Tuesday, November 6, 2007 : 3:40 p.m.

Use of Carbon Isotope Ratios to Distinguish PCE Plumes in Soil and Ground Water

Alan W.A. Jeffrey and Shaoneng He, DPRA/Zymax Forensics

PCE, TCE, and cis-DCE were extracted from both water and soil samples using a Solid Phase Micro Extraction (SPME) fibre.  These volatile compounds were then desorbed in the injection port of an inline GC/oxidation furnace/Isotope Ratio Mass Spectrometer system, and the carbon isotope ratios of PCE, TCE, and cis-DCE measured.  Reliable isotope ratios of chlorinated solvents can be measured on concentrations as low as 10 to 20 ppb.

 This compound-specific isotope analysis (CSIA) technique has been successfully applied at several sites to distinguish the sources of chlorinated solvent contaminants.  At one site, distinct differences in PCE isotope ratios in two plumes indicated that the PCE came from different sources.  At a second site, PCE isotope ratios were very similar in both soil and groundwater, suggesting either a single source for the PCE, or more than one source, using PCE from the same manufacturer.

Alan W.A. Jeffrey, DPRA/Zymax Forensics Dr. Jeffrey received his PhD in Chemical Oceanography from Texas A&M University for research using stable isotope ratios to determine the origin of natural gas. He has over 20 years of U.S. and international experience in environmental and petroleum geochemistry. Much of his work has focused on the use of geochemical techniques to solve environmental problems, including sources of spilled hydrocarbon fuels and fugitive methane seeps.


Petroleum Hydrocarbons and Organic Chemicals in Ground Water: Prevention, Detection, and Remediation® Conference