ratio), and using two layers of TFE for the samples
how the samples were collected, after five or more
days of storage at 4C, the TCE concentration esti-
covered with this material. Two trends established
by these experiments were 1) analyte concentra-
mates were consistently lower than the mean of
tion stability was markedly better for the desic-
the adjacent samples by more than 90%. In addi-
cated condition and 2) aluminum foil was supe-
tion, all of the samples covered with aluminum
rior to TFE as a barrier for the prevention of vola-
foil and wrapped with PVC tape showed concen-
trations of Tol ranging from 0.1 to 0.3 g/g after
tilization losses. The first trend can be explained
by a dry mineral surface's greater affinity for the
five days of storage. Since Tol was not observed in
sorption of VOCs (Chiou and Shoup 1985, Smith
any of the other field samples collected for this
et al. 1990). This is a condition under which physi-
study, its source was most likely the adhesive used
cal processes, perhaps involving van de Waals
in the PVC tape. This assumption was confirmed
forces, help retain the VOCs (Sawhney and Gent
by the analysis of this material.
1990). The stability of the analytes on the desic-
The results of the laboratory experiments per-
cated soil can, therefore, be attributed to the con-
formed with modified core liners are shown in
dition of grain surfaces prior to treatment. The sec-
Table 3. These samples differed from those ob-
ond trend can be explained by the observation that
tained in the field by being laboratory fortified,
sheets of pliable TFE, used for covering ends of
held in a brass cup (smaller exposed surface/mass
Table 3. Analyte concentrations (g/g) in modified core liners laboratory experiments,
before and after covering with TFE sheets or aluminum foil and storing at 4C.
Condition/covering/
Storage period
analyte
Day 0
Day 1
Day 2
Day 3
Day 7
Day 14
Desiccated/TFE/
TDCE
3.1/3.1
1.9
1.5
1.3
0.56
ND*
Ben
4.4/4.3
4.4
4.2
4.3
4.0
2.9
TCE
7.1/7.0
7.3
6.3
6.3
5.3
2.4
Tol
6.7/6.6
7.0
6.8
7.0
6.4
6.1
Desiccated/aluminum/
TDCE
3.1/3.1
3.0
0.92
0.97
2.2
1.5
Ben
4.4/4.3
4.4
4.2
4.3
4.3
4.4
TCE
7.1/7.0
7.3
6.2
6.8
6.9
6.4
Tol
6.7/6.6
7.0
6.9
7.0
6.8
7.1
10% Moisture/TFE/
0.028†
TDCE
1.8/1.8
0.074
0.010
ND
Ben
7.9/8.1
0.45
0.20
0.10
0.040
TCE
5.1/5.2
0.24
0.12
0.071
0.032
Tol
7.2/7.2
0.31
0.26
0.13
0.056
10% Moisture/aluminum/
TDCE
1.8/1.8
0.41
0.21/0.21
0.24
0.053
Ben
7.9/8.1
2.5
1.1/1.1
1.5
0.37
TCE
5.1/5.2
1.1
0.35/0.36
0.65
0.14
Tol
7.2/7.2
2.0
0.49/0.46
1.3
0.19
1% Moisture/TFE/
0.0640.02**
TDCE
3.0/3.1
0.170.5
Ben
4.5/4.3
0.250.08
TCE
7.2/7.1
0.390.08
Tol
6.7/6.7
1% Moisture/aluminum/
0.500.11
TDCE
3.0/3.1
1.20.5
Ben
4.5/4.3
1.40.3
TCE
7.2/7.1
2.60.6
Tol
6.7/6.7
* ND not detected
† Sample replicate lost
** Mean and standard deviation, n = 5; 1-day storage.
6
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