Geoscience Reference
In-Depth Information
Fig. 8.44 Kerosene residual
content (KRC) of soils as a
function of clay and moisture
contents. Reprinted from Fine
and Yaron (
1993
). Copyright
1994 with permission of
Elsevier
clay content of the soils, with KRC values of clayey soils being 1.5 times greater
than for less clayey ones.
The OM content also contributes to the KRC. The relationship between clay,
OM, and moisture contents and KRC is described by
KRC ¼ 0
:
13½%clay
þ
1
:
48½%OM
0
:
32½%moisture
þ
4
:
31
:
ð
8
:
7
Þ
KRC exhibits a linear relationship toward the combination of clay and OM con-
tents and an inverse correlation to moisture content. The range of values of the
three independent variables was clay, 0.3-74 %; OM, 0-5.2 %; and moisture
content, 0-49 %. The crucial effect of moisture content on KRC of the soils was
demonstrated by comparing the fine clay material to dune sand. The respective
KRCs were 14.8 and 3.2 mL/100 g for air-dried materials and 2.17 and 1.84 mL/
100 g for moist materials at 33 % pK
a
tension. Hayden et al. (
1997
) investigated
the influence of NOM on the residual content of another petroleum product,
gasoline, and found that higher organic content leads to a higher residual saturation
under air-dried environmental conditions. Contamination with gasoline when the
soils are water saturated leads to a virtually identical gasoline residual content
value, despite the differences in the soil OM content.
8.5 Contaminant Release
Contaminant release can result from a change in physicochemical characteristics
of the liquid phase surrounding the retaining solid phase. Such a release usually is
obtained by lowering the contaminant concentration in the solution, which pre-
viously reached equilibrium with the solid phase. Changes in the liquid phase
concentration can occur as a result of physicochemical or biologically induced
processes. Moreover, the release of trace elements can occur following a decrease
