tached to a metal extrusion tool, the cap is re-
Core barrel liners
moved, and the sample is extruded directly into
Laboratory experiments
the prepared VOA vial. By design the 5-g En Core
One experiment considered the diffusion of
sampler fits into the mouth of a 40-mL VOA vial.
VOC vapors through two different formulations
of Teflon sheeting. Nine 1.5-mL VOA vials were
Empty VOA vials
filled with 2 g of air-dried soil, then placed un-
When using an empty VOA vial as a chamber, a
capped in a desiccator with CaCO3. A 4-mm hole
5-g sample is transferred with a modified syringe
was punched out of the middle of each septum,
as described above. The VOA vial into which the
and then they were placed in the caps so that the
sample is placed should already contain a Teflon-
Teflon side faced out (in this configuration the sili-
coated stir bar if it is to be analyzed directly using
cone side of the septa faced the glass vial). Three
a purge-and-trap step (e.g., low-level Method
8-mm disks were punched out of a sheet of Teflon
5035). After transferring, the sample the VOA vial
that was white and had elastic properties (≈0.02-
is capped and placed in a cooler held at 4 2C. In
mm-thickness "plumber's tape"), and three more
a laboratory setting, 5.00 mL of water or MeOH
came from a sheet that was translucent with no
would be added to a VOA vial by piercing the sep-
elastic properties (≈0.05-mm thickness, obtained
tum. If performed manually, a 23-gauge or smaller
from Art's Manufacturing & Supply, Inc.). After
needle should be used. If MeOH is introduced the
two days the desiccant was removed. Then six
soil samples should be gently dispersed by swirl-
disks were placed over the tops of separate vials
ing the VOA vial so that the majority of the inner
and covered with the hole punched septa and caps.
glass surfaces are rinsed. This step should be re-
Caps and hole punched septa were also placed on
peated a second time after allowing the sample to
the three vials with no covering. Then an organic
sit for a couple of minutes. Then the excess pres-
solution spiked with trans-1,2-dichloroethene
sure caused by introducing 5.00 mL of MeOH can
(TDCE), cis-1,2-dichloroethene (CDCE), TCE,
be released and the VOA vial resealed. Caution
tetrachloroethene (PCE), benzene (Ben), toluene
should be taken during sample dispersion not to
(Tol), ethylbenzene (E-Ben), p-xylene (p-Xyl), and
wet the Teflon-coated septum, because this could
o-xylene (o-Xyl), was introduced and the desicca-
compromise the resealing after venting. If an aque-
tor closed. Additional information concerning this
ous solution is introduced manually the VOA vial
vapor fortification procedure can be found else-
can be vigorously shaken after adding the solu-
where (Hewitt and Grant 1995). After two days
tion because the cap is not removed to release the
of exposure, the vials were quickly removed from
pressure. An aqueous solution can also be added
the desiccator, their cap assemblies removed,
mechanically by some automated purge-and-trap
and then each was placed into a 22-mL VOA vial
systems, via a needle sparger.
containing 10 mL of water and quickly capped for
analysis.
A second experiment involved 18 brass core
barrel liners, 3.75 3.75 cm, that had been filled
EXPERIMENTAL METHODS
with relatively clean soil by pushing into a freshly
exposed surface. After the external walls of each
All of the experiments described below used
core barrel liner were wiped clean the bottoms
soils obtained at the Cold Regions Research and
were covered as follows: (1) four with a sheet of
Engineering Laboratory (CRREL). The soil from
white, elastic Teflon, (2) four with a sheet of trans-
this site is characterized as a cohesive silty-clay
lucent, nonelastic Teflon, (3) four with a thin metal
with an organic carbon content of less than 1.0%
disk that was the same diameter as the core barrel
(Hach method 8097) and ranging in moisture from
liner followed by a sheet of translucent, nonelas-
10 to 20% (ASTM D2216-66). Two types of samples,
tic Teflon, and (4) four with a sheet of aluminum
field and spiked, were used in these experiments.
foil. Plastic end caps were used to hold all of these
Contaminated field samples are available at
coverings in place. The soil in each core barrel liner
CRREL, because of the mishandling of TCE more
was then spiked with 1.00 mL of an aqueous solu-
than 20 years ago. Soil samples were also obtained
tion containing approximately 50 mg/L of each
from areas where TCE contamination is relatively
low (<0.01 mg/kg), then spiked with chlorinated
of the nine analytes previously mentioned. Infor-
and aromatic compounds that are frequently
mation about the preparation of this aqueous so-
found on hazardous waste sites (Plumb and
lution and this spiking procedure is available else-
Pitchford 1985).
where (Hewitt 1995a). The spikes were transferred
6
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