Drivers of leaf carbon exchange capacity across biomes at the continental scale

Ecology ◽  
2018 ◽  
Vol 99 (7) ◽  
pp. 1610-1620 ◽  
Author(s):  
Nicholas G. Smith ◽  
Jeffrey S. Dukes
Keyword(s):  
Exchange Capacity ◽  
Carbon Exchange ◽  
Continental Scale

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

2016 ◽  
Vol 4 (3) ◽  
pp. 675-684 ◽  
Author(s):  
Maarten Lupker ◽  
Christian France-Lanord ◽  
Bruno Lartiges
Keyword(s):  
Cation Exchange ◽  
Chemical Weathering ◽  
Sediment Load ◽  
Relative Proportion ◽  
River System ◽  
Exchange Capacity ◽  
Sediment Flux ◽  
Continental Scale ◽  
The Impact

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 Ca2+ (76 %) and Mg2+ (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 Ca2+ for marine Na+ yields a maximal additional Ca2+ flux of 28  ×  109 mol yr−1 of calcium to the ocean, which represents an increase of ca. 6 % of the actual river dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga–Brahmaputra is responsible for an additional Ca2+ flux of 23  ×  109 mol yr−1, while ca. 27  ×  109 mol yr−1 of Na+, 8  ×  109 mol yr−1 of Mg2+ and 4  ×  109 mol yr−1 of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ 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 Mg2+ 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.

scholarly journals Linking flux network measurements to continental scale simulations: ecosystem carbon dioxide exchange capacity under non-water-stressed conditions

2007 ◽  
Vol 0 (0) ◽  
pp. 070621084512032-???
Author(s):  
KATHERINE E. OWEN ◽  
JOHN TENHUNEN ◽  
MARKUS REICHSTEIN ◽  
QUAN WANG ◽  
EVA FALGE ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Exchange Capacity ◽  
Carbon Dioxide Exchange ◽  
Network Measurements ◽  
Continental Scale ◽  
Ecosystem Carbon

scholarly journals Precipitation thresholds regulate net carbon exchange at the continental scale

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhihua Liu ◽  
Ashley P. Ballantyne ◽  
Benjamin Poulter ◽  
William R. L. Anderegg ◽  
Wei Li ◽  
...  
Keyword(s):  
Carbon Exchange ◽  
Continental Scale ◽  
Net Carbon Exchange ◽  
Precipitation Thresholds

scholarly journals Impact of sediment-seawater cation exchange on Himalayan chemical weathering fluxes

2016 ◽  
Author(s):  
Maarten Lupker ◽  
Christian France-Lanord ◽  
Bruno Lartiges
Keyword(s):  
Cation Exchange ◽  
Chemical Weathering ◽  
Relative Proportion ◽  
River System ◽  
Exchange Capacity ◽  
Continental Scale ◽  
Main Effect ◽  
The Ganges ◽  
The Impact

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 Ganges-Brahmaputra River system based on cation exchange capacity (CEC) measurements of riverine sediments. CEC values of sediments are variable throughout the water column but average at ca. 6.5 meq/100 g for the Ganges-Brahmaputra. The cationic charge of sediments in the river is dominated by bivalent ions Ca2+ (76 %) and Mg2+ (16 %) followed by monovalent K+ (6 %) and Na+ (2 %) and the relative proportion of these ions is constant among all samples and rivers. Assuming a total exchange of exchangeable Ca2+ for marine Na+ yields an maximal additional Ca2+ flux of 28 x 109 mol/yr of calcium to the ocean, which represents an increase of ca. 6 % of the actual dissolved Ca2+ flux. In the more likely event that only a fraction of the adsorbed riverine Ca2+ is exchanged, not only for marine Na+ but also Mg2+ and K+, estuarine cation exchange for the Ganga-Brahmaputra is responsible for an additional Ca2+ flux of 23 x 109 mol/yr, while ca. 27 x 109 mol/yr of Na+, 8 x 109 mol/yr of Mg2+ and 4 x 109 mol/yr of K+ are re-absorbed in the estuaries. This represents an additional riverine Ca2+ 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 Mg2+ are reabsorbed by the sediments in the estuaries. The impact of estuarine sediment-seawater cation exchange is therefore limited if 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.

TEM observation of iron oxide pillars in montmorillonite

1990 ◽  
Vol 48 (4) ◽  
pp. 882-883
Author(s):  
H. Mori ◽  
Y. Murata ◽  
H. Yoneyama ◽  
H. Fujita
Keyword(s):  
Aqueous Solution ◽  
Iron Oxide ◽  
Fine Particles ◽  
Aqueous Suspension ◽  
Volume Ratio ◽  
Exchange Capacity ◽  
Nano Composites ◽  
Pillared Montmorillonite ◽  
Topographic Features ◽  
Transmission Electron

Recently, a new sort of nano-composites has been prepared by incorporating such fine particles as metal oxide microcrystallites and organic polymers into the interlayer space of montmorillonite. Owing to their extremely large specific surface area, the nano-composites are finding wide application[1∼3]. However, the topographic features of the microstructures have not been elucidated as yet In the present work, the microstructures of iron oxide-pillared montmorillonite have been investigated by high-resolution transmission electron microscopy.Iron oxide-pillared montmorillonite was prepared through the procedure essentially the same as that reported by Yamanaka et al. Firstly, 0.125 M aqueous solution of trinuclear acetato-hydroxo iron(III) nitrate, [Fe3(OCOCH3)7 OH.2H2O]NO3, was prepared and then the solution was mixed with an aqueous suspension of 1 wt% clay by continuously stirring at 308 K. The final volume ratio of the latter aqueous solution to the former was 0.4. The clay used was sodium montmorillonite (Kunimine Industrial Co.), having a cation exchange capacity of 100 mequiv/100g. The montmorillonite in the mixed suspension was then centrifuged, followed by washing with deionized water. The washed samples were spread on glass plates, air dried, and then annealed at 673 K for 72 ks in air. The resultant film products were approximately 20 μm in thickness and brown in color.

Isotope Exchange Capacity on Li4SiO4 and Comparison of Tritium Inventory in Various Solid Breeder Blankets.

2001 ◽  
Vol 38 (11) ◽  
pp. 944-951 ◽  
Author(s):  
Masabumi NISHIKAWA ◽  
Noriaki NAKASHIMA ◽  
Kazuhisa HASHIMOTO ◽  
Serguei BELOGLAZOV
Keyword(s):  
Isotope Exchange ◽  
Exchange Capacity
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