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3. LITERATURE REVIEW
A. Chemical Characteristics of Monitored PAHs
Creosote contains a substantial amount of PAHs, about
85% by weight (Table 2). Understanding the chemical
characteristics of PAHs and the associated implications for
bioremediation is very important (Table 3). In general, as
PAH molecular weight increases, aqueous solubility
decreases. Typically, mass transfer of contaminant from
solid to liquid phase is required for removal of soil
contamination. Many PAHs are considered to be
biodegradable, but the rate of PAH biodegradation appears
to be limited by dissolution rates, which are directly
correlated to aqueous solubility (Brubaker et al., 1992).
Log KOW and log KOC are both equilibrium constants that
provide an indication of constituent sorption onto soil or
organic matter, respectively. KOW is defined as the
concentration of a constituent in octanol (soil) divided by
the aqueous concentration of the constituent. The KOW of a
constituent is a measure of hydrophobicity. KOC has been
defined as KD divided by fOC. The Freundlich isotherm
constant, KD, is the mass of contaminant adsorbed per unit
mass of media divided by the contaminant concentration in
solution. FOC is the fraction of organic carbon in a soil
sample. In general, as PAH molecular weight increases, log
KOW and KOC also increase. Larger values of both constants
indicate preference of the constituent to be sorbed onto
soil or organic matter than be present in the aqueous
phase. The higher the affinity of a constituent to sorb to
soil, the less likely it will be available for
bioremediation.
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Table 2: Predominant Polycyclic Aromatic Hydrocarbon (PAH) Constituents in
Creosote
PAH Constituent
Percent by weight of Total PAHs
Naphthalene
13
Anthracene
13
2-Methylnaphthalene
13
Phenanthrene
13
Biphenyl
8
Fluorene
8
1-Methylnaphthalene
8
2,3-Dimethylnaphthalene
4
2,6-Dimethylnaphthalene
4
Acenaphthene
4
Fluoranthene
4
Chrysene
2
Pyrene
2
Anthraquinone
1
2-Methylanthracene
1
2,3-Benzo(b) fluorene
1
Benzo(a)pyren