Thumbnail Image

Transition metal availability to speleothems controlled by organic binding ligands

Speleothems are important archives of Quaternary palaeoclimate. However, climate proxies based on trace elements in speleothems are currently limited to the metals which exhibit simple partitioning (Mg²⁺, Sr²⁺, Ba²⁺). This study aims to expand understanding of the processes controlling the divalent first row transition metals (M²⁺) in these systems. Adsorptive cathodic stripping voltammetry was used to determine Cu speciation in speleothem dripwater, stream and pool samples from five limestone caves located in diverse climatic settings. Our results demonstrate that Cu binding and stabilisation by organic ligands (L) is a universal property of cave waters, which decreases the available Cu concentration ([Cu’]) by ~5 orders of magnitude relative to total Cu concentration ([CuT]). Furthermore, [Cu’] does not change meaningfully with increases in either [CuT] or [L], meaning that Cu²⁺ substitution in Ca²⁺ valence sites in precipitating CaCO₃ speleothems is likely to be inhibited by organic complexation. We suggest that the residence time of speleothem thin water films (1/drip rate), the dissociation rates of labile metal-organic complexes, and the stability of adsorbed (ternary) metal-organic complexes will determine M²⁺ incorporation in speleothems.
Journal Article
Type of thesis
Hartland, A., & Zitoun, R. (2018). Transition metal availability to speleothems controlled by organic binding ligands. Geochemical Perspectives Letters, 8, 22–25. https://doi.org/10.7185/geochemlet.1824
European Association of Geochemistry
This work is distributed under the Creative Commons Attribution Non-Commercial No-Derivatives 4.0 License, which permits unrestricted distribution provided the original author and source are credited. The material may not be adapted (remixed, transformed or built upon) or used for commercial purposes without written permission from the author. Additional information is available at http://www.geochemicalperspectivesletters.org/ copyright-and-permissions.