Kinetics of Ce and Nd scavenging in Black Sea waters

Johan Schijf, Hein J W de Baar, Frank J Millero

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Mixing experiments were performed during Leg 5 of the 1988 Black Sea Expedition in order to learn more about the mechanism and kinetics of rare earth element (REE) scavenging at the oxic-anoxic interface of anoxic basins and, more specifically, in the suboxic zone of the Black Sea. Water from the depth of the dissolved REE maxima (300 dbar) was mixed in a thermostated reaction vessel with water from the depth of the particle maximum (PM) that had previously been equilibrated with the atmosphere. Subsamples were taken from the reaction vessel over a period of 24 h and analyzed for dissolved Ce (a redox reactive REE) and Nd (a non-redox reactive REE). During the first 2.5 h both Ce and Nd were removed from solution at a high rate, presumably as a result of adsorption onto fresh Mn and/or Fe oxides that formed during equilibration of the PM end-member with the atmosphere. The rates of Ce and Nd removal were approximately the same, suggesting that oxidative scavenging of Ce was of minor importance. After 2.5 h both Ce and Nd were released again at a rate much lower than that of the initial removal, presumably as a result of reductive dissolution of the Mn and/or Fe oxides onto which they were adsorbed. While this reductive dissolution may have been caused by sulfide that was introduced with the 300 dbar end-member, the results of a separate mixing experiment in the presence of a bio-inhibitor (formaldehyde) suggest that Mn and Fe reducing bacteria also played a significant role. The initial removal as well as the subsequent release of Ce and Nd were found to obey pseudo first-order kinetics.

Original languageEnglish (US)
Pages (from-to)345-359
Number of pages15
JournalMarine Chemistry
Volume46
Issue number4
DOIs
StatePublished - 1994

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Scavenging
Rare earth elements
rare earth element
seawater
kinetics
Kinetics
Water
Oxides
Dissolution
vessel
dissolution
oxide
atmosphere
Sulfides
formaldehyde
Formaldehyde
inhibitor
Bacteria
experiment
Experiments

ASJC Scopus subject areas

  • Chemistry(all)
  • Oceanography

Cite this

Schijf, J., de Baar, H. J. W., & Millero, F. J. (1994). Kinetics of Ce and Nd scavenging in Black Sea waters. Marine Chemistry, 46(4), 345-359. https://doi.org/10.1016/0304-4203(94)90031-0

Kinetics of Ce and Nd scavenging in Black Sea waters. / Schijf, Johan; de Baar, Hein J W; Millero, Frank J.

In: Marine Chemistry, Vol. 46, No. 4, 1994, p. 345-359.

Research output: Contribution to journalArticle

Schijf, J, de Baar, HJW & Millero, FJ 1994, 'Kinetics of Ce and Nd scavenging in Black Sea waters', Marine Chemistry, vol. 46, no. 4, pp. 345-359. https://doi.org/10.1016/0304-4203(94)90031-0
Schijf, Johan ; de Baar, Hein J W ; Millero, Frank J. / Kinetics of Ce and Nd scavenging in Black Sea waters. In: Marine Chemistry. 1994 ; Vol. 46, No. 4. pp. 345-359.
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