Compound-Specific Stable Carbon Isotope Analysis of MTBE in Groundwater Contamination Fingerprinting Studies: The Use of Hydrogeologic Principles to Assess Its Validity

Methyl-tert-butyl ether (MTBE) is an oxygenate added to gasoline in the United States and elsewhere to boost the octane ratio and reduce tailpipe emissions. Because of its known usage time frame, the presence of MTBE can help estimate the age of gasoline releases to the environment. However, because of its ubiquity, its presence can no longer be used to fingerprint, or differentiate, gasoline plumes in groundwater. Compound-specific stable carbon isotope analysis has recently become a method for differentiating MTBE sources and plumes affecting groundwater. In the present study, groundwater samples were collected from 20 monitoring wells located at two gasoline service stations in central New Jersey in an attempt to differentiate the dissolved gasoline plumes and possibly identify their sources. The carbon isotope ratio (13C/12C expressed as δ13C) values for each sample were determined through gas chromatography–isotope ratio–mass spectrometry (GCIRMS), and the impacted area for each plume was delineated....