Geoscience Reference
In-Depth Information
Fig. 12.46 Distribution of (1) mineral oil, (2) soltrol-220, and (3) water in a silt loam soil 8 h
after adding water to dry soil and 4 h after adding the hydrocarbons (Cary et al.
1989
)
When the NAPL consists of a mixture of hydrocarbons with different vapor
pressure, the liquid composition is affected by changes in temperature occurring
during infiltration into the subsurface. Increased temperature enhances the partial
volatilization of constituents in the liquid mixture, leading to viscosity changes,
and thus affecting transport of the remaining liquid phase. Figure
12.47
a shows the
effect of viscosity changes on the conductivity of kerosene, a petroleum product
containing more than 100 hydrocarbons, in three types of soils with different
physicochemical properties. Changes in kerosene composition, due to volatiliza-
tion of the light fractions, result in increased viscosity and decreased mass flow
through porous media of the residual NAPL.
Soil Moisture Effect The effects of soil moisture content and soil texture and
pore size distribution on kerosene conductivity were studied by Gerstl et al.
(
1994
). Figure
12.47
b shows kerosene conductivity in sand, loam, and clay soil
columns, as the initial moisture content varies from 0 % (oven-dried) to field
capacity.
The kerosene conductivity of the soil was affected strongly by the soil texture
and initial moisture content. In sand, the kerosene conductivity was affected
slightly by the initial moisture content, as high as 70 % field capacity, but
decreased thereafter. The kerosene conductivity of the loam soil was similar in
oven-dried and air-dried soils and increased significantly in soils at 70 % and full
