Table 3. Concentrations (mg kg1) at to (methylene chloride ex-
traction + sonication).
Fraction
Heavy-oil mean
Diesel mean
309
267
TPHgravimetric
11389
8480
266
291
TPHgas chromatography
6072
8348
ing treatments during the to to t54 interval.
Cold season incubation: elapsed time, 54 to 238
Because diesel has a larger percentage of
days, 21 September 1995 to 16 May 1996
volatile and mobile constituents than heavy oil,
Diesel
the to to t54 data suggested that volatilization and
TPH concentrations decreased for all treatments
diffusion accounted for a portion of the initial
during t54 to t238 (Fig. 2). During a significant por-
losses.
tion of this time, the soil was frozen. However, an
Heavy oil
unusual warm period in September 1995 kept the
During the to to t54 interval, decreases in TPH
soil warmer for longer than normal and this
concentrations were much less in the heavy-oil-
probably contributed to the decrease in TPH levels
contaminated soil than in the diesel-contaminated
during this period. The rates of TPH decrease dur-
soil (Fig. 3). We observed the same ranking for
ing this time were not significantly different for the
efficacy of treatments as we did for the diesel-
two landfarming treatments and averaged 13.6 mg
kg1 day1. TPH reduction rates for the two bio-
contaminated soil; landfarming with nutrient
amendments again was statistically the best treat-
venting treatments were also similar to each other,
averaging 23.8 mg kg1 day1. However, the TPH
ment. In contrast to the diesel-contaminated soil,
there was essentially no decrease in heavy oil TPH
reduction rates in bioventing treatments were sig-
levels in the bioventing treatments during the ini-
nificantly greater than in landfarming treatments
tial treatment phase.
during this time. From our data, we cannot sepa-
Figure 2. TPH reduction, diesel (LF = landfarming; BV = bioventing).
5
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