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Occurrence Of Lepidocrocite And its Association With Goethite in Natal Soils
Author(s) -
Schwertmann U.,
Fitzpatrick R. W.
Publication year - 1977
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1977.03615995004100050042x
Subject(s) - lepidocrocite , goethite , crystallinity , soil water , mineralogy , chemistry , geology , materials science , inorganic chemistry , soil science , crystallography , organic chemistry , adsorption
Hydromorphic soils (pseudogleys) in a highland‐montane climate of Natal (South Africa) contain appreciable amounts of lepidocrocite. Its occurrence appears to be restricted to imperfectly drained lower positions on southern (cooler) slopes at an altitude between 1,300–1,900 m. In these positions, Fe is reduced under anaerobic Conditions leading to lepidocrocite formation on reoxidation. Goethite is closely associated with lepidocrocite and increases on approaching better aerated microzones such as root channels and textural boundaries where it usually forms crusts. Both FeOOH forms were determined quantitatively by XRD. Simultaneous formation of the two Fe‐oxides is inferred from synthesis experiments in which an increasing partial pressure of CO 2 in an O 2 ‐CO 2 gas mixture to oxidize a FeCl 2 solution favored goethite at the expense of lepidocrocite. The crystallinity of lepidocrocite (as measured by XRD line broadening) decreased when approaching root channels. This is attributed to a decreased in pH and agrees again with synthesis experiments where the same effect was observed. Goethite is generally less crystalline than lepidocrocite.