Universität zu Köln

Guinoiseau, D., Galer, S. J. G., Abouchami, W., Frank, M., Achterberg, E. P. and Haug, G. H. (2019). Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones-A Case Study of the Angola Basin. Glob. Biogeochem. Cycle, 33 (12). S. 1746 - 1764. WASHINGTON: AMER GEOPHYSICAL UNION. ISSN 1944-9224

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Abstract

Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient-like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient-like consumption-regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been proposed. In this study, we report Cd stable isotope and concentration data for seven vertical seawater profiles sampled during GEOTRACES cruise GA08 in the northern Cape and Angola Basins, which feature a significant ODZ along their eastern margins. Outside the ODZ, Cd cycling is similar to that previously reported for the South Atlantic. While water mass mixing largely controls deep ocean Cd isotope signatures, Cd isotope fractionation in surface waters can be modeled as an open system at steady state buffered by organic ligand complexation. In the ODZ, stronger Cd depletion relative to PO4 is associated with a shift in delta Cd-114 toward heavier values, which is indicative of CdS precipitation. Our interpretation is supported by experimental CdS precipitation data and a size-resolved particle model involving bacterial sulfate reduction as a precursor of CdS. Our estimates of the CdS flux to the seafloor (10(7) to 10(9) mol/yr) indicate that CdS precipitation is a significant process of Cd removal and constitutes a nonnegligible Cd sink that needs to be better quantified by Cd isotope analyses of marine sediments.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Guinoiseau, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Galer, S. J. G. UNSPECIFIED UNSPECIFIED UNSPECIFIED Abouchami, W. UNSPECIFIED UNSPECIFIED UNSPECIFIED Frank, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Achterberg, E. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Haug, G. H. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-125283
DOI:	10.1029/2019GB006323
Journal or Publication Title:	Glob. Biogeochem. Cycle
Volume:	33
Number:	12
Page Range:	S. 1746 - 1764
Date:	2019
Publisher:	AMER GEOPHYSICAL UNION
Place of Publication:	WASHINGTON
ISSN:	1944-9224
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SOUTHERN-OCEAN; PHOSPHATE RELATIONSHIP; DISSOLVED CADMIUM; SINKING VELOCITY; ATLANTIC-OCEAN; WATER COLUMN; ZINC; FRACTIONATION; DISTRIBUTIONS; CIRCULATION Multiple languages Environmental Sciences; Geosciences, Multidisciplinary; Meteorology & Atmospheric Sciences Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/12528