Stable carbon isotope fractionation of individual light hydrocarbons in the C6–C8 range in crude oil as induced by natural evaporation: Experimental results and geological implications

Xiao, Qilin; Sun, Yongge; Zhang, Yongdong; Chai, Pingxia

doi:10.1016/j.orggeochem.2012.06.003

Cited by 22 publications

(12 citation statements)

References 29 publications

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“…Xiao et al 17 (eq. 6 in their work) does not give any quantitative explanation of the evaporation 325 phenomenon: indeed, it overestimates the diffusive fractionation by a factor of 2-3.…”

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confidence: 99%

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Julien

Nun

Robins

et al. 2015

Environ. Sci. Technol.

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Position-specific isotope effects (PSIEs) have been measured by isotope ratio monitoring (13)C nuclear magnetic resonance spectrometry during the evaporation of 10 liquids of different polarities under 4 evaporation modes (passive evaporation, air-vented evaporation, low pressure evaporation, distillation). The observed effects are used to assess the validity of the Craig-Gordon isotope model for organic liquids. For seven liquids the overall isotope effect (IE) includes a vapor-liquid contribution that is strongly position-specific in polar compounds but less so in apolar compounds and a diffusive IE that is not position-specific, except in the alcohols, ethanol and propan-1-ol. The diffusive IE is diminished under forced evaporation. The position-specific isotope pattern created by liquid-vapor IEs is manifest in five liquids, which have an air-side limitation for volatilization. For the alcohols, undefined processes in the liquid phase create additional PSIEs. Three other liquids with limitations on the liquid side have a lower, highly position-specific, bulk diffusive IE. It is concluded that evaporation of organic pollutants creates unique position-specific isotope patterns that may be used to assess the progress of remediation or natural attenuation of pollution and that the Craig-Gordon isotope model is valid for the volatilization of nonpolar organic liquids with air-side limitation of the volatilization rate.

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“…Xiao et al 17 (eq. 6 in their work) does not give any quantitative explanation of the evaporation 325 phenomenon: indeed, it overestimates the diffusive fractionation by a factor of 2-3.…”

mentioning

confidence: 99%

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Julien

Nun

Robins

et al. 2015

Environ. Sci. Technol.

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“…The majority of these studies focus upon the δ 13 C signatures of high molecular weight homologues ( n‐ C 8+ ) of the n‐ alkane compound class, with only a limited number of studies reporting results for the low molecular weight n‐ alkanes and other compounds. Moreover, of those studies which do include low molecular weight and non‐ n‐ alkane compounds, most are primarily focused on biodegradation . Crude oils are complex mixtures of a vast number of different compounds with a variety of diverse compound classes, with varying degrees of chemical functionality often depending upon source, thermal history and the influence of biological activity .…”

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confidence: 99%

Measurement of compound‐specific carbon isotope ratios (δ¹³C values) via direct injection of whole crude oil samples

Barrie

Taylor²,

Zumberge

2016

Rapid Comm Mass Spectrometry

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RATIONALE: Stable isotope analysis is a powerful tool in understanding the generation, history and correlation of hydrocarbons. Compound-specific δ 13 C measurements of oils allow detailed comparison of individual compound groupings; however, most studies of these sample materials separate and isolate individual fractions based on the chemistries of particular compound groups, potentially losing considerable valuable isotopic data. Even if all fractions are analyzed, this represents a large increase in the data-processing burden, effectively multiplying data evaluation time and effort by the number of fractions produced. Gas chromatography/isotope ratio mass spectrometry (GC/IRMS) of untreated, whole crude oils allows the immediate collection of a larger suite of valuable isotopic data for these studies. METHODS: Untreated ('neat', undiluted), whole crude oils were directly injected and measured on a GC/IRMS system, using split (40:1) injections and a 50 m HP-PONA column. The GC method, 97 min in duration, was designed to maximize baseline separation of target analyte peaks, while an additional oxygen flow was admitted into the combustion reactor to maximize the lifetime of the combustion chemicals. RESULTS: The method and setup utilized allow the measurement of a much greater range of the n-alkanes (n-C 4 to n-C 25+ ) than traditional methods, while also retaining important cycloalkane, aromatic and isoprenoid peaks within the same analysis. Carbon isotope (δ 13 C) evaluation of these additional compound classes reveals trends in maturity and origins which are not identifiable when exclusively assessing the traditional n-alkane package (>n-C 12 ). CONCLUSIONS: The described setup and method open up new possibilities for assessing the origins and histories of crude oil samples. The data generated for the whole oil n-alkanes by this method is equivalent to that reported for isolated n-alkane studies, while also providing valuable additional data on many other important compounds. The end result of this method is a more complete assessment of the carbon isotopic composition of crude oils.

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“…The evaporation-controlled process usually results in ''inverse isotope fractionation,'' characterizing of enriching 13 C in the vapor phase (Baertschi et al 1953;Balabane and Letolle 1985;Huang et al 1999;Poulson and Drever 1999;Wang and Huang 2001;Jeannottat and Hunkeler 2012;Xiao et al 2012), whereas diffusion-controlled vaporization, which depends on the system itself and intermolecular free energy due to the van der Waals attractive forces among molecules, results in the ''normal isotope fractionation,'' characterizing of enriching 13 C in the residual liquids (Shin and Lee 2010;Xiao et al 2012;Kuder et al 2009;Bouchard et al 2008a, b, c;Jeannottat and Hunkeler 2012;Hayes 1993;Wang and Huang 2001). Table 4 lists the carbon isotope enrichment factors of the LMWHs considered here and in previous studies, along with values calculated using Eq.…”

Section: Possible Mechanism Of Carbon Isotope Fractionation Of Lmwhs mentioning

confidence: 99%

Carbon isotopic fractionation during vaporization of low molecular weight hydrocarbons (C6–C12)

et al. 2017

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Three series of laboratory vaporization experiments were conducted to investigate the carbon isotope fractionation of low molecular weight hydrocarbons (LMWHs) during their progressive vaporization. In addition to the analysis of a synthetic oil mixture, individual compounds were also studied either as pure single phases or mixed with soil. This allowed influences of mixing effects and diffusion though soil on the fractionation to be elucidated. The LMWHs volatilized in two broad behavior patterns that depended on their molecular weight and boiling point. Vaporization significantly enriched the 13 C present in the remaining components of the C 6 -C 9 fraction, indicating that the vaporization is mainly kinetically controlled; the observed variations could be described with a Rayleigh fractionation model. In contrast, the heavier compounds (n-C 10 -n-C 12 ) showed less mass loss and almost no significant isotopic fractionation during vaporization, indicating that the isotope characteristics remained sufficiently constant for these hydrocarbons to be used to identify the source of an oil sample, e.g., the specific oil field or the origin of a spill. Furthermore, comparative studies suggested that matrix effects should be considered when the carbon isotope ratios of hydrocarbons are applied in the field.

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Stable carbon isotope fractionation of individual light hydrocarbons in the C6–C8 range in crude oil as induced by natural evaporation: Experimental results and geological implications

Cited by 22 publications

References 29 publications

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Measurement of compound‐specific carbon isotope ratios (δ¹³C values) via direct injection of whole crude oil samples

Carbon isotopic fractionation during vaporization of low molecular weight hydrocarbons (C6–C12)

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Stable carbon isotope fractionation of individual light hydrocarbons in the C6–C8 range in crude oil as induced by natural evaporation: Experimental results and geological implications

Cited by 22 publications

References 29 publications

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Insights into Mechanistic Models for Evaporation of Organic Liquids in the Environment Obtained by Position-Specific Carbon Isotope Analysis

Measurement of compound‐specific carbon isotope ratios (δ13C values) via direct injection of whole crude oil samples

Carbon isotopic fractionation during vaporization of low molecular weight hydrocarbons (C6–C12)

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Measurement of compound‐specific carbon isotope ratios (δ¹³C values) via direct injection of whole crude oil samples