Date of Award

12-1995

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Glen P. Perram, PhD

Abstract

Slow desorption of contaminants from soil presents one of the greatest challenges to modeling contaminant fate and transport and implementing effective remediation technologies. The kinetics of long-term desorption of trichloroethylene (TCE) from powdered clay soils were studied to determine the desorption rates and mechanism. Infrared absorption spectroscopy was used to monitor the concentration of TCE desorbed from contaminated flint clay for 71 hours. Observed gas phase TCE concentrations as a function of time were compared to that predicted by a one-site Langmuir desorption mechanism. The Langmuir model, with a single type of bonding site, did not account for the release of entrained contaminant past the rapid desorption phase, indicating the need for a desorption model based more than one type of binding site. A second model, based on a Gamma distribution of desorption rate coefficients, fit the entire desorption profile. Application of infrared absorption spectroscopy to measure long-term desorption allowed continuous measurement of desorption over long time periods (days). A multiplex design in the optical detection system improved measurement capabilities, allowing quantification of contaminant to 0.06 torr of TCE. The ability to measure such small changes in contaminant concentration is an important development in characterizing and understanding long-term desorption trends.

AFIT Designator

AFIT-GEE-ENP-95D-09

DTIC Accession Number

ADA306366

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