Geoenvironment Impact Mitigation and Management - Sustainable Practices in Geoenvironmental Engineering - page 389

Site conditions

Geological and
hydrogeological settings
Pore water chemistry
pH and Eh

Soil composition and
assimilative capacity

Patterns of natural attenuation

Knowledge
requirements for
lines of evidence
(LOE) indicators

Evidence from hydrogeochemistry

Evidence of prior
occurrence of natural
attenuation

Evidence of natural
bioremediation

Supporting laboratory tests and analyses

Microcosm studies Transport and fate modeling

Analysis of nature of contaminants in
contaminated site

Laboratory tests on partitioning
and attenuation

FIGURE 10.17
Required information and analyses for LOE indicators.

of contaminants. To determine this, it is necessary to recall the various mechanisms and
processes that establish retention and transformation of the various kinds of contaminants
generally found in the subsoil. In addition, one needs to determine or assess the environ-
mental mobility of the contaminants in the site under consideration. These are necessary
pieces of information for prescription of indicators for the lines of evidence (LOE).

10.8.1 Organic Chemical Compounds

The previous chapters have shown that organic chemicals such as organic solvents, paints,
pesticides, oils, gasoline, creosotes, greases, etc., are responsible for many of the chemi-
cals found in contaminated sites. These chemicals are known generally as xenobiotic com-
pounds. It is not possible to categorize them all in respect to how they would interact in a
soil-water system. The more common organic chemicals found in contaminated sites can
be grouped into three broad groups:

• Hydrocarbons , including the PHCs (petroleum hydrocarbons), the various alkanes,
and alkenes, and aromatic hydrocarbons such as benzene, MAHs (multicyclic aro-
matic hydrocarbons), e.g., naphthalene, and PAHs (polycyclic aromatic hydrocar-
bons), e.g., benzopyrene
• Organohalide compounds , of which the chlorinated hydrocarbons are perhaps the
best known. These include TCE (trichloroethylene), carbon tetrachloride, vinyl
chloride, hexachlorobutadiene, polychlorinated biphenyls (PCBs), and polybromi-
nated biphenyls (PBBs)