devices, Imbrigiotta et al. (1988) noted that the data for the samples collected with the bailers
exhibited the lowest precision of the seven sampling devices investigated.
When sampling NAPLs, bailers should never be dropped into a well and should be
removed from the well in a manner that causes as little agitation of the sample as possible.
For example, the bailer should not be removed in a jerky fashion or be allowed to continually
bang against the well casing as it is raised. When transferring the sample from a bailer to a
container, it is preferable to use a bottom emptying device with a valve that allows the
LNAPL or DNAPL to slowly drain from the bailer. Bailers should not be used if the well
has not been purged by drawing water from the air/water interface because as the bailer is
raised through the water column, the bailer may sample stagnant water located above the
screened interval. When using bailers to collect LNAPL or DNAPL samples for inorganic
analyses, the Agency recommends that the bailer be composed of fluorocarbon resin. Bailers
used to collect LNAPL or DNAPL samples for organic analyses should be constructed of
stainless steel. The cable used to raise and lower the bailer should be composed of an inert
material (e.g., stainless steel) or coated with an inert material (e.g., PTFE).
A syringe bailer is distinguished from other bailers by the means of water entry
(Morrison, 1984). The syringe is lowered into a well and water is drawn into the chamber by
activating a plunger via suction. To recover the sample, the syringe is withdrawn and the
sample is transferred into a collection bottle or injected directly into an appropriate instrument
for water quality analysis. The syringe bailer is often used as both a sampler and a sample
container. The small syringe size is a limitation when large sample volumes are required.
Moreover, researchers believe that in waters with high concentrations of suspended solids,
syringe bailers may leak around the plunger. Imbrigiotta et al. (1988) concluded that for
sampling volatile organic compounds, syringe samplers (bailers) were inferior in comparison
to other sampling devices. Imbrigiotta et al. attributed the poor performance of the syringe
sampler to exposure of the sample to widely fluctuating pressures during the sampling process
caused by leakage of the seal between the piston and the syringe barrel.
Pump mechanisms historically used for ground water sampling include bladder pumps,
helical rotor electric submersible pumps, gas drive piston pumps, gear drive electric
submersible pumps, centrifugal pumps, peristaltic pumps, gas lift pumps, and gas drive
pumps. The following sections describe each of these types of pumps and their applications
and limitations with regard to collecting ground water samples.