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Impacts of an ethanol-blended fuel release on groundwater and fate of produced methane: simulation of field observations

Water Resources Research

By:
, , , , , , , and
DOI: 10.1002/wrcr.20382

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Abstract

In a field experiment at Vandenberg Air Force Base (VAFB) designed to mimic the impact of a small-volume release of E10 (10% ethanol and 90% conventional gasoline), two plumes were created by injecting extracted groundwater spiked with benzene, toluene, and o-xylene, abbreviated BToX (No-Ethanol Lane) and BToX plus ethanol (With-Ethanol Lane) for 283 days. We developed a reactive transport model to understand processes controlling the fate of ethanol and BToX. The model was calibrated to the extensive field dataset and accounted for concentrations of sulfate, iron, acetate, and methane along with iron-reducing bacteria, sulfate-reducing bacteria, fermentative bacteria, and methanogenic archaea. The benzene plume was about 4.5 times longer in the With-Ethanol Lane than in the No-Ethanol Lane. Matching this different behavior in the two lanes required inhibiting benzene degradation in the presence of ethanol. Inclusion of iron reduction with negligible growth of iron-reducers was required to reproduce the observed constant degradation rate of benzene. Modeling suggested that vertical dispersion and diffusion of sulfate from an adjacent aquitard were important sources of sulfate in the aquifer. Matching of methane data required incorporating initial fermentation of ethanol to acetate, methane loss by outgassing, and methane oxidation coupled to sulfate and iron reduction. Simulation of microbial growth using dual Monod kinetics, and including inhibition by more favorable electron acceptors, generally resulted in reasonable yields for microbial growth of 0.01-0.05.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Impacts of an ethanol-blended fuel release on groundwater and fate of produced methane: simulation of field observations
Series title:
Water Resources Research
DOI:
10.1002/wrcr.20382
Volume
49
Issue:
8
Year Published:
2013
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
National Research Program - Western Branch
Description:
20 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Water Resources Research
First page:
4907
Last page:
4926
Country:
United States
State:
California
Other Geospatial:
Vandenberg Air Force Base