HR: 0800h
AN: OS51C-1326    [Abstracts]
TI: Carbonate Removal from Sediment Samples for Elemental and Isotopic (\delta$^{13}$C and \Delta$^{14}$C) Analyses: Comparison of HCl Vapor and Sulfurous Acid
AU: * Komada, T
EM: tkomada@sfsu.edu
AF: Romberg Tiburon Center for Environmental Studies, San Francisco State University 3152 Paradise Drive, Tiburon, CA 94920 United States
AU: Xu, X
EM: xxu@uci.edu
AF: University of California Irvine, Department of Earth System Science, Irvine, CA 92697 United States
AU: Druffel, E R
EM: edruffel@uci.edu
AF: University of California Irvine, Department of Earth System Science, Irvine, CA 92697 United States
AB: Removal of carbonate minerals from environmental samples is critical for accurate determination of organic carbon (OC) content. Vaporous HCl and sulfurous acid (H$_{2}$SO$_{3}$) were compared as decarbonation agents for a series of particulate samples ranging from dolomitic shale to marine sediment. The performance of these acids was compared under two contexts: (1) for simultaneous determination of percent OC (%OC) and \delta$^{13}$C of OC using coupled elemental analyzer-isotope ratio mass spectrometry, and (2) for determination of \Delta$^{14}$C of OC using accelerator mass spectrometry (sealed-tube combustion followed by reduction to graphite). In case (1), HCl vapor and H$_{2}$SO$_{3}$ treatments both sufficiently removed carbonates from all samples tested. Percent OC and \delta$^{13}$C of OC obtained by these two methods were similar, although H$_{2}$SO$_{3}$ treatment may underestimate %OC due to sample loss. Overexposure to HCl vapor also resulted in significantly lower \delta$^{13}$C values depending on sample type. In case (2), it was possible to successfully decarbonate all samples using HCl vapor with minimal introduction of blank C. In contrast, effervescence made acidification by H$_{2}$SO$_{3}$ difficult when handling sample sizes required for accelerator mass spectrometry. Incomplete removal of S (as SO$_{2}$) may also pose negative effects on the graphitization process.
DE: 4825 Geochemistry
DE: 4894 Instruments and techniques
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting