Figure 3. TPH reduction, heavy oil (LF = landfarming; BV = bioventing).
ing samples, the lag-time preceding soil freez-
rate TPH reductions that may have been caused
ing may have allowed longer treatment time
by biodegradation during the early portion of this
in the bioventing cells vs. the landfarming
time, or transport processes that may have been
cells.
influenced by freezing and freezethaw cycles
during the winter and early spring. Some samples
taken on 16 May 1996 were still partially frozen,
Summer incubation: elapsed time, 238 to 362
suggesting that temperatures sufficiently high for
days, 16 May to 17 September 1996
significant biodegradation to occur following soil
Diesel
thawing had not yet been attained. The TPH con-
Nutrient amendments appeared to have a
centrations for the diesel-contaminated soil on 16
greater effect than either landfarming or
May were not significantly different (P < 0.05) for
bioventing on the TPH concentrations by t362 (Fig.
any of the treatments.
2). TPH concentrations in the nutrient-amended
Heavy oil
bioventing treatment continued to decrease dur-
TPH concentrations decreased more rapidly for
ing the summer and at t362 were less than those in
both of the bioventing treatments than for either
the nutrient-amended landfarming treatment.
of the landfarming treatments during the cold-
There was little change from t238 to t362 in the treat-
season phase of the operation (Fig. 2). Similar to
ments where no nutrients had been applied.
the diesel-contaminated soil, the nutrient-
amended and no-nutrient bioventing treatments
Heavy oil
decreased TPH concentrations in the heavy-oil-
Changes in the TPH concentrations in the heavy
contaminated soil at similar rates, averaging
oil concentrations from t238 to t362 are noticeable;
16.2 mg kg1 day1. TPH reduction rates in
the TPH concentrations appear to actually increase
the landfarming treatments were only 5.5 mg
in both bioventing treatments and remain constant
kg1 day1 during this time. In contrast to the
in the landfarming treatments (Fig. 3). Land-
diesel-contaminated soil, the samples taken on
farming with nutrients tended towards greater
16 May from the bioventing treatments in the
TPH reduction than the other three treatments, but
heavy-oil-contaminated soil had significantly
this effect was not significant. The variability in
lower TPH concentrations than did the
TPH concentrations at t362 for both landfarming
landfarming treatments. Because these samples
treatments was greater than for either bioventing
were from a greater depth than the landfarm-
treatments, suggesting that the processes causing
6
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