Transformation of Fe-minerals in hydromorphic soils

Abstract

In hydromorphic soils are important not only sustainable Fe-minerals, defined traditionally in dried soil, but also unstable Fe-minerals, changing the colors of the clay after extracting the sample fr om the soil, as well as — weakening gley signs in the dry season. New indicators are offered for the additional characteristic of Fe-minerals. The first is that it characterizes the interaction of active Fe-minerals with colloids, it is index I: I = CEC/Fe (free), wh ere CEC is the cation exchange capacity. The second indicator is the change in the gley color after drying, assessed by the change in the redness Да*. In Fe-enriched, reduced gley Gr with a low index value (/0,1) and a strong increase Aa* ~ 9 after drying, the green rust is transformed into a brown lepidocrocite. During the humidity decrease, the transition of the reduction gley to the oxidized gley is accompanied by a change in the composition of the green rust: the transformation of fougerite into a trebeurdendite: Fe-ephemera with a higher degree of Fe oxidation and the growth of Да* ~ 3. When oxidized gley Go with the index I = 2—8 is dried, the slow Да* growth is caused by the inhibition of Fe-hydroxide crystallization by colloids. In the “de-ironed” gley Gdf with a high value the index 1= 6—27, the lack of red growth (a* « 0) on drying, is probably due to the Fe clay minerals inertia.

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