Uranium isotope geochemistry in modern coastal sediments: Insights from Toulon Bay, France

Uranium isotope geochemistry in modern coastal sediments: Insights from Toulon Bay, France By assessing U geochemistry in marine sediments of Toulon Bay (NW Mediterranean Sea), authigenic U accumulation was found to be tightly linked to that of Mo and V with slight differences in accumulation rate depending on sediment redox conditions. In sediments collected on a transect along a river plume, the authigenic accumulation of these redox-sensitive elements appears to be linked to sediment grain size which probably drives the redox status of the sediments. A typical U loss in re-oxidized sediments was observed in sediments that had been previously disturbed. However, the dissolved U profiles do not show a simple and typical depletion trend but rather a depletion in the top 10 cm followed by release in deeper pore waters that could be linked to a potential reoxidation/mobilization of authigenic U(IV). The released U could be further scavenged as a U-P precipitate.The U isotopic data (δ238U), which are the first reported for the coastal hypoxic sediments of Toulon Bay, average −0.12 ± 0.12‰ in surface sediments. However, sediments situated in front of river mouths show higher values of δ238U (up to +0.75‰); these high values are reported for the first time in sediments below an oxic water column. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Chemical Geology Elsevier

Uranium isotope geochemistry in modern coastal sediments: Insights from Toulon Bay, France

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Publisher
Elsevier
Copyright
Copyright © 2018 Elsevier B.V.
ISSN
0009-2541
eISSN
1872-6836
D.O.I.
10.1016/j.chemgeo.2018.01.032
Publisher site
See Article on Publisher Site

Abstract

By assessing U geochemistry in marine sediments of Toulon Bay (NW Mediterranean Sea), authigenic U accumulation was found to be tightly linked to that of Mo and V with slight differences in accumulation rate depending on sediment redox conditions. In sediments collected on a transect along a river plume, the authigenic accumulation of these redox-sensitive elements appears to be linked to sediment grain size which probably drives the redox status of the sediments. A typical U loss in re-oxidized sediments was observed in sediments that had been previously disturbed. However, the dissolved U profiles do not show a simple and typical depletion trend but rather a depletion in the top 10 cm followed by release in deeper pore waters that could be linked to a potential reoxidation/mobilization of authigenic U(IV). The released U could be further scavenged as a U-P precipitate.The U isotopic data (δ238U), which are the first reported for the coastal hypoxic sediments of Toulon Bay, average −0.12 ± 0.12‰ in surface sediments. However, sediments situated in front of river mouths show higher values of δ238U (up to +0.75‰); these high values are reported for the first time in sediments below an oxic water column.

Journal

Chemical GeologyElsevier

Published: Mar 20, 2018

References

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