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| Titel |
Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean |
| VerfasserIn |
M. Boye, B. D. Wake, P. Lopez Garcia, J. Bown, A. R. Baker, E. P. Achterberg |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 8 ; Nr. 9, no. 8 (2012-08-23), S.3231-3246 |
| Datensatznummer |
250007245
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| Publikation (Nr.) |
 copernicus.org/bg-9-3231-2012.pdf |
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| Zusammenfassung |
| Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved
cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are
presented along a section between 34° S and 57° S in the southeastern
Atlantic Ocean and the Southern Ocean to the south off South Africa. The
vertical distributions of Cu and Ag display nutrient-like profiles similar
to silicic acid, and of Cd similar to phosphate. The distribution of Mn
shows a subsurface maximum in the oxygen minimum zone, whereas Pb
concentrations are rather invariable with depth. Dry deposition of aerosols
is thought to be an important source of Pb to surface waters close to South
Africa, and dry deposition and snowfall may have been significant sources of
Cu and Mn at the higher latitudes. Furthermore, the advection of
water masses enriched in trace metals following contact with continental
margins appeared to be an important source of trace elements to the surface,
intermediate and deep waters in the southeastern Atlantic Ocean and the
Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source
of trace metals to the deep waters over the Bouvet Triple Junction ridge
crest, as suggested by relatively enhanced dissolved Mn concentrations. The
biological utilization of Cu and Ag was proportional to that of silicic acid
across the section, suggesting that diatoms formed an important control over
the removal of Cu and Ag from surface waters. However, uptake by dino- and
nano-flagellates may have influenced the distribution of Cu and Ag in the
surface waters of the subtropical Atlantic domain. Cadmium correlated
strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical
surface waters where phosphate concentrations were below 0.95 μM. The
greater depletion of Cd relative to P observed in the Weddell Gyre compared
to the Antarctic Circumpolar Current could be due to increase Cd uptake
induced by iron-limiting conditions in these high-nutrient–low-chlorophyll
waters. Similarly, an increase of Mn uptake under Fe-depleted conditions may
have caused the highest depletion of Mn relative to P in the surface waters of
the Weddell Gyre. In addition, a cellular Mn-transport channel of Cd was
possibly activated in the Weddell Gyre, which in turn may have yielded
depletion of both Mn and Cd in these surface waters. |
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