removed and immediately sampled as described
for core liner VI. Shortly thereafter, the core liners
covered with aluminum foil were wrapped with
PVC tape, sealing both the edges of the foil and
~5 cm
plastic cap to the core liners' exterior walls.
The third and fourth experiments used the same
general format as the second, except that the ref-
erence samples and those taken from the core lin-
Figure 2. Sample collection pattern for extruded
ers were collected without discarding the top 1.2
cm of soil. The last experiment used 18, 3-cm3 sy-
soil cores.
ringes: 12 were positioned exterior to the core lin-
mL of water contained in a 500-mL jar and capped
ers, and 3 each into core liners I and VI. Once they
with a Teflon-backed silicone septum top. These
all were in position (pushed 2.5 cm into the ex-
jars have a special opening in the cap to allow for
posed soil surface) they were sequentially removed
syringe penetration. All covered samples were
and the plug of soil obtained in each syringe was
stored at 4C until the day of analysis, whereupon
transferred to a prepared VOA vial.
the caps and coverings were removed and the cups
For all of these field experiments the entire sam-
quickly submersed into 300 mL of water contained
pling operation, from the point of inserting the core
in 500-mL jars.
liners until the last sample was collected, took
approximately 15 minutes. Covered core liners
were stored in a refrigerator (4C) for either 5 or
Extruded soil cores
This study initially compared soil samples ob-
10 days before being sampled in the laboratory
tained with 10- and 3-cm3 syringes and extruded
using the same procedure that had been used in
directly into 44- or 22-mL VOA vials containing
the field.
water, respectively. Samples for this initial com-
parison were collected at a depth of 33 cm after
Laboratory experiment
inserting five of each size of the syringes into the
Three laboratory experiments were performed
with modified core liners (3.6-cm-i.d. 3.4 cm
bottom of the hole. The syringes were positioned
in a tight array (12 5 cm) in two rows (Fig. 2). A
high) made by soldering a brass cap onto one end,
making a cup. The matrix used was a sandy soil
second experiment, performed in the same hole at
desiccated with CaSO4 or moistened with water
a depth of 38 cm, collected two separate arrays of
eight soil samples, using first the 10-cm3 then the
to 1% or 10%. In each case 50 g of the soil was
packed (1.4 g/cm3) into 12 brass cups, leaving <2
3-cm3 syringes. Again all eight syringes were po-
mm of space between the soil surface and rim. Un-
sitioned, prior to being sequentially removed, plac-
covered, the surface area to sample mass ratio was
ing alternating soil plugs into VOA vials contain-
ing water, or into small (7.5-cm 5-cm) plastic
approximately 0.20 cm2/g. Handling one sample
at a time, we then spiked each of the 12 replicates
Ziploc bags and sealing. Those transferred to the
by inserting the needle (gauge 26s) of a 10-L sy-
Ziploc bags were held for 1 to 2 minutes; then the
ringe to the bottom of a soil-filled cup and inject-
bags were cut open with scissors so that the plugs
ing 5 L of a methanol (MeOH) standard contain-
of soil could be easily transferred (Ziploc bags have
ing trans-1,2-dichloroethylene (TDCE), trichloro-
a lip that interfered with the sliding of a plug of
ethylene (TCE), benzene (Ben) and toluene (Tol).
soil). Special care was taken for those plugs ex-
Upon removing the needle, the soil was tamped
truded into the plastic bags so that they would
down filling the injection channel. These experi-
remain intact until immersed in the water present
ments were performed in conjunction with others
in the VOA vials. Once extruded into the plastic
not reported here; thus, for convenience, different
bags the soil samples had a surface area/mass ex-
posure ratio of approximately 2.0 and 3.6 cm2/g
methanol standard solution was used for the 10%
for the 10- and 3-cm3 syringes, respectively.
moisture experiment than was used for the desic-
cated and 1% moisture experiments. Of the 12 rep-
licates, five were covered with two sheets of TFE,
Collection vessel preparation
and five were covered with aluminum foil, then
This experiment assesses the effect of introduc-
capped and taped as described previously. The
ing a solvent to a sample after it has been trans-
remaining two samples were immediately taken
ferred to an empty VOA vial compared to samples
for analysis, by submersing the entire cup into 300
transferred to VOA vials with water present. Six-
3
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