You are visiting the web site of the EPSCI Program at the U.S. Dept. of Energy's Ames Laboratory, Ames, IA

Ames Lab fielded this technology at the Marshalltown, Iowa FMGP site. The contractor was Northeast Research, Inc., Farmington, CT

In the Marshalltown ESC project, passive soil gas measurements were used in the early screening phase of work at sampling points uniformly distributed across the site. Samplers were installed at two different depths in the ground at each point, with the intent of determining an approximate distribution vertically and horizontally of the contaminants of interest. The samplers were inserted into open-ended copper pipe installed in pilot holes created by an active soil gas collection probe (Geoprobe).

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Soil gases diffuse through the opening of the uncapped sampler and adsorb onto the activated carbon. After an appropriate period of time, the sampler is retrieved from the borehole, resealed, and submitted for analysis. Analysis is performed on the individual collectors using thermal desorption (TD) and a quadrupole mass spectrometer (MS). Data is reported as the ion counts from the mass spectral peak which indicates the presence of a particular compound. Second collectors from selected samplers are also analyzed by TD-GC (gas chromatography)/MS to confirm and identify more completely the compounds presented in the TD-MS analysis.

The method is highly sensitive for the detective of very small concentrations of organics. For this reason, extreme care is required in the handling and placement of the samplers so that organic molecules in the open atmosphere or on a persons skin do not attach to any significant degree to the collectors.

General Description

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Last Modified: 1 January 2002 by dave eckels
Expedited Site Characterization: etd/technologies/projects/esc/technologies/passivesoildemo.html