Grantee Research Project Results
2000 Progress Report: Gas chromatography-isotope ratio mass spectrometry-A novel approach for monitoring the origin and fate of hydrocarbon contaminants in the environment
EPA Grant Number: R826178Title: Gas chromatography-isotope ratio mass spectrometry-A novel approach for monitoring the origin and fate of hydrocarbon contaminants in the environment
Investigators: Philp, R. Paul , Kuder, Tomasz , Smallwood, B.
Current Investigators: Philp, R. Paul , Kuder, T. , Smallwood, B.
Institution: University of Oklahoma
EPA Project Officer: Aja, Hayley
Project Period: October 1, 1997 through September 30, 2000
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: $313,743
RFA: Exploratory Research - Environmental Chemistry (1997) RFA Text | Recipients Lists
Research Category: Water , Air , Safer Chemicals , Land and Waste Management
Objective:
The objective of the research project is to demonstrate that the isotopic compositions of individual compounds, as determined by gas chromatography-isotope ratio mass spectrometry (GCIRMS), may be used to correlate weathered and unweathered samples of fossil fuel origin in the environment, even when extensive weathering may render the more conventional techniques, such as gas chromatography (GC) and gas chromatography/mass spectrometry (GCMS) highly impractical.
Progress Summary:
In the present year, most of the work has been focused on development and refining of methods for compound-specific isotopic analysis of aqueous volatile and semivolatile contaminants. In particular, purge and trap and a cost-effective technique of solid phase microextraction (SPME) were applied with GCIRMS. In addition, work on general aspects of stable isotopic fractionation of organic compounds upon weathering was continued. In extension of previous work on carbon isotope composition of MTBE from various suppliers, preliminary results on the range of stable hydrogen composition of tertbutyl methyl ester (MTBE) were obtained.
Purge and Trap. Purge and trap was demonstrated to be a viable sample preparation tool for isotopic analysis of volatiles in water and soil in the previous funding year. In the present year it was successfully applied to actual environmental samples of water contaminated with MTBE and benzene, toluene, ethylbenzene, and xylene (BTEX).
Solid Phase Microextraction. SPME is a relatively recent method for extraction of volatile and semivolatile organics from a range of matrices such as water, soil, physiological liquids, etc. It utilizes a sorbent polymer fiber, which is introduced into the sample or the headspace over the sample. SPME was tested on artificial and environmental aquatic matrices and was found to produce replicable stable isotopic data. Classes of chemicals examined included MTBE and potential MTBE degradation products (TBA, TBF), gasoline and light crude oil range hydrocarbons (BTEX, naphthalene and methylnaphthalenes, C4-C14 aliphatics). Sensitivity of the method was appropriate to low concentrations of pollutants, typically well below the U.S. Environmental Protection Agency (EPA) enforced values for drinking water quality. For the compounds examined, the minimum concentration was in the ppt to lower ppb range. The extent of isotopic fractionation observed during SPME ranged from none to approximately 1 per mil 13C, depending of the specific compound and the sorbent type. This did not limit the utility of the method for correlation. As long as the fractionation extent was checked beforehand for a given compound, its actual isotopic composition also could be obtained.
Environmental Fractionation of 13C of Organic Compounds. Spill to source correlation based on stable isotope data can be made more difficult if the original isotopic signature is distorted by any fractionation process. In other words, it is crucial for the isotopic signal to be as inert as possible to facilitate correlation. Preliminary data (FY 1999) suggested that this is the case at least for some gasoline components, especially naphthalenes, remaining isotopically stable during water washing and in gasoline evaporation residue. On the other hand, if the original isotopic composition is known and/or if a series of samples from a plume gradient are analyzed, the extent of fractionation can be informative on remediation processes taking place after the spill. Our results showed that MTBE becomes isotopically heavier during aerobic biodegradation. Fractionation due to inorganic weathering (e.g., evaporation) also can be significant. A number of light end gasoline products were shown to fractionate upon evaporation, precluding their possible use as a reliable source of information for spill to source correlation.
Future Activities:
As this is the last funding year of the project, the only future activity is processing of the obtained data for publication, especially in the novel analytical development area (SPME-GCIRMS).
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 13 publications | 3 publications in selected types | All 2 journal articles |
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Smallwood B, Philp RP, Burgoyne TW, Allen J. The use of stable isotopes to differentiate specific source markers for MTBE. Environmental Forensics 2000. |
R826178 (2000) R826178 (Final) |
not available |
Supplemental Keywords:
groundwater, soil, chemicals, VOC, organics, NAPL, remediation, bioremediation, environmental chemistry, analytical methods, petroleum, refined products., Air, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Waste, Ecological Risk Assessment, Fate & Transport, Chemistry, Ecology, Biology, Environmental Chemistry, Engineering, Chemistry, & Physics, gasoline, gas chromatography, hydrocarbon, mass spectrometry, weathering, isotope ratio mass spectrometry, MTBE, oil spills, analytical models, wildlife , fate and transport, chemical kineticsRelevant Websites:
http://parker.gcn.ou.edu/~geol/n/philp.html
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.