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Chapter 19: In Situ Measurement of Induced Flux
Low flow collection 325
for analysis
Surface
Probe or well
Diffusion of
contaminants,
daughter compounds
or nutrients
around soil void
after the purge
In Situ void
COVERED BY US PATENTS
1400
1200
Concentrations (in ppm) 1000 Initial concentration
800
600
400
200
0
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
Time (in minutes)
Figure 19.5. Concentrations reached after the purging period as an estimate of migrating compounds
due to diffusion surrounding soil void
in contaminant concentration at any given location may result from spatial hetero-
geneity in soil properties or hydrogeological conditions. Natural attenuation processes
may fluctuate as a function of season or of changing geochemical conditions.
MNA is demonstrated in most cases by the occurrence of specific biodegrada-
tion processes. Conventional monitoring techniques assess biodegradation processes
via the comparison of product and reactant concentrations in up gradient locations
with those in the plume. Relative concentrations of these analytes in up gradient
versus plume locations are used to identify which natural attenuation processes are
actually occurring (Wiedemeier et al., 1995). A common problem with using such a
