Monitoring Biodegradation of Methyl <i>tert</i>-Butyl Ether (MTBE) Using Compound-Specific Carbon Isotope Analysis

Hunkeler, Daniel; Butler, Barbara J.; Aravena, Ramón; Barker, James

doi:10.1021/es001338w

Cited by 85 publications

(68 citation statements)

References 38 publications

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“…Alkanes n-C15-n-C17 showed the largest fractionation (∼12-25 ( 1.2‰), n-C18 showed an intermediate amount of fractionation (∼8 ( 1.2 ‰), and n-C19-n-C27 showed relatively little fractionation (∼0-6 ( 1.2‰). A possible explanation for this correlation is that during biodegradation the kinetic isotope effects occur mainly with respect to the bond that is broken in the initial transformation step (11). However, our isotopic analyses measure all of the hydrogen atoms in a molecule.…”

Section: Resultsmentioning

confidence: 99%

“…Because the isotopic compositions of pollutants from different sources are generally different, the isotopic profile of a contaminant plume can be used to trace its origin (5,8). Furthermore, during biodegradation the isotopic compositions of residual compounds often become enriched with time (9,11,15), indicating that CSIA can also be used to monitor in-situ bioremediation.…”

Section: Introductionmentioning

confidence: 99%

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Hydrogen Isotopic Composition of Individual n-Alkanes as an Intrinsic Tracer for Bioremediation and Source Identification of Petroleum Contamination

Pond

Huang

Wang

et al. 2002

Environ. Sci. Technol.

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The isotopic signatures of crude oil hydrocarbons are potentially powerful intrinsic tracers to their origins and the processes by which the oils are modified in the environment. Stable carbon isotopic data are of limited use for studying petroleum contaminants because of the relatively small amount of isotopic fractionation that occurs during natural processes. Hydrogen isotopes, in contrast, are commonly fractionated to a much greater extent and as a result display larger variations in delta values. We studied the effect of in vitro aerobic biodegradation on the hydrogen isotopic composition of individual n-alkanes from crude oil. The isotopic analysis was conducted using gas chromatography-thermal conversion-isotope ratio mass spectrometry. In general, biodegradation rates decreased with increasing hydrocarbon chain length, consistent with previous studies. More importantly the n-alkanes that were degraded at the fastest rates (n-C15 to n-C18) also showed the largest overall isotopic fractionation (approximately 12-25 per thousand deuterium enrichment), suggesting that the lower molecular weight n-alkanes can be used to monitor in-situ bioremediation of crude oil contamination. The hydrogen isotopic compositions of the longer chain alkanes (n-C19 to n-C27) were relatively stable during biodegradation (<5%o overall deuterium enrichment), indicating that these compounds are effective tracers for oil-source identification studies.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrogen Isotopic Composition of Individual n-Alkanes as an Intrinsic Tracer for Bioremediation and Source Identification of Petroleum Contamination

Pond

Huang

Wang

et al. 2002

Environ. Sci. Technol.

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“…After replacing tetraethyl lead in gasoline, MTBE has become an important groundwater contaminant, and its natural attenuation has been of great interest. 8 Carbon 3 kin values of MTBE measured with microbial cultures clustered around À2& for aerobic degradation, 74,75 but around À9& for anaerobic degradation; 29 hydrogen 3 kin values showed the opposite trend, clustering around À40& in aerobic degradation 74 and around only À10& in anaerobic degradation. 29 A careful analysis in terms of kinetic isotope effects showed that the pronounced hydrogen and small carbon isotope fractionation under aerobic conditions was again consistent with C-H bond cleavage.…”

Section: Deriving Transformation Mechanisms From Isotope Fractionationmentioning

confidence: 88%

Stable isotope fractionation to investigate natural transformation mechanisms of organic contaminants: principles, prospects and limitations

2010

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Gas chromatography-isotope ratio mass spectrometry (GC-IRMS) has made it possible to analyze natural stable isotope ratios (e.g., (13)C/(12)C, (15)N/(14)N, (2)H/(1)H) of individual organic contaminants in environmental samples. They may be used as fingerprints to infer contamination sources, and may demonstrate, and even quantify, the occurrence of natural contaminant transformation by the enrichment of heavy isotopes that arises from degradation-induced isotope fractionation. This review highlights an additional powerful feature of stable isotope fractionation: the study of environmental transformation mechanisms. Isotope effects reflect the energy difference of isotopologues (i.e., molecules carrying a light versus a heavy isotope in a particular molecular position) when moving from reactant to transition state. Measuring isotope fractionation, therefore, essentially allows a glimpse at transition states! It is shown how such position-specific isotope effects are "diluted out" in the compound average measured by GC-IRMS, and how a careful evaluation in mechanistic scenarios and by dual isotope plots can recover the underlying mechanistic information. The mathematical framework for multistep isotope fractionation in environmental transformations is reviewed. Case studies demonstrate how isotope fractionation changes in the presence of mass transfer, enzymatic commitment to catalysis, multiple chemical reaction steps or limited bioavailability, and how this gives information about the individual process steps. Finally, it is discussed how isotope ratios of individual products evolve in sequential or parallel transformations, and what mechanistic insight they contain. A concluding session gives an outlook on current developments, future research directions and the potential for bridging the gap between laboratory and real world systems.

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“…Degradation of MTBE was absent or very slow in most aquifers (1,6,18). Biodegradation of MTBE was however observed in laboratory experiments under aerobic and anaerobic conditions and resulted occasionally in the transient accumulation of tert-butyl alcohol (TBA) as an intermediate of MTBE degradation (1,(19)(20)(21). Field data on the fate of ethanol at gasoline spill sites are scarce (12), perhaps because ethanol is not a regulated pollutant.…”

Section: Introductionmentioning

confidence: 99%

Small-Volume Releases of Gasoline in the Vadose Zone: Impact of the Additives MTBE and Ethanol on Groundwater Quality

Dakhel

Pasteris

Werner

et al. 2003

Environ. Sci. Technol.

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A controlled gasoline spill experiment was performed under outdoor conditions typical for winter in temperate regions to study the fate of methyl tert-butyl ether (MTBE), ethanol, benzene, and selected other petroleum hydrocarbons. Artificial gasoline containing MTBE and ethanol (5% w/w of each) was placed at a defined depth into a 2.3 m thick unsaturated zone of alluvial sand overlying a gravel aquifer in a lysimeter. During an initial period of 41 days without recharge, MTBE and hydrocarbon vapors migrated by vapor-phase diffusion to groundwater, while ethanol vapors were naturally attenuated. In a subsequent period of 30 days with 5-mm daily recharge, all soluble compounds including ethanol were transported to the groundwater. Ethanol disappeared concomitantly with benzene and all other petroleum hydrocarbons except isooctane from the aerobic groundwater due to biodegradation. MTBE persisted for longer than 6 months at concentrations larger than 125000 microg L(-1). No evidence for MTBE biodegradation was found, whereas > 99.6% of ethanol removal from the lysimeter was due to biodegradation. It is concluded that MTBE-free gasoline would be less harmful for groundwater resources and that ethanol is an acceptable substitute.

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Monitoring Biodegradation of Methyl tert-Butyl Ether (MTBE) Using Compound-Specific Carbon Isotope Analysis

Cited by 85 publications

References 38 publications

Hydrogen Isotopic Composition of Individual n-Alkanes as an Intrinsic Tracer for Bioremediation and Source Identification of Petroleum Contamination

Hydrogen Isotopic Composition of Individual n-Alkanes as an Intrinsic Tracer for Bioremediation and Source Identification of Petroleum Contamination

Stable isotope fractionation to investigate natural transformation mechanisms of organic contaminants: principles, prospects and limitations

Small-Volume Releases of Gasoline in the Vadose Zone: Impact of the Additives MTBE and Ethanol on Groundwater Quality

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