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| Titel |
Extraneous carbon assessment in ultra-microscale radiocarbon analysis using benzene polycarboxylic acids (BPCA) |
| VerfasserIn |
Ulrich M. Hanke, Cameron P. McIntyre, Michael W. I. Schmidt, Lukas Wacker, Timothy I. Eglinton |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127304
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| Publikation (Nr.) |
 EGU/EGU2016-7167.pdf |
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| Zusammenfassung |
| Measurements of the natural abundance of radiocarbon (14C) concentrations in inorganic and
organic carbon-containing materials can be used to investigate their date of origin.
Particularly, the biogeochemical cycling of specific compounds in the environment may be
investigated applying molecular marker analyses. However, the isolation of specific
molecules from environmental matrices requires a complex processing procedure resulting in
small sample sizes that often contain less than 30 μg C. Such small samples are sensitive to
extraneous carbon (Cex) that is introduced during the purification of the compounds (Shah
and Pearson, 2007).
We present a thorough radiocarbon blank assessment for benzene polycarboxylic acids
(BPCA), a proxy for combustion products that are formed during the oxidative
degradation of condensed polyaromatic structures (Wiedemeier et al, in press).
The extraneous carbon assessment includes reference material for (1) chemical
extraction, (2) preparative liquid chromatography (3) wet chemical oxidation which are
subsequently measured with gas ion source AMS (Accelerator Mass Spectrometer,
5-100 μg C). We always use pairs of reference materials, radiocarbon depleted
(14Cfossil) and modern (14Cmodern) to determine the fraction modern (F14C) of Cex.Our
results include detailed information about the quantification of Cex in radiocarbon
molecular marker analysis using BPCA. Error propagation calculations indicate that
ultra-microscale samples (20-30 μg) are feasible with uncertainties of less than
10 %. Calculations of the constant contamination reveal important information
about the source (F14C) and mass (μg) of Cex (Wacker and Christl, 2011) for each
sub procedure. An external correction of compound specific radiocarbon data is
essential for robust results that allow for a high degree of confidence in the 14C
results.
References
Shah and Pearson, 2007. Ultra-microscale (5-25μg C) analysis of individual lipids by 14C
AMS: Assessment and correction for sample processing blanks. Radiocarbon 49(1),
69-82.
Wacker, L. and M. Christl. 2011. Data reduction for small radiocarbon samples – error
propagation using the model of constant contamination. Ion Beam Physics, ETH Zurich,
Annual report 2011.
Wiedemeier, D.B., S.Q. Lang, M. Gierga, S. Abiven, S.M. Bernasconi, G.L.
Bernasconi-Green, I. Hajdas, U.M. Hanke, M.D. Hilf, C.P. McIntyre, M.P.W. Schneider, R.H.
Smittenberg, L. Wacker, G.L.B. Wiesenberg, M.W.I. Schmidt. Characterization,
quantification and compound-specific isotopic analysis of pyrogenic carbon using
benzene polycarboxylic acids (BPCA). Journal of Visualized Experiments. In press. |
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