Tri-Service Site Characterization and Analysis Penetrometer System (SCAPS) Thermal Desorption Sampler for Volatile Organic Compounds
Abstract
The Thermal Desorption Sampler (TDS) is designed to collect a soil sample and perform an in situ analysis for the presence of Volatile Organic Compounds (VOCs). The TDS system performs rapid field screening to determine either the presence or absence of VOCs within the unsaturated subsurface soil of a site. In addition, the TDS interfaced to an Ion Trap Mass Spectrometer (ITMS) provides identification of specific analytes based on their mass spectra and provides estimates of contaminant concentrations. The TDS system is deployed by the Tri-Service Site Characterization and Analysis Penetrometer System (SCAPS). The TDS principle of operation is based on capturing a known volume of subsurface soil in situ , heat ing the sample chamber, and purging the VOC contaminants with helium carrier gas while heating the soil. The VOCs in the carrier gas are then collected on a sorbent trap that concentrates the VOCs prior to introduction into the ITMS for quantification and identification of the VOCs. The TDS system was demonstrated at five separate DoD facilities located in diverse geological conditions. The TDS/ITMS system performed well during the collection and analysis of 170 in situ samples. More than 600 verification samples were also collected for off-site laboratory analysis. There was a strong correlation between the off-site laboratory verification sample results and the TDS ex situ mode analysis results. Limitations of the TDS system involve the mechanical operation of the probe and the desorption efficiency of the sampler. Lithologies containing gravels, cobbels, and clay may prevent the sample chamber from opening properly and filling with soil. Clay and saturated soils may exhibit reduced VOC desorption efficiencies that necessitate heating the sample chamber for increased sampling times. Cost of operating the TDS system is comparable to conventional sample collection and analysis techniques.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2001
- Accession Number
- ADA607323
Entities
People
- John H. Ballard
- Karen F. Myers
Organizations
- United States Army Corps of Engineers