Sustainable Geoenvironmental Engineering Practice - Sustainable Practices in Geoenvironmental Engineering - page 476

Highest (optimum) soil quality

Baseline for soil
quality
sustainability

Aridification,
salinization, acidification

Increasing time t

Time t = 0

FIGURE 13.3
Illustration of increasing (enhanced) and decreasing (diminished) soil quality in relation to time. The soil
quality index is a composite index determined on the basis of measures of achievement of levels required by
prescribed physical, chemical, and biological indicators. Note that different soil quality indices are needed,
depending on whether one is concerned with agricultural production or, for example, the use of soil for waste
management.

SQI and WQI permits one to arrive at determinations that show whether the material and,
inally, the system itself, will be sustaining. Taking the SQI as an example and referring
to Figure 13.3, when calculations show that the SQI at any one particular time is greater
than the baseline value, we will have increasing soil quality, and we can be assured of
sustainability of the function served by the soil. Evaluation and quantiication of SQI is
application or function-speciic, i.e., they depend on management goals for the material
(water and soil).

13.4.1.1 Example of SQI Development

To illustrate the procedures that one would follow to evaluate and determine the appro-
priate SQI, we will use the role of soil as a resource material for management of the
impacts from contaminant discharge into the ground. We recall from the previous chap-
ters that the basic properties contributing to the development of the assimilative capabil-
ity of soils are physical, chemical, and biological. From this starting point, determination
of what pertinent attributes are signiicant and measurable is required. Furthermore, it
needs to be determined whether or how these attributes vary with circumstances spe-
ciic to the problem at hand, i.e., functions or use of the soil. Figure 13.4 is a schematic
illustration of the physical, chemical, and biological properties that are considered to
be signiicant in the development of the assimilative capability of the soil. If one were
to compare the kinds of attribute data sets with the information given in Figure 9.19 in
Chapter 9, it would be immediately evident that many of the basic interactions devel-
oped between contaminants and contaminants have been incorporated in the measured