Transformation of Fe-Minerals in Hydromorphic Soils

Autor: A. T. Savichev, Yu. N. Vodyanitskii
Rok vydání: 2020
Předmět:
Zdroj: Moscow University Soil Science Bulletin. 75:1-7
ISSN: 1934-7928
0147-6874
DOI: 10.3103/s014768742001007x
Popis: Unstable Fe-minerals, which change the color of gley after the sample extraction from soil and make less pronounced the features of gleying in the dry season, are important in hydromorphic soils parallel to stable Fe-minerals conventionally detected in dried soil. Two new parameters are proposed for the additional characteristic of Fe-minerals. The first one—index I—characterizes the interaction of active Fe-minerals with colloids and is determined as I = CEC/Fefree, where CEC is the cation exchange capacity. The second parameter is the change in the redness of gley after drying (Δа*) according to the CIE–L*a*b* optic system. In iron-enriched reduced gley (Gr) with low I ~ 0.1 and a strong increase in Δа* (≈9) after drying, the green rust is transformed into brown lepidocrocite. During a decrease in humidity, the transformation of reduced gley into oxidized one is accompanied by a rise in Δа* (≈3) and by a change in the composition of the green rust: the transformation of fougerite into trebeurdenite (Fe-ephemer with a higher oxidation rate of iron). When oxidized gley Go with I = 2–8 dries up, a slow increase in Δа* is caused by the inhibition of crystallization of Fe-hydroxides by colloids. In the deferruginated gley (Gdf) with high I = 6–27, the absence of a rise in the red color (Δа* ≈ 0) during drying is probably related to the inactivity of Fe-phyllosilicates.
Databáze: OpenAIRE
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