TRICHLOROETHYLENE ADSORPTION IN SEDIMENTS FROM THE NEW JERSEY NAVAL AIR WARFARE CENTER

Trichloroethylene (TCE) is one of the most frequently detected organic groundwater contaminants in the United States. Our work focuses on TCE contamination in the fractured sedimentary rock aquifer at the Naval Air Warfare Center (NAWC) in Trenton, New Jersey, where TCE sorption is nonlinear and significantly variable. The viability of trichlorofluoroethylene (TCFE) as a tracer of TCE biodegradation has been established. However, its use as a simultaneous use as a sorbing tracer in rocks such as NAWC is not well studied. A clearer pattern of nonlinear sorption behavior can be elucidated by utilizing a displacer, whose purpose is to competitively sorb against TCE or TCFE. To accurately determine the mass of sorbed contaminant a multistep process was developed. This consisted of allowing the sediment samples, a displacer, and a known concentration of contaminant to equilibrate over several days before analyzing the supernatant. We completed a preliminary experiment to select among the possible displacers by testing for TCE or TCFE sorption inhibition; this test also checked for co-solvent on TCE or TCFE by the displacers. A suite of four possible displacer compounds were chosen based upon density, octanol-water coefficient, solubility, index of refraction and pKa. Two sediment samples of varying organic carbon content were treated with an 825 ug/mL solution of TCE or TCFE. The displacer was successful if equal amounts of TCE or TCFE were expelled back into the aqueous phase. Gas chromatography to measure concentrations and a mass balance approach were used to determine the sorbed TCE concentration in the sediment in each experiment. Studying an array of TCE and TCFE concentrations with a displacer will yield a more thorough understanding of nonlinear sorption and its effects on TCE remediation in the underlying sedimentary bedrock.