Figure 3. Changes in air, stockpiled untreated, and DCR-treated material temperatures.
Fig. 3) could potentially have an adverse effect on
Fifteen peaks of elevated temperatures for var-
soil microorganisms. On the other hand, the de-
ious DCR-treated batches were recorded on 2627
hydration produced a drier soil material, which
January 1994 (Fig. 3). Sharp temperature peaks
should facilitate its reuse. The original tar-soil
were the result of placing the probes in a batch for
mixture was very dark and consisted of many
short periods. Plateaus and steady declines in
large tar masses, some weighing 25 kg. The end-
temperature were the result of leaving the probes
product was more soil-like, drier, with only a few
in a given batch for extended periods. The tem-
small (0.5-kg) tar balls. The DCR process, overall,
perature of treated material increased to between
35 and 95C. The temperature of untreated mate-
improved the physical properties of this asphalt
rial was close to 0C, and no change was ob-
tar material for reuse.
Many of the volatile organics in the asphalt tar-
served on either sampling day. On 26 January, air
soil were below the limits of detection (Brar and
temperatures started increasing after 1130 hours
and reached a maximum of 6C in an unshielded
Marion 1995). Statistically significant differences
between untreated and DCR-treated soils were
position.
only found for acetone, 2-butanone, 4-methyl2-
The DCR reaction was both highly exothermic
and dehydrating. The high temperatures (> 90C,
pentanone, and total xylenes (Table 4). With the
Table 4. Total extractable concentrations of TPH and volatile organ-
ics in asphalt-tar samples (mean 1 SE).
Minimum
detectable
Compound
Units
limit
Untreated
Treated
g kg1
Acetone*
--
66
14a
466
14b
g kg1
2Butanone
2.3
11
5a
226
12b
g kg1
Benzene
1.0
0.5
0.0a
3.9
2.1a
g kg1
4Methyl2pentanone
2.3
1.2
0.0a
21
2b
g kg1
Toluene
0.58
7.1
1.8a
4.8
1.6a
g kg1
2Hexanone
1.9
30
23a
49
13a
g kg1
Ethylbenzene
0.56
6.7
1.4a
6.5
1.5a
g kg1
Total xylenes
1.1
64
13a
31
3b
mg kg1
TPH
--
2602
621a
2160
254a
* Also detected in method blanks run with with samples.
Statistically significant differences are designated by different lower-case letters.
9
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