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
Iron Oxides as Major Available Interface Component in Loamy Arable Topsoils
TL;DR: In this article, the contribution of weakly crystalline and crystalline oxides to soil specific surface area (SSA) of particle size fractions was determined, and stable microaggregates were present in the coarse and medium silt fractions of all soils that could not be dispersed physically even at the highest ultrasonic dispersion energy and were probably stabilized by organic matter and iron oxides.
Journal ArticleDOI
Relationship of soil properties to parent material and landscape position in eastern Madre de Dios, Peru
L.J Osher,Stanley W. Buol +1 more
TL;DR: In this article, properties of soils in the eastern part of Madre de Dios, Peru were characterized and related to landscape position and parent material texture, and data for eight soil profiles representative of the region are presented.
Journal ArticleDOI
Geochemical investigation of soils developed in different lithologies in Bhutan, Eastern Himalayas
TL;DR: In this article, a comprehensive set of major, trace and rare earth element (REE) contents has been compiled for the first time within a project studying soil genesis on the southern slopes of the Eastern Himalayas, where six saprolites and their associated pedons were sampled on metamorphic, migmatitic and leucogranitic parent materials at altitudes ranging from 1520 to 3770m.
Journal ArticleDOI
Micromorphology and development of loess-derived surface and buried soils along a precipitation gradient in Northern Iran
Farhad Khormali,Martin Kehl +1 more
TL;DR: In this paper, eight pedons of modern soils and six paleosols were selected in order to investigate the types of modern and past soil forming processes and to compare the degree of soil development of surface and buried soils.
Journal ArticleDOI
Fluxes of dissolved organic carbon in two tropical forest ecosystems of East Kalimantan, Indonesia
Kazumichi Fujii,Mari Uemura,Chie Hayakawa,Shinya Funakawa,Sukartiningsih,Takashi Kosaki,Seiichi Ohta +6 more
TL;DR: In this paper, the role of DOC leaching in soil organic carbon cycle was evaluated by quantifying the fluxes of DOC in throughfall and soil solution in the Ultisols under tropical secondary and pristine forests in East Kalimantan, Indonesia.
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.