Validation of a New Method for Screening Soil and Water for TCE Contamination


ASTM Method D 7203-06, Standard Test Method for Screening Trichloroethylene (TCE)-Contaminated Media Using a Heated Diode Sensor, (ASTM 2006) can be used to screen a sample of soil or water known to contain the halogenated volatile organic compound (HVOC) TCE. The method calls for measuring the TCE concentration in the headspace above the sample using a heated diode sensor device. From this measurement, an estimated concentration of TCE in the sample can be determined. Detection limits are typically in the low parts per billion range, depending on the sample. The method can also be used for screening the headspace above a sample of soil or water to indicate the presence or absence of HVOC contamination in the sample. The heated diode sensor device is selective for HVOCs. Water vapor does not interfere with the performance of the heated diode sensor, and hydrocarbon fuels are not detected by the sensor.

This article describes two validation studies that were conducted to evaluate the performance of ASTM Method D 7203. In both studies, the performance of the screening method was evaluated by comparing sample screening data with data generated from analysis of samples collected from the same location at the same time and analyzed in the laboratory using gas chromatography/mass spectroscopy (GC/MS). In both studies, an X-Wand® heated diode sensor device was used to perform the ASTM method.


The site selected for the soil validation study was contaminated with TCE more than 20 years ago. Contamination is near the soil surface and is known to be relatively uniform so that adjacent samples having similar contaminant levels can be collected. The soil at the site is a cohesive silty-clay with an organic carbon content of less than 1.0% and a moisture content of 10 to 20%.

For the study, contaminated soil samples were collected at depths ranging from approximately 2 to 12 inches at 18 locations within the site. At each of the contaminated locations, three side-by-side samples were collected in 25-gram En Core® samplers to evaluate the screening method. One of these samples was placed in a cooler for shipment to a commercial laboratory for TCE analysis by GC/MS, one of these was placed in a cooler for shipment to a research laboratory for TCE analysis by GC/MS, and one of the samples was placed in a third cooler for on-site screening. The sample coolers contained ice packs to maintain cooler temperatures at 4 ± 2 ºC during sample storage. In addition to the 18 contaminated locations, two locations believed to be uncontaminated were also sampled. Three side-by-side samples were collected at each of these locations, two samples for laboratory analysis and one sample for on-site screening.

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