Passive diffusion bag sampler

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nitrogen gas to pressurize the system during ascent and descent. Currently there

are three models available: a 2-liter model and two 0.5-liter models with different

outer diameters of 1.5 inch and 1 inch. Typically, this device is raised and

lowered with an automated winch system. The price for these devices (plus spool

for tubing and regulator) runs from ||content|| ,050 to 1,800 (depending upon the model

required). We have not found any published studies that evaluated this device.

Passive diffusion bag sampler

For the diffusion-based samplers, organic analytes permeate a plastic,

or polymeric, membrane into a chamber that initially contained distilled or

deionized water. Diffusion of analytes in and out of the device continues until

equilibrium is reached. The time required to reach equilibrium depends upon the

rate of exchange within the well, water temperature, the analyte, and the type of

membrane. These samplers integrate analyte concentrations over time but are

recommended for profiling discrete levels of contamination in the screened

interval.

Figure 5. USGS passive diffusion bag sampler.

The USGS passive diffusion bag (PDB) sampler is among the more

commonly known examples of this type of device. The PDB sampler (Fig. 5)

is a cylindrical bag made of low-density polyethylene that is suspended on a

weighted line (with a stainless steel weight). The PDB can also be purchased