Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products to Monitor Their Fate in the Environment
EPA Grant Number: X83-2428-01
Title: Utilization of the Carbon and Hydrogen Isotopic Composition of Individual Compounds in Refined Hydrocarbon Products to Monitor Their Fate in the Environment
Investigators: R. Paul Philp (pphilp@ou.edu) and Tomasz Kuder
Institutions: University of Oklahoma
EPA Project Officer: Bala Krishnan
Project Period: 12-5-05 to 12-4-06
Project Amount: $149,298
Research Category: Environmental Technology - Natural attenuation
Description:
Objective: The objective of this proposal is to evaluate the use of compound-specific stable isotope analysis (CSIA) for monitoring in-situ biodegradation for natural attenuation projects, to develop a cost-effective method for site evaluation. CSIA data from microcosm biodegradation experiments and preliminary field observations provide a strong indication that changes in the d13C and dD values of MTBE, and other contaminants (e.g., BTEX, chlorinated solvents), have the potential to be used as “indicators” of in-situ biodegradation. The primary focus of the study will be MTBE. MTBE is a particularly well suited for the CSIA approach, as standard field site evaluation protocols do not permit unequivocal verification for MTBE biodegradation, instead, demonstrating biodegradation of MTBE requires expensive and time-consuming laboratory microcosm studies. Application of CSIA to other gasoline-range contaminants, such as BTEX, will be also investigated.
Approach: In order to achieve the objective of the project, the following topics will be investigated: 1) the range of carbon and hydrogen isotopic compositions of commercial MTBE, BTEX etc. to be used as a benchmark for detecting changes due to biodegradation; 2) characterize carbon and hydrogen isotopic effects due to various aerobic and anaerobic mechanisms of degradation; 3) determine the effect of environmental controls on the magnitude of isotope effects.
Expected Results: Upon completion, the proposed study will provide the following information: 1) verification of the hypothesis that degradation is the primary factor leading to isotopic fractionation in the field; 2) a database of isotope fractionation by available microbial cultures, primarily of MTBE biodegradation, and as applicable – other gasoline compounds; 3) a database of stable isotopic composition of MTBE and other gasoline compounds; 4) a set of case studies of contaminated sites, primarily on MTBE and TBA. Ultimately, this information will permit to propose a commercially viable protocol for site characterization based on the CSIA technique.
Key Words: Natural attenuation, biodegradation, groundwater contaminants, MTBE, TBA, BTEX, gasoline, stable isotopes, compound-specific isotope analysis (CSIA), GC-IRMS.