\displaystyle \sum _{j=1}^{\text{All}\text{outputs}}{r}_j}=r_{\text{Tot}}^{\text{Out}}$

$\text{Residence}\text{time}\text{for}\text{flow-only:}{\tau }_F=\frac{V_i}{G_i^{\text{Outf}}}$

Time-Variable Systems

$\text{Rate}\text{of}\text{change}\text{in}\text{total}\text{moles}=\left(\text{total}\text{input}\text{rate}\right)-\left(\text{total}\text{output}\text{rate}\right)$

$\frac{d\left(\text{total}\text{moles}\right)}{dt}=r_{\text{Tot}}^{\text{In}}-r_{\text{Tot}}^{\text{Out}}$

$t_{1/2}=\frac{0.693}{k^{\text{Loss}}}{t}_{0.37}=\frac{1}{k^{\text{Loss}}}{t}_{0.9}=\frac{2.303}{k^{\text{Loss}}}$

We recommend that the reader consult Appendix B to confirm the system of units used in this and later chapters. Of particular importance are units of concentration that differ from conventional usage in chemistry.

1.1 Introduction

Since the first edition of this book in 1991, there have been revolutions in environmental science. Climate change is now recognized as a global priority, requiring modeling and international actions to ensure that our planet remains habitable. The number of chemicals in commerce has greatly increased. We are now able to measure environmental concentrations at picogram (10⁻¹² g) levels. There have been enormous advances in toxicology, revealing increasingly subtle effects of chemicals on organisms, including ourselves. The explosion in information technology has revolutionized access to data on environmental systems and chemical properties. More than ever we need models to provide a quantitative accounting of chemical fate in our environment and to guide regulation and remediation efforts.

There is a common public perception and concern that when chemical substances are present in air, water, or food, there is a risk of adverse effects to human health. Assessment of this risk is difficult (a) because the exposure is usually (fortunately) well below levels at which lethal toxic effects and often sub-lethal effects cannot be measured with statistical significance against the “noise” of natural population variation and (b) because of the simultaneous multiple toxic influences of other substances, some taken voluntarily and others involuntarily. There is a growing belief that it is prudent to ensure that the functioning of natural ecosystems is unimpaired by these chemicals, not only because ecosystems have inherent value but also because they can act as sensing sites or early indicators of possible impact on human well-being.

Accordingly, there has developed a b...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Acknowledgments
• Authors
• Chapter 1 Basic Concepts
• Chapter 2 Equilibrium Partitioning
• Chapter 3 Advection and Reaction
• Chapter 4 Transport within and between Compartments
• Chapter 5 Evaluative Fugacity Models and Calculations
• Chapter 6 Specific Fugacity Models and Calculations
• Chapter 7 Chemical Uptake by Organisms
• Chapter 8 Human Health
• Appendix A: Estimated Properties of Chemicals of Environmental Concern for use in Modeling Exercises
• Appendix B: Units
• References
• Index