PARENT SESSION

1B+C Abiotic Transformation
Hall 9
8:30 AM - 12:30 PM, Monday, 28 April 2003
Chair: Peijnenburg, W.¹, ¹
Co-chair: Jafvert, C.T.², Gombar, V.K.³, ^{2 3}

(MO9/5) Measuring Increases in Reductive-Dechlorination Rates Using Trichlorofluoroethene in TCE-Contaminated Groundwater.

Hageman, Kimberly¹, Semprini, Lew¹, Istok, Jonathan¹, Field, Jennifer¹, ¹ Oregon State University, Corvallis, Oregon, U.S.A.

ABSTRACT- Methods for measuring trichloroethene (TCE) reductive-dechlorination rates in TCE-contaminated aquifers are needed for the purpose of site characterization and to determine the potential for in situ bioremediation. Trichlorofluoroethene (TCFE) was selected as a surrogate for TCE for use in single well push-pull tests conducted in TCE-contaminated aquifers to determine the rates of in situ reductive dechlorination. Single well push-pull tests consist of injecting a test solution composed of substrates and conservative tracers into a groundwater well followed by extracting the test solution/groundwater mixture from the same well over time. Samples of the test solution/groundwater mixture are analyzed for the injected substrates and transformation products in order to construct breakthrough curves and to determine transformation rates. TCFE was selected because laboratory and field studies indicated that it undergoes reductive dechlorination in a manner analogous to TCE. For this field study, single well push-pull tests were conducted with TCFE in wells before and after successive additions of fumarate in order to determine if the additions of fumarate enhanced the in situ rates of reductive dechlorination. Initial TCFE reductive-dechlorination rates, prior to additions of fumarate, ranged from below detection to 0.21 micromoles/day. Fumarate reduction to succinate occurred in wells where TCFE reductive-dechlorination rates were highest and increased between initial and final fumarate injections. After fumarate additions, TCFE reductive-dechlorination rates increased 2.4 to 10 times. Furthermone, TCFE reductive dechlorination was observed in 2 wells that had previously shown no evidence of reductive dechlorination activity, which indicates that fumarate addition enhanced the in situ rates of reductive dechlorination.

Key words: groundwater, trichloroethene, reductive dechlorination