HR: 0800h
AN: B21D-0914    [Abstracts]
TI: Identification of Biologically-Produced Organic Matter in an Aquifer System using Stable Isotope Labeling
AU: * Kujawinski, E B
EM: ekujawinski@whoi.edu
AF: Dept. of Marine Chemistry & Geochemistry; Woods Hole Oceanographic Institution, 360 Woods Hole Rd. MS #25, Woods Hole, MA 02543 United States
AU: Mailloux, B J
EM: bjm2103@columbia.edu
AF: Columbia Earth Insitute, 535 W. 116th Street, New York, NY 10027 United States
AU: Morrison, L
EM: lmorrison@whoi.edu
AF: Dept. of Marine Chemistry & Geochemistry; Woods Hole Oceanographic Institution, 360 Woods Hole Rd. MS #25, Woods Hole, MA 02543 United States
AB: The carbon cycle in aquifer systems is poorly understood. In particular, the role of prokaryotic and eukaryotic microbes in the cycling of organic matter (OM) has not been well documented. The goal of this work was to utilize stable isotopes in combination with geochemical and microbial methods to study microbially-mediated OM transformations in aquifers and aquifer sediments. A laboratory flow-through column experiment was conducted with sediment collected from a pristine, shallow, coastal plain aquifer. The groundwater medium was amended with low levels of an isotopically labeled nutrient, 13C-acetate. At pre-determined time points, organic matter (OM) was isolated from the sediment and groundwater. OM components were analyzed by isotope-ratio GC-MS and electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The incorporation of 13C was examined for both the aqueous phase and sediment bound OM. Analyzing both dissolved and adsorbed fractions enabled us to determine the relative importance of each on microbe-mediated OM transformations. The incorporation of 13C allowed us to estimate residence times of different organic matter fractions and to answer fundamental questions about organic matter lability in the subsurface environment.
DE: 4805 Biogeochemical cycles (1615)
DE: 4806 Carbon cycling
DE: 4815 Ecosystems, structure and dynamics
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting