LOUISE V. PARKER AND THOMAS A. RANNEY
INTRODUCTION
ried in suspension. A surface-active agent, or sur-
factant such as soap or detergent, is commonly
Decontamination is necessary to reduce the
added to 1) improve the wetting ability of the
possibility of cross contamination when ground-
cleaning solution once removed from the surface,
water sampling devices are not dedicated to a par-
2) separate the contaminant from the solid sur-
ticular well. Also, it may be prudent to decontam-
face, and 3) keep the contaminants in suspension/
inate dedicated sampling devices if they are not
solution.
stored inside the well. Presumably this would
Typically, smaller sampling devices, such as
eliminate any contamination from the storage
bailers, are washed by soaking in a bath contain-
area or handling. In addition, there is some debate
ing the cleaning solution, with or without scrub-
in the groundwater monitoring industry regard-
bing. Larger items, such as pumps, are usually
ing whether devices that are left installed in the
cleaned in place by circulating the cleaning solu-
well should also be decontaminated prior to each
tions and rinse water. In addition, steam cleaners
sampling event to prevent cross contamination
or high-pressure washing systems are sometimes
from sample to sample.
recommended for decontaminating sampling de-
vices, especially to remove gross contamination
Currently used decontamination protocols
such as dirt and oils.
Mickam et al. (1989) surveyed the various de-
With steam cleaning, pressure developed in the
contamination procedures required by state and
steam boiler imparts a high velocity to a mixture
other regulatory agencies, and Parker (1995) pub-
of water droplets and steam, which is directed
lished a literature review on decontamination
from a nozzle onto the target surface. Detergent
methods. Both reported that there is a lot of dis-
and heat from the steam weaken the bonds be-
parity between the numerous protocols that have
tween the dirt and surface while the high velocity
been published and that there has been almost no
of the water droplets has sufficient power to re-
systematic study on the effectiveness of these pro-
move the debris from the surface (Summers 1982).
cedures. Although decontamination procedures
Depending upon the contaminant, steam can also
vary considerably in their methodology, most uti-
facilitate volatilization and hydrolysis, and may
lize some type of aqueous cleaning method and
aid in the removal of subsurface contaminants.
often use solvent cleaning as a final or additional
Problems associated with steam cleaning include
rinse. A typical protocol might be the following:
workers being burned, corrosion of metal surfac-
wash with detergent, rinse with tap water, rinse
es, and warping of some polymers. From what we
with (high quality) acids and solvents, rinse with
have been able to determine, the "steam cleaners"
some type of high quality water (e.g., distilled,
that are typically used to decontaminate ground-
deionized, organic-free reagent water), and air
water sampling devices are actually hot-water
(99C), high-pressure washing systems.
dry (Mickham et al. 1989).
Aqueous cleaning is used to remove gross con-
With pressurized water washing systems,
tamination and particles. Water acts as a solvent
high-pressure pumps produce a stream of water
for water-soluble contaminants, and as a dispersal
rather than the small droplets produced by steam
medium for insoluble substances that can be car-
cleaning. The advantages of this type of cleaning
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