engleski

On the nature of dissolved copper ligands in the early buoyant plume of hydrothermal vents

The apparent speciation of Cu in the early buoyant plume of two black smokers (Aisics and Y3) from the hydrothermal vent field Lucky Strike (Mid-Atlantic Ridge) was investigated using competitive ligand exchangeadsorptive cathodic stripping voltammetry (CLE–AdCSV). We have assessed the apparent Cu-binding ligand concentration ([L]) and the corresponding conditional stability constant (log K0) for 24 samples. At the smoker Aisics, [L] ranged from 18.2 to 2970 nM. Log K0CuL ranged from 12.4 to 13.4. At Y3, the binding capacity of natural ligands was from 32.5 to 1020 nM, with Log K0CuL ranging from 12.5 to 13.1. Total dissolved Cu ranged from 7.0 to 770 nM and from 12.7 to 409 nM at Aisics and Y3, respectively. Our results show that the amount of ligand L increases with dissolved Mn (dMn) concentrations, suggesting a hydrothermal origin of the Cu-binding ligands detected. In addition, such high concentrations of Cu- binding ligands can only be explained by an additional abiotic source differing from organic processes. Based on the massive in situ concentrations of free sulfides (up to 300 mM) and on the striking similarities between our log K0CuL and the log K0Cu(HS) previously published, we infer that the Cu-binding ligands could be predominantly inorganic sulfur species in the early buoyant plume of the two vent sites studied.

copper ; speciation ; CLE-AdCSV ; hydrothermal vents ; organic ligands

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