Stressors and Soil Contamination - Sustainable Practices in Geoenvironmental Engineering - page 39

and all other substances that are nonthreatening to human health and the environment. In
other words, the term contaminants is used when we wish to refer to non-indigenous ele-
ments, substances, etc., found at a site or in a material under investigation.
In reference to Figure 2.2, the source of the contaminant plume at the site in question is
at the ground surface, e.g., dump site, landill, toxic dump. For this discussion, the reasons
for locating the dump site, landill, toxic dump, etc., are not addressed, even though they
result in creating the contaminant source. Our interest is directed toward the impacts
generated by the presence of these sources. The terms stressor sources and impacts need to
be carefully differentiated. For the particular problem shown in Figure 2.2, the event or
action product responsible for the contaminant plume is the landill itself. The stressor source
is the leachate plume containing fugitive contaminants—obtained as a result of dissolu-
tion of the waste material contained in the landill. The stressors , which are the fugitive
contaminants, are chemical stressors.
Some of the evident impacts to the geoenvironment resulting from the contaminants in
the contaminated ground shown in Figure 2.2 include:
• Contaminants in the atmosphere carried into the atmosphere by evaporation and
volatilization.
• Contaminants on the land surface within and outside the contaminated site,
resulting from deposition of the airborne contaminants.
• Contaminants in the contaminated ground.
• Contaminated groundwater and surface water due to transport of the contami-
nant plume and also to deposition of contaminants in the atmosphere.
• Threats to habitats of terrestrial and aquatic biota.
• Threats to human health.
The impacts shown in the preceding list illustrate the targets (receptors) of the four
members (land element, receiving waters, humans, and terrestrial and aquatic biota) of
the reference frame. Using these as targets, one determines not only what is being impacted ,
but also the nature of the impact. There are obviously many more impacts that can be
cited. We can, for example, discuss or speculate on the impact of the contaminants in the
contaminated ground on the possible loss of biodiversity in the affected region, and the
impact on the quality of the land and how this affects future land use. These impacts can
be covered in the impact statements that need to be produced or developed in association
with speciic projects and events. These will be discussed in greater detail at various times
throughout the topic when speciic projects and/or events are considered.
2.3.2 Characterization of Geoenvironmental Impacts
In addition to the geoenvironmental impact frame of reference, there needs to be a mecha-
nism or means or criteria for one to determine what constitutes an impact to the geoenviron-
ment . The group of questions that needs to be addressed include:
1. Whether reversibility (of damage) should be used as one of the decision mecha-
nisms for determination of impacts.
2. How man-made improvements, amelioration, mitigation, and remediation pro-
cedures to the geoenvironment can be factored into the process of evaluation of
geoenvironmental impacts and their effects.