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Titolo:
SALT MARSHES - AN IMPORTANT COASTAL SINK FOR DISSOLVED URANIUM
Autore:
CHURCH TM; SARIN MM; FLEISHER MQ; FERDELMAN TG;
Indirizzi:
UNIV DELAWARE,COLL MARINE STUDIES NEWARK DE 19716
Titolo Testata:
Geochimica et cosmochimica acta
fascicolo: 20, volume: 60, anno: 1996,
pagine: 3879 - 3887
SICI:
0016-7037(1996)60:20<3879:SM-AIC>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
SEA SEDIMENTS; PORE WATERS; GEOCHEMISTRY; DELAWARE; BEHAVIOR; THORIUM; CHEMISTRY; ISOTOPES; ENRICHMENT; ESTUARIES;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
41
Recensione:
Indirizzi per estratti:
Citazione:
T.M. Church et al., "SALT MARSHES - AN IMPORTANT COASTAL SINK FOR DISSOLVED URANIUM", Geochimica et cosmochimica acta, 60(20), 1996, pp. 3879-3887

Abstract

The global budget for marine uranium demands another geochemical sinkother than deepsea systems, and the coastal environment may host someor all of this missing sink. In a previous paper (Sarin and Church, 1994), we have shown that some large subtidal estuaries are seasonal summer sinks at low salinities. In this paper, we show that intertidal salt marshes are even stronger sinks at all salinities, if for somewhatdifferent reasons. Uranium was sampled in dissolved and particulate fractions over several tidal cycles and seasons for a lower Delaware Bay salt marsh (Canary Creek, Lewes, Delaware, USA), and uniquely, during summer months, the dissolved uranium is nonconservative. Moreover, because uranium extraction is greater on higher tides and occurs over the entire salinity gradient, this processing appears associated with surface of vegetated high marsh. We hypothesize that either (1) uraniumscavenging occurs during the process of tidal mixing and attendant flocculation of humic acids and iron oxides-favoring this process is thepresence of sulfonate complexes in salt marsh humic substances, and iron coprecipitation during its extensive redox cycling in the salt marsh-or (2) uranium extraction occurs at the marsh surface during extensive flooding of the salt marsh surface sediments-favoring this processis the increase in sulfuric acidity at the summer salt marsh surface that could destabilize the tetracarbonate species of U(VI). The latteroption is favored conditions, and selective extraction of sediment phases where uranium is found as adsorbed and complexed forms in the ascorbate-citrate and humic acid fractions, respectively. Mass balance calculations show that under steady-state conditions, nearly two-thirds of the uranium extracted from tidal waters is retained in the sediments, while one-third is exported as U-enriched particles during ebbing tides. Independent confirmation of this balance comes from the measuredaccumulation rate of uranium buried at depth. This represents the netinventory buried below the geochemically reactive surface responsiblefor the initial extraction and redistribution of uranium onto sediment or tidally exported phases. Extrapolated globally, uranium burial insalt marshes alone or total marine wetlands including mangroves couldcomprise at least 10% and perhaps as much as 50% the total marine sink for uranium, or on an area specific basis, up to 50 times their marine areal extent.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 30/11/20 alle ore 19:48:18