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| Titel |
Cadmium Isotope Variations in the Peruvian Oxygen Minimum Zone - New Constraints on Micronutrient Cycling |
| VerfasserIn |
Zichen Xue, Mark Rehkamper, Tina van de Flierdt, Patricia Grasse, Martin Frank |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250046220
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| Zusammenfassung |
| Recent studies have recognized that micronutrient elements, such as cadmium (Cd), play an
important role in marine biological productivity. The distribution of dissolved seawater Cd is
correlated with that of phosphate [1], with low concentrations in surface waters due to
biological utilization and higher abundances at depth from remineralization of organic
material.
Previous studies have furthermore shown that biological uptake of Cd in the surface
seawater can generate significant Cd isotope variability, whilst the deep ocean appears to
be characterized by a relatively constant Cd isotope composition of É114-110Cd
- +3 [2,3], which is roughly similar to results obtained for the silicate Earth [4]
(É114-110Cd is the deviation of the 114Cd/110Cd ratio of a sample from the NIST
3108 Cd isotope standard in parts per 10,000). The most fractionated Cd isotope
compositions have been determined for highly nutrient depleted open ocean surface
waters from the Atlantic and Pacific Ocean, which exhibit É114-110Cd values of
between +20 and +40. In contrast, the comparatively nutrient rich surface waters of the
Southern Ocean HNLC region display relatively high Cd contents of up to 0.2 nM and
only limited Cd isotope fractionation with É114-110Cd values of between + 5 and
+8.
These results are of interest because they provide new constraints on the cycling
of the micronutrient Cd in the present oceans [2,3]. In addition, they also imply
that Cd isotopes may be a useful proxy for the study of past changes in marine
nutrient utilization. This conclusion is supported by further results that were recently
obtained for seawater samples from the oxygen minimum zone (OMZ) of the coastal
upwelling area in the South Pacific Ocean off Peru. Cadmium concentration and
isotope data were obtained for 9 depth profiles in this region at between 3Ë S and 12Ë
S.
The surface water samples from these locations display É114-110Cd-[Cd] signatures that
are distinct from those found in the Southern Ocean HNLC region and nutrient depleted open
ocean areas. In the Peruvian OMZ, the seawater from |
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