Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids

Homoky, William B.; Hembury, Deborah J.; Hepburn, Laura; Mills, Rachel A.; Statham, Peter J.; Fones, Gary R.; Palmer, Martin R.

doi:10.1016/j.gca.2011.06.019

Cited by 70 publications

(66 citation statements)

References 88 publications

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“…The fluxes calculated for Mn are high and are similar to those determined from volcanogenic sediments around Montserrat (Homoky et al, 2011).…”

Section: Pore Water Fe and Mn Distributionssupporting

confidence: 71%

“…The highest fluxes have been attributed to low oxygen bottom waters and high organic carbon oxidation rates (Severmann et al, 2010;Homoky et al, 2012;Noffke et al, 2012), while bio-irrigation of ferruginous sediments may enhance the efficacy of benthic exchange (Elrod et al, 2004;Severmann et al, 2010). There is additional evidence for high rates of Fe and Mn dissolution during the alteration of volcanic minerals (Homoky et al, 2011), which is suggested to result from inorganically driven mineral dissolution (Radic et al, 2011;Homoky et al, 2011;. However the mechanisms, distribution and significance of these diagenetic settings are rarely examined, despite being a potentially important source of dissolved Fe and Mn to bottom waters across ocean basins.…”

Section: Introductionmentioning

confidence: 99%

“…Shipboard determinations of dissolved oxygen content in the upper sediment were carried out on a dedicated core from each site as described by Homoky et al (2011;. A Unisense OX50 micro-sensor was calibrated between O 2 -saturated and anoxic seawater solutions with temperature and salinity equivalent to bottom waters.…”

Section: Introductionmentioning

confidence: 99%

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Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

Aquilina¹,

Homoky²,

Hawkes³

et al. 2014

Geochimica et Cosmochimica Acta

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Please cite this article as: Aquilina, A., Homoky, W.B., Hawkes, J.A., Lyons, T.W., Mills, R.A., Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica, Geochimica et Cosmochimica Acta (2014), doi: http://dx.doi.org/10.1016/j.gca. 2014.04.003 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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“…The fluxes calculated for Mn are high and are similar to those determined from volcanogenic sediments around Montserrat (Homoky et al, 2011).…”

Section: Pore Water Fe and Mn Distributionssupporting

confidence: 71%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

Aquilina¹,

Homoky²,

Hawkes³

et al. 2014

Geochimica et Cosmochimica Acta

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“…The sFe forms may be simple ionic species, nano-particulate forms or may contain small ferrozine-reactive Fe(II) organic complexes. This contrasts with findings from deep sea sediments in the Crozet region, where on average 80% of Fe and 61% of Mn was in the colloidal size fraction (0.02-0.2 lm) (Homoky et al 2009(Homoky et al , 2011. Porewater dFe mainly being in the reduced form in the shelf log k = -3.60 log k = -3.49 log k = -3.30 Fig.…”

Section: Discussioncontrasting

confidence: 61%

“…This process is associated with the removal of heavy Fe isotopes leading to further enrichment of light Fe isotopes in the porewater (Severmann et al 2006;Homoky et al 2009). Within more oxidizing sediments, the isotopic signature of dFe is close to crustal compositions, e.g., 0.0-0.2% (Homoky et al 2009(Homoky et al , 2013, and the dFe fraction consists mainly of Fe colloids (0.02-0.2 lm), that are argued to originate from ''non-reductive'' dissolution processes (Radic et al 2011;Homoky et al 2011Homoky et al , 2013. The Fe isotopic composition in the water column may serve as a tool to trace benthic Fe fluxes which originate from different dissolution processes and are transported to the ocean interior (Conway and John 2014).…”

Section: Introductionmentioning

confidence: 84%

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

et al. 2017

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Shelf sediments underlying temperate and oxic waters of the Celtic Sea (NW European Shelf) were found to have shallow oxygen penetrations depths from late spring to late summer (2.2-5.8 mm below seafloor) with the shallowest during/after the spring-bloom (mid-April to mid-May) when the organic carbon content was highest. Sediment porewater dissolved iron (dFe,\0.15 lm) mainly ([85%) consisted of Fe(II) and gradually increased from 0.4 to 15 lM at the sediment surface to *100-170 lM at about 6 cm depth. During the late spring this Fe(II) was found to be mainly present as soluble Fe(II) ([85% sFe, \0.02 lm). Sub-surface dFe(II) maxima were enriched in light isotopes (d 56 Fe -2.0 to -1.5%), which is attributed to dissimilatory iron reduction (DIR) during the bacterial decomposition of organic matter. As porewater Fe(II) was oxidised to insoluble Fe(III) in the surface sediment layer, residual Fe(II) was further enriched in light isotopes (down to -3.0%). Ferrozine-reactive Fe(II) was found in surface porewaters and in overlying core top waters, and was highest in the late spring period. Shipboard experiments showed that depletion of bottom water Responsible Editor: Martin Solan.Electronic supplementary material The online version of this article (doi:10.1007/s10533-017-0309-x) contains supplementary material, which is available to authorized users. 49-67 DOI 10.1007/s10533-017-0309-x oxygen in late spring can lead to a substantial release of Fe(II). Reoxygenation of bottom water caused this Fe(II) to be rapidly lost from solution, but residual dFe(II) and dFe(III) remained (12 and 33 nM) after [7 h. Iron(II) oxidation experiments in core top and bottom waters also showed removal from solution but at rates up to 5-times slower than predicted from theoretical reaction kinetics. These data imply the presence of ligands capable of complexing Fe(II) and supressing oxidation. The lower oxidation rate allows more time for the diffusion of Fe(II) from the sediments into the overlying water column. Modelling indicates significant diffusive fluxes of Fe(II) (on the order of 23-31 lmol m -2 day -1 ) are possible during late spring when oxygen penetration depths are shallow, and pore water Fe(II) concentrations are highest. In the water column this stabilised Fe(II) will gradually be oxidised and become part of the dFe(III) pool. Thus oxic continental shelves can supply dFe to the water column, which is enhanced during a small period of the year after phytoplankton bloom events when organic matter is transferred to the seafloor. This input is based on conservative assumptions for solute exchange (diffusion-reaction), whereas (bio)physical advection and resuspension events are likely to accelerate these solute exchanges in shelf-seas.

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Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

Lenstra

Hermans

Séguret

et al. 2020

Limnology & Oceanography

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Continental shelves are a major source of iron (Fe) and manganese (Mn) to marine waters. Here, we investigate controls on benthic release of Fe and Mn and the impact on the water column in the Baltic Sea. We find high in situ benthic release rates of dissolved Fe and Mn at seasonally hypoxic sites (bottom water oxygen between 0-63 μmol L −1) receiving high inputs of organic matter. We find that benthic Fe and Mn release is sensitive to bottom water oxygen concentrations. Benthic Fe release is likely additionally controlled by Fe-sulfur redox chemistry in the surface sediment. For Mn, benthic release correlates positively with Mn oxide availability in the surface sediment. Benthic release contributes to high dissolved Fe and Mn concentrations in the water column and is amplified by repeated cycling of Fe and Mn between the sediment and overlying water through benthic release, oxidation in the water column, deposition as metal oxides, followed by reductive dissolution. Most water column Fe ($ 80%) is present in particulate form near the seafloor. In contrast to Fe, a large percentage of the Mn remains dissolved ($ 50%). We show that easily reducible Fe and Mn oxides are key forms of particulate Fe and Mn in suspended matter. The Baltic Sea represents a highly eutrophic, low oxygen end-member when compared to other modern coastal systems. Our results imply that, upon continued eutrophication and deoxygenation of the coastal ocean, benthic release of dissolved Fe and Mn from continental shelves could become greater than previously thought.

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Iron and manganese diagenesis in deep sea volcanogenic sediments and the origins of pore water colloids

Cited by 70 publications

References 88 publications

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

Stability of dissolved and soluble Fe(II) in shelf sediment pore waters and release to an oxic water column

Coastal hypoxia and eutrophication as key controls on benthic release and water column dynamics of iron and manganese

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