Enhanced chemical weathering of albite under seawater conditions and its potential effect on the Sr ocean budget

Gruber, Chen; Harlavan, Yehudit; Pousty, Dana; Winkler, Daniel; Ganor, Jiwchar

doi:10.1016/j.gca.2019.06.049

Cited by 14 publications

(7 citation statements)

References 65 publications

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“…Our results suggesting that <5% of the CNSi was Na 2 CO 3 extractable indicate that ASi phases are negligible within this size fraction and that the CNSi may dissolve less readily than ASi in seawater. Feldspar minerals are traditionally considered to have low solubility in the ocean, although recent research has suggested that the dissolution of feldspars in seawater may be more significant than previously appreciated and should be accounted for to resolve marine elemental budgets (Gruber et al, 2019; Jeandel & Oelkers, 2015). Furthermore, rock‐crushing experiments have also demonstrated that submicron‐size feldspar particles are formed during physical grinding processes and that these phases are highly unstable in solution and rapidly dissolve to form DSi (Holdren & Berner, 1979).…”

Section: Discussionmentioning

confidence: 99%

The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

Pryer

Hawkings

Wadham

et al. 2020

Global Biogeochemical Cycles

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Glaciated environments have been highlighted as important sources of bioavailable nutrients, with inputs of glacial meltwater potentially influencing productivity in downstream ecosystems. However, it is currently unclear how riverine nutrient concentrations vary across a spectrum of glacial cover, making it challenging to accurately predict how terrestrial fluxes will change with continued glacial retreat. Using 40 rivers in Chilean Patagonia as a unique natural laboratory, we investigate how glacial cover affects riverine Si and Fe concentrations, and infer how exports of these bioessential nutrients may change in the future. Dissolved Si (as silicic acid) and soluble Fe (<0.02 μm) concentrations were relatively low in glacier-fed rivers, whereas concentrations of colloidal-nanoparticulate (0.02-0.45 μm) Si and Fe increased significantly as a function of glacial cover. These colloidal-nanoparticulate phases were predominately composed of aluminosilicates and Fe-oxyhydroxides, highlighting the need for size-fractionated analyses and further research to quantify the lability of colloidal-nanoparticulate species. We also demonstrate the importance of reactive particulate (>0.45 μm) phases of both Si and Fe, which are not typically accounted for in terrestrial nutrient budgets but can dominate riverine exports. Dissolved Si and soluble Fe yield estimates showed no trend with glacial cover, suggesting no significant change in total exports with continued glacial retreat. However, yields of colloidal-nanoparticulate and reactive sediment-bound Si and Fe were an order of magnitude greater in highly glaciated catchments and showed significant positive correlations with glacial cover. As such, regional-scale exports of these phases are likely to decrease as glacial cover disappears across Chilean Patagonia, with potential implications for downstream ecosystems. Glacial weathering processes have been identified to be particularly important in the generation of potentially bioavailable iron (Fe) (

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Section: Discussionmentioning

confidence: 99%

The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

Pryer

Hawkings

Wadham

et al. 2020

Global Biogeochemical Cycles

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“…The undersaturation of Si minerals is known to include most primary and secondary silicates; thus dissolution extends beyond BSi in marine sediments (Isson and Planavsky, 2018, and references therein). Indeed, a suite of experiments have shown that primary silicates and clay minerals can rapidly release Si when placed in DSi-undersaturated seawater and take up Si in DSi-enriched waters (Siever, 1968;Mackenzie et al, 1967;Lerman et al, 1975;Hurd et al, 1979;Fanning and Schink, 1969;Mackenzie and Garrels, 1965;Gruber et al, 2019;Pickering, 2020). Lerman et al (1975) determined in one such experiment that the dissolution of eight clay minerals could be described by a first-order reaction rate law driven by the saturation state, consistent with that applied here.…”

Section: Steady State Reaction-transport Modellingmentioning

confidence: 99%

Benthic silicon cycling in the Arctic Barents Sea: a reaction–transport model study

et al. 2022

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Abstract. Over recent decades the highest rates of water column warming and sea ice loss across the Arctic Ocean have been observed in the Barents Sea. These physical changes have resulted in rapid ecosystem adjustments, manifesting as a northward migration of temperate phytoplankton species at the expense of silica-based diatoms. These changes will potentially alter the composition of phytodetritus deposited at the seafloor, which acts as a biogeochemical reactor and is pivotal in the recycling of key nutrients, such as silicon (Si). To appreciate the sensitivity of the Barents Sea benthic system to the observed changes in surface primary production, there is a need to better understand this benthic–pelagic coupling. Stable Si isotopic compositions of sediment pore waters and the solid phase from three stations in the Barents Sea reveal a coupling of the iron (Fe) and Si cycles, the contemporaneous dissolution of lithogenic silicate minerals (LSi) alongside biogenic silica (BSi), and the potential for the reprecipitation of dissolved silicic acid (DSi) as authigenic clay minerals (AuSi). However, as reaction rates cannot be quantified from observational data alone, a mechanistic understanding of which factors control these processes is missing. Here, we employ reaction–transport modelling together with observational data to disentangle the reaction pathways controlling the cycling of Si within the seafloor. Processes such as the dissolution of BSi are active on multiple timescales, ranging from weeks to hundreds of years, which we are able to examine through steady state and transient model runs. Steady state simulations show that 60 % to 98 % of the sediment pore water DSi pool may be sourced from the dissolution of LSi, while the isotopic composition is also strongly influenced by the desorption of Si from metal oxides, most likely Fe (oxyhydr)oxides (FeSi), as they reductively dissolve. Further, our model simulations indicate that between 2.9 % and 37 % of the DSi released into sediment pore waters is subsequently removed by a process that has a fractionation factor of approximately −2 ‰, most likely representing reprecipitation as AuSi. These observations are significant as the dissolution of LSi represents a source of new Si to the ocean DSi pool and precipitation of AuSi an additional sink, which could address imbalances in the current regional ocean Si budget. Lastly, transient modelling suggests that at least one-third of the total annual benthic DSi flux could be sourced from the dissolution of more reactive, diatom-derived BSi deposited after the surface water bloom at the marginal ice zone. This benthic–pelagic coupling will be subject to change with the continued northward migration of Atlantic phytoplankton species, the northward retreat of the marginal ice zone and the observed decline in the DSi inventory of the subpolar North Atlantic Ocean over the last 3 decades.

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“…The undersaturation of Si minerals is known to include most primary and secondary silicates, thus dissolution extends beyond BSi in marine sediments (Isson and Planavsky (2018) and references therein). Indeed, a suite of experiments have shown that primary silicates and clay minerals can rapidly release Si when placed in DSi undersaturated seawater and take up Si in DSi enriched waters (Siever, 1968;Mackenzie et al, 1967;Lerman et al, 1975;Hurd et al, 1979;Fanning and Schink, 1969;Mackenzie and Garrels, 1965;Gruber et al, 2019;Pickering, 2020). Lerman et al (1975) determined in one such experiment that the dissolution of eight clay minerals could be described by a first-order reaction rate law driven by the saturation state, consistent with that applied here.…”

Section: Steady State Reaction-transport Modellingmentioning

confidence: 99%

Benthic Silicon Cycling in the Arctic Barents Sea: a Reaction-Transport Model Study

Ward

Hendry

Arndt

et al. 2022

Preprint

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Abstract. Over recent decades the highest rates of water column warming and sea ice loss across the Arctic Ocean have been observed in the Barents Sea. These physical changes have resulted in rapid ecosystem adjustments, manifesting as a northward migration of temperate phytoplankton species at the expense of silica-based diatoms. These changes will potentially alter the composition of phytodetritus deposited at the seafloor, which acts as a biogeochemical reactor, pivotal in the recycling of key nutrients, such as silicon (Si). To appreciate the sensitivity of the Barents Sea benthic system to the observed changes in surface primary production, there is a need to better understand this benthic-pelagic coupling. Stable Si isotopic compositions of sediment pore waters and the solid phase from three stations in the Barents Sea reveal a coupling of the iron (Fe) and Si cycles, the contemporaneous dissolution of lithogenic silicate minerals (LSi) alongside biogenic silica (BSi) and the potential for the reprecipitation of dissolved silicic acid (DSi) as authigenic clay minerals (AuSi). However, as reaction rates cannot be quantified from observational data alone, a mechanistic understanding of which factors control these processes is missing. Here, we employ reaction-transport modelling together with observational data to disentangle the reaction pathways controlling the cycling of Si within the seafloor. Processes such as the dissolution of BSi are active on multiple timescales, ranging from weeks to hundreds of years, which we are able to examine through steady state and transient model runs. Steady state simulations show that 60 to 98 % of the sediment pore water DSi pool may be sourced from the dissolution of LSi, while the isotopic composition is also strongly influenced by the desorption of Si from metal oxides, most likely Fe (oxyhydr)oxides (FeSi), as they reductively dissolve. Further, our model simulations indicate that between 2.9 and 37 % of the DSi released into sediment pore waters is taken up with a fractionation factor of approximately −2 ‰, most likely representing reprecipitation as AuSi. These observations are significant, as the dissolution of LSi represents a source of new Si to the ocean DSi pool and precipitation of AuSi an additional sink, which could address imbalances in the current regional ocean Si budget. Lastly, transient modelling suggests that at least one-third of the total annual benthic DSi flux could be sourced from the dissolution of more reactive, diatom-derived BSi deposited after the surface water bloom at the marginal ice zone. This benthic-pelagic coupling will be subject to change with the continued northward migration of Atlantic phytoplankton species, northward retreat of the marginal ice zone and the observed decline in DSi inventory of the subpolar North Atlantic Ocean over the last three decades.

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Enhanced chemical weathering of albite under seawater conditions and its potential effect on the Sr ocean budget

Cited by 14 publications

References 65 publications

The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

The Influence of Glacial Cover on Riverine Silicon and Iron Exports in Chilean Patagonia

Benthic silicon cycling in the Arctic Barents Sea: a reaction–transport model study

Benthic Silicon Cycling in the Arctic Barents Sea: a Reaction-Transport Model Study

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