Carbon isotopic fractionation during reductive dehalogenation of chlorinated ethenes by metallic iron

Dayan, H; Abrajano, T.A.; Sturchio, Neil C.; Winsor, Linda

doi:10.1016/s0146-6380(99)00058-3

Cited by 80 publications

(73 citation statements)

References 7 publications

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“…Harris et al [40] compared purge-and-trap and headspace SPME methods for 13 C analysis of gasoline-range hydrocarbons, and concluded that both methods can yield accurate and precise results if injection conditions are carefully optimized. Dayan et al [41] used headspace SPME to measure 13 C in chlorinated solvents, and observed a consistent 0.3? enrichment of 13 C relative to bulk (offline) analyses.…”

Section: Injection Methodsmentioning

confidence: 94%

Isotope‐ratio detection for gas chromatography

Sessions¹

2006

J of Separation Science

244

270

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Isotope-ratio detection for gas chromatographyInstrumentation and methods exist for highly precise analyses of the stable-isotopic composition of organic compounds separated by GC. The general approach combines a conventional GC, a chemical reaction interface, and a specialized isotoperatio mass spectrometer (IRMS). Most existing GC hardware and methods are amenable to isotope-ratio detection. The interface continuously and quantitatively converts all organic matter, including column bleed, to a common molecular form for isotopic measurement. C and N are analyzed as CO 2 and N 2 , respectively, derived from combustion of analytes. H and O are analyzed as H 2 and CO produced by pyrolysis/reduction. IRMS instruments are optimized to provide intense, highly stable ion beams, with extremely high precision realized via a system of differential measurements in which ion currents for all major isotopologs are simultaneously monitored. Calibration to an internationally recognized scale is achieved through comparison of closely spaced sample and standard peaks. Such systems are capable of measuring 13 C/ 12 C ratios with a precision approaching 0.1? (for values reported in the standard delta notation), four orders of magnitude better than that typically achieved by conventional "organic" mass spectrometers. Detection limits to achieve this level of precision are typically a1 nmol C (roughly 10 ng of a typical hydrocarbon) injected on-column. Achievable precision and detection limits are correspondingly higher for N, O, and H, in that order.

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Section: Injection Methodsmentioning

confidence: 94%

Isotope‐ratio detection for gas chromatography

Sessions¹

2006

J of Separation Science

244

270

View full text Add to dashboard Cite

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“…All of these parameters (type of intrinsic reaction, number of carbon centers involved, commitment to catalysis) can be expected to depend critically on the properties and corrosion state of the manufactured iron. It is, therefore, not surprising that reported bulk values for this reaction have been found to vary considerably (PCE: -5.7‰ to -25.3‰ (90,91); TCE: -7.5‰ to -24.8‰ (90)(91)(92)(93); cis-DCE: -6.9‰ to -16.0‰ (90,91); VC: -6.9‰ to -19.3‰ (90)). Evidence for a subtle influence of iron pretreatment on observed bulk values is also given by a recent study of Slater et al (92).…”

Section: Reduction Of C-cl Bondsmentioning

confidence: 99%

A New Concept Linking Observable Stable Isotope Fractionation to Transformation Pathways of Organic Pollutants

Elsner

Zwank

Hunkeler

et al. 2005

Environ. Sci. Technol.

511

803

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Measuring stable isotope fractionation of carbon, hydrogen, and other elements by Compound Specific Isotope Analysis (CSIA) is a new, innovative approach to assess organic pollutant degradation in the environment. Central to this concept is the Rayleigh equation which relates degradation-induced decreases in concentrations directly to concomitant changes in bulk () average over the whole compound) isotope ratios. The extent of in situ transformation may therefore be inferred from measured isotope ratios in field samples, provided that an appropriate enrichment factor ( bulk ) is known. This bulk value, however, is usually only valid for a specific compound and for specific degradation conditions. Therefore, a direct comparison of bulk values for different compounds and for different types of reactions has in general not been feasible. In addition, it is often uncertain how robust and reproducible bulk values are and how confidently they can be used to quantify contaminant degradation in the field. To improve this situation and to achieve a more in-depth understanding, this critical review aims to relate fundamental insight about kinetic isotope effects (KIE) found in the physico(bio)chemical literature to apparent kinetic isotope effects (AKIE) derived from bulk values reported in environmentally oriented studies. Starting from basic rate laws, a quite general derivation of the Rayleigh equation is given, resulting in a novel set of simple equations that take into account the effects of (1) nonreacting positions and (2) intramolecular competition and that lead to position-specific AKIE values rather than bulk enrichment factors. Reevaluation of existing bulk literature values result in consistent ranges of AKIE values that generally are in good agreement with previously published data in the (bio)-chemical literature and are typical of certain degradation reactions (subscripts C and H indicate values for carbon and hydrogen): AKIE C ) 1.01-1.03 and AKIE H ) 2-23 for oxidation of C-H bonds; AKIE C ) 1.03-1.07 for S N 2-

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“…In contrast, physical processes such as dissolution, volatilization, or sorption are usually not accompanied by significant isotope fractionation (9)(10)(11)(12). Large isotope effects with respect to carbon have been observed during reductive dechlorination (8,13,14) and oxidation (15,16) of chlorinated solvents while much smaller isotope effects occurred during biodegradation of BTEX (13,17,18). As a consequence, carbon isotope ratios are not a very sensitive indicator for biodegradation of BTEX, and significant shifts of the carbon isotope ratio are only observed after a large fraction of the BTEX has been biodegraded.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen and Carbon Isotope Fractionation during Aerobic Biodegradation of Benzene

Hunkeler

Andersen

Aravena

et al. 2001

Environ. Sci. Technol.

165

112

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The main aim of the study was to evaluate hydrogen and carbon isotope fractionation during biodegradation of benzene as a possible tool to trace the process in contaminated environments. Aerobic biodegradation of benzene by two bacterial isolates, Acinetobacter sp. and Burkholderia sp., was accompanied by significant hydrogen and carbon isotope fractionation with hydrogen isotope enrichment factors of -12.8 ( 0.7‰ and -11.2 ( 1.8‰, respectively, and average carbon isotope enrichment factors of -1.46 ( 0.06‰ and -3.53 ( 0.26‰, respectively. Inorganic carbon produced by Acinetobacter sp. was depleted in 13 C by 3.6-6.2‰ as compared to the initial δ 13 C of benzene, while the produced biomass was enriched in 13 C by 3.8‰. The secondary aim was to determine isotope ratios of benzenes from different manufacturers with regard to the use of isotopes for source differentiation. While two of the four analyzed benzenes had similar δ 13 C values, each of them had a distinct δ 2 H-δ 13 C pair and δ 2 H values spread over a range of 66.5‰. Thus, combined analyses of hydrogen and carbon isotopes may be a more promising approach to trace sources and/or biodegradation of benzene than measuring carbon isotopes only.

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Carbon isotopic fractionation during reductive dehalogenation of chlorinated ethenes by metallic iron

Cited by 80 publications

References 7 publications

Isotope‐ratio detection for gas chromatography

Isotope‐ratio detection for gas chromatography

A New Concept Linking Observable Stable Isotope Fractionation to Transformation Pathways of Organic Pollutants

Hydrogen and Carbon Isotope Fractionation during Aerobic Biodegradation of Benzene

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