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THE OXIDATION OF IRON SULPHIDES IN SOILS IN RELATION TO THE FORMATION OF ACID SULPHATE SOILS, AND OF OCHRE DEPOSITS IN FIELD DRAINS
Author(s) -
BLOOMFIELD C.
Publication year - 1972
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1972.tb01636.x
Subject(s) - pyrite , soil water , chemistry , ferric , environmental chemistry , inorganic chemistry , sulfur , sulfate , iron oxide , mineralogy , geology , soil science , organic chemistry
Summary Aerating pyritic soils causes acidification and the forrnation of acid sulphate soils, or cat‐clay. The Oxidation of pyrite in soils is associated with the deposition in tile drains of a form of ochre quite distinct from that formed by the action of filamentous iron bacteria. Pyrite‐derived ochre results from the action of Thiobacillus ferrooxidans , which, below pH 3.5–4.0, catalyses the Oxidation of Fe 2+ and pyrite. In soils less acid than c. pH 4, pyrite oxidizes relatively slowly by chemical reactions to Fe 2+ and SO 2 4 − . Under these conditions iron enters the drains as Fe 2+ and is there oxidized by T. ferrooicidans and deposited as hydrated ferric oxide. Once the soil becomes acid enough for T. ferrooxidans to multiply, the rate at which pyrite oxidizes increases several‐fold, and at c. pH 3 iron appears in the drainage water in the ferric form. Liming seems to decrease the rate of Oxidation.