Stressors and Soil Contamination - Sustainable Practices in Geoenvironmental Engineering - page 50

2.4.2 Organic Chemical Contaminants

Organic chemical contaminants found in the geoenvironment classify as organic chem-
ical pollutants. These have origins in (a) industries producing various chemicals and
pharmaceuticals, e.g., reineries, production of specialty chemicals; (b) waste streams
and disposal of chemical products, e.g., sludges, spills; and (c) utilization of various
chemical products, e.g., use of petroleum products, pesticides, organic solvents, paints,
oils, creosotes, and greases. There are at least a million organic chemical compounds
registered in the various chemical abstracts services available, with many thousands of
these in commercial use. By and large, organic chemicals found in the geoenvironment
can be traced to sources and activities associated with humans. Figure 2.6 shows some
of the main sources of contaminants (inorganic and organic) found in the land compart-
ment of the geoenvironment.
The more common organic chemicals found in the physical landscape of the land envi-
ronment can be grouped as follows:

• 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., benzo-pyrene.

Airborne contaminants

Wastewater discharge

Waste
landfill

Contaminant
source (spill)

Contaminant
plume Leachate

(contaminant)
plume

Underground
storage tank

Flow direction

Bedrock

FIGURE 2.6
Schematic showing (a) leachate plume with contaminants emanating from a waste landill, (b) contaminant
plumes from a leaking underground storage tank and wastewater discharge, (c) deposition of airborne contami-
nants onto land surface, and (d) a surface contaminant source (spill). (Adapted from Yong, R.N. and Mulligan,
C.N., Natural Attenuation of Contaminants in Soils , CRC Press, Boca Raton, 310 pp., 2004.)