Yellowing of a Red South African Kandiudult, Studied by Means of Mössbauer Spectroscopy

• Published in: Soil science Vol. 181; no. 2; pp. 75 - 81
• Main Authors: Van Ranst, Eric, Padmanabhan, Eswaran, Vandenberghe, Robert E, De Grave, Eddy, Mees, Florias
• Format: Journal Article
• Language: English
• Published: Baltimore Copyright Wolters Kluwer Health, Inc. All rights reserved 01-02-2016; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Dissolved organic matter; Fractionation; Iron oxides; Leaching; Soil profiles; Soil sciences; Soils; Spectroscopy; Spectrum analysis; South Africa; KwaZulu-Natal Province South Africa; South Africa, Kwazulu-Natal Prov
• ISSN: 0038-075X; 1538-9243
• DOI: 10.1097/SS.0000000000000143

ABSTRACTAn Acrudoxic Kandiudult soil profile from Farmhill, KwaZulu-Natal Province, South Africa, was analyzed by Mössbauer spectroscopy as an example of a red soil with yellowish surface horizons, a common sequence for which iron oxide characteristics are only poorly documented. In the red lower part of the profile (62+ cm), the Fe oxide fraction consists of hematite and well-crystallized pure goethite. In the yellowish upper part (0–62 cm), the relative hematite content is lower, goethite shows a high degree of Al-for-Fe substitution, and ferrihydrite is present. Processes found to have affected the Fe oxide fraction are hematite dissolution, partial leaching, goethite precipitation with a high degree of Al incorporation, and ferrihydrite formation in conditions with a high organic matter content; the so-called DOM (dissolved organic matter) ferrihydrites.