Redox dynamics in the Chesapeake Bay: The effect on sediment/water uranium exchange

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90173-2· OSTI ID:6823482

Shaw, T J; Sholkovitz, E R; Klinkhammer, G ^[1]

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1. Univ. of Maryland, Solomons, MD (United States)

The effect of seasonal variations in productivity and redox dynamics on the sediment/water exchange of uranium was investigated on a twelve cruise time series in the Chesapeake Bay. The deep waters of the bay undergo seasonal anoxia in response to high primary productivity and water column stratification from late spring to early fall. Dissolved oxygen was used to monitor sediment redox conditions. Dissolved [sup 238]U was measured in the water column and sediment porewaters to monitor water column/sediment exchange. Uranium incorporation in bay sediments results from two distinct processes: productivity-dependent scavenging from the water column and redox-dependent cycling of uranium between sediments and bottomwater. Uranium is removed from surface waters of the bay by scavenging with biodetritus during periods of high primary productivity. Bottomwater and sediment redox conditions determine whether this particle-bound uranium is buried or released to overlying water. Particulate uranium is released to bottomwaters and porewaters during the degradation of biodetritus and oxidation of authigenic uranium. Low oxygen in bottomwaters in the summer results in minimal exchange of uranium between the sediments and bottomwater, due to the stability of reduced U(IV). High bottomwater oxygen concentrations associated with bay turnover in the fall results in release of authigenic uranium by oxidation to the soluble (VI) form. Enrichment of uranium in fall bottomwater suggests that authigenic uranium is very labile when exposed to oxic environmental conditions. This process is enhanced by physical mixing when anoxic sediments are resuspended into the oxic bottomwaters.

• OSTI ID: 6823482
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:14; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540330* -- Environment
Aquatic-- Radioactive Materials Monitoring & Transport-- (1990-)
ACTINIDE ISOTOPES
ACTINIDE NUCLEI
ACTINIDES
ALPHA DECAY RADIOISOTOPES
CHEMICAL REACTIONS
ELEMENTS
ENVIRONMENTAL TRANSPORT
EVEN-EVEN NUCLEI
HEAVY NUCLEI
INTERFACES
ISOTOPES
MASS TRANSFER
METALS
NUCLEI
RADIOISOTOPES
REDOX REACTIONS
SEDIMENT-WATER INTERFACES
SPONTANEOUS FISSION RADIOISOTOPES
URANIUM
URANIUM 238
URANIUM ISOTOPES
YEARS LIVING RADIOISOTOPES