A Literature Review on Decontaminating
Groundwater Sampling Devices
Organic Pollutants
LOUISE V. PARKER
INTRODUCTION
SORPTION AND DESORPTION
OF ORGANIC CONTAMINANTS
Dedicating a sampling device to a particular
well reduces the potential of cross contamination
Several studies have shown that nonperme-
from other wells. However, many sampling de-
able surfaces (e.g., glass, stainless steel) do not
vices currently are not dedicated, and decontami-
sorb most organic contaminants. Specifically, two
nation methods are used to reduce the possibility
studies (Gillham and O'Hannesin 1990, Parker et
of cross contamination. In addition, some current
al. 1990) have shown that, under conditions where
regulatory guidance (e.g., U.S. EPA 1992) recom-
there should not be any losses due to biological
mends that dedicated sampling devices that are
activity, there were no losses of a suite of organic
routinely stored outside the well should be
contaminants from aqueous solutions exposed
cleaned or decontaminated prior to use. Typical-
to stainless steel surfaces. (The contaminants in
ly, decontamination procedures for sampling
these studies all had log Kow values less than 4.)
devices range from simply washing with clean
Reynolds et al. (1990) also found no loss of vola-
(high-quality) water to complex cleaning involv-
tile organic compounds (VOCs) (log Kow < 4)
ing acid and solvent rinses. It is the purpose of
from aqueous solutions exposed to glass surfac-
this paper to review the literature on decontami-
es. However, more hydrophobic contaminants,
nation of groundwater sampling devices that are
such as polychlorinated biphenyls (PCBs), chlo-
used for sampling organic contaminants.
rinated pesticides, and polyaromatic hydrocar-
The type of sampling device and surface(s) to
bons, most likely would be adsorbed by these sur-
be decontaminated and the physical characteris-
faces. Thus, decontamination of nonpermeable
tics of the organic contaminant, such as its solu-
surfaces such as metals and glass would involve
bility in water, its volatility, and its propensity
removing only those highly hydrophobic con-
to adsorb on or absorb into materials used in the
taminants that have adsorbed to the surface
sampling device, will determine how readily de-
(i.e., no absorbed analytes) and any surface con-
contamination can occur. Contact time and the
taminants contained in any residual film (either
degree of initial contamination on the surface are
wet or dry) that is left on the surface when the
also critical factors. Cleaning a surface that has
sampling device is removed from the well.
been exposed to trace-level organic contami-
In contrast, several studies (Barcelona et al.
nants is much easier than cleaning a surface ex-
1985, Reynolds and Gillham 1985, Gillham and
posed to neat (pure product) hydrocarbons or or-
O'Hannesin 1990, Parker et al. 1990) have shown
ganic solvents. Other types of contaminants such
that permeable materials, such as polymeric well
as grease and oil may also affect removal. Gener-
casings and tubings used in sampling pumps, sorb
ally, nonpermeable surfaces such as metals will
substantial quantities of some organic contami-
be more readily decontaminated than perme-
nants from aqueous solutions. All these research-
able surfaces, because desorption of absorbed
ers agree that diffusion within the polymer ma-
contaminants may be a factor with permeable
trix has occurred. In several studies (Barcelona et
surfaces. Temperature also has an effect on these
al. 1985, Gillham and O'Hannesin 1990, Ranney
processes, with sorption and desorption slower
and Parker, in prep.), researchers have noted that
in the cold.
generally the less rigid the material, the more
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