Environmental Engineering Reference
In-Depth Information
conceptualization, but also the capability to render these into the appropriate mathemati-
cal relationships.
Problem conceptualization includes
1. Problem recognition. This encompasses more than an adequate description of the
site and interacting elements. To structure the output requirements for the model
and the manner in which the results need to be expressed, knowledge of the end
purpose (use) of the results is required. The three different areas of application of
models shown at the top of the illustration shown in Figure 9.9 (risk, design, foren-
sic) will not have the same input and output requirements inasmuch as the decision-
making process and the decisions required are different between them. Taking the
problem of the contaminant plume emanating from the landill, shown in the top
left-hand corner of the igure, the differences between the outputs obtained from
analysis (or prediction) of plume advance in respect to risk management, design of
barrier systems, or determination of source-pathway-receptor are obvious.
2. Elements involved in the total system within the problem domain. In the exam-
ple shown in Figure 9.10, the contaminant plume emanating from the landill in
Figure 9.10 passes through the capillary fringe before meeting the saturated zone
under the water table. The elements involved in the example problem include not
only the interacting elements typiied by the soil fractions, porewater and con-
taminants, and microorganisms, but also the problem setting, i.e., the capillary
fringe and water-saturated zone.
3. Mechanisms and processes of interactions between participating elements, initial
and boundary conditions, and output requirements.
Waste
landfill
Full saturation under
water table
Contaminant
plume
Water
table
Bedrock
FIGURE 9.10
Schematic showing leachate plume as a contaminant plume spreading downward toward the water table and
spreading in the direction of low of the groundwater.
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