MATERIALS AND METHODS
ly capped. The sample jars were filled randomly
from one of two 4-L bottles of groundwater and
Materials
were stored in the dark at room temperature. There
Five types of 5-cm-diameter (2-in.) well cas-
were three replicate samples for each treatment
ings or pipes were used in this study. For PTFE,
and time, including the controls. Contact times
FRP, FRE, and PVC, we used well casings manu-
were 1, 5, 20, and 40 days. Controls consisted of
factured specifically for groundwater monitoring.
jars filled only with groundwater.
We were unable to find a manufacturer that made
On the sampling day, the jars were opened, the
FEP well casings, but did find one that made "pipe
ring section was removed, and 2 mL of concen-
for sampling groundwater." We will refer to all of
trated nitric acid was added to the sample jar (giv-
these materials as casings throughout this report.
ing a final pH of <1 and an acid concentration of
Because the thickness of the walls of the five
2% v/v). This was done because acidification to a
casing materials differed, we cut rings of the cas-
pH of less than 1.5 has been shown to be effective
ings to varying lengths (~2 cm long) so that the
in preventing losses of trace metals from natural
surface area would be constant (80 cm2). The ma-
waters and aids in recovery of sorbed metals from
terial surface-area-to-aqueous-solution-volume
the vessel walls (Subramanian et al. 1978, Hewitt
ratio was 0.82 cm2/cm3. Special care was taken to
1989). The jars were then recapped, swirled for 10
seconds, and left until the analyses were conduct-
solvent, etc. during the cutting process. The PTFE,
ed at the end of the study.
FEP, and PVC casings were cut with a high-speed
steel slotting saw (VASCO M-2). The two fiber-
Procedure for the
glass materials, FRE and FRP, were cut with a
sorption study
high-speed steel (1076) diamond band saw. The
The procedure for the sorption study was sim-
ratio of cut surface area to total surface area was
ilar to the leaching study except that one mL of a
approximately 18% for PTFE and PVC, 17% for
mixed metal spike solution containing 5 mg/L
FRP, 15% for FEP, and 7% for FRE.
As, Cr, Pb, and 2 mg/L Cd was added to 97 mL of
The ring sections were rinsed with several vol-
groundwater in a PP jar. The mixed metal spike
umes of deionized (Millipore) water and allowed
solution was prepared from serial dilutions in
to air dry in a Class 100 clean room where all
deionized water of certified (Fisher Scientific Co.)
subsequent cleaning and prep work was done.
metal standards (1,000 mg/L). Cd and Pb were in
Plastic gloves and nylon tweezers were used to
solution as cations, while Cr (as dichromate) and
handle the ring sections.
As (as arsenite or arsenate) were anions. After add-
Polypropylene (PP) jars (125 mL) with PP screw
ing the metal spike, each jar was swirled to mix
caps were used as the sample containers. The jars,
the solution, the section of casing was placed in
PP Eppendorf pipet tips, PP volumetric flasks with
the jar, and the jar was then tightly capped. Con-
PP screw caps, nylon tweezers, PE autosampler
trols consisted of jars filled with the test solution
cups, and two 4-L brown glass bottles used to
but no casing material. Final concentrations were
approximately 51 g/L for As, Cr, and Pb and 20
being used. The equipment was acid cleaned by
g/L for Cd. The samples were stored in the dark
soaking in a 10% v/v of redistilled nitric acid and
at room temperature. There were three replicate
deionized water for several days, rinsing with
samples for each casing material and time, includ-
deionized water, soaking in deionized water for
ing the controls. Contact times were 1, 8, 24, and
several more days, rinsing with deionized water,
72 hours. When a sample was taken, the jar was
and air drying. A Brinkman dispensette was
opened, the ring section was removed, and the
flushed with several volumes of 2% v/v nitric
remaining solution was acidified as described pre-
acid solution and rinsed with several volumes of
viously.
in this study was from a well (45 m deep) located
Analyses
in Hartland, Vermont.
Analyses were performed by Graphite Furnace
Atomic Absorption (GFAA) using a Perkin-Elmer
Procedure for the
leaching study
Model 5100 Atomic Absorption Spectrophotome-
One of the ring sections was placed in a PP jar,
ter, with a Perkin-Elmer model 5100 Zeeman back-
98 mL of groundwater was added using a cali-
ground correction module, a Perkin-Elmer model
brated Brinkman dispensette, and the jar was tight-
600 graphite furnace, and a Perkin-Elmer model
3