Start |Author Index | View Uploaded Presentations | Meeting Information

2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 12
Presentation Time: 11:15 AM

Tert-Butyl Alcohol (TBA) Production from MTBE Plumes Under Sulfate Reducing Conditions Under the Influence of Ethanol


CHAKRABORTY, Irina, Land, Air & Water Resources, University of California - Davis, 1 Shields Ave, Davis, CA 95616, MACKAY, Douglas M., Land, Air, and Water Resources, University of California Davis, One Shields Avenue, Davis, CA 95616-8627, SCOW, Kate M., Land, Air & Water Resources, University of California - Davis, Davis, CA 95616 and SUBLETTE, Kerry, Center for Applied Biogeosciences, Department of Chemical Engineering, University of Tulsa, 600 South College Avenue, Tulsa, OK 74104, ior@ucdavis.edu

Tert-butyl alcohol (TBA) is an increasingly important contaminant at leaking underground storage tank (LUST) sites. In existing methyl tert-butyl ether (MTBE) plumes, incomplete degradation of MTBE under anaerobic conditions results in the production of TBA. An important question is whether there is significant anaerobic degradation of TBA under sulfate reducing conditions, the electron accepting process driving most degradation in fuel contaminated aquifers. We present results of long term experiments in a confined sulfate-reducing aquifer at Vandenberg Air Force Base (VAFB), where we have investigated the effect of ethanol, a recently introduced fuel additive, hypothesized to stimulate conversion of existing MTBE plumes to TBA.

Deployment of 13C-labeled biotraps at the site suggested the presence of sulfate-reducing, TBA-degrading microbes, yet there was no clear macroscopic evidence from plume monitoring that TBA was biodegraded under sulfate reducing conditions at a practically significant rate. Microcosms of site material amended with TBA and incubated under anaerobic conditions indicated that high concentrations (~1,000 ppm) of TBA were degraded under sulfate reducing and methanogenic conditions; however, results for more environmentally relevant concentrations (~1 ppm) were inconclusive.

Field measurements of changes in population densities of bacteria and archaea following ethanol and MTBE injection indicated increases in numbers of both groups. Bacterial communities, as represented by terminal restriction fragment length polymorphism (TRFLP) fingerprints, remained distinct in the portion of the aquifer downstream of the injection zone. Our results suggest that TBA, MTBE and ethanol-induced methane concentrations are strong determinants of the composition of the indigenous microbial community that develops during MTBE transformation. Some of the changes in microbial communities induced by ethanol may be long lasting, thus potentially altering the natural attenuation capacity of the impacted aquifer.

Session No. 241

T152. In Situ Approaches for Measuring Biodegradation Potential and Rates in Subsurface Environments
Tuesday, 7 October 2008: 8:00 AM-12:00 PM
Geological Society of America Abstracts with Programs. Vol. 40, No. 6, p.344
© Copyright 2008 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
Back to: T152. In Situ Approaches for Measuring Biodegradation Potential and Rates in Subsurface Environments
<< Previous Abstract | Next Abstract >>