The behavior of scavenged isotopes in marine anoxic environments: [sup 210]Pb and [sup 210]Po in the water column of the Black Sea

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Geochimica et Cosmochimica Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(94)90537-1· OSTI ID:7034437

Wei, C L ^[1]; Murray, J W ^[2]

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1. National Taiwan Univ., Taipei (Taiwan, Province of China)
2. Univ. of Washington, Seattle, WA (United States)

Vertical profiles of dissolved and particulate [sup 210]Pb and [sup 210]Po were determined at two stations in the Black Sea in June 1988. Vertical fluxes of [sup 210]Pb and [sup 210]Po were also measured in the upper 150 m, using floating sediment traps. The fractionation of [sup 210]Pb between dissolved and particulate phases in the Black Sea is strongly influenced by the redox conditions in the water column. Dissolved [sup 210]Pb dominates in the oxic zone, while particulate [sup 210]Pb is the major form in the deep sulfide-rich anoxic zone. The distribution of [sup 210]Pb across the suboxic zone appears to be mainly controlled by redox cycling of manganese and iron. In the sulfide-rich layer coprecipitation of lead with iron sulfide is probably the dominant scavenging mechanism. A simple scavenging model was used to calculate the residence times of dissolved and particulate [sup 210]Pb in the oxic, suboxic, and anoxic zones. The residence times of dissolved [sup 210]Pb relative to scavenging by particles are 0.5-1, 2-3, and 3.5 years in the oxic, suboxic, and anoxic layers, respectively. The corresponding residence times of particulate [sup 210]Pb relative to particle removal processes in the same layers are 0.1, 1.5-2.5, and 8.5 years, respectively. A particle settling velocity of about 40 m y[sup [minus]1] was derived from the [sup 210]Pb/[sup 226]Ra disequilibrium in the deep Black Sea. The relatively short residence times of [sup 210]Pb support the hypothesis that anoxic basins are important sites for boundary scavenging of [sup 210]Pb. The [sup 210]Po profiles indicate that biological rather than inorganic particles are the major carrier phases for Po in the Black sea. Based on the magnitude of distribution coefficients, the relative partitioning of Pb, Po, and Th to particles found in the oxic and anoxic layers of the Black Sea are Po > Th > Pb and Po = Pb > Th, respectively. Colloidal phases may be important for the scavenging of these radionuclides.

• OSTI ID: 7034437
• Journal Information: Geochimica et Cosmochimica Acta; (United States), Journal Name: Geochimica et Cosmochimica Acta; (United States) Vol. 58:7; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES
540330* -- Environment
Aquatic-- Radioactive Materials Monitoring & Transport-- (1990-)
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BETA DECAY RADIOISOTOPES
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