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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Book ChapterDOI
Iron-bound phosphorus in marine sediments as measured by bicarbonate-dithionite extraction
TL;DR: In this article, a bicarbonate buffered dithionite solution (BD-reagent) was used to extract iron-bound P from sediment from 16 m water depth in Aarhus Bay, DK and in two other marine sediments: Kattegat at 56 m and Skagerrak at 695 m depth.
Journal ArticleDOI
Fire-induced transformation of C- and N- forms in different organic soil fractions from a Dystric Cambisol under a Mediterranean pine forest (Pinus pinaster)
TL;DR: In this article, the authors analyzed the quality and quantity of humic materials extracted from the A horizons (0-15 cm) of a fire-affected (FA) and a control fire-unaffected (FU) Dystric Cambisol from the Sierra de Aznalcollar (Spain).
Journal ArticleDOI
An improved method for extracting marine sediment fractions and its application to Sr and Nd isotopic analysis
Germain Bayon,Christopher R. German,R.M. Boella,James A. Milton,Rex N. Taylor,Robert W. Nesbitt +5 more
TL;DR: In this paper, the radiogenic isotopic composition of both detrital and Fe-Mn fractions in marine sediments is used in paleoceanography to infer changes of bottom-water circulation.
Journal ArticleDOI
Spectral Reflectance Methodology in Comparison to Traditional Soil Analysis
TL;DR: In this paper, the spectral reflectance (SR) was used to measure soil attributes using satellite data as an alternative to traditional methods, such as traditional soil analyses are expensive, time-consuming, and may also result in environmental pollutants.
Journal ArticleDOI
Al-substituted goethite—An indicator of pedogenic and other weathering environments in South Africa
Rob Fitzpatrick,Udo Schwertmann +1 more
TL;DR: In this article, X-ray powder diffraction (XRD) was used to identify goethite-containing samples from widely diverse environments along the eastern seaboard of South Africa.
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.