Introduction to Soil Chemistry
Introduction to Soil Chemistry
Introduction to Soil Chemistry
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CHAPTER<br />
2<br />
SOIL BASICS II<br />
MICROSCOPIC TO ATOMIC ORBITAL DESCRIPTION OF<br />
SOIL CHEMICAL CHARACTERISTICS<br />
In this chapter soil components will first be considered as individual independent,<br />
noninteracting entities. Then the interaction between the various<br />
components in soil will be discussed. However, it is essential <strong>to</strong> know<br />
and remember that components in soil never act independently of each<br />
other. In addition, surfaces always have a coating of some type that is not<br />
continuous, varies in thickness, and sometimes exposes the underlying<br />
surface. Sometimes this first coating will have another, different, coating on<br />
<strong>to</strong>p of it.<br />
Before an understanding of the interactions between soil components and<br />
surfaces is possible, it is essential <strong>to</strong> know the composition of uncoated soil<br />
components. Once this is known, it is then possible <strong>to</strong> discern the interactions<br />
and bonding patterns of these components with and without coatings.<br />
The solid portion of soil is made up of sand, silt, clays, and organic matter.<br />
Elements and inorganic and organic molecules and ions are also present. The<br />
soil solution is a combination of elements and inorganic and organic ions and<br />
molecules. The gaseous portion contains gases commonly found in the atmosphere.<br />
However, the concentrations of these gases are very different in soil air<br />
than in the atmosphere. All components are subject <strong>to</strong> partitioning between<br />
these three phases.<br />
The chemistry of soil is contained in the chemistry of these phases, the<br />
elements present, their bonding, and the a<strong>to</strong>mic and molecular orbitals<br />
available for bonding and reaction. For the solid phase the chemistry will<br />
depend on the amount and type of surface available for reaction. In the liquid<br />
phase solubility will be the most important characteristic determining the<br />
chemistry occurring. In the gaseous phase gas solubility and the likelihood that<br />
the component can be in the gaseous form (i.e., vapor pressure) will control<br />
reactivity.<br />
<strong>Introduction</strong> <strong>to</strong> <strong>Soil</strong> <strong>Chemistry</strong>: Analysis and Instrumentation, By Alfred R. Conklin, Jr.<br />
Copyright © 2005 by John Wiley & Sons, Inc.<br />
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