Uranium geochemistry on the Amazon shelf: Evidence for uranium release from bottom sediments

Journal Article · Thu Oct 01 00:00:00 EDT 1987 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(87)90157-8· OSTI ID:7003453

McKee, B A; DeMaster, D J; Nittrouer, C A ^[1]

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1. North Carolina State Univ., Raleigh (USA)

In Amazon-shelf waters, as salinity increases to 36.5 x 10{sup {minus}3}, dissolved uranium activities increase to a maximum of 4.60 dpm 1{sup {minus}1}. This value is much higher than the open-ocean value (2.50 dpm 1{sup {minus}1}), indicating a source of dissolved uranium to shelf waters in addition to that supplied from open-ocean and riverine waters. Uranium activities are much lower for surface sediments in the Amazon-shelf sea bed (mean: 0.69 {plus minus} .09 dpm g{sup {minus}1}) than for suspended sediments in the Amazon river (1.82 dpm g{sup {minus}1}). Data suggest that the loss of particulate uranium from riverine sediments is probably the result of uranium desorption from the ferric-oxyhydroxide coatings on sediment particles, and/or uranium release by mobilization of the ferric oxyhydroxides. The total flux of dissolved {sup 238}U from the Amazon shelf (about 1.2 x 10{sup 15} dpm yr{sup {minus}1}) constitutes about 15% of uranium input to the world ocean, commensurate to the Amazon River's contribution to world river-water discharge. Measurement of only the riverine flux of dissolved {sup 238}U underestimates, by a factor of about 5, the flux of dissolved {sup 238}U from the Amazon shelf to the open ocean.

• OSTI ID: 7003453
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 51:10; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540330* -- Environment
Aquatic-- Radioactive Materials Monitoring & Transport-- (1990-)
58 GEOSCIENCES
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ACTINIDE COMPOUNDS
AMAZON RIVER
BRAZIL
CHEMICAL COMPOSITION
CHEMISTRY
CONCENTRATION RATIO
CONTINENTAL MARGIN
CONTINENTAL SHELF
DEVELOPING COUNTRIES
DISSOLUTION
GEOCHEMISTRY
ISOTOPE APPLICATIONS
ISOTOPES
LATIN AMERICA
RADIOISOTOPES
RADIONUCLIDE KINETICS
RIVERS
SEDIMENTS
SOLUTES
SOUTH AMERICA
STREAMS
SURFACE WATERS
TRACER TECHNIQUES
URANIUM COMPOUNDS
WATER CHEMISTRY