Journal ArticleDOI
Iron Oxide Removal from Soils and Clays by a Dithionite-Citrate System Buffered with Sodium Bicarbonate
TLDR
In this article, the bicarbonate-buffered Na2S2O4-citrate system was used for removing free iron oxides from latosolic soils, and the least destructive of iron silicate clays.Abstract:
The oxidation potential of dithionite (Na2S2O4) increases from 0.37 V to 0.73 V with increase in pH from 6 to 9, because hydroxyl is consumed during oxidation of dithionite. At the same time the amount of iron oxide dissolved in 15 minutes falls off (from 100 percent to less than 1 percent extracted) with increase in pH from 6 to 12 owing to solubility product relationships of iron oxides. An optimum pH for maximum reaction kinetics occurs at approximately pH 7.3. A buffer is needed to hold the pH at the optimum level because 4 moles of OH are used up in reaction with each mole of Na2S2O4 oxidized. Tests show that NaHCO3 effectively serves as a buffer in this application. Crystalline hematite dissolved in amounts of several hundred milligrams in 2 min. Crystalline goethite dissolved more slowly, but dissolved during the two or three 15 min treatments normally given for iron oxide removal from soils and clays. A series of methods for the extraction of iron oxides from soils and clays was tested with soils high in free iron oxides and with nontronite and other iron-bearing clays. It was found that the bicarbonate-buffered Na2S2O4-citrate system was the most effective in removal of free iron oxides from latosolic soils, and the least destructive of iron silicate clays as indicated by least loss in cation exchange capacity after the iron oxide removal treatment. With soils the decrease was very little but with the very susceptible Woody district nontronite, the decrease was about 17 percent as contrasted to 35–80 percent with other methods.read more
Citations
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Journal ArticleDOI
Weathering sequences of clay minerals in soils along a serpentinitic toposequence
TL;DR: In this article, four soil pedons were selected along a toposequence from the summit (Entisol), shoulder (Vertisol), backslope (Alfisol) to footslope position to explore the contributions and the significance of landscape and weathering status of serpentinitic rock with regard to clay mineral transformations in eastern Taiwan.
Journal ArticleDOI
Roles of soil organic carbon and iron oxides on aggregate formation and stability in two paddy soils
Bin Xue,Li Huang,Yanan Huang,Fangliang Zhou,Feng Li,Kashif Ali Kubar,Xiaokun Li,Jianwei Lu,Jun Zhu +8 more
TL;DR: In this paper, the effects of organic carbon (SOC) and different forms of iron oxides on the stability of aggregates of paddy soils were determined by applying the Le Bissonnais (LB) and extractions method by water, oxalate (OA), dithionite-citrate-bicarbonate (DCB), or hydrogen peroxide (H2O2).
Journal ArticleDOI
Comparison of Sequential Extraction and Bioaccessibility Analyses of Lead Using Urban Soils and Reference Materials
TL;DR: In this paper, a study was performed using urban soils in Detroit, MI and reference materials (cerussite, anglesite, pyromorphite, apatite, goethite, calcite and pyrolusite) to determine which geochemical forms of Pb measured by sequential extraction analysis are bioaccessible.
Journal ArticleDOI
Characterization of the Chinese loess-paleosol stratigraphy by whiteness measurement
TL;DR: In this article, whiteness and magnetic susceptibility were compared from four loess-paleosol sequences in central China, and the results showed that the two parameters are highly correlated in the four sequences studied.
Journal ArticleDOI
Least limiting water range and soybean yield in a long-term, no-till, integrated crop-livestock system under different grazing intensities
Diego Cecagno,Sérgio Costa,Ibanor Anghinoni,Taise Robinson Kunrath,Amanda Posselt Martins,José Miguel Reichert,Paulo Ivonir Gubiani,Fabrício Balerini,Jessé Rodrigo Fink,Paulo César de Faccio Carvalho +9 more
TL;DR: In this article, the authors evaluated the efficiency of the least limiting water range in determining the influence of grazing intensities on soybean yield in an Oxisol managed in a long no-till, integrated soybean-beef cattle system.
References
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Soil Chemical Analysis
TL;DR: Soil chemical analysis, Soil Chemical Analysis (SCA), this paper, is a technique for soil chemical analysis that is used in the field of Soil Chemistry and Chemical Engineering.
Journal ArticleDOI
Iron Oxide Removal from Soils and Clays1
N. H. Aguilera,M. L. Jackson +1 more
TL;DR: In this article, a procedure is presented which employs sodium dithionite (Na2S2O4, hyposulfite, or "hydrosulfite") as the reductor, and 0.3 molar citrate with or without Fe-3 specific Versene as the chelating reagent.