Page 325 - gas transport in porous media
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Clean gas Tartre
injection Gas collection
for analysis Surface
Probe or well
Partitioning
contaminants,
daughter compounds
or nutrients
around soil void
during the purge
In Situ void
COVERED BY US PATENTS
2500
2000
Concentrations (ppm) 1500
1000
500
A
0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 8
Time (in minutes)
Figure 19.4. Steady state concentrations reached during the purging period as an estimate of advective
flux of compounds surrounding the soil void
with the last example by the slope on Figure 19.5. The chemical gradient is the
differencebetweentheinitialconcentrationandtheconcentration“B”,wheretheslope
is calculated (Figure 19.6). Diffusive flux may be evaluated for different chemical
gradients from the same set of data.
19.6 EVALUATION OF BIODEGRADATION PROCESSES
The success of the natural attenuation application depends on both hydrogeological
and geochemical parameters. Documenting decreased contaminant concentrations
over time is not sufficient to demonstrate that natural attenuation processes are occur-
ring (Commission on Geosciences, Environment and Resources, 2000). A reduction
