Slow coordination reactions in seawater

Journal Article · Wed Mar 01 04:00:00 EST 1989 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(89)90004-5· OSTI ID:5098070

Hering, J G; Morel, F M.M. ^[1]

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1. Massachusetts Institute of Technology, Cambridge (USA)

The rates of reaction of transition metals with free or protonated ligands are intrinsically fast. Yet the observed rate of formation of metal complexes with strong ligands in seawater containing a mixture of ligands is remarkably slow. When Cu(II) is added to mixtures of natural and synthetic ligands, the equilibrium distribution of metal species may be established only after hours, days, or even months. Initial reaction of the stronger ligand with the added metal is retarded in the presence of seawater concentrations of Ca. Thus Cu complexes are initially formed with the weaker ligands. Final equilibrium metal speciation is attained slowly through a series of ligand- and metal-exchange reactions. Observations of slow kinetics of coordination reactions in model systems demonstrate that re-equilibration of a natural system undergoing perturbations of metal or ligand concentrations, under natural or analytical conditions, cannot be assumed to be rapid. This study also suggests that the concentration of strong complexing agents in seawater may be underestimated in measurements of metal complexation that involve metal additions.

• OSTI ID: 5098070
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 53:3; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ACTIVATION ENERGY
CHELATING AGENTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
COPPER COMPLEXES
ENERGY
EQUILIBRIUM
GEOCHEMISTRY
HYDROGEN COMPOUNDS
KINETICS
LIGANDS
OXYGEN COMPOUNDS
REACTION KINETICS
SEAWATER
THERMODYNAMIC ACTIVITY
TRANSITION ELEMENT COMPLEXES
WATER