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
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Book ChapterDOI
Silicon in Soils and Plants
Brenda Tubana,Joseph R. Heckman +1 more
TL;DR: In this paper, the outcomes of many years of research conducted on silicon are consolidated to understand the state of knowledge for silicon fertilization guidelines in crop production, and many aspects of the role of silicon in soil science remain understudied.
Journal ArticleDOI
Sorption of dissolved organic nitrogen by acid subsoil horizons and individual mineral phases
Klaus Kaiser,Wolfgang Zech +1 more
TL;DR: In this article, the binding of dissolved organic matter from the forest floor to amorphous Al(OH)3, goethite, kaolinite, and illite and to subsoils was examined in laboratory experiments.
Journal ArticleDOI
Soil Color as an Indicator of Slash‐and‐Burn Fire Severity and Soil Fertility in Sumatra, Indonesia
TL;DR: In this article, field experiments were conducted in Sepunggur, Jambi Province, Sumatra, Indonesia to test the correlation between fire severity, burned soil color, and soil fertility.
Journal ArticleDOI
The Reductive Dissolution of Synthetic Goethite and Hematite in Dithionite
TL;DR: In this paper, the reductive dissolution of Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated.
Journal ArticleDOI
Spatial variations of magnetic susceptibility of Chinese loess for the last 600 kyr: Implications for monsoon evolution
Qingzhen Hao,Zhengtang Guo +1 more
TL;DR: In this paper, the authors examined magnetic susceptibility (MS) over the Loess Plateau in China based on 50 sections in order to identify spatial changes in monsoon climate at key glacial, interglacial, and interstadial intervals for the last 600 kyr.
References
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Book
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.