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UV Photochemical Oxidation and Extraction of Marine Dissolved Organic Carbon at UC Irvine: Status, Surprises, and Methodological Recommendations

Published online by Cambridge University Press:  15 April 2019

Brett D Walker Open the ORCID record for Brett D Walker [Opens in a new window] ,
Steven R Beaupré ,
Sheila Griffin  and
Ellen R M Druffel
Brett D Walker*
Affiliation:
Department of Earth and Environmental Sciences, University of Ottawa, Ottawa, ON K1N 6N5, Canada Department of Earth System Science, University of California Irvine, CA 92697-3100, USA
Steven R Beaupré
Affiliation:
School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA
Sheila Griffin
Affiliation:
Department of Earth System Science, University of California Irvine, CA 92697-3100, USA
Ellen R M Druffel
Affiliation:
Department of Earth System Science, University of California Irvine, CA 92697-3100, USA
*
*Corresponding author. Email: brett.walker@uottawa.ca.
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Abstract

The first ultraviolet photochemical oxidation (UVox) extraction method for marine dissolved organic carbon (DOC) as CO2 gas was established by Armstrong and co-workers in 1966. Subsequent refinement of the UVox technique has co-evolved with the need for high-precision isotopic (Δ14C, δ13C) analysis and smaller sample size requirements for accelerator mass spectrometry radiocarbon (AMS 14C) measurements. The UVox line at UC Irvine was established in 2004 and the system reaction kinetics and efficiency for isolating seawater DOC rigorously tested for quantitative isolation of ∼1 mg C for AMS 14C measurements. Since then, improvements have been made to sampling, storage, and UVox methods to increase overall efficiency. We discuss our progress, and key UVox system parameters for optimizing precision, accuracy, and efficiency, including (1) ocean to reactor: filtration, storage and preparation of DOC samples, (2) cryogenic trap design, efficiency and quantification of CO2 break through, and (3) use of isotopic standards, blanks and small sample graphitization techniques for the correction of DOC concentrations and Fm values with propagated uncertainties. New DOC UVox systems are in use at many institutions. However, rigorous assessment of quantitative UVox DOC yields and blank contributions, DOC concentrations and carbon isotopic values need to be made. We highlight the need for a community-wide inter-comparison study.

Keywords

dissolved organic carbonphotochemical oxidationradiocarbon datingseawaterstable isotopeUV
Type
Conference Paper
Information
Radiocarbon , Volume 61 , Issue 5: Radiocarbon 2018 Conference Proceedings Trondheim, Norway, June 17–22, 2018 Part 1 of 2 , October 2019 , pp. 1603 - 1617
Copyright
© 2019 by the Arizona Board of Regents on behalf of the University of Arizona 

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Footnotes

Selected Papers from the 23rd International Radiocarbon Conference, Trondheim, Norway, 17–22 June, 2018

References

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