Trace element data of competitive ligand exchange experiments on water and soils from eight Aotearoa-New Zealand caves

Description

This dataset provides the underlying experimental data discussed in the manuscript "Characterising the decay of organic metal complexes in speleothem-forming cave waters" by Sebastian N. Höpker, Sebastian F. M. Breitenbach, Megan Grainger, Claudine H. Stirling, and Adam Hartland. The dataset is the basis for the kinetic characterisation of organic metal complex (OMC) dissociation rates in water samples (drips and cave streams) and soil extracts (1:10 weight:volume CaCl2 extraction) from eight cave systems in Aotearoa-New Zealand. The study aimed to explore the magnitude and variability of OMC stability in various karst systems to assess the role of OMC decay in determining speleothem (cave carbonate) trace metal concentrations. Kinetic experiments were conducted using competitive ligand exchange (CLE) with Chelex-100 resin as competing ligand. Cave water samples were spiked with 5 ppb of Co, Ni, Cu prior to analysis. Experiments were carried out at solution pH 8.5 and ca. 22 °C. Upon addition of Chelex-100, 11 aliquots were taken over the course of 2 hours via a syringe, and immediately filtered using 0.45 micron filters. Quantification of metal concentrations as reported here was carried out by inductively-coupled plasma mass spectrometry (ICP-MS). Most experiments clearly depict an exponential decrease in metal concentrations in the test solutions over time, reflecting the dissociation of OMCs present in the solution. The data were used to fit kinetic models and derive dissociation rate constants discussed in the manuscript.

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