Kinetics of Ce and Nd scavenging in Black Sea waters

Author(s): Schijf, Johan; de Baar, Hein J. W.; Millero, Frank J.
Author Affiliation(s): Primary:
University of Utrecht, Department of Earth Sciences, Amsterdam, Netherlands
Other:
Netherlands Institute for Sea Research, Netherlands
University of Miami, United States
Volume Title: Marine Chemistry
Source: Marine Chemistry, 46(4), p.345-359. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0304-4203 CODEN: MRCHBD
Note: In English. 27 refs.; illus., incl. 3 tables, sketch map
Summary: 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 (300dbar) 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 24h and analyzed for dissolved Ce (a redox reactive REE) and Nd (a non-redox reactive REE). During the first 2.5h 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 2.5h 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 300dbar 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.
Year of Publication: 1994
Research Program: DSDP Deep Sea Drilling Project
Key Words: 02 Geochemistry; Anaerobic environment; Black Sea; Cerium; Deep Sea Drilling Project; East Mediterranean; Geochemistry; Hydrochemistry; Kinetics; Leg 5; Mediterranean Sea; Metals; Neodymium; Rare earths; Sea water
Coordinates: N430600 N430600 E0340000 E0340000
Record ID: 1995009840
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands