Towards organic carbon isotope records from stalagmites: coupled δ13C and 14C analysis using wet chemical oxidation

Lechleitner, F. A., Lang, S. Q., Haghipour, N., McIntyre, C. , Baldini, J. U.L., Prufer, K. M. and Eglinton, T. I. (2019) Towards organic carbon isotope records from stalagmites: coupled δ13C and 14C analysis using wet chemical oxidation. Radiocarbon, 61(03), pp. 749-764. (doi:10.1017/RDC.2019.35)

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Abstract

Speleothem organic matter can be a powerful tracer for past environmental conditions and karst processes. Carbon isotope measurements (δ13C and 14C) in particular can provide crucial information on the provenance and age of speleothem organic matter, but are challenging due to low concentrations of organic matter in stalagmites. Here, we present a method development study on extraction and isotopic characterization of speleothem organic matter using a rapid procedure with low laboratory contamination risk. An extensive blank assessment allowed us to quantify possible sources of contamination through the entire method. Although blank contamination is consistently low (1.7 ± 0.34 – 4.3 ± 0.86 μg C for the entire procedure), incomplete sample decarbonation poses a still unresolved problem of the method, but can be detected when considering both δ13C and 14C values. We test the method on five stalagmites, showing reproducible results on samples as small as 7 μg C for δ13C and 20 μg C for 14C. Furthermore, we find consistently lower non-purgeable organic carbon (NPOC) 14C values compared to the carbonate 14C over the bomb spike interval in two stalagmites from Yok Balum Cave, Belize, suggesting overprint of a pre-aged or even fossil source of carbon on the organic fraction incorporated by these stalagmites.

Item Type:Articles
Additional Information:This research was supported by the European Research Council grant 240167grant to JULB, and by Swiss National Science Foundation grant P2EZP2_172213 to FAL.Field collection was supported additionally by the National Science Foundation (grantHSD 0827305) and the Alphawood Foundation.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Mcintyre, Dr Cameron
Authors: Lechleitner, F. A., Lang, S. Q., Haghipour, N., McIntyre, C., Baldini, J. U.L., Prufer, K. M., and Eglinton, T. I.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Radiocarbon
Publisher:Cambridge University Press
ISSN:0033-8222
ISSN (Online):1945-5755
Published Online:23 April 2019
Copyright Holders:Copyright © 2019 by the Arizona Board of Regents on behalf of the University of Arizona
First Published:First published in Radiocarbon 61(3):749-764
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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