Geoscience Reference
In-Depth Information
Part III
Contaminant Partitioning in the
Subsurface
Contaminants may reach the subsurface in a gaseous phase, dissolved in water, as
an immiscible liquid, or as suspended particles. Contaminant partitioning in the
subsurface is controlled by the physicochemical properties and the porosity of the
earth materials, the composition of the subsurface water, as well as the properties
of the contaminants themselves. While the physicochemical and mineralogical
characteristics of the subsurface solid phase define the retention capacity of
contaminants, the porosity and aggregation status determine the potential volume
of liquid and air that are accessible for contaminant redistribution among the
subsurface phases. Environmental factors, such as temperature and water content
in the subsurface prior to contamination, also affect the pollution pattern.
Under natural conditions, subsurface contaminants can be composed of single
organic or inorganic compounds or mixtures thereof. These compounds have
different properties, so they react differently, even if they reach the subsurface
simultaneously. Therefore, knowledge of subsurface partitioning among individual
components in a contaminant mixture is of major importance.
Chapter 5
discusses contaminant adsorption on geosorbents and includes a short
description of the surface properties of adsorbents and the methodology for
quantifying adsorption. The chapter continues with a presentation of adsorption of
various types of toxic chemicals on the subsurface solid phase. In addition to
physicochemical adsorption, contaminants can be retained in the subsurface by
precipitation, deposition, and trapping. These topics, as well as hysteresis phe-
nomena and formation of bound residues, are discussed.
Contaminant partitioning is described in the following chapters.
Chapter 6
examines aqueous solubility equilibria as affected by environmental factors and
the apparent solubility of toxic chemicals in the presence of natural and industrial
ligands, cosolvents, and electrolytes. Volatilization of contaminants from the water
phase is discussed in
Chap. 7
. A significant portion of Part III is devoted to the
presentation of numerous examples, selected from literature, that illustrate con-
taminant partitioning among the subsurface solid, aqueous, and gaseous phases.
