Reactivity of biogenic silica: Surface versus bulk charge density

Loucaides, Socratis; Behrends, Thilo; Cappellen, Philippe Van

doi:10.1016/j.gca.2009.10.038

Cited by 68 publications

(60 citation statements)

References 79 publications

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“…Future work should focus on (i) the quantification of this pool, (ii) physicochemical analyses of its components and (iii) their dissolution kinetics in lab experiments. The combination of modern microscopical (SEM-EDX, laser scanning microscopy) (this study; Puppe et al, 2016;Sommer et al, 2013) and spectroscopical (FTIR and micro-FTIR spectroscopy) (Liu et al, 2013;Loucaides et al, 2010;Rosén et al, 2010) methods might introduce new insights to this field.…”

Section: Discussionmentioning

confidence: 99%

How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil–plant system

et al. 2017

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Abstract. The significance of biogenic silicon (BSi) pools as a key factor for the control of Si fluxes from terrestrial to aquatic ecosystems has been recognized for decades. However, while most research has been focused on phytogenic Si pools, knowledge of other BSi pools is still limited. We hypothesized that different BSi pools influence short-term changes in the water-soluble Si fraction in soils to different extents. To test our hypothesis we took plant (Calamagrostis epigejos, Phragmites australis) and soil samples in an artificial catchment in a post-mining landscape in the state of Brandenburg, Germany. We quantified phytogenic (phytoliths), protistic (diatom frustules and testate amoeba shells) and zoogenic (sponge spicules) Si pools as well as Tironextractable and water-soluble Si fractions in soils at the beginning (t 0 ) and after 10 years (t 10 ) of ecosystem development. As expected the results of Tiron extraction showed that there are no consistent changes in the amorphous Si pool at Chicken Creek (Hühnerwasser) as early as after 10 years. In contrast to t 0 we found increased water-soluble Si and BSi pools at t 10 ; thus we concluded that BSi pools are the main driver of short-term changes in water-soluble Si. However, because total BSi represents only small proportions of water-soluble Si at t 0 (< 2 %) and t 10 (2.8-4.3 %) we further concluded that smaller (< 5 µm) and/or fragile phytogenic Si structures have the biggest impact on short-term changes in water-soluble Si. In this context, extracted phytoliths (> 5 µm) only amounted to about 16 % of total Si contents of plant materials of C. epigejos and P. australis at t 10 ; thus about 84 % of small-scale and/or fragile phytogenic Si is not quantified by the used phytolith extraction method. Analyses of small-scale and fragile phytogenic Si structures are urgently needed in future work as they seem to represent the biggest and most reactive Si pool in soils. Thus they are the most important drivers of Si cycling in terrestrial biogeosystems.

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Section: Discussionmentioning

confidence: 99%

How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil–plant system

et al. 2017

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“…We note that the acidity of silanol groups may depend not only on hydrogen bonding to surface O atoms, but also on the electrostatic screening of charged >SiO -sites by ions in the electrical double layer 11 and on the dielectric screening of those sites by interfacial water 77,81,84 , both of which may vary with confinement or interfacial curvature.…”

Section: Water Density Distributionmentioning

confidence: 96%

“…(1) determines silica surface charge, an important parameter in the reactivity of silicate glasses and minerals 7,11,72,73 and the design of nanofluidic devices 74,75 . According to bond valence models [76][77][78][79] , the intrinsic pK a value of silanol groups may be sensitive to the number of hydrogen bonds received by the silanol O atom.…”

Section: Water Density Distributionmentioning

confidence: 99%

Molecular Dynamics Simulations of Water Structure and Diffusion in Silica Nanopores

2012

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We present molecular dynamics (MD) simulations of water-filled silica nanopores such as those that occur in ordered oxide ceramics (MCM-41, SBA-15), controlled pore glasses (such as Vycor glass), mesoporous silica, bioglasses, and hydrous silica gel coatings of weathered minerals and glasses. Our simulations overlap the range of pore diameters (1 to 4 nm) where confinement causes the disappearance of bulk-liquid-like water. In ≥ 2 nm diameter pores, the silica surface carries three statistical monolayers of density-layered water, interfacial water structure is independent of confinement or surface curvature, and bulk-liquid-like water exists at the center of the pore (this last finding contradicts assumptions used in most previous neutron diffraction studies and in several MD simulation studies of silica nanopores). In 1 nm diameter pores, bulk-liquidlike water does not exist and the structural properties of interfacial water are influenced by confinement. Predicted water diffusion coefficients in 1 to 4 nm diameter pores agree with quasi-elastic neutron scattering (QENS) data and are roughly consistent with a very simple "core-shell" conceptual model whereupon the first statistical water monolayer is immobile and the rest of the pore water diffuses as rapidly as bulk liquid water.

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“…Diatom frustules from the sediments have naturally lower solubility and are more resistant to dissolution than fresh diatom material, even after treatment with acid and other cleanings (Lewin 1961;Dixit et al 2001;Van Cappellen et al 2002). This may be due to the decreased reactivity of the silica surfaces and increasing organization of the internal structure with age due to the polymerization of the silanol groups in the silica (Loucaides et al 2010;Van Cappellen 1996;Van Cappellen et al 2002). Such permanent structural changes to reactive properties would render them more resistant to chemical attack during prolonged exposure to hydrogen peroxide and/or to any adverse effects of organic solutes.…”

Section: Implications For Sedimentary Cleaning Protocolsmentioning

confidence: 99%

Cleaning methods for the isotopic determination of diatombound nitrogen in non‐fossil diatom frustules

Morales

Sigman

Horn

et al. 2013

Limnology & Ocean Methods

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Ground-truthing the stable isotope ratio of diatom frustule-bound organic nitrogen (N) as a paleoceanographic proxy of phytoplankton nutrient consumption calls for studies of modern diatoms from cultures and the field. This work has been hindered by the lack of a method to prepare fresh diatom material, which has significant geochemical differences from sedimentary fossil diatom, for analysis. We tested and compared the performance of five oxidative treatment protocols in cleaning fresh diatom frustules of external organic material for isotopic analysis of diatom frustule-bound N. We applied each treatment to diatom material from a T. weissflogii culture and measured the diatom-bound N content and isotopic composition (d 15 N) of samples. A favored treatment is described that includes a multi-step, progressive, oxidative cleaning. The results suggest that the application of H 2 O 2 to fresh biogenic opal for more than 20 min increased the accessibility of the N within the opal matrix to subsequent chemical treatment, an effect not observed for diatom frustules from deep ocean sediments. We attribute this effect to structural alteration and dissolution of the diatom opal by the H 2 O 2 , consistent with previous observations regarding the high reactivity of fresh diatom opal and its subsequent chemical hardening in the sedimentary environment. In addition, the presence of high levels of organic matter upon treatment with H 2 O 2 may exacerbate the chemical alteration of frustules. We find that the d 15 N of diatom-bound N is ~3 ‰ higher than that of the bulk culture biomass, consistent with expectations from surface sediment and down-core measurements.

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Reactivity of biogenic silica: Surface versus bulk charge density

Cited by 68 publications

References 79 publications

How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil–plant system

How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil–plant system

Molecular Dynamics Simulations of Water Structure and Diffusion in Silica Nanopores

Cleaning methods for the isotopic determination of diatombound nitrogen in non‐fossil diatom frustules

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