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Seasonal changes in speciation of dissolved chromium in the surface Sargasso Sea

Seasonal changes in speciation of dissolved chromium in the surface Sargasso Sea
Seasonal changes in speciation of dissolved chromium in the surface Sargasso Sea
The concentrations of Cr (III) and Cr (VI) were determined in the upper 500 m of the Sargasso Sea at different times of the year. Total Cr concentrations ranged between 2.5 and 4.5 nM, and the predominant species of Cr was the thermodynamically favoured Cr (VI). Cr (III) concentrations were greatest during periods of high biological activity, as indicated by strong correlations between the ratio of Cr (III):Cr (VI) and both bacterial biomass and primary productivity. Whilst the oxidation state varied substantially over the seasonal cycle, the upper water column inventory of Cr was relatively constant. The long residence time of Cr in the surface Sargasso Sea estimated with respect to atmospheric inputs (1410–2240 years) is indicative of the largely conservative behaviour of this element. Deep particle fluxes of Cr are similar or somewhat greater than atmospheric inputs, and this downward flux of Cr is well correlated with organic carbon fluxes from the upper Sargasso Sea. The long residence time coupled with the seasonal changes in oxidation state of Cr implies rapid seasonal recycling of Cr between redox states, with only slow removal via particles to the deep ocean at this site.
Sargasso Sea, Chromium, Chemical speciation, Seasonality, Particle export
0967-0637
1975-1988
Connelly, D.P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Knapp, A.H.
d6c5ef26-c577-48ce-9a06-1ac42c26d679
Connelly, D.P.
d49131bb-af38-4768-9953-7ae0b43e33c8
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Knapp, A.H.
d6c5ef26-c577-48ce-9a06-1ac42c26d679

Connelly, D.P., Statham, P.J. and Knapp, A.H. (2006) Seasonal changes in speciation of dissolved chromium in the surface Sargasso Sea. Deep Sea Research Part I: Oceanographic Research Papers, 53 (12), 1975-1988. (doi:10.1016/j.dsr.2006.09.005).

Record type: Article

Abstract

The concentrations of Cr (III) and Cr (VI) were determined in the upper 500 m of the Sargasso Sea at different times of the year. Total Cr concentrations ranged between 2.5 and 4.5 nM, and the predominant species of Cr was the thermodynamically favoured Cr (VI). Cr (III) concentrations were greatest during periods of high biological activity, as indicated by strong correlations between the ratio of Cr (III):Cr (VI) and both bacterial biomass and primary productivity. Whilst the oxidation state varied substantially over the seasonal cycle, the upper water column inventory of Cr was relatively constant. The long residence time of Cr in the surface Sargasso Sea estimated with respect to atmospheric inputs (1410–2240 years) is indicative of the largely conservative behaviour of this element. Deep particle fluxes of Cr are similar or somewhat greater than atmospheric inputs, and this downward flux of Cr is well correlated with organic carbon fluxes from the upper Sargasso Sea. The long residence time coupled with the seasonal changes in oxidation state of Cr implies rapid seasonal recycling of Cr between redox states, with only slow removal via particles to the deep ocean at this site.

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Published date: 2006
Keywords: Sargasso Sea, Chromium, Chemical speciation, Seasonality, Particle export

Identifiers

Local EPrints ID: 43814
URI: http://eprints.soton.ac.uk/id/eprint/43814
ISSN: 0967-0637
PURE UUID: cd9bdb48-90e6-4c9c-b6cb-e975fc06dcdf

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Date deposited: 30 Jan 2007
Last modified: 15 Mar 2024 08:58

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Contributors

Author: D.P. Connelly
Author: P.J. Statham
Author: A.H. Knapp

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