Publication Date:
2022-05-25
Description:
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Organic Geochemistry 38 (2007):1824-1837, doi:10.1016/j.orggeochem.2007.07.008.
Description:
We have investigated the relationships between radiocarbon (14C) and stable
carbon (13C) isotopic composition and the different modes of binding of organic matter
(OM) present in surficial sediments from near-shore and continental margin sites that
vary in terms of input and depositional conditions. To improve our understanding of the
entire OM pool, isotopic analysis of sedimentary sub-fractions, as opposed to individual
compounds, was performed. This was achieved by sequentially treating sediments by
solvent extraction to examine unbound compounds, followed by saponification to
cleave ester linked moieties. Isotopic analysis was then performed on the bulk sediment
and resulting residues. The molecular composition of the extracts was examined using
gas chromatography/mass spectrometry (GC/MS), and the relative contributions of
terrestrial and marine biomarkers were assessed. Radiocarbon abundances (Δ14C) of the
bulk sediment reflect a mixture of modern, pre-aged and fossil carbon. Offsets in Δ14C
between the bulk sediment and sediment residues demonstrate varying associations of
these carbon pools. For the majority of sites, a negative offset between extracted (EX2
RES) and saponified (SA-RES) sediment 1 residues results from the removal of relatively
4C-rich material during saponification. Saponification extracts (SAEs) are mainly
composed of short chain (n-C12 to n-C24) alkanoic acids with an even/odd dominance
indicating a predominantly marine algal or microbial source. This provides evidence for
the protection of labile marine carbon by chemical binding. This study aims to bridge
the gap between molecular level and bulk OM analyses in marine sediments.
Description:
The work was supported by funds from the National Science Foundation
(CHE-0089172; OCE-0526268).
Keywords:
Radiocarbon
;
Stable carbon
;
Marine
;
Sediments
;
Biomarker
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/pdf
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