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Storage and Hydrolysis of Seawater Samples for Inorganic Carbon Isotope Analysis

Published online by Cambridge University Press:  09 February 2016

Charlotte L Bryant*
Affiliation:
NERC Radiocarbon Facility, Scottish Universities Environmental Research Centre (SUERC), Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride G75 0QF, United Kingdom
Sian F Henley
Affiliation:
School of Geosciences, King's Buildings, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, United Kingdom
Callum Murray
Affiliation:
NERC Radiocarbon Facility, Scottish Universities Environmental Research Centre (SUERC), Scottish Enterprise Technology Park, Rankine Avenue, East Kilbride G75 0QF, United Kingdom
Raja S Ganeshram
Affiliation:
School of Geosciences, King's Buildings, University of Edinburgh, West Mains Road, Edinburgh EH9 3JW, United Kingdom
Richard Shanks
Affiliation:
AMS Laboratory, SUERC, Rankine Avenue, East Kilbride G75 0QF, United Kingdom
*
2Corresponding author. Email: charlotte.bryant@glasgow.ac.uk.

Abstract

Preservation of seawater samples was tested for total inorganic carbon (∑CO2), stable carbon isotope (δ13C), and radiocarbon (14C) applications using foil bags and storage by refrigeration and freezing. The aim was to preserve representative samples with minimal storage effects but without using toxic methods such as mercuric chloride poisoning. Hydrolysis of samples to CO2 was based on existing methods. Results of IAEA-C2 standard used with deionized water stored in the foil bags showed complete reaction yields, 14C results within 2σ of the consensus value, and δ13C that were internally consistent, indicating that there were no procedural effects associated with the foil bags. 14C results were statistically indistinguishable across the storage times, for frozen and refrigerated seawater samples from a coastal site, Elie Ness, Fife, UK. The scatter of ∑CO2 concentrations and δ13C was within scatter observed in other studies for lake- and seawater samples preserved by acidification or using mercuric chloride. However, both ∑CO2 and δ13C were less variable for frozen samples compared with refrigerated samples. The foil bags are lighter, safer to transport, and similar in cost to glass bottles and allow sample collection in the field and transfer to the hydrolysis vessel without exposure of the sample to atmosphere. Storage of seawater samples in the foil bags was considered a reliable, alternative method to poisoning for ∑CO2, δ13C, and 14C, and freezing the samples is recommended for storage time beyond a week.

Type
Articles
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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