Preferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning

Yu, J. and Elderfield, H. and Greaves, M. J. and Day, J. (2007) Preferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning. G3 Geochemistry Geophysics Geosystems, 8. Q06016. DOI 10.1029/2006GC001571

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Abstract

We have investigated the effect of cleaning procedures on eight element/Ca ratios in three widely used benthic foraminifera species from core top and down core sediments. Two cleaning techniques were employed: (1) comparison between “Mg-cleaning” and “Cd-cleaning” methods and (2) comparison between the various constituent reagents. Li/Ca, B/Ca, and Sr/Ca ratios remained unchanged for samples subjected to different treatments, but Mg/Ca, Mn/Ca, Zn/Ca, Cd/Ca, and U/Ca were substantially decreased when foraminifera shells were cleaned with reagents containing citrate. In contrast, no significant decreases in element/Ca ratios were observed for samples cleaned in N2H4 without citrate, indicating that the role of N2H4 was insignificant during reductive cleaning and that citrate is responsible for decreases of Mg/Ca, Mn/Ca, Zn/Ca, Cd/Ca, and U/Ca. Decreases in these ratios are most likely due to (1) removal of contaminant particles enriched in Mg, Mn, Zn, Cd and U and/or (2) preferential leaching of CaCO3 by the formation of stable metal complexes through chelation between citrate and metals heterogeneously distributed in foraminiferal shells. Due to the negligible effect of N2H4 and preferential dissolution of CaCO3 during reductive cleaning, it is suggested that the reductive cleaning step should be omitted and the “Mg-cleaning” method [Barker et al., 2003] could be employed to clean foraminiferal shells for trace element measurements.

Item Type: Article
Uncontrolled Keywords: 2007 AREP IA54 2007 P
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: G3 Geochemistry Geophysics Geosystems
Volume: 8
Page Range: Q06016
Identification Number: 10.1029/2006GC001571
Depositing User: Sarah Humbert
Date Deposited: 16 Feb 2009 13:04
Last Modified: 23 Jul 2013 09:54
URI: http://eprints.esc.cam.ac.uk/id/eprint/823

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