Photoreduction of manganese oxides in seawater and its geochemical and biological implications

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Authors:Sunda, W. G.; Huntsman, S. A.; Harvey, G. R.
Author Affiliations:Primary:
Natl. Mar. Fish. Serv., Southeast Fish. Cent., Beaufort, NC 28516, United States
Other:
NOAA, United States
Volume Title:Nature (London)
Source:Nature (London), 301(5897), p.234-236. Publisher: Macmillan Journals, London, United Kingdom. ISSN: 0028-0836
Publication Date:1983
Note:In English. 30 refs.; illus.
Summary:According to thermodynamic considerations, Mn should exist in oxic waters as MnO2 which is insoluble and, therefore, not directly available for plant nutrition. In contrast to thermodynamic predictions, however, most of the Mn in near-surface sea-water exists as soluble reduced Mn(II). Although slow oxidation kinetics are at least partially responsible for the presence of Mn(II) in oxic waters, reduced Mn, nevertheless, should be converted to particulate Mn oxides (at rates that depend on several kinetic factors) and be lost from the water column by sinking. Experiments are reported that demonstrate photoreduction of Mn oxides by dissolved organic substances (humic substances) in sea-water. Such reactions appear to be important in maintaining Mn in a dissolved reduced form in photic waters, thereby enhancing its supply to phytoplankton, and can partially explain the unusual vertical distribution pattern of Mn in the ocean. [T.R.]
Subjects:Geochemistry; Humic acids; Humic substances; Manganese oxides; Organic acids; Organic compounds; Oxides; Particles; Photochemistry; Photosynthesis; Phytoplankton; Plankton; Reduction; Sea water; Solution; Organic materials
Abstract Numbers:84M/3022
Record ID:1985083124
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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