Extraction citrate-bicarbonate-dithionite

To assess the correlation of iron and aluminum oxides with iodine content, we used a selective extraction to target the different fractions of Fe and A1 in the soil samples. Citrate-bicarbonate-dithionite (CBD) extractable Fe contains crystalline iron oxide minerals, such as hematite, goethite, lepidocrocite, and ferrihydrite, while ammonium oxalate (NH4—Ox) extraction targets noncrystalline ( free ) Fe oxides, including ferrihydrite and ferrihydrite-hke minerals (Loeppert and Inskeep, 1996). The CBD and NH4—Ox extractions also remove some crystaUine and noncrystalline aluminum oxide phases, respectively. 

To extract different forms of Ee, the clay fractions from the fine earth of bulk, LAR and TAR were dispersed in NaOH at pH 8.5 and treated with acidic (pH 3) NH4-oxalate (Blakemore et al., 1981), citrate-bicarbonate-dithionite (CBD) (Mehra and Jackson, 1960) and 0.1 M hydroxylamine hydrochloride (HAHC) (Chao, 1972). The Ee extracted was measured by atomic absorption with a Perkin-Elmer llOOB spectrophotometer. 

Fe extracted by acid NH4-oxalate, citrate-bicarbonate-dithionite (CBD), and hydroxy-lamine hydrochloride (HAHC) from the clay from bulk and rhizosphere soil of the 2C1 and 2C2 horizons nnder Genista aetnensis at Mount Vetore (Sicily, Italy). Standard errors in parentheses (n = 3)... 

See also Section 3.2.35.18.2. MX80 Wyoming bentonite was washed with 0.5 M NaCl and 0.1 M acetic acid, extracted with dithionite-citrate-bicarbonate, treated with 3% H2O2, and then washed with 0.5 M NaCl again. 

Extracted with dithionite-citrate-bicarbonate, treated with 3% H2O2. 

Fig. 7.16 Pore water and extraction results from hemipelagic sediments off Uruguay (redrawn from Haese et al. 2000). Dissolution and precipitation of Fe is reflected by the easy reducible iron oxyhydroxide fraction whereas less reducible iron oxides soluble by subsequent citrate/dithionite/bicarbonate (CDB) extraction remain constant. A concurrent liberation of Mn and Fe indicates dissimilatory iron reduction and subsequent iron reoxidation by manganese oxides, which results in the build-up of Mn Under these conditions the actual dissimilatory iron reduction rate is higher than deduced from iron pore water gradients.

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