Geoscience Reference
In-Depth Information
Fig. 12.45 Mean (M) center of atrazine mass and individual centers of mass for ten high-quality
water (HQW) and ten effluent (EFF) profiles (Graber et al.
1995
)
in the second case, NAPL properties are altered during transport. In the case of
dense NAPLs, the contaminant plume reaches the aquifer and is subject to long-
term, continuous, slow ''local'' redistribution due to groundwater flushing-disso-
lution processes. These plumes become contamination source zones that evolve
over time, often with major negative impacts on groundwater quality.
Experiments carried out in Canada, Israel, Sweden, and the United States, are
used
here
to
illustrate
aspects
of
NAPL
transport
and
redistribution
in
the
subsurface.
12.5.1 Infiltration into the Subsurface
Viscosity Effect The infiltration and redistribution of two hydrocarbons in moist
silt loam and loamy sand soils, with viscosities of 4.7 (soltrol) and 77 (mineral oil)
times greater than that of water, was reported by Cary et al. (
1989
). The spatial
distribution of the two hydrocarbons and water is presented in Fig.
12.46
: the
infiltration rate of hydrocarbons is inversely related to their viscosity. The mineral
oil remains in the upper layer of the soil column, while the soltrol redistribution is
similar to that of water.
