PARENT SESSION

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

(MOP/32) In Situ Transformation of Deuterated Toluene, Xylene, and Ethylbenzene to Benzylsuccinate Analogs in BTEX-Contaminated Aquifers.

Field, Jennifer¹, Reusser, Dominik², Alumbaugh, Robert¹, Beller, Harry³, Istok, Jonathan¹, ¹ Oregon State University, Corvallis, Oregon, U.S.A.² University of Osnabruck, Osnabruck, Germany, Germany³ Lawrence Livermore National Laboratory, Livermore, California, U.S.A.

ABSTRACT- Techniques for detecting and quantifying anaerobic transformations of benzene, toluene, ethylbenzene, and xylenes (BTEX) are needed to assess the feasibility of using in situ bioremediation to remediate BTEX-contaminated groundwater aquifers. Deuterated surrogates of toluene, o-xylene or m-xylene, and ethylbenzene were injected into two BTEX-contaminated aquifers during single-well push-pull tests. The formation of deuterated benzylsuccinate (BSA), methylbenzylsuccinate (methyl-BSA), and ethybenzylsuccinate (ethyl-BSA), which are unambiguous metabolites arising from anaerobic toluene, xylenes, and ethylbenzene transformation, were monitored in order to determine in situ transformation rates. In the first set of tests, test solutions (250 L) containing toluene-d8 (9 - 22 micromolar), o-xylene-d10 (4 - 9 micromolar, a conservative bromide tracer (1.3 millimolar), and nitrate (4 millimolar) were injected into wells at two BTEX-contaminated field sites near Portland, Oregon and Kansas City, Missouri. Detection of deuterated BSA-d8 and o-methyl-BSA-d10 in groundwater samples collected from the injection well unequivocally demonstrated in situ anaerobic toluene-d8 and o-xylene-d10 transformation with calculated zero-order formation rates ranging from 1.0 to 7.4 nanomoles/day. Concurrent utilization of co-injected nitrate was rapid in all tests at both sites with zero-order rates ranging from 13 to 39 micromoles/hr. Results from a second round of push-pull tests at the Portland site (currently in progress) will be discussed in which (ring-labeled) toluene-d5 and ethylbenzene-d5 were injected along with perdeuterated m-xylene. The field tests conducted in this study represent the first reported use of deuterated aromatic hydrocarbons to detect and quantify anaerobic BTEX transformation product formation in the subsurface.

Key words: BTEX, anaerobic biodegradation, groundwater