Cation-exchange characteristics of Amazon River suspended sediment and its reaction with seawater

Sayles, F.L.; Mangelsdorf, Paul C.

doi:10.1016/0016-7037(79)90260-6

Cited by 82 publications

(47 citation statements)

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“…The equilibrium constant, K v , for sediments of the Ganga, Brahmaputra and lower Meghna is relatively similar (between 1.7 and 2 for p = 1) despite the use of average dissolved river water compositions that do not take into account for the compositional variability of these rivers (Galy and France-Lanord, 1999;Singh et al, 2005). Using a p value of 0.76 as found in Amazon sediments (Sayles and Mangelsdorf, 1979), the calculated K v ranges from 2.1 to 2.5, also in agreement with the equilibrium constants found on the Amazon (Table 1). 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.…”

Section: Nature Of Adsorbed Cationsmentioning

confidence: 99%

“…Molar fractions occupied by the major cations on the river sediments are indicated as X Na , X K , X Ca and X Mg . The exchange coefficient for a binary Ca-Mg exchange in an average Ganga, Brahmaputra and lower Meghna river water composition is given for a p-exponent value of 1 and 0.76 as in Sayles and Mangelsdorf (1979); see text for more details. Samples BR1027 and BR207 are average values of n = 7 replicates each.…”

Section: Nature Of Adsorbed Cationsmentioning

confidence: 99%

“…The composition of sediment exchangeable cations is, to a first order, imposed by the dissolved composition of the river water transporting these sediments. For the two most abundant adsorbed cations, the binary Ca / Mg exchange is commonly described as an exchange isotherm with an equilibrium constant K v (Sayles and Mangelsdorf, 1979), such that…”

Section: Total Cation Exchange Capacitymentioning

confidence: 99%

“…For the Amazon, Sayles and Mangelsdorf (1979) estimated that cation exchange fluxes remained under 10 % of the dissolved flux for the major elements Na, Mg, Ca and K. On a global scale, first-order estimates suggest that cation exchange can account for an extra Ca 2+ flux to the ocean ranging from 5 to 20 % of the riverine dissolved flux (Berner and Berner, 2012;Berner et al, 1983;Holland, 1978). Nevertheless, these exchange fluxes to the oceans have received little attention and are currently poorly constrained.…”

mentioning

confidence: 99%

“…Nevertheless, these exchange fluxes to the oceans have received little attention and are currently poorly constrained. Global estimates mainly rely on the upscaling of the Amazon data from Sayles and Mangelsdorf (1979) and the magnitude of these fluxes has so far not been assessed for other major river systems.…”

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confidence: 99%

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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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Section: Nature Of Adsorbed Cationsmentioning

confidence: 99%

Section: Nature Of Adsorbed Cationsmentioning

confidence: 99%

Section: Total Cation Exchange Capacitymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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

2016

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The Power Exchange Function: A General Model for Metal Adsorption onto Geological Materials

Langmuir

1981

Adsorption From Aqueous Solutions

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Fresh Water Geochemistry, Overview

Depetris¹

2017

Encyclopedia of Sustainability Science and Technology

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Aquifer An underground layer of water-bearing permeable rock, rock fractures, or porous unconsolidated materials (gravel, sand, or silt) from which groundwater can be obtained by means of a water well. Colloid A mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. The dispersed-phase particles have a diameter of approximately between 1 and 1000 nanometers (1 nm = 10 À9 m). Congruent dissolution A mineral or salt is completely dissolved in water, adding elements to the solvent in the same proportions that existed in the original solid. Conservative elements Cl À , SO 4 2À , NO 3 À , Ca 2+ , Mg 2+ , Na + , and K + are considered conservative in the sense that their concentrations are unaltered by changes in pH, temperature, or pressure, assuming that no precipitation or dissolution of solid phases or biological transformations occur within the ranges normally found near the surface of the Earth. Denudation Involves the processes that cause the wearing away of the Earth's surface by moving water, by ice, by wind, and by waves, leading to a reduction in elevation and in relief of landforms and landscapes. Exogenous cycle The sum of processes triggered by forces on or above the Earth's surface. Hydrolysis A chemical reaction wherein a water molecule and a reactant exchange functional

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Cation-exchange characteristics of Amazon River suspended sediment and its reaction with seawater

Cited by 82 publications

References 10 publications

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

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

The Power Exchange Function: A General Model for Metal Adsorption onto Geological Materials

Fresh Water Geochemistry, Overview

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