Mineralogical and chemical variability of fluvial sediments 2. Suspended-load silt (Ganga–Brahmaputra, Bangladesh)

Garzanti, Eduardo; Andó, Sergio; France‐Lanord, Christian; Censi, P.; Vignola, Pietro; Galy, Valier; Lupker, Maarten

doi:10.1016/j.epsl.2010.11.043

Cited by 329 publications

(222 citation statements)

References 81 publications

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“…These different end-members may be induced by mineralogical sorting of different minerals 328 bearing Na such as albite (Garzanti et al, 2010;2011) The isotopic composition of carbonates is shown in Figure 10 and is in agreement with 419 published data for bedload samples from the Ganga basin (Galy et al, 1999 Chambal sediment contribution to the Ganga sediment load also highlights that even in these 553 large systems, the transfer of suspended sediments can be rapid and vary on an annual basis. 554…”

Section: Introduction 26 27supporting

confidence: 77%

“…Albite being the main Nacarrier in Ganga sediments (Garzanti et al, 2011), the release of Na is mainly attributed to its 692 weathering into kaolinite or smectite. …”

Section: Possible Weathering Mechanisms 687 688mentioning

confidence: 99%

“…Calcite and dolomite are also abundant. For detailed mineralogical analysis see 263 Garzanti et al (2010) and Garzanti et al (2011). In the Ganga River basin, sediment load 264 increases bottomward by a factor of 2 to 3 between the shallowest and deepest samples.…”

Section: Introduction 26 27mentioning

confidence: 99%

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Predominant floodplain over mountain weathering of Himalayan sediments (Ganga basin)

Lupker

France‐Lanord

Galy

et al. 2012

Geochimica et Cosmochimica Acta

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1We present an extensive river sediment dataset covering the Ganga basin from the Himalayan 2 front downstream to the Ganga mainstream in Bangladesh. These sediments were mainly 3 collected over several monsoon seasons and include depth profiles of suspended particles in 4 the river water column. Mineral sorting is the first order control on the chemical composition 5 of river sediments. Taking into account this variability we show that sediments become 6 significantly depleted in mobile elements during their transit through the floodplain.

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Section: Introduction 26 27supporting

confidence: 77%

“…Albite being the main Nacarrier in Ganga sediments (Garzanti et al, 2011), the release of Na is mainly attributed to its 692 weathering into kaolinite or smectite. …”

Section: Possible Weathering Mechanisms 687 688mentioning

confidence: 99%

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Predominant floodplain over mountain weathering of Himalayan sediments (Ganga basin)

Lupker

France‐Lanord

Galy

et al. 2012

Geochimica et Cosmochimica Acta

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265

210

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“…These very similar constants show that the behaviour of Himalayan sediments with respect to the cation exchange composition is very similar to the sediments transported by the Amazon. These similarities most probably stem from the first-order resemblance of the mineralogical composition of both rivers (Garzanti et al, 2011;Martinelli et al, 1993).…”

Section: Nature Of Adsorbed Cationsmentioning

confidence: 98%

“…It should nevertheless be kept in mind that our estimates are formulated based on the Himalayan system at present. On longer timescales, the variability in both sediment (Goodbred and Kuehl, 2000) and weathering fluxes (Lupker et al, 2013) means that the relative importance of cation exchange fluxes in the global weathering budget has likely varied and hence should be treated carefully. Finally, it is worth mentioning that these estimates of weathering impact on the carbon cycle do not take into account the role of chemical weathering through sulfuric acid (Galy and France-Lanord, 1999;Turchyn et al, 2013) that is known to also contribute to the weathering budget of Himalayan erosion and does counteract long-term carbon sequestration (Calmels et al, 2007).…”

Section: Effect Of Cation Exchange On the Long-term Carbon Budget Of mentioning

confidence: 99%

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

2016

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Abstract. Continental-scale chemical weathering budgets are commonly assessed based on the flux of dissolved elements carried by large rivers to the oceans. However, the interaction between sediments and seawater in estuaries can lead to additional cation exchange fluxes that have been very poorly constrained so far. We constrained the magnitude of cation exchange fluxes from the Ganga-Brahmaputra river system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the river water column as a result of hydrological sorting of minerals with depth that control grain sizes and surface area. The average CEC of the integrated sediment load of the Ganga-Brahmaputra is estimated ca. 6.5 meq 100 g −1 .The cationic charge of sediments in the river is dominated by bivalent ions Ca 2+ (76 %) and Mg 2+ (16 %) followed by monovalent K + (6 %) and Na + (2 %), and the relative proportion of these ions is constant among all samples and both rivers. Assuming a total exchange of exchangeable Ca 2+ for marine Na + yields a maximal additional Ca 2+ flux of 28 × 10 9 mol yr −1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca 2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca 2+ is exchanged, not only for marine Na + but also Mg 2+ and K + , estuarine cation exchange for the GangaBrahmaputra is responsible for an additional Ca 2+ flux of 23 × 10 9 mol yr −1 , while ca. 27 × 10 9 mol yr −1 of Na + , 8 × 10 9 mol yr −1 of Mg 2+ and 4 × 10 9 mol yr −1 of K + are re-absorbed in the estuaries. This represents an additional riverine Ca 2+ flux to the ocean of 5 % compared to the measured dissolved flux. About 15 % of the dissolved Na + flux, 8 % of the dissolved K + flux and 4 % of the Mg 2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange appears to be limited when evaluated in the context of the long-term carbon cycle and its main effect is the sequestration of a significant fraction of the riverine Na flux to the oceans. The limited exchange fluxes of the Ganga-Brahmaputra relate to the lower than average CEC of its sediment load that do not counterbalance the high sediment flux to the oceans. This can be attributed to the nature of Himalayan river sediment such as low proportion of clays and organic matter.

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Anthropophile elements in river sediments: Overview from the Seine River, France

Chen

Gaillardet

Bouchez

et al. 2014

Geochem Geophys Geosyst

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In contrast to larger river systems that drain relatively pristine basins, little is known about the sediment geochemistry of rivers impacted by intense human activities. In this paper, we present a systematic investigation of the anthropogenic overprints on element geochemistry in sediments of the humanimpacted Seine River, France. Most elements are fractionated by grain size, as shown by the comparison between suspended particulate matter (SPM) and riverbank deposits (RBD). The RBD are particularly coarse and enriched in carbonates and heavy minerals and thus in elements such as Ba, Ca, Cr, Hf, Mg, Na, REEs, Sr, Ti, Th, and Zr. Although the enrichment/depletion pattern of some elements (e.g., K, REEs, and Zr) can largely be explained by a binary mixture between two sources, other elements such as Ag, Bi, Cr, Cd, Co, Cu, Fe, Mo, Ni, Pb, Sb, Sn, W, and Zn in SPM in Paris show that a third end-member having anthropogenic characteristics is needed to account for their enrichment at low water stage. These ''anthropophile'' elements, with high enrichment factors (EFs) relative to the upper continental crust (UCC), display a progressive enrichment downstream and different geochemical behaviors with respect to the hydrodynamic conditions (e.g., grain size) compared to elements having mainly a natural origin. Our findings emphasize the need for systematic studies of these anthropophile elements in other human-impacted rivers using geochemical normalization techniques, and stress the importance of studying the chemical variability associated with hydrodynamic conditions when characterizing riverine element geochemistry and assessing their flux to the ocean.

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Mineralogical and chemical variability of fluvial sediments 2. Suspended-load silt (Ganga–Brahmaputra, Bangladesh)

Cited by 329 publications

References 81 publications

Predominant floodplain over mountain weathering of Himalayan sediments (Ganga basin)

Predominant floodplain over mountain weathering of Himalayan sediments (Ganga basin)

Impact of sediment–seawater cation exchange on Himalayan chemical weathering fluxes

Anthropophile elements in river sediments: Overview from the Seine River, France

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