McKay, Donald. "Front matter" Multimedia Environmental Models ...

C S = K PC W benzene = 1.1 ¥ 0.001 = 0.0011 mg/g
DDT = 10320 ¥ 0.001 = 12.7 mg/g
Note the much higher DDT concentration because of its hydrophobic character.
The concentrations in the organic carbon are C WK OC or 0.055 mg/g for benzene
and 635 mg/g for DDT. If octanol was exposed to this water, similar concentrations
of C WK OW or 0.135 µg/cm 3 for benzene and 1549 mg/cm 3 for DDT would be established
in the octanol.
5.5.3 Lipid-Water and Fish-Water Partition Coefficients
Studies of fish-water partitioning by workers such as Spacie and Hamelink
(1982), Neely et al. (1974), Veith et al. (1979), and Mackay (1982) have shown that
the primary sorbing or dissolving medium in fish for hydrophobic organic chemicals
is lipid or fat. A similar approach can be taken as for soils, but there is a more
reliable relationship between K OW and K LW, the lipid-water partition coefficient. For
most purposes, they can be assumed to be equal although, for the very hydrophobic
substances, Gobas et al. (1987) suggest that this breaks down, possibly because of
the structured nature of the lipid phases. It is thus possible to calculate an approximate
fish-to-water bioconcentration factor or partition coefficient if the lipid content
of the fish is known. Mackay (1982) reanalyzed a considerable set of bioconcentration
data and suggested the simple linear relationship,
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K FW = 0.048 K OW
This can be viewed as containing the assumption that fish is about 4.8% lipid.
Lipid contents vary considerably, and it is certain that there is some sorption to nonlipid
material, but it appears that, on average, the fish behaves as if it is about 4.8%
octanol by volume.
In summary, Z for lipids can be equated to Z O for octanol. For a phase such as
a fish of lipid volume fraction L, Z F is LZ O.
5.5.4 Mineral Matter-Water Partition Coefficients
Partition coefficients of hydrophobic organics between mineral matter and water
are generally fairly low and do not appear to be simply related to K OW. Typical values
of the order of unity to 10 are observed as reviewed by Schwarzenbach et al. (1993).
A notable exception occurs when the mineral surface is dry. Dry clays display very
high sorptive capacities for organics, probably because of the activity of the inorganic
sorbing sites. This raises a problem that some soils may display highly variable
sorptive capacities as they change water content as a result of heating, cooling, and
rainfall during the course of diurnal or seasonal variations. Some pesticides are
supplied commercially in the form of the active ingredient sorbed to an inorganic
clay such as bentonite.
In the environment, most clay surfaces appear to be wet and thus of low sorptive
capacity. Most mineral surfaces that are accessible to the biosphere also appear to