H2S events in the Peruvian oxygen minimum zone facilitate enhanced dissolved Fe concentrations.

Schlosser, Christian , Streu, Peter, Frank, Martin, Lavik, Gaute, Croot, Peter L., Dengler, Marcus and Achterberg, Eric P. (2018) H2S events in the Peruvian oxygen minimum zone facilitate enhanced dissolved Fe concentrations. Open Access Scientific Reports, 8 . Art.Nr. 12642. DOI 10.1038/s41598-018-30580-w.

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Abstract

Dissolved iron (DFe) concentrations in oxygen minimum zones (OMZs) of Eastern Boundary Upwelling Systems are enhanced as a result of high supply rates from anoxic sediments. However, pronounced variations in DFe concentrations in anoxic coastal waters of the Peruvian OMZ indicate that there are factors in addition to dissolved oxygen concentrations (O2) that control Fe cycling. Our study demonstrates that sediment-derived reduced Fe (Fe(II)) forms the main DFe fraction in the anoxic/euxinic water column off Peru, which is responsible for DFe accumulations of up to 200 nmol L-1. Lowest DFe values were observed in anoxic shelf waters in the presence of nitrate and nitrite. This reflects oxidation of sediment-sourced Fe(II) associated with nitrate/nitrite reduction and subsequent removal as particulate Fe(III) oxyhydroxides. Unexpectedly, the highest DFe levels were observed in waters with elevated concentrations of hydrogen sulfide (up to 4 µmol L-1) and correspondingly depleted nitrate/nitrite concentrations (<0.18 µmol L-1). Under these conditions, Fe removal was reduced through stabilization of Fe(II) as aqueous iron sulfide (FeSaqu) which comprises complexes (e.g., FeSH+) and clusters (e.g., Fe2S2|4H2O). Sulfidic events on the Peruvian shelf consequently enhance Fe availability, and may increase in frequency in future due to projected expansion and intensification of OMZs.

Document Type: Article
Keywords: trace metals, iron, sulfide, denitrification, OMZ, Peru
Research affiliation: OceanRep > SFB 754 > B10
OceanRep > SFB 754
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-P-OZ Paleo-Oceanography
OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-CH Chemical Oceanography
OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: Yes
DOI etc.: 10.1038/s41598-018-30580-w
ISSN: 2045-2322
Projects: SFB754
Expeditions/Models/Experiments:
Date Deposited: 03 Sep 2018 10:28
Last Modified: 01 Feb 2019 15:02
URI: http://oceanrep.geomar.de/id/eprint/44119

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