Tuesday, June 24, 2008 : 1:20 p.m.

Using Compound Specific Isotope Analysis to Document MTBE Remediation: Case Study Reviews

Patrick W. McLoughlin, Ph.D. and Robert J. Pirkle, Ph.D., Microseeps Inc.

The use of Compound Specific Isotope Analysis (CSIA) to document MTBE biodegradation has received a lot of attention in the academic sector, from regulatory agencies and from private parties. However, to date it has been hampered by the limited availability of CSIA services, particularly by the lack of commercial laboratories providing CSIA to the environmental market with ground water detection levels commensurate with many MCL’s. This void is now filled and case studies are presented in which CSIA has been employed at a field site.

 CSIA, in conjunction with other routinely collected data, can differentiate between non-destructive attenuation such as dillution and biodegradation. Further, it can assess the extent of biodegradation and under some circumstances the rate of that biodegradation, allowing for the estimation of timelines. Interpretation of the CSIA results is presented. Since these results are otherwise obtainable only at significant expense, a comparison of the time and monetary costs that would be incurred reaching that interpretation with and without CSIA is presented.

 The quality requirements for CSIA have not been explicitly developed by a regulatory agency. It is up to the regulated community to work with regulators to develop an appropriate quality assurance/quality control (QAQC) plan. By providing a detailed report that documents that QAQC CSIA becomes more accessible and more acceptable to regulators. Key features of that report, and the role of those key features, are presented.

 While CSIA is a powerful and reasonably priced tool, both it and its interpretation present a difficult cost to justify if CSIA is to be “one more analysis”. Instead, CSIA is not meant to be an analysis performed repetitively for each site, but employed only as needed to answer specific questions. In each presented case it is stressed why CSIA was used and what the benefits to its use were.  

Patrick W. McLoughlin, Ph.D., Microseeps Inc. Pat received his B.S. degree in chemistry from the University of Notre Dame and M.S. and Ph.D. from Cornell University. He is the Technical Director at Microseeps. His duties include managing an extensive Quality Control program, directing the R&D program, and specializing in in-situ remediation and analytical methods development. He developed the Microseeps hydrogen sampling system and the high-sensitivity volatile-fatty acids analysis. He has authored many interpretive reports that use site-specific geo-chemical data and modeling to assess natural attenuation. His current emphasis is upon the development of a rigorous, defendable compound specific isotopic analyses and the interpretation of CSIA data.


2008 NGWA Conference on Eastern Regional Ground Water Issues