Assessment of MTBE biodegradation in contaminated groundwater using 13C and 14C analysis: Field and laboratory microcosm studies

Thornton, Steven F.; Bottrell, Simon H.; Spence, Keith H.; Pickup, Roger W.; Spence, Michael; Shah, Nadeem; Mallinson, Helen; Richnow, Hans H.

doi:10.1016/j.apgeochem.2011.02.004

Cited by 14 publications

(11 citation statements)

References 45 publications

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“…The chlorine versus carbon dual isotope slope for fringe-degradation may, however, not show a gentle incline, but rather moves into the fourth quadrant on a dual isotope plot (Figure F). Underestimation or nondetecting biodegradation at pollution fringes based on CSIA data may occur for pollutants which have low fractionation factors for oxidation depending on the microorganisms involved (e.g., MTBE: ε C = −0.2 to −2.5 ‰, ε H ≈ 0 to −100 ‰; − 1,2,4-trichlorobenzene: ε C ≤ −0.4 ‰; toluene: ε C = −0.4 to −6.2 ‰, but ε H ≫ −2 ‰), especially under conditions favoring the HDIF effect. This study also pointed out the key role of diffusion on contaminant transport and degradation.…”

Section: Resultsmentioning

confidence: 99%

Transverse Hydrodynamic Dispersion Effects on Isotope Signals in Groundwater Chlorinated Solvents’ Plumes

Breukelen

Rolle

2012

Environ. Sci. Technol.

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The effects of transverse hydrodynamic dispersion on altering transformation-induced compound-specific isotope analysis (CSIA) signals within groundwater pollution plumes have been assessed with reactive transport modeling accommodating diffusion-induced isotope fractionation (DIF) and implementing different parameterizations of local transverse dispersion. The model reproduced previously published field data showing a negative carbon isotope pattern (-2 ‰) at the fringes of a nondegrading PCE plume. We extended the study to reactive transport scenarios considering vinyl chloride as a model compound and assessing, through a detailed sensitivity analysis, the coupled effects of transverse hydrodynamic dispersion (with and without DIF) and aerobic fringe degradation on the evolution of carbon and chloride isotope ratios. Transformation-induced positive isotope signals were increasingly attenuated with distance from the source and higher degradation rate. The effect of DIF on the overall isotope signal attenuation was greatest near the source and for low values of groundwater flow velocity, transverse dispersion coefficient, molecular weight, rate constant, and isotope fractionation factor, α, of the degradation reaction. Models disregarding DIF underestimate the actual α. The approximately twice larger DIF effect for chlorine than for carbon together with the low α for oxidation resulted in strong chlorine CSIA depletions for VC at the plume fringe.

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Section: Resultsmentioning

confidence: 99%

Transverse Hydrodynamic Dispersion Effects on Isotope Signals in Groundwater Chlorinated Solvents’ Plumes

Breukelen

Rolle

2012

Environ. Sci. Technol.

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“…Martienssen et al (2006) reported biodegradation of MTBE in an aquifer in Germany under what they termed “microaerobic” conditions (dissolved oxygen under 0.4 mg/L) that occurred naturally. Thornton et al (2011) discussed lab experiments with sediments from an MTBE-contaminated chalk aquifer in the UK which showed evidence of “ubiquitous potential for aerobic MTBE degradation in the aquifer”, concluding that significant aerobic MTBE biodegradation could occur under the low oxygen concentrations in the reactive fringes of such plumes.…”

Section: Biodegradation Of Mtbe and Tbamentioning

confidence: 99%

Role of back diffusion and biodegradation reactions in sustaining an MTBE/TBA plume in alluvial media

Rasa

Chapman

Bekins

et al. 2011

Journal of Contaminant Hydrology

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A methyl tert-butyl ether (MTBE) / tert-butyl alcohol (TBA) plume originating from a gasoline spill in late 1994 at Vandenberg Air Force Base (VAFB) persisted for over 15 years within 200 feet of the original spill source. The plume persisted until 2010 despite excavation of the tanks and piping within months after the spill and excavations of additional contaminated sediments from the source area in 2007 and 2008. The probable history of MTBE concentrations along the plume centerline at its source was estimated using a wide variety of available information, including published details about the original spill, excavations and monitoring by VAFB consultants, and our own research data. Two-dimensional reactive transport simulations of MTBE along the plume centerline were conducted for a 20-year period following the spill. These analyses suggest that MTBE diffused from the thin anaerobic aquifer into the adjacent anaerobic silts and transformed to TBA in both aquifer and silt layers. The model reproduces the observation that after 2004 TBA was the dominant solute, diffusing back out of the silts into the aquifer and sustaining plume concentrations much longer than would have been the case in the absence of such diffusive exchange. Simulations also suggest that aerobic degradation of MTBE or TBA at the water table in the overlying silt layer significantly affected concentrations of MTBE and TBA by limiting the chemical mass available for back diffusion to the aquifer.

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“…However, no significant δ 13 C fractionation was found in an onsite pilot reactor amended with groundwater and aerobic ETBE degraders (Fayolle-Guichard et al 2012 ). Similarly, no significant δ 13 C fractionation was found in MTBE at a field site with proven MTBE biodegradation potential using 14 C assays (Thornton et al 2011 ). 13 C CSIA also produced inconclusive results on MTBE biodegradation at another polluted field site (Lesser et al 2008 ).…”

Section: Isotopic Methods To Assess Anaerobic Biodegradation Of Etbe ...mentioning

confidence: 98%

“…Aerobic laboratory microcosms indicated that biodegradation of 90–99% of the initial MTBE concentration resulted in a 5.5 to 6.4 ± 0.2‰ enrichment of 13 C. The enrichment during aerobic treatment at the field site was only 25% of that found in the microcosm studies and did not deviate from the background noise in the data, although the decrease in MTBE concentration was similar (Lesser et al 2008 ). Possible explanations for these observations are mixing during sampling of the groundwater, or the simultaneous occurrence of different biodegradation mechanisms in situ (Lesser et al 2008 ; Thornton et al 2011 ). Including the analysis of oxygen isotopes may improve the sensitivity of CSIA analyses for the detection of MTBE, ETBE, or TBA degradation (Kendall and Caldwell 1998 ).…”

Section: Isotopic Methods To Assess Anaerobic Biodegradation Of Etbe ...mentioning

confidence: 99%

Potential of stable isotope analysis to deduce anaerobic biodegradation of ethyl tert-butyl ether (ETBE) and tert-butyl alcohol (TBA) in groundwater: a review

van der Waals,

Thornton,

Rolfe

et al. 2024

Environ Sci Pollut Res

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Understanding anaerobic biodegradation of ether oxygenates beyond MTBE in groundwater is important, given that it is replaced by ETBE as a gasoline additive in several regions. The lack of studies demonstrating anaerobic biodegradation of ETBE, and its product TBA, reflects the relative resistance of ethers and alcohols with a tertiary carbon atom to enzymatic attack under anoxic conditions. Anaerobic ETBE- or TBA-degrading microorganisms have not been characterized. Only one field study suggested anaerobic ETBE biodegradation. Anaerobic (co)metabolism of ETBE or TBA was reported in anoxic microcosms, indicating their biodegradation potential in anoxic groundwater systems. Non-isotopic methods, such as the detection of contaminant loss, metabolites, or ETBE- and TBA-degrading bacteria are not sufficiently sensitive to track anaerobic biodegradation in situ. Compound- and position-specific stable isotope analysis provides a means to study MTBE biodegradation, but isotopic fractionation of ETBE has only been studied with a few aerobic bacteria (εC −0.7 to −1.7‰, εH −11 to −73‰) and at one anoxic field site (δ2H-ETBE +14‰). Similarly, stable carbon isotope enrichment (δ13C-TBA +6.5‰) indicated TBA biodegradation at an anoxic field site. CSIA and PSIA are promising methods to detect anaerobic ETBE and TBA biodegradation but need to be investigated further to assess their full potential at field scale. Graphical abstract

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Assessment of MTBE biodegradation in contaminated groundwater using 13C and 14C analysis: Field and laboratory microcosm studies

Cited by 14 publications

References 45 publications

Transverse Hydrodynamic Dispersion Effects on Isotope Signals in Groundwater Chlorinated Solvents’ Plumes

Transverse Hydrodynamic Dispersion Effects on Isotope Signals in Groundwater Chlorinated Solvents’ Plumes

Role of back diffusion and biodegradation reactions in sustaining an MTBE/TBA plume in alluvial media

Potential of stable isotope analysis to deduce anaerobic biodegradation of ethyl tert-butyl ether (ETBE) and tert-butyl alcohol (TBA) in groundwater: a review

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