HR: 14:25h
AN: B13G-04    [Abstracts]
TI: Temporal Dynamics of Terrestrial Organic Matter Transfer to the Ocean
AU: * Drenzek, N
EM: ndrenzek@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Eglinton, T
EM: teglinton@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Hughen, K
EM: khughen@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Montlucon, D
EM: dmontlucon@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Druffel, E
EM: edruffel@uci.edu
AF: Department of Earth System Science, University of California Irvine, Irvine, CA 92697, United States
AU: Southon, J
EM: jsouthon@uci.edu
AF: Department of Earth System Science, University of California Irvine, Irvine, CA 92697, United States
AU: dos Santos, G
EM: gdossant@uci.edu
AF: Department of Earth System Science, University of California Irvine, Irvine, CA 92697, United States
AU: Poussart, P
EM: poussart@princeton.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Schefuss, E
EM: schefuss@uni-bremen.de
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AU: Dickens, A
EM: dickens@mtholyoke.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, United States
AB: Little is known about the amount of time that elapses between the synthesis of terrestrial organic matter by vascular plants and its ultimate incorporation into marine sediments, yet this information is critical to investigations of terrigenous carbon export to the world's oceans. Although bulk radiocarbon analyses of dissolved and particulate phases yield important clues about the scale of such ‘terrestrial residence times', their interpretation is often complicated by the influence of potentially large and variable inputs from petrogenic or other non-vascular plant sources. In order to more fully resolve these components, we performed compound-specific radiocarbon and stable carbon analysis of several higher plant and petroleum biomarkers extracted from margin sediments adjacent to an array of river systems that vary in drainage basin size and relief, bedrock lithology, and climatic setting. A first- order relationship appears to exist between their radiocarbon age and latitude, implying a strong influence of temperature on the rate of organic matter cycling within, and export from, watersheds. Coupled molecular isotope mass balances further suggest that up to half of the total organic carbon preserved in some river-dominated margin sediments is ultimately weathered from ancient sedimentary rocks. In order to further apportion the temporal characteristics of the more active carbon pools, detailed down core Δ¹⁴C profiles of individual, vascular plant-derived fatty acids were constructed for anoxic marine basins located at both tropical and temperate latitudes and compared to the Δ¹⁴C evolution of atmospheric CO₂ in a simple, steady state modeling framework. Results indicate that the majority of these compounds were sequestered in various temporal reservoirs by several thousand ¹⁴C years before delivery to marine sediments, with the remaining inventory delayed for a far shorter time of only one or two decades. Moreover, the fraction of each fatty acid homologue passing through these ‘millennial' and ‘decadal' reservoirs systematically decreases at shorter chain length, possibly reflecting the influence of different molecular-level properties such as degradation rate and/or physiochemical sorption. The implications of these findings for climate and carbon cycle reconstructions will also be explored.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
DE: 1040 Radiogenic isotope geochemistry
DE: 1055 Organic and biogenic geochemistry
SC: Biogeosciences [B]
MN: 2007 Fall Meeting