Environmental Engineering Reference
In-Depth Information
Figure 10.4
Transport and fate modeling from a point source (the curves show the decreasing
concentration with increasing distance from the source).
result in a complex variable system. To predict the behavior of the contaminants in
this complex environment, transport and fate models and IT tools are necessary.
Fate and transport models are based on mass balance and are used to predict the
migration of chemical constituents through soil, groundwater and air (or a combi-
nation thereof) over time, with most models focusing on specific fate and transport
processes. Fate (i.e., physical, chemical and biological) processes address persistence of
a constituent while transport (mainly physico-chemical) processes address the motion
of constituents along the migration pathway. According to the ASTM Compendium
(1999), the processes incorporated into fate and transport models include advection,
dispersion, diffusion, equilibrium partitioning of constituent mass between solid and
fluid portions of the environmental medium (as a result of volatilization, solubilization,
sorption, partition and equilibrium chemical reactions), biodegradation and bioaccu-
mulation of constituents, and phase separation of immiscible liquids. Several modeling
tools exist for assessing the impact from a contaminated site/source on soil, ground-
water, surface water, as well as on all of the environmental compartments (multimedia
models). These models can be simple mathematical (analytical) models based on an
equation, which describe the changes in a system. These analytical tools which rely on
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