36. HIGH-RESOLUTION SILICA PORE-WATER PROFILES IN …

The silica pore-water concentration in the intervals between 50 and 250 mbsf appears to be rather low and relatively stable, with only a minor decrease with depth (Fig. 1). The occurrence of organic-rich turbidites containing some biogenic silica coincides with enhanced levels of pore-water silica in the sediments of the upper 50 mbsf (Fig.

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Ecological significance of biogenic silica in the East ...

ine flux of dissolved silica has decreased, but those of dissolved inorganic nitrogen and phosphate have in-creased in the Changjiang, leading to decreasing Si:N and Si:P ratios in the adjacent coastal waters, with poten-tial silica limitation of diatom growth (Li & Cheng 2001). The Si:N ratios in the Changjiang may decrease in the

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Organic matter mineralization in the pore water of a ...

The chemical composition of the pore water from the sediment of a eutrophic lake is dominated by high concentrations of total dissolved CO 2 (up to 12 mM), reduced soluble iron (up to 2 mM) and dissolved silica (up to 1 mM). The pH lies within the range of 6.70 ± 0.02; this reflects that the pore water is efficiently buffered by the CO 2 acid/base system.

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Question: Does Silica Dissolve In Water - SeniorCare2Share

Reactive silica is dissolved in water as the bisilicate ion making it a very weak acid. This form is a polymeric form of silica where the particles are ultra-fine and cannot be filtered out of the water using normal filtration techniques. Colloidal silica cannot be removed using ion-exchange methods.

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Dissolution of silica and the development of concentration ...

The pore water concentrations of dissolved silica in sediment cores from the continental slope offshore from Cape Hatteras, North Carolina, varied from 150 to almost 700 mu M with depth in the top ...

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Porewater nutrients from sediments collected during the ...

Porewater nutrients from sediments collected during the SWERUS-C3 expedition 2014 on the East Siberian shelf and slope Volker Brüchert, Xiaole Sun This dataset contains the major nutrients ammonium, dissolved silica, dissolved inorganic phosphate collected from the porewaters of sediment from 16 stations in the Laptev and East Siberian Sea in ...

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EarthChem Library - Repository | Dataset Information

Bottom water and porewater dissolved phosphate, ammonium, nitrate, nitrite and silica concentration in winter, summer and fall treatment incubation cores collected from a peat bog in Karrendorfer Wiesen, Germany. Also included are the polyphosphate concentration, dissolved and sediment elemental concentration from the winter treatment.

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Biogenic silica dissolution in sediments of the Southern ...

The principal oceanographic control on pore water silica build-up in the cores studied is the ratio of the deposition fluxes of biogenic silica and detrital material. Solubility differences inherited from the biomineralization process in the surface waters do not appear to have a significant effect on the observed pore water silica levels.

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(PDF) Freshwater marshes as dissolved silica recyclers in ...

Freshwater marshes as dissolved silica recyclers in an estuarine environment (Schelde estuary, Belgium) ... pore water) along these estuaries and to quantify. the fluxes between these compartments.

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Water column anomalies in dissolved silica over opaline ...

Recent estimates based on pore water studies and mass balance considerations put the average flux of dissolved silica from the sediments into the deep water at about 3 μmol cm -2 yr -1 . This flux, if mixed uniformly in a bottom layer 100 m thick, results in an anomaly increment of 0.3 μmol kg -1 yr -1 .

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Alkali-Silica Reaction and High Performance Concrete

Also, the amount of alkalis present in the pore water is related to the amount of soluble alkalis present in the cement. The hydroxide ions will attack a silica surface. If the silica is well crystallized the vulnerable sites are only at the exterior surface of the aggregate (Figure 1a), but in the case of poorly crystallized silica, there are many

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Diffusivity of dissolved silica in rock pore water at 25 ...

Diffusivity of dissolved silica in rock pore water at 25 Cas characterized by through-diffusion experiments Tadashi Yokoyama1 Received 8 March 2013; revised 8 November 2013; accepted 25 November 2013; published 11 December 2013. [1] The diffusivity of dissolved Si in rock pore water at 25 C was evaluated by through-diffusion experiments for ...

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Dissolved silica concentrations and reactions in pore ...

The pore water concentrations of dissolved silica in sediment cores from the continental slope offshore from Cape Hatteras, North Carolina, varied from 150 to almost 700 μ,M with depth in the top 40 cm of sediment. Sediment cores from 630 to 2010 m depth had very similar profiles of dissolved silica in their pore waters, even though these cores came from regions greatly different in slope ...

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Freshwater marshes as dissolved silica recyclers in an ...

The marsh was shown to act as silica recycler, resupplying biologically available dissolved Si to the estuarine ecosystem. Extrapolations show that during summer and spring months, when dissolved silica is depleted due to diatom growth, almost half of the total dissolved silica load in the main river channel could result from marsh recycling.

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Dissolved Silca — UCL Department of Geography

Silica standard: stabilise approximately 30g of Na 2 SiO 3 .5H 2 O by placing it in a desiccator for 3 hours. Dissolve 17.65g of the stable compound in water and dilute to 1 litre. Pipette 10ml of this solution into a volumetric flask and make up to 1 litre with deionised water. 1.00ml = 0.050mg SiO 2.

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SILICA - Master Water

Silica, such as quartz, is present in most of the earth's minerals. Silica is a hard, glassy-like mineral that is found dissolved in water as a result from the bedrock it passes through, like sandstone and granite. In well and surface water, it can range from 1-100 parts per million as dissolved (reactive) or undissolved (colloidal) silica.

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Diffusivity of dissolved silica in rock pore water at 25°C ...

[1] The diffusivity of dissolved Si in rock pore water at 25°C was evaluated by through-diffusion experiments for three types of rock (Fontainebleau sandstone, Berea sandstone, and Tenjyosan rhyolite). Comparisons of the effective diffusion coefficients of Si, K +, and Cl − (,, and ) at neutral pH (unbuffered) showed that the values obtained for the three rocks were 2.3–3.0 times ...

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Dissolved Silica - an overview | ScienceDirect Topics

Accumulations of dissolved silica in bulk solution as well as within pore water of gel layers reduce reaction rates with time. Such "saturation effect" implies that local equilibrium is reached between dissolved silica and alkali-depleted basaltic glass surface [61]. In both cases, silica-saturated or unsaturated situations, similar ...

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Vegetation and proximity to the river control amorphous ...

Although ASi concentrations in soils were low (between 0.1 and 1% of soil dry weight), ASi controlled the availability of dissolved silica (DSi) in the porewater, and thus potentially the exchange of DSi with the nearby river system through both diffusive and advective fluxes.

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(PDF) Porewater evidence for a dynamic sedimentary iron ...

tation kinetics, and porewater solutions Dissolved silica and ammonium were al- strongly supersaturated for these minerals ways higher at the sandier, western site (Figs. have been reported (Postma 198 1; Lord 5, 6). Chloride concentrations at both sites 1980). ...

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Hydrothermal flow through the Mariana Mounds: Dissolution ...

Abstract. We apply one-dimensional advection-diffusion-reaction equations to interpret amorphous silica, dissolved silica, organic carbon, and dissolved nitrate concentrations from the Mariana Mounds ridgeflank hydrothermal system as a means of elucidating the effects of convectively driven porewater flow on the dissolution of amorphous silica and degradation of organic carbon in sediments.

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Distribution and budget of biogenic silica in the Yangtze ...

The distribution, source, transportation and transformation of biogenic silica (BSi) in suspended particulate matter (SPM) and core sediments were comprehensively investigated; dissolved silica (DSi) in pore water was also analyzed in this work.

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The ebb and flood of Silica: Quantifying dissolved and ...

Net fluxes indicated that the marsh is a point source of dissolved silica to the estuary in the summer with a net flux of approximately 169 mol h -1, demonstrating that this system exports DSi on the same magnitude as some nearby, mid-sized rivers. ... and porewater, and therefore, have the potential to play a substantial role in the ...

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Effects of pore size on water dynamics in mesoporous silica

Water confined in mesoporous silica plays a central role in its many uses ranging from gas sorption to nanoconfined chemical reactions. Here in this paper, the influence of pore diameter (2.5–5.4 nm) on water hydrogen bond (H-bond) dynamics …

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(PDF) Effect of Dissolved Silica on Immobilization of ...

range of dissolved species in the pore water. Among these, dissolved silica is frequently the dominant. species when magnesium oxide is mixed with the soils, as the solubility of silica minerals ...

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Diffusion Coefficient of Silica in Seawater | Nature ...

THE diffusion coefficient of dissolved monomeric silica in seawater of 36.1% salinity has been determined at 25° C by the diaphragm cell method. The value of the coefficient D is 1.0±0.05×10− ...

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SILICIFICATION

controls (matrix and pore-water geochemistry). There is a temporal pattern of silicification—it is more common in Paleozoic rocks than younger rocks—but it is also strongly linked to local factors (i.e., high dissolved silica levels associated with volcanic deposits). Linking that pattern to

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Silicon isotope composition of dissolved silica in surface ...

Land ocean silica fluxes pass estuaries. Recent data suggest that the isotopic composition of dissolved silica (DSi) is not altered during this transition. This could have major implication for the oceanic isotopic silicon cycle. To improve our knowledge about isotopic Si cycling in estuaries we investigate the silicon isotopic composition (δ30Si) of DSi of the Elbe Estuary and for the …

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Effects of pore size on water dynamics in mesoporous silica

of the silica pores consists of 1.9 ps and 14.6 ps components. Con-trasting these time scales with the core (and bulk liquid) values of 0.5 ps and 1.6 ps indicates dramatically slower H-bond dynamics near the surface. Finally, in contrast to the usual assumption of a uniformly distributed probe in the nanostructure,7,14,21 the simula-

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Survey Data Report in Support of the Sediment Ecological ...

dissolved organic carbon in pore water, (2) conducting sea urchin, Arbacia punctulata, fertilization and embryological development porewater toxicity tests (3) conducting porewater toxicity test with embryolarval redfish, Sciaenops ocellatus, and (4) conducting algal zoospoore, Ulva fasciata, germination and growth porewater toxicity tests.

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