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Total Uncertainty of Radiocarbon Measurements of Marine Dissolved Organic Carbon and Methodological Recommendations

Published online by Cambridge University Press:  09 February 2016

Ellen R M Druffel ,
Sheila Griffin ,
Brett D Walker ,
Alysha I Coppola  and
Danielle S Glynn
Ellen R M Druffel*
Affiliation:
Department of Earth System Science, University of California Irvine, Irvine, California 92697-3100, USA
Sheila Griffin
Affiliation:
Department of Earth System Science, University of California Irvine, Irvine, California 92697-3100, USA
Brett D Walker
Affiliation:
Department of Earth System Science, University of California Irvine, Irvine, California 92697-3100, USA
Alysha I Coppola
Affiliation:
Department of Earth System Science, University of California Irvine, Irvine, California 92697-3100, USA
Danielle S Glynn
Affiliation:
Department of Earth System Science, University of California Irvine, Irvine, California 92697-3100, USA
*
1Corresponding author. Email: [email protected].
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Abstract

We report results of duplicate measurements of dissolved organic carbon concentrations ([DOC] as μM) and Δ14C in seawater in order to assess the total uncertainty of reported [DOC] and Δ14C measurements via the UV oxidation method. In addition, pure International Atomic Energy Agency standards analyzed over a 4-yr period are evaluated. We find the total uncertainty of Δ14C measurements to be ±4.0. However, in samples that were thawed, subsampled, and refrozen prior to UV oxidation, the total uncertainty of Δ14C measurements is on the order of ±10. The [DOC] measurements of these samples were also higher by 1.8 ± 0.3 μM. The reason(s) for these documented increases in total [DOC] and Δ14C uncertainty are unclear. In order to minimize any effects on sample measurements, we recommend the following: 1) regular monitoring of duplicate samples, DOC standards, and diluent (Milli-Q™) water for Δ14C and [DOC] measurements; 2) thawing a sample immediately and only once prior to UV oxidation; 3) avoid the use of DOC-leachable plumbing (such as PVC pipe) in both water systems feeding and within Milli-Q systems; and 4) consider the use of DOC-free diluents (i.e. pre-UV oxidized Milli-Q or sample water).

Type
Radiocarbon Reservoir Effects
Information
Radiocarbon , Volume 55 , Issue 3: Proceedings of the 21st International Radiocarbon Conference (Part 2 of 2) , 2013 , pp. 1135 - 1141
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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