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Influence of Different Acid Treatments on the Radiocarbon Content Spectrum of Sedimentary Organic Matter Determined by RPO/Accelerator Mass Spectrometry

Published online by Cambridge University Press:  13 November 2018

Rui Bao*
Affiliation:
Geological Institute, ETH Zurich, Zurich, Switzerland National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole Oceanographic Institution, Woods Hole, MA, USA Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
Ann P McNichol
Affiliation:
National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
Jordon D Hemingway
Affiliation:
Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA MIT/WHOI, Joint Program in Oceanography/Applied Ocean Science and Engineering, Cambridge, MA, USA Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
Mary C Lardie Gaylord
Affiliation:
National Ocean Sciences Accelerator Mass Spectrometry Facility, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
Timothy I Eglinton
Affiliation:
Geological Institute, ETH Zurich, Zurich, Switzerland Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
*
*Corresponding author. Email: rui.bao@erdw.ethz.ch.

Abstract

In practice, obtaining radiocarbon (14C) composition of organic matter (OM) in sediments requires first removing inorganic carbon (IC) by acid-treatment. Two common treatments are acid rinsing and fumigation. Resulting 14C content obtained by different methods can differ, but underlying causes of these differences remain elusive. To assess the influence of different acid-treatments on 14C content of sedimentary OM, we examine the variability in 14C content for a range of marine and river sediments. By comparing results for unacidified and acidified sediments [HCl rinsing (RinseHCl) and HCl fumigation (FumeHCl)], we demonstrate that the two acid-treatments can affect 14C content differentially. Our findings suggest that, for low-carbonate samples, RinseHCl affects the Fm values due to loss of young labile organic carbon (OC). FumeHCl makes the Fm values for labile OC decrease, leaving the residual OC older. High-carbonate samples can lose relatively old organic components during RinseHCl, causing the Fm values of remaining OC to increase. FumeHCl can remove thermally labile, usually young, OC and reduce the Fm values. We suggest three factors should be taken into account when using acid to remove carbonate from sediments: IC abundance, proportions of labile and refractory OC, and environmental matrix.

Information

Type
Research Article
Copyright
© 2018 by the Arizona Board of Regents on behalf of the University of Arizona 

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