Does sorption influence isotope ratios of chlorinated hydrocarbons under field conditions?

Wanner, Philipp; Parker, Beth L.; Chapman, S.; Aravena, Ramón; Hunkeler, Daniel

doi:10.1016/j.apgeochem.2017.07.016

Cited by 34 publications

(13 citation statements)

References 57 publications

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“…We note, however, that such residual concentrations would come to lie below the sensitivity of current compound-specific isotope analysis. On the basis of the results from this and other studies, ,, we therefore recommend that conservative interpretations of CSIA field data may be accomplished if an additional uncertainty in carbon isotope values of ±1‰ is considered in addition to the present analytical uncertainty of ±2‰ suggested by EPA . This would apply to contaminations by chlorinated solvents and gasoline contaminants (but not natural gases such as methane or ethane) and would be adequate to consider the effect of aqueous diffusion and dispersion (but not the influence from sorption, volatilization or gas phase diffusion).…”

Section: Environmental Significancementioning

confidence: 82%

“…This magnitude is in agreement with 13 C/ 12 C effects between −0.2‰ and −0.3‰ determined by Wanner and Hunkeler 6 in the same Stokes' cell setup for diffusion of representative chlorinated groundwater pollutants (trichloroethylene, dichloroethane, and dichloromethane). 6,45 In combination, these data put an upper limit of about −0.2‰ to −0.4‰ to the magnitude of aqueous diffusion isotope effects to be expected for typical pollutants at contaminated sites including petroleum and chlorinated hydrocarbons (but not natural gas constituents such as methane, ethane, etc.). Under these boundary conditions, simulations of Wanner and Hunkeler for low permeability sediments (aquitards) suggest that the resulting diffusion-induced changes in δ 13 C-values would be below Δδ 13 C = 1.5‰.…”

Section: ■ Results and Discussionmentioning

confidence: 98%

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Magnitude of Diffusion- and Transverse Dispersion-Induced Isotope Fractionation of Organic Compounds in Aqueous Systems

Sun

Peters

Thullner

et al. 2021

Environ. Sci. Technol.

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Determining whether aqueous diffusion and dispersion lead to significant isotope fractionation is important for interpreting the isotope ratios of organic contaminants in groundwater. We performed diffusion experiments with modified Stokes diaphragm cells and transverse-dispersion experiments in quasi-two-dimensional flow-through sediment tank systems to explore isotope fractionation for benzene, toluene, ethylbenzene, 2,6-dichlorobenzamide, and metolachlor at natural isotopic abundance. We observed very small to negligible diffusion- and transverse-dispersion-induced isotope enrichment factors (ε < −0.4 ‰), with changes in carbon and nitrogen isotope values within ±0.5‰ and ±1‰, respectively. Isotope effects of diffusion did not show a clear correlation with isotopologue mass with calculated power-law exponents β close to zero (0.007 < β < 0.1). In comparison to ions, noble gases, and labeled compounds, three aspects stand out. (i) If a mass dependence is derived from collision theory, then isotopologue masses of polyatomic molecules would be affected by isotopes of multiple elements resulting in very small expected effects. (ii) However, collisions do not necessarily lead to translational movement but can excite molecular vibrations or rotations minimizing the mass dependence. (iii) Solute–solvent interactions like H-bonds can further minimize the effect of collisions. Modeling scenarios showed that an inadequate model choice, or erroneous choice of β, can greatly overestimate the isotope fractionation by diffusion and, consequently, transverse dispersion. In contrast, available data for chlorinated solvent and gasoline contaminants at natural isotopic abundance suggest that in field scenarios, a potential additional uncertainty from aqueous diffusion or dispersion would add to current instrumental uncertainties on carbon or nitrogen isotope values (±1‰) with an additional ±1‰ at most.

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Section: Environmental Significancementioning

confidence: 82%

Section: ■ Results and Discussionmentioning

confidence: 98%

Magnitude of Diffusion- and Transverse Dispersion-Induced Isotope Fractionation of Organic Compounds in Aqueous Systems

Sun

Peters

Thullner

et al. 2021

Environ. Sci. Technol.

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show abstract

“…Cases have been described in which the high concentrations of CT and CF in the source can harm or partly inhibit microbial dechlorinating activity (Da Lima, and Sleep, 2010). However, these pollutants, like other chlorinated solvents, can be degraded naturally by biotic and abiotic reductive dechlorination under appropriate redox anoxic conditions (Ramsburg et al, 2010) in the source and the plume (Hunkeler et al, 2011;Wanner et. al, 2016).…”

Section: *Conflict Of Interest Statement Introductionmentioning

confidence: 99%

Natural attenuation of pools and plumes of carbon tetrachloride and chloroform in the transition zone to bottom aquitards and the microorganisms involved in their degradation

Puigserver

Herrero

Parker

et al. 2020

Science of The Total Environment

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“…In addition, physical processes (e.g. volatilization, diffusion, sorption) can produce isotopic fractionation; although, they are less important than the processes that lead to PCE transformation (Braeckevelt et al 2012; Wanner and Hunkeler 2015; Wanner et al 2017). Several samples showed slight isotopic enrichment of PCE (δ 13 C values heavier than −24.2‰, Figure 3A), which can be related to the initial phase of the reductive dehalogenation and/or to physical processes that produce isotopic fractionation.…”

Section: Resultsmentioning

confidence: 99%

A New Method for Determining Compound Specific Carbon Isotope of Chlorinated Solvents in Porewater

Herrero¹,

Puigserver²,

Parker³

et al. 2021

Groundwater Monitoring Rem

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A new method for the extraction of chlorinated solvents (CSs) from porewater with dimethylacetamide (DMA) used as a solvent and the determination of δ13C by gas chromatography‐isotope ratio mass spectrometry (GC‐IRMS) with solid‐phase microextraction (SPME) are presented. This method was used for the determination of δ13C of chloroethenes and chloromethanes. The extraction of the CSs from porewater with DMA led to a minimal loss of mass of solvent and chlorinated compounds. The accuracy of the method was verified with the analysis of the pure injected compounds using elemental analyzer—isotope ratio mass spectrometry (EA‐IRMS). It has been effectively applied in a study area in saturated soil samples of a pollutant source zone of perchloroethylene (PCE) and trichloroethylene (TCE). The limit of quantification of the new method was 0.034 μg/g for PCE and TCE for 10–20 g of soil sample. This new method allows for compound‐specific isotope analysis of CSs in porewater, which can be beneficial in sites where the identification of contamination sources and the behavior of the contaminants are not clear.

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Does sorption influence isotope ratios of chlorinated hydrocarbons under field conditions?

Cited by 34 publications

References 57 publications

Magnitude of Diffusion- and Transverse Dispersion-Induced Isotope Fractionation of Organic Compounds in Aqueous Systems

Magnitude of Diffusion- and Transverse Dispersion-Induced Isotope Fractionation of Organic Compounds in Aqueous Systems

Natural attenuation of pools and plumes of carbon tetrachloride and chloroform in the transition zone to bottom aquitards and the microorganisms involved in their degradation

A New Method for Determining Compound Specific Carbon Isotope of Chlorinated Solvents in Porewater

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