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Personen: Kersten, Michael (Autor) 
Kulik, Dmitrii (Autor) 
Titel: Competitive scavenging of trace metals by HFO and HMO during Redox-driven early diagenesis of ferromanganese nodules : dedicated to Prof. Dr. Ulrich Förstner on his 65th birthday
Quelle: Journal of soils and sediments. Bd. 5. H. 1. Landsberg : Ecomed Publ. S. 37 - 47
Erscheinungsjahr:    2005
ISBN / ISSN: 1439-0108
URL der Originalveröffentlichung doi:10.1065/jss2005.02.130
Zeitschriftenaufsatz Zeitschriftenaufsatz
Sprache: Englisch
Open Access:
Person der Universität:    Kersten, Michael  In UnivIS suchen  
Einrichtung: Institut für Geowissenschaften
DDC-Sachgruppe:    Geowissenschaften
ID: 15425  Universitätsbibliothek Mainz
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Abstract: Background. Surface complexation models (SCM) alone have yet less successfully reproduced sorption isotherms of hydrous manganese oxides (HMO). This is in part due to the fact that the HMO structure may vary with pH, and also because microbially formed natural HMO has an oxidation number O/Mn < 2, i.e. is of non-stoichiometrical composition. The former effect has often led to severe artefacts, such as an underprediction of metal sequestration at low pH, and non-comparable pK and pH(ZPC) values in literature. The latter effect is of particular importance for environments of varying redox conditions like sediments. Objectives. We propose therefore a new sorption model comprising of amphoteric site SCM, ion exchange due to permanent charge compensation, and solid solution formation, in order to comply at least in part with the redox complexity of HMO phases of stable birnessite- and buserite-type structures. Methods. The model is run by a new Gibbs energy minimization code which is shown to be particularly suitable for such a sorption continuum approach. Results and Discussion. Initial calibration of the model was performed by experimental literature data on simple laboratory systems. Thus parameterised, we simulated on the basis of available field data the effect of redox-driven dissolution of a ferromanganese nodule on the partitioning of metals between the interacting HMO, HFO, and marine water phases. Our scenario model suggests that significant fraction of Mn and other metals, probably 50% or more, may be recycled to water column from the surface of the ferromanganese nodule upon gradual development of the bottom water stagnation, except of Zn for which a by far stronger net retention was found. Conclusion and Outlook. Our model, even if only a first approximation, clearly shows that stagnation in the marine bottom water, once occurring, can drastically change primary element proxy records in ferromanganese nodules, smoothing out any anomalous patterns in the most recent record.
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