HR: 0800h
AN: B31A-0983    [Abstracts]
TI: Constraining Rates of Biodegradation of Chlorinated Ethenes at Steep Concentration Gradients Using Stable Carbon Isotopes
AU: * Morrill, P L
EM: p.morrill@gl.ciw.edu
AF: The Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Rd., N.W. , Washington, DC 20015 United States
AU: Seepersad, D J
EM: david.seepersad@utoronto.ca
AF: University of Toronto, 22 Russell st., Toronto, Ont M5S 3B1 Canada
AU: Lacrampe-Couloume, G
EM: glc@zircon.geology.utoronto.ca
AF: University of Toronto, 22 Russell st., Toronto, Ont M5S 3B1 Canada
AU: Edwards, E A
EM: edwards@chem-eng.utoronto.ca
AF: University of Toronto, 22 Russell st., Toronto, Ont M5S 3B1 Canada
AU: Sleep, B E
EM: sleep@civ.utoronto.ca
AF: University of Toronto, 22 Russell st., Toronto, Ont M5S 3B1 Canada
AU: McMaster, M L
EM: MMcMaster@GeoSyntec.com
AF: Geosyntec Consultants, 130 Research Lane, Guelph, On N1G 5G3 Canada
AU: Major, D W
EM: dmajor@geosyntec.com
AF: Geosyntec Consultants, 130 Research Lane, Guelph, On N1G 5G3 Canada
AU: Sherwood Lollar, B
EM: bslollar@chem.utoronto.ca
AF: University of Toronto, 22 Russell st., Toronto, Ont M5S 3B1 Canada
AB: Enhanced biodegradation of emplaced dense non-aqueous phase liquid (DNAPL) sources of tetrachloroethene (PCE) was monitored in a 2-dimensional model aquifer and in a Dover Air Force Base pilot field study. The stable carbon isotope values of PCE and its biodegradation products were monitored along steep concentration gradients near the PCE source zones to quantify first order biodegradation rate constants during a study that assessed the potential for biological enhancement of PCE DNAPL dissolution . Stable carbon isotope measurements are an ideal tool to assess the relative rate of biodegradation versus dissolution since while biodegradation of chlorinated ethenes involves a substantial carbon isotope fractionation, dissolution of chlorinated ethenes is a largely non-fractionating process. Within the dissolved plumes that developed down gradient from the emplaced sources, the isotopic fractionation of PCE and its degradation products in both the model aquifer and field study were consistent with those previously observed in batch laboratory studies. A maximum isotope fractionation of 2.3 permil was observed in the dissolved PCE downgradient, while close to the source zone the carbon isotopic signature of the dissolved PCE remained largely unchanged, due to the continuing dissolution of unfractionated PCE DNAPL. Significant carbon isotopic fractionation was observed adjacent to and/or downstream from the source in the degradation products trichloroethene (TCE), 1,2-dichloroethene (cDCE), and vinyl chloride (VC). Therefore, close to the source zone, confirmation of PCE degradation is based primarily on the appearance of the lesser chlorinated ethene degradation products and isotopic signatures of those products consistent with biodegradation. This trend was observed on a small scale in the model aquifer and similar trends were observed in the field at a larger scale. In both cases biodegradation was correlated with enhanced rates of DNAPL dissolution compared to non-dechlorinating controls.
DE: 0418 Bioremediation
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Biogeosciences [B]
MN: Fall Meeting 2005