FORENSIC ANALYSIS OF THE STABLE CARBON ISOTOPE FRACTIONATION DURlNG ABIOTIC OXIDATION OF METHYL TERT BUTYL ETHER (MTBE)

摘要

Methyl tert Butyl Ether (MTBE) is a common contaminant encountered in environmental forensic investigations and is frequently the primary contaminant of concern. An understanding of its chemical and physical transformations in the subsurface is important in properly interpreting forensic evidence, especially when MTBE is used as a diagnostic tracer for age dating a contaminant plume in groundwater. Given that forensic investigations are frequently performed during or after active remediation of MTBE, the degradation properties of MTBE relative to various remediation technologies is similarly important to understand. MTBE is synthetic compound, which is added to gasoline globally to improve fuel performance and combustion efficiency. It was first blended with gasoline in the late 1970's, added in small concentrations to replace alkyl lead as an "anti-knocking" agent. Its function however changed with the introduction, within the United States of America, of the Clean Air Act Amendments in 1990. The percentage added to gasoline increased, with concentrations of up to 15% (by volume), to supply oxygen for improved combustion thereby reducing emissions of carbon monoxide (CO) and ozone (O3). Environmental benefits, of improved air quality, have however been lessened by the increased contamination of ground and surface water '' 2 and marine and estuarine systems3' 4 by point and non-point sources of MTBE. The high solubility of MTBE and its poor affinity for organic matter suggests that it has the potential to migrate significant distances once it enters water. 5 Hence, significant attention has been devoted to the investigation of the efficiency of both biological and abiological remediation processes, which may accelerate the degradation of MTBE in the environment.