The continental Si cycle and its impact on the ocean Si isotope budget

Frings, Patrick J.; Clymans, Wim; Fontorbe, Guillaume; Rocha, Christina L. De La; Conley, Daniel J.

doi:10.1016/j.chemgeo.2016.01.020

Cited by 212 publications

(298 citation statements)

References 258 publications

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“…This last sample is significantly depleted in 30 Si compared to the other studied silt fractions, possibly due to partial contamination by clays during our grainsize separation procedure. In contrast, clay-size fractions display Si isotopic compositions (d 30 Si clay ) from À0.11‰ (Fraser) to À2.16‰ (Rio Caura and Rio Caroni), which almost encompass the full range of d 30 Si data reported in the literature for bulk soils and clays (between about À2.95 and À0.16‰; Opfergelt and Delmelle, 2012;Frings et al, 2016). Many samples investigated during this study were collected in the marine environment, hence with the possibility that they could include some authigenic clays formed by early diagenetic processes (e.g.…”

Section: Resultsmentioning

confidence: 99%

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The silicon isotopic composition of fine-grained river sediments and its relation to climate and lithology

Bayon

Delvigne

Ponzevera

et al. 2018

Geochimica et Cosmochimica Acta

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The d 30 Si stable isotopic composition of silicon in soils and fine-grained sediments can provide insights into weathering processes on continents, with important implications on the Si budget of modern and past oceans. To further constrain the factors controlling the distribution of Si isotopes in sediments, we have analysed a large number (n = 50) of separate size-fractions of sediments and suspended particulate materials collected near the mouth of rivers worldwide. This includes some of the world's largest rivers (e.g. Amazon, Congo, Mackenzie, Mississippi, Murray-Darling, Nile, Yangtze) and rivers from the case study areas of the Congo River Basin and Northern Ireland. Silt-size fractions exhibit a mean Si isotopic composition (d 30 Si = À0.21 ± 0.19‰; 2 s.d.) similar to that previously inferred for the upper continental crust. In contrast, clay-size fractions display a much larger range of d 30 Si values from À0.11‰ to À2.16‰, which yield a global d 30 Si clay of À0.57 ± 0.60‰ (2 s.d.) representative of the mean composition of the average weathered continental crust. Overall, these new data show that the Si isotopic signature transported by river clays is controlled by the degree of chemical weathering, as inferred from strong relationships with Al/Si ratios. At a global scale, the clay-bound Si isotopic composition of the world's largest river systems demonstrates a link with climate, defining a general correlation with mean annual temperature (MAT) in corresponding drainage basins. While the distribution of Si isotopes in river sediments also appears to be influenced by the tectonic setting, lithological effects and sediment recycling from former sedimentary cycles, our results pave the way for their use as paleo-weathering and paleo-climate proxies in the sedimentary record.

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Section: Resultsmentioning

confidence: 99%

“…On continents, this 30 Si-enriched dissolved load is then available for biogeochemical cycling in diatoms and plants within the freshwater watersheds and being ultimately discharged into the oceans (e.g. Frings et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

The silicon isotopic composition of fine-grained river sediments and its relation to climate and lithology

Bayon

Delvigne

Ponzevera

et al. 2018

Geochimica et Cosmochimica Acta

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“…The canonical figure for annual bSi production is 240 Tmol (Tréguer and De La Rocha 2013), approximately 259 annual inputs of Si to the ocean (Frings et al 2016). Various approaches consistently indicate a large fractionaround 50%-60%-is remineralised in the upper 100 m. This leaves around 100 Tmol year -1 bSi as export production (Tréguer and De La Rocha 2013).…”

Section: Introductionmentioning

confidence: 99%

Revisiting the dissolution of biogenic Si in marine sediments: a key term in the ocean Si budget

Frings

2017

Acta Geochim

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Of the *240 9 10 12 mol year -1 of biogenic silica (bSi) produced by diatoms and other silicifying organisms, only roughly 3%-4% escapes dissolution to be permanently buried. At the global scale, how, where and why bSi is preserved in sediment is not well understood. To help address this, I compile 6245 porewater dissolved Si concentrations from 453 sediment cores, to derive the concentration gradient at the sediment-water interface and thus diffusive fluxes out of the sediment. These range from \0.002 to 3.4 mol m -2 year -1 , and are independent of temperature, depth and latitude. When classified by sediment lithology, predominantly siliceous sediments unsurprisingly have higher mean diffusive fluxes than predominantly calcareous or clay-rich sediment. Combined with the areal extent of these lithologies, the 'best-guess' global sedimentary bSi recycling flux is 69 9 10 12 mol year -1 .

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“…Diatoms are estimated to contribute up to 45% of the total ocean primary production (DeMaster, 1981;Tréguer et al, 1995;Mann, 1999;Yool and Tyrrell, 2003;Tréguer and De La Rocha, 2013;Bristow et al, 2017). Like the other nutrient cycles (nitrogen, phosphorus), the silicate cycle is linked with the global carbon cycle and participates in carbon dioxide (CO 2 ) sequestering in the ocean (Dugdale et al, 1995;Dugdale and Wilkerson, 1998;Falkowski et al, 1999;Yool and Tyrrell, 2003;Arrigo, 2005;Matear et al, 2010;Frings et al, 2016). To better understand the biogeochemical cycles, and the global carbon cycle and evaluate the consequences of anthropogenic nutrients releases and climate change, oceanic data are required with a very high spatio-temporal resolution.…”

Section: Introductionmentioning

confidence: 99%

First Deployment and Validation of in Situ Silicate Electrochemical Sensor in Seawater

et al. 2018

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An electrochemical sensor is proposed to measure silicate concentration, in situ, in the ocean without any addition of liquid reagent. From the analytical principle to the laboratory prototype toward the first in situ, immersible sensor, the evolution of the mechanical design is presented and discussed. The developed in situ electronics were compared to the commercial potentiostat and gave promising results to detect low silicate signals with a limit of quantification of 1 µmol L −1 .The flow rate of the pump appeared to be a crucial parameter in order to transfer the silicomolybdic complex formed from the "complexation cell" to the "detection cell" without dilution as well as to fill and rinse the whole circuit. The study of temperature effect revealed no influence on the electrochemical signal between ∼7 • and ∼21 • C. Finally the sensor was successfully deployed for the very first time on a mooring off Coquimbo, Chile and also integrated onto a PROVOR profiling float in the Mediterranean Sea off Villefranche-sur-Mer, France. The data collected and/or sent through satellite were in good agreement with the 2 reference samples and previously published values illustrating the great potential of this electrochemical sensor. A 7 days silicate time series from the mooring deployment off Chile is also presented.

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The continental Si cycle and its impact on the ocean Si isotope budget

Cited by 212 publications

References 258 publications

The silicon isotopic composition of fine-grained river sediments and its relation to climate and lithology

The silicon isotopic composition of fine-grained river sediments and its relation to climate and lithology

Revisiting the dissolution of biogenic Si in marine sediments: a key term in the ocean Si budget

First Deployment and Validation of in Situ Silicate Electrochemical Sensor in Seawater

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