The geochemistry of rare earth elements in the seasonally anoxic water column and porewaters of Chesapeake Bay

Journal Article · Tue Sep 01 00:00:00 EDT 1992 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(92)90386-W· OSTI ID:7159457

Sholkovitz, E R; Shaw, T J; Schneider, D L ^[1]

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1. Woods Hole Oceanographic Inst., MA (United States)

A twelve cruise time-series study of a seasonally anoxic basin in Chesapeake Bay was carried out between February 1988 and February 1989. Data from filtered bottom water and upper (0-1 cm) porewater samples are presented. This is the first study in which time-series measurements have been employed to understand the low temperature geochemistry of rare earth elements (REEs). The focus is on the coupling between REDOX (Reduction-Oxidation) variations and REE cycling, fractionation of trivalent REEs and development of cerium anomalies. The time-series results demonstrate that REEs have large seasonal cycles in both the water column and porewaters in response to the development of anoxia in the spring and reoxygenation in the fall. The transition from oxic to suboxic to anoxic conditions results in the release of REEs into the upper porewaters and bottom waters. The release of REEs and Fe are coincident in the bottom waters, while the release of REEs lags Fe by approximately 50 days in the upper porewaters. The release of REEs to the upper porewaters and bottom water are accompanied by (1) fractionation across the trivalent REE series and by (2) the preferential input of Ce relative to its trivalent-only REE neighbors. REE(III) fractionation is such that the relative rate of release increases from Lu to La (light REE > middle REE > heavy REE). During reoxygenation, removal of dissolved REEs occurs from both the water column and upper porewaters and follows the same relative rates, LREE > MREE > HREE. Cerium removal occurs faster than its neighbor REE(III), indicating a rapid oxidation of Ce(III) to Ce(IV).

• OSTI ID: 7159457
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 56:9; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ANAEROBIC CONDITIONS
ATLANTIC OCEAN
BAYS
CHEMICAL REACTIONS
CHEMISTRY
CHESAPEAKE BAY
COASTAL WATERS
ECOLOGICAL CONCENTRATION
ELEMENTS
GEOCHEMISTRY
GROUND WATER
HYDROGEN COMPOUNDS
INTERFACES
INTERSTITIAL WATER
METALS
MINERAL CYCLING
OXYGEN COMPOUNDS
RARE EARTHS
REDOX REACTIONS
SEAS
SEASONAL VARIATIONS
SEAWATER
SEDIMENT-WATER INTERFACES
SURFACE WATERS
VARIATIONS
WATER
WATER CHEMISTRY